DOS Times March-April 2023

CONTENTS PAGE NO. TITLE 05 From the President’s DESK 06 From the DESK of Chief Editor Subspeciality Appliances What’s New 08 35 19 77 82 57 62 71 73 23 29 09 41 54 15 45 Epicapsular star: a rare congenital anomaly Phacoemulsification in Eyes with operated glaucoma filtering surgery Insights into role of ASOCT in strabismus Anterion – A multimodal Imaging Platform for Anterior Segment Wnt Signaling Pathway in Ophthalmology: Emerging Paradigms A Study of Ocular abnormalities in children with Cerebral palsy An overview of Optical Coherence Tomography Angiography Clinical Perspective: Low Dose Atropine for Myopia Control Small incision lenticule extraction (SMILE) surgery to treat Megalocornea Role of Scleral Contact Lenses in Keratoconus Descemet Membrane Detachment: An overview Intraocular lens implantation in pediatric cataract surgery Single site vs double site for combined Phaco-Trabeculectomy A stitch in time, saves nine: A diagnosis in time, saves life Shallow anterior chamber post cataract surgery: Causes and Management Tonometry and Recent Advances Cataract Glaucoma Squint Neuro-Ophthalmology Retina Refraction Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 DOS EXECUTIVE MEMBERS (2021-2023) 01 Dr. Om Prakash Anand Dr. Prafulla Kumar Maharana Dr. Rajendra Prasad President Prof. Rohit Saxena Vice President Dr. Gagan Bhatia Dr. Amar Pujari Dr. Jatinder Singh Bhalla Secretary Dr. Vivek Gupta Dr. Bhupesh Singh Dr. Sandhya Makhija Joint Secretary Dr. Vivek Kumar Jain Dr. Pankaj Varshney Dr. Alkesh Chaudhary Treasurer Prof. Kirti Singh Editor Dr. Jatinder Bali Library Officer DOS Office Bearers Executive Members Dr. Pawan Goyal Prof. Namrata Sharma Ex-Officio Members

Know Your Editor Editor Chief Editor DOS Times Dr. Jatinder Singh Bhalla MS, DNB, MNAMS Hony. General Secretary Delhi Ophthalmological Society DDU Hospital, Hari Nagar Dr. Prafulla Kumar Maharana, MD Associate Professor of Ophthalmology Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 02 Section Editor - Retina & Uvea Prof. (Col) Sanjay Kumar Mishra, HOD, Dept of Ophthalmology (vitreo retina surgeon), Army Hospital (R&R) Section Editor - Retina & Uvea Dr. Alkesh Chaudhary MBBS, MS, FMRF Head Consultant M.D. Eye Care & Laser Centre Section Editor - Uvea & Ocular Inflammatory Disorders Dr. Naginder Vashisht MD, FRCS, FICO Director & Senior Consultant Ophthalmology, Kailash Eye Care, Patel Nagar, New Delhi Senior Consultant Ophthalmology, Artemis Hospitals, Gurugram Section Editor - Retina & Uvea Dr. Raghav Malik, MS Fellowship Cataract & Refractive Surgery Associate Consultant Dept of Cataract, Cornea & Refractive Services, CFS, New Delhi Section Editor - Uvea & Ocular Inflammatory Disorders Dr. Prateek Kakkar (Retina Specialist), MD Ex-Senior Resident (Vitreo-retina, AIIMS, New Delhi) Section Editors - Retina & Uvea Dr. Deepankur Mahajan MBBS, MD (AIIMS), FICO, FAICO (Retina and Vitreous) Consultant Ophthalmologist and Vitreoretina Specialist, New Delhi Section Editor - Uvea & Ocular Inflammatory Disorders Dr. Aman Kumar MD, Senior Resident Vitreo-Retina, Uvea, ROP services Dr. R P Centre for Ophthalmic Sciences, AIIMS, New Delhi Section Editor - Retina & Uvea Dr. Rushil Kumar Saxena Dept of Vitreoretina Dr. Shroff’s Charity Eye Hospital, New Delhi Section Editor - Retina & Uvea Dr. Ankur Singh Assistant professor Dept of Ophthalmology University College of Medical Sciences and GTB Hospital, Delhi Section Editor - Retina & Uvea Dr. Abhishek Jain D.O., D.N.B., FAICO RBM Eye Institute, Delhi ADK Jain eye hospital, Bhagpat Section Editor - Cornea & External Eye Disease Dr. Sameer Kaushal Senior Consultant & Head (Ophthalmology) Artemis Hospital and PL Memorial Eye Clinic, Gurgaon Section Editor - Cornea & External Eye Disease Dr. Abha Gour Senior Consultant Cornea and Anterior Segment Dr. Shroffs Charity Eye Hospital, New Delhi

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 03 Section Editor - Ocular Surface Dr. Rajat Jain MBBS, MS (Gold Medalist), FICO (UK) Fellow- Cornea and Anterior Segment- LVPEI Hyderabad Section Editor - Cataract & Comprehensive Ophthalmology Dr. Ritin Goyal Director & Cornea, Cataract and LASIK surgeon at Goyal Eye Group of Eye Centers. Section Editor - Refractive Surgery Dr. Manpreet Kaur MD, Assistant Professor Cornea, Cataract & Refractive Surgery Services Dr. R P Centre for Ophthalmic Sciences AIIMS, New Delhi Section Editor - Ocular Surface Dr. Jaya Gupta Consultant Cornea Cataract & Refractive Surgery The Healing Touch Eye Care Centre, New Delhi Section Editor - Cataract & Comprehensive Ophthalmology Dr. Wangchuk Doma Venu Eye Institute and Research Centre Section Editor - Refractive Surgery Dr. Pranita Sahay, MD (AIIMS), FRCS (Glasgow), DNB, FICO, FICO (Cornea), FAICO (Ref Sx) Consultant, CFS, New Delhi Section Editor - Ocular Surface Dr. Abhishek Dave Consultant Cornea, Cataract & Refractive Surgery - CFS, New Delhi Section Editor - Ocular Surface Dr. Amrita Joshi Assistant Professor Department of Ophthalmology Army Hospital (R&R) Section Editor - Cataract & Comprehensive Ophthalmology Dr. Amit Mehtani MBBS, MS, DNB DDU HOSPITAL Section Editor - Ocular Surface Dr. Neeraj Verma MS (Ophthal) Senior Consultant Centre For Eye Care Kirti Nagar, New Delhi Section Editor - Cornea & External Eye Disease Dr. Ritu Nagpal MD Senior Research Associate Consultant, Eye7 Hospitals, Lajpat Nagar, New Delhi Section Editor - Cornea & External Eye Disease Dr. Parul Jain MBBS, MS, FICO, FAICO, MRCSEd Associate Professor GNEC, Maulana Azad Medical College Dr. Jyoti Batra Consultant, Oculoplasty and Ocular Oncology, ICARE Eye Hospital and Post graduate Institute, Noida Section Editor - Oculoplasty & Asthetics Section Editor - Oculoplasty & Asthetics Dr. Rwituja Thomas Grover Consultant Oculoplastics, Orbit, Ocular Oncology and Aesthetics services, Vision Eye Centres, New Delhi Section Editor - Oculoplasty and Orbit Dr. Sanjiv Gupta Lotus Eye Center, Naraina Vihar, New Delhi Dr. Anuj mehta Consultant and Professor Vardhman Mahavir Medical College and Safdarjung Hospital Section Editor - Oculoplasty & Asthetics Section Editor - Glaucoma Dr. Kiran Bhanot MS, DNB Senior Consultant & Hod GGS Hospital & Indira Gandhi Hospital, Dwarka, New Delhi Section Editor - Glaucoma Dr. Suneeta Dubey Head - Glaucoma Services Medical Superintendent Chairperson - Quality Assurance Dr. Shroff’s Charity Eye Hospital New Delhi, India Section Editor - Glaucoma Dr. Prathama Sarkar Consultant in Eye7 Chaudhary Eye Centre Section Editor - Glaucoma Dr. Kanika Jain MBBS, MS, DNB Senior Resident, Dept of Ophthalmology, DDU Hospital, Hari Nagar, New Delhi. Section Editor - Glaucoma Dr. Shweta Tripathi DNB, MNAMS, FMRF Senior Consultant Glaucoma Services Indira Gandhi Eye Hospital and Research Centre, Lucknow

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 04 Prof. Swati Phuljhale Dr. R P Centre for Ophthalmic Sciences, AIIMS, New Delhi Section Editor - Strabismus Dr. Gunjan Saluja Ex SR Strabismus, Oculoplasty and Neuro-Ophthalmology services, Dr. R P Centre, AIIMS, New Delhi Section Editor - Strabismus Dr. Suraj Singh Senjam Community Ophthalmology Dr. R P Centre for Ophthalmic Sciences, AIIMS, New Delhi Section Editor - Community Ophthalmology Dr. V Rajshekhar MS, FICO Professor & Consultant Dept of Ophthalmology VMMC & Safdarjung Hospital, New Delhi Section Editor - Community Ophthalmology Dr. Digvijay Singh Affiliation, Noble Eye Care, Gurugram Section Editor - Residents Corner Dr. Vineet Sehgal MBBS, MD Fellowship in Glaucoma Senior Consultant & Incharge Glaucoma Sharp Sight Eye Hospitals Section Editor - Residents Corner Dr. Sima Das Head, Oculoplasty and Ocular Oncology Services Incharge, Medical Education Dr. Shroff’s Charity Eye Hospital New Delhi Section Editor - Ocular Oncology Dr. Arpan Gandhi Dr. Shroff’s Charity Eye Hospital New Delhi Section Editor - Ocular Pathology and Microbiology Prof. Bhavna Chawla Professor of Ophthalmology Dr. R P Centre, AIIMS, New Delhi Section Editor - Ocular Oncology Dr. Paromita Dutta Associate Professor Guru Nanak Eye Centre Maharaja Ranjit Singh Marg New Delhi Section Editor - Strabismus Dr. Sumit Monga, Senior Consultant. Pediatric, Strabismus and Neuro-Ophthalmology Services, CFS group of Eye Hospitals, Delhi-NCR Section Editor - Neuro-Ophthalmology Dr. Amar Pujari Assistant Professor Dr. R P Centre for Ophthalmic Sciences, AIIMS, New Delhi Section Editor - Neuro-Ophthalmology Dr. Rebika Dhiman Assistant Professor Strabismus and NeuroOphthalmology services, Dr. R P Centre, AIIMS, New Delhi Section Editor - Neuro-Ophthalmology Dr. Simi Gulati I/C and Specialist Charak palika hospital (ndmc) Moti bagh, New Delhi Section Editor - Glaucoma Dr. Dewang Angmo MD, FRCS, FICO Dr R P Centre for Ophthalmic Sciences AIIMS Section Editor - Glaucoma Dr. Kavita Bhatnagar Professor & Head, Dept of Ophthalmology, AIIMS, Basani Phase-2, Jodhpur Section Editor - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 05 From the President's DESK Dr. Rajendra Prasad MBBS, MD DOS TIMES Respected Seniors and Dear Friends It has been gratifying to witness the success of DOS times and we are delighted to present the next issue in the series. A lot of credit goes to our Editors and Authors. DOS times serves, to provide a medium for learning, sharing and understanding the subject amongst the researchers, students and readers. This issue of DOS times focuses on general ophthalmology and covers wide range of topics, on the basic and applied research issues. The authors have made an attempt to present the most interesting articles in such a way as to give the reader a general picture of the basic science involved in many of the clinical and surgical situation and help in understanding many of the important concepts and their applications. I hope you will find this issue of DOS times helpful in learning and understanding the basic concepts of clinical problems and surgical techniques. “The real aim of science is to seek the simplest explanations of complex situations. A world without problems to be solved would be devoid of science.” Dr. Rajendra Prasad President DOS

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 06 DOS TIMES From the DESK of Chief Editor Dr. J S Bhalla, MS, DNB, MNAMS Secretary Delhi Ophthalmological Society Respected Seniors and Friends, Delhi Ophthalmological Society has been a role model for all state ophthalmological societies as this is the largest society in terms of membership with over 10,359 members as on January 2023. DOS Times has carved a niche in the Ophthalmology arena in clinical and academic work over the years. We are really enthused by the encouraging response to our previous issues & we promise to satiate your academic expectations in this as well as forthcoming issues of DOS Times. We have an efficient editorial team that centrifuges the submitted articles through a gradient, and all of the great academic content lines up in one layer. And these excellent articles are provided on a platter for your enjoyable reading. We have informative articles in this issue on Pan Ophthalmology: Tonometry and Recent Advances, Overview of OCTA, Low Dose Atropine for Myopia Control, Descemet Membrane Detachment, IOL Implantation in Pediatric Cataract Surgery, Role of ASOCT in Strabismus, Phacoemulsification in Eyes with Operated Glaucoma Filtering Surgery, Ocular Abnormalities in Children with Cerebral Palsy & many more. I really wish that we have path breaking articles on original Research. Research is to see what everybody else has seen, and to think what nobody else has thought. -Albert Szent-Györgyi The IDOS Conference at picturesque Phuket was a grand success. It was a grand conglomeration of science, networking & socializing. We have organised Global webseries on Virtual mode on Cataract, Glaucoma, Squint & Physical meets on Retina & Cornea + Cataract. We also organised Finals of DOS ENTOD Mega Quiz. Looking forward to meet you all soon at upcoming DOS meetings. I thank our Editorial team, our honourable readers and esteemed contributors. We wish you all a pleasant and enjoyable reading from beginning to finish. What we learn from reading is the vastness of our ignorance Dr. Jatinder Singh Bhalla, MS, DNB, MNAMS Chief Editor - DOS Times, Consultant & Academic Incharge (Ophthalmology) DDU Hospital, Hari Nagar

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 07

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 08 09 Epicapsular Star: A Rare Congenital Anomaly Anushree Gupta, DNB, MBBS, Anil Kumar Verma, MD Dr Radhakrishnan Government Medical College and Hospital, Hamirpur, Himachal Pradesh. Epicapsular stars are remnants of persistent pupillary membrane which presents as multiple, star shaped, tiny golden flecks over the anterior lens capsule, also known as chicken tracks. It is a rare congenital anomaly that results from incomplete involution of the ‘tunica vasculosa lentis’. The tunica vasculosa lentis is a vascular network of capillaries that surrounds the lens during development of the embryo and then slowly disappears near the time of birth.[1] Duke-Elder has classified persistent pupillary membrane into several variants[2]: • Type 1 membranes that are attached solely to the iris. • Type 2 membranes are iridolenticular adhesions. A subvariant of type 2 is epicapsular stars. • Type 3 membranes, which are attached to the cornea, typically occur in Axenfeld-Rieger syndrome. They do not affect vision but rarely can impede vision if they are confluent and located across the visual axis. The remnants of pupillary membrane are seen in about 95% of neonates and 20% of adults. Many theories state that closure of blood vessels is hindered by intrauterine intraocular inflammations or metabolic factors, thus preventing resorption.[3] The treatment of persistent pupillary membrane includes conservative management, laser technique or surgical method depending on visual function. Declaration of Patient Consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial Support and Sponsorship Nil. Conflicts of Interest There are no conflicts of interest. References 1. Zeng R, Liang X, Wang G. Epicapsular Stars. Ophthalmology. 2016 Oct;123(10):2076. doi: 10.1016/j.ophtha.2016.03.016. PMID: 27664910. 2. Duke-Elder S. System of Ophthalmology, Vol. 3. 1st ed. London: Henry Kimpton; 1964. p. 775. 3. Hadi AA, Hobbs CL. Effect of chronic intrauterine stress on the disappearance of tunica vasculosa lentis of the fetal eye: a neonatal observation. Am J Perinatol 1990;7(1):23-5. Dr. Anushree Gupta, DNB, MBBS Senior Resident, Dr Radhakrishnan Government Medical College and Hospital. Corresponding Author: Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 08 09 Intraocular Lens Implantation in Pediatric Cataract Surgery Vaishali Vasavada, MS, Shail Vasavada, DO, DNB, FICO, FRCS, Deepa Agrawal, MS Iladevi Cataract & IOL Research Centre & Raghudeep Eye Hospital, Ahmedabad, India. Introduction Management of pediatric cataracts poses several challenges, right from diagnosis to timely surgery, intraoperative challenges and postoperative visual rehabilitation. Early correction of aphakic refractive error is the most critical component in pediatric cataract surgery to prevent the development of amblyopia. Spectacles, contact lenses, and intraocular lens (IOL) implantation have been used for correction of surgical aphakia. However usage of spectacles/contact lenses for young children is associated with practical problems or wearing, additional economic burden and emotional turmoil for the child. Primary IOL implantation has the advantage of providing atleast a partial optical correction at all times.[1-4] However, this benefit should be carefully weighed against the potential risks for intra as well as postoperative complications. IOL implantation in children older than 2 years of age is now an accepted practice worldwide, particularly in developing countries.[5-7] Surgeons are still cautious about implanting an IOL in infants keeping in mind the severity of the intraoperative and postoperative complications including exaggerated inflammatory response, high rate of visual axis obscuration (VAO), and secondary glaucoma. When surgeons choose IOL implantation in an infant eye at the time of congenital cataract surgery, they need to carefully weigh the benefits of surgery against the risks associated with the procedure. This chapter aims to summarise views from recently published literature on the pros and cons of IOL implantation during cataract surgery in unilateral and bilateral pediatric cataracts, with a special focus on issues arising in developing countries. What IOL Type Should be Implanted in Pediatric Eyes? Today, foldable hydrophobic acrylic IOLs have become the preferred IOL choice for most pediatric cataract surgeons[2,3,8,9-18] instead of the PMMA IOLs which were once the IOLs of choice.[15,19,20] Being foldable, these IOLs offer all the benefits of smaller incision cataract surgery. Further, the hydrophobic acrylic material has excellent biocompatibility and is reported to cause lesser and more delayed onset posterior capsule opacification (PCO).[3,21,22] Recently, there have also been reports regarding the safety of hydrophilic IOLs[23] in pediatric eyes. IOL implantation in Unilateral Cataracts In the 1970s it was believed by ophthalmologists that unilateral cataracts should not be operated upon since they are associated with very poor visual prognosis.[24] Subsequently, it was shown in studies[25-29] that cataract surgery in unilateral cataracts yields good outcomes. Unilateral cataractous eyes may have comorbid conditions such as microphthalmos, persistent fetal vasculature, microcornea, colobomas etc. Further, the amblyogenic potential of unilateral cataracts is much more than bilateral cataracts, and therefore timely surgery followed by intensive amblyopia treatment and monitoring is required to prevent amblyopia and squint.[5,6,30,31] Aphakic spectacles are practically not a viable option for these eyes due to their unilateral nature. Contact lenses are the only non-surgical modality for optical correction of aphakia in these eyes. Advantages of contact lenses include the ability to change the contact lens power as needed to keep up with the rapidly growing eye’s refractive needs, and avoiding spectacle wear during the first few years of life. However, the use of contact lenses in infants has its own set of problems pertaining to difficulty in insertion and removal of the lens, the complications involved in fitting the lens onto the steep corneas of infants, as well as compliance issues. In developing countries, the repeated cost of replacing contact lenses due to frequent losses as well as change in refraction is often a limiting factor, alongwith parental education and hygiene levels that may prohibit effective contact lens usage. In infants there is still some controversy as to what should be the youngest age for implantation. Recently, a randomized, multicentric, clinical trial[32] comparing primary IOL implantation versus aphakia and contact lens wear was conducted in the United States of America in children younger than 7 months of age with unilateral cataracts. To summarize the results of this trial, at 4.5 years followup they reported that there was no significant difference in the median visual acuity whether an IOL was implanted or contact lenses were used. However, they did report significantly more adverse events (i.e. inflammatory sequelae, resurgeries for PCO) and reoperation rate in the eyes which received a primary in the bag IOL. Based on this study, the authors recommend that primary IOL implantation in unilateral cataracts <7 months of age should be reserved for infants, where, in the surgeon’s opinion, the cost and handling of a contact lens will be so burdensome as to result in significant periods of uncorrected aphakia. In another study[33], the British Isles Congenital Cataract Interest Group reported that in unilateral cataracts, there is no added visual benefit, or protection from glaucoma. However, primary IOL implantation did increase the odds for additional anaesthesia in this young population, who may be vulnerable to the effects of anaesthetic agents particularly affecting neurodevelopment. On the other Subspecialty - Cataract

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 10 11 hand, there have also been studies which report better visual acuity with primary IOL implantation as compared to primary aphakia.[34-36] Thus, based on the available evidence today, it may be fair to conclude that unilateral cataracts carry an inherent risk of amblyopia and despite best efforts are prone to develop poor visual outcomes and squint. Therefore, timely diagnosis, surgery as well as aggressive amblyopia therapy plays a crucial role in improving visual acuity as well as binocular function. IOL implantation should be the goal in all older children, but in younger children, particularly those below the age of 1 year, the risks of complications/reoperations should be carefully weighed against the potential visual benefit, keeping in mind the compliance with contact lens as well as adherence to patching. In the hands of lesser experienced surgeons, leaving the child aphakic may become a better option. Here, the role of through preoperative and frequent postoperative examinations, if required, under anesthesia cannot be undermined. IOL Implantation in Bilateral Cataracts For optical correction of children with bilateral cataracts, both aphakic spectacles and contact lenses are viable options. The debate on whether or not to perform primary IOL implantation is only in children younger than 2 years of age. There have traditionally been two schools of thought as far as bilateral cataract IOL implantation is concerned-one that believes aphakic spectacles are compatible with good vision and secondary IOL implantation can be performed once the child grows up, and the other, that believes in primary IOL implantation for faster and better quality visual rehabilitation. A recent randomized, clinical trial published by us[37] is the only randomized study that addresses complications and visual outcomes in bilateral aphakia versus bilateral pseudophakia. We found that visual recovery was much faster when primary IOL implantation was performed, and yet, the rate of serious postoperative complications was comparable 5 years after surgery in both groups. There are also other studies[38-40] who report favourable outcomes with bilateral primary IOL implantation in younger children. Thus, there is increasing evidence that primary IOL implantation is the way to go even in infant eyes with bilateral cataracts, wherever an in the bag IOL implantation can be performed. However, it should be kept in mind that in the bag is the preferred site for implantation in all pediatric eyes, particularly infant eyes. Biometry and IOL Power Selection in Pediatric Eyes Despite all efforts, predicting the axial growth of the eye and therefore, selecting an IOL of appropriate power for the eye is one of the biggest enigmas in pediatric cataract surgery. Most often, a handheld keratometry needs to be performed under general anesthesia. It is now quite well accepted that immersion ultrasound biometry is more accurate than contact biometry for children.[41] Implanting an IOL without performing biometry and keratometry should not be attempted. Whether to aim for emmetropia or undercorrect the child anticipating a future myopic shift is still not clear. The general consensus, particularly for young children is to perform varying degrees of undercorrection (leaving behind residual hyperopic refractive error). In general, younger the child, more should be the undercorrection. Several factors need to be considered before IOL power selection in pediatric eyes, such as-age, laterality, fellow eye status, history of myopia in family, and anticipated compliance with optical correction as well as amblyopia therapy. Several formulae, including the SRK-II, SRK-T, Hoffer Q, Holladay 1, Holladay 2, as well as Pediatric IOL Power calculator have been shown to be effective in IOL power calculation. However, achieving targeted refraction still remains an enigma that has not been solved till date.[42-47] It appears that all modern IOL power calculation formulae (eg. SRK/T, Holladay 2, Barrett Universal formula, Haigis) are more or less similar in their ability to achieve targeted refraction. Absolute and Relative Contraindications for IOL implantation in Pediatric Cataract Surgery Microcornea and microphthalmos remain absolute contraindications to primary IOL implantation, regardless of the age at surgery. Microcornea is usually defined as a horizontal corneal diameter of <9mm, and microphthalmos is defined as an axial length (AL) which is less than 2 standard deviations of the reported normal AL for that age.[48,49] Persistent fetal vasculature and juvenile/idiopathic arthritis, once considered as contraindications to IOL implantation are not absolute contraindications nowadays due to better techniques and technology. However, in both these conditions, presence of microphthalmos, microcornea or severe, persistent, intractable uveitis maybe considered as an absolute contraindication. Surgical Tips for IOL Implantation in Pediatric Cataract Surgery The one surgical strategy that differentiates pediatric cataract surgery from adult cataract surgery is the management of posterior capsule. A posterior capsulotomy (manual/vitrectorhexis) is usually performed with or without anterior vitrectomy in children younger than 6 years. Therefore, special care needs to be taken in implanting IOLs in these eyes. • Preferred site of IOL implantation. Primary Iol Implantation: In the bag placement of the IOL implantation is the preferred site of implantation (Figure-1). A posterior capsulotomy maybe performed prior to or following IOL implantation in the bag. Often, in infants and very young children, an IOL maybe implanted in its most physiologic position, that is, the capsular bag, and subsequently either a manual posterior capsulorhexis (PCCC) is performed with or without vitrectomy, or a vitrectorhexis alongwith anterior vitrectomy is performed. This approach ensures that the IOL can be implanted in the bag safely without the risk of an inadvertently large PCCC that may endanger in the bag placement. When implanting the IOL, care should be taken to use an appropriate injector-cartridge system Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 10 11 for the incision size. It maybe better to enlarge the incision a little so as to make IOL implantation smooth and comfortable. Using a heavy molecular weight cohesive ophthalmic viscosurgical device (OVD) is helpful, since it keeps the capsular bag expanded. Choosing an IOL material and design that allows controlled and slow unfolding is ideal, since the posterior capsule maybe open, and we want to avoid sudden jerky shooting of the IOL through the posterior capsule. However, there are often situations where there maybe preexisting or iatrogenic ruptures in the anterior and/or posterior capsules. In these conditions, it may become necessary to implant the IOL in the ciliary sulcus with or without capture of the IOL optic through the anterior or posterior capsulorhexes. In general, it maybe recommended that ciliary sulcus implantation of IOL is not the preferred site for IOL fixation, and should be performed only in the event of a posterior capsule rupture or inadvertently large PCCC that precludes in the bag implantation. Optic Capture of IOL: Visual axis obscuration (VAO) is one of the biggest hurdles for successful visual rehabilitation following successful pediatric cataract surgery (Figure-2), particularly when surgery is performed at a young age.[50-55] This is the reason why anterior vitrectomy has become an integral part of the surgical strategy for children younger than 5 to 6 years of age. However, the technique of optic capture, which was first described for pediatric eyes by Dr Howard Gimbel[56] offers a strategy whereby anterior vitrectomy can be avoided and yet VAO can be delayed or reduced. Here, an IOL is placed in the capsule bag following anterior and posterior capsulorhexes, and thereafter, the IOL optic is slid behind the PCCC margin, so as to “lock it” in position (Figure-3). This ensures both, IOL stability as well as retardation of VAO since the fusion of anterior and posterior capsulorhexes margins behind the IOL optic prevents central migration of proliferating lens epithelial cells. In a recent randomized study[57] we have shown that performing in the bag IOL implantation with anterior vitrectomy has similar Toric IOLs in Pediatric Cataract Surgery: Pre-existing corneal astigmatism is a problem in both adult and pediatric cataract surgery. Further, astigmatism has the potential to cause meridional amblyopia in the pediatric population. Since toric IOLs have been largely successful in adult eyes, surgeons have started adopting the use of these IOLs to deal with preexisting corneal astigmatism even in pediatric eyes. Although, there are not many reports in literature[58,59], the technology appears promising by aiming to correct one of the amblyogenic factors in the growing population. However, it is important that only children above the age of 5 years and those who are able to co-operate for reliable biometry, keratometry and corneal topography measurements be selected for toric IOL implantation. This is due to the fact that the corneal curvature only stabilizes by 5 to 6 years of age, and then. Secondary IOL Implantation: Often, children maybe left aphakic during their primary surgery, Figure 1: Anterior and posterior manual capsulorhexes with an intraocular lens placed in the capsular bag. Figure 2: Fierce visual axis obscuration caused by proliferation of residual lens epithelial cells following pediatric cataract surgery. Figure 3: Three piece foldable intraocular lens placed in the capsular bag and the optic captured through the posterior capsulorhexis. safety and complication rates as performing optic capture of a three-piece foldable IOL without any anterior vitrectomy. Subspecialty - Cataract

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 12 13 either due to young age, surgeon’s preference or conditions that preclude IOL implantation during. Secondary IOL implantation is a feasible option once the child grows up, and more importantly, the eye achieves an AL and corneal diameter suitable for IOL implantation. Most surgeons would prefer to perform secondary IOL implantation after the child achieves an age of atleast 3 years. In case a young child is being left aphakic, care should be taken during primary surgery to perform meticulously sized anterior and posterior capsulorhexes alongwith complete cortical removal, so that adequate capsular support is available for future IOL implantation. As for the site of IOL placement, the IOL can be placed in the capsular bag or in the ciliary sulcus. In the bag IOL placement requires the surgeon to open up the fused capsules and create space in the capsular bag. Although idea, this surgical strategy is challenging and may not be possible in a large number of eyes due to fused capsules. In this situation, a ciliary sulcus IOL should be placed, and the optic maybe captured through the anterior capsulorhexis if the rhexis size allows. It should be kept in mind that only three piece foldable IOLs should be implanted in the ciliary sulcus. Single piece foldable IOLs should not be implanted in the sulcus, as they are known to cause inflammation and/or glaucoma.[60] There are reports in literature that suggest successful outcomes following secondary IOL implantation, both in the ciliary sulcus and in the capsular bag.[61,62] However, it has also been reported that in the bag implantation may have lower inflammation and corneal edema in the postoperative period. Further, whenever secondary IOL implantation is performed, close followup should be maintained to watch for postoperative inflammation, glaucoma and retinal complications. Thus, in summary, with evolution of pediatric cataract surgery, there have been significant changes in the management paradigms of pediatric cataracts, especially IOL implantation. Primary IOL implantation is now gaining more acceptance in pediatric cataract surgeons worldwide for younger children. However, it is in the youngest infants that IOL implantation still poses some challenges. Future research as well as randomized, clinical trials from across the globe will hopefully pave the way to better and better anatomical and functional outcomes following pediatric cataract surgery. References 1. Lambert SR, Lynn M, Drews-Botsch C, et al. A comparison of grating visual acuity, strabismus and reoperation outcomes among children with aphakia and pseudophakia after unilateral cataract surgery within the first 6 months of life. J AAPOS 2001;5:70-75. 2. Plager D, Yang S, Neely D, et al. Complications in the first year following cataract surgery with and without IOL in infants and older children. J AAPOS 2002;6:9-14. 3. Trivedi RH, Wilson ME Jr, Bartholomew LR, et al. Opacification of the visual axis after cataract surgery and single acrylic intraocular lens implantation in the first year of life. J AAPOS 2004;8:156-64. 4. Tuncer S, Gucukoglu A, Gozum N. Cataract extraction and primary hydrophobic acrylic intraocular lens implantation in infants. J AAPOS 2005;9:250-56. 5. Ruth AL, Lambert SR. Amblyopia in the phakic eye after unilateral congenital cataract extraction. J AAPOS 2006;10:587-88. 6. Lewis TL, Maurer D, Brent HP. Development of grating acuity in children treated for unilateral or bilateral congenital cataract. Invest Ophthal Vis Sci 1995;36:2080-95. 7. Allen RJ, Speedwell L, Russell-Eggit I. Long-term visual outcome after extraction of unilateral congenital cataracts. Eye 2010;24:1263-67. 8. Serrafino M, Trivedi RH, Levin AV, et al. Use of the Delphi process in pediatric cataract management. Br J Ophthalmol 2016;100:611-15. 9. Vasavada AR, Nath VC, Trivedi RH. Anterior vitreous face behavior with Acrysof in pediatric cataract surgery. J AAPOS 2003;7:384-88. 10. Vasavada AR, Trivedi RH, Nath VC. Visual axis opacification after Acrysof intraocular lens implantation in children. J Cataract Refract Surg 2004;30:1073-81. 11. Dahan E. Implantation in children. Curr Opinion Ophthalmol 2000;11:51-55. 12. Stagner DR Jr, Weakly DR Jr, Hunter LS. Long term rates of PCO following small incision foldable acrylic intraocular lens implantation in children. J Pediatr Ophthalmol Strabismus 2003;39:73-76. 13. Kugelberg M, Zetterstorm C. Pediatric cataract surgery with or without vitrectomy. J Cataract Refract Surg 2002;28:1770-73. 14. Ram J, Brar S, Kaushik S. Role of posterior capsulotomy with vitrectomy and intraocular lens design and material in reducing posterior capsule opacification after pediatric cataract surgery. J Cataract Refract Surg 2003;29:1579-84. 15. Rowe NA, Biswas S, Lloyd IC. Primary IOL implantation in children. A risk analysis of foldable acrylic versus PMMA lenses. J Cataract Refract Surg 2004;88:481-85. 16. Raina UK, Mehta DK, Monga S, et al. Functional outcomes of acrylic intraocular lenses in pediatric cataract surgery. J Cataract Refract Surg 2004;30:1082-91. 17. Trivedi RH, Wilson ME Jr. Single piece acrylic intraocular lens implantation in children. J Cataract Refract Surg 2003;29:1738-43. 18. Kugelberg M, Kugelberg U, Bobrova N, et al. After cataract in children having cataract surgery with or without anterior vitrectomy implanted with a single piece Acrysof intraocular lens. J Cataract Refract Surg 2005;31:757-62. 19. Ram J, Jain VK, Agarwal A, Kumar J. Hydrophobic acrylic versus polymethyl methacrylate intraocular lens implantation following cataract surgery in the first year of life. Graefes Arch Clin Exp Ophthalmol 2014;252:1443-49. 20. Wilson ME, Trivedi RH. Choice of intraocular lens for pediatric cataract surgery: Survey of AAPOS members. J Cataract Refract Surg 2007;33:1666-67. 21. Linebarger EJ, Hardten DR, Shah GK, Lindstrom RL. Phacoemulsification and modern cataract surgery. Surv Ophthalmol 1999;44:123-47. 22. Trivedi RH, Wilson ME Jr. Single piece acrylic intraocular lens implantation in children. J Cataract Refract Surg 2003;29:1738-43. 23. Kugelberg M, Kugelberg U, Bobrova N, et al. After cataract in children having cataract surgery with or without anterior vitrectomy implanted with a single piece Acrysof intraocular lens. J Cataract Refract Surg 2005;31:757-62. 24. Sukhija J, Kaur S, Ram J. Outcome of a new acrylic intraocular lens implantation in pediatric cataract. J Pediatr Ophthalmol Strabismus 2015;52:371-6. Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 12 13 25. Hubel DH, Weisel TN. Receptive fields of cells in striate cortex of very young, visually unexperienced kittens. J Neurophysiol 1963;26:994- 1002. 26. Hubel DH, Weisel TN. Effects of monocular deprivation in kittens. Naunyn Schmeidebergs Arch Exp Pathol Pharmakol 1964;248:492- 497. 27. Weisel TN, Hubel DH. Effects of visual deprivation on morphology and physiology of cells in the cat’s lateral geniculate body. J Neurophysiol 1963;26:978-993. 28. Weisel TN, Hubel DH. Single-cell responses in striate cortex of kittens deprived of vision in one eye. J Neurophysiol 1963;26:1003-17. 29. Frey T, Friendly D, Wyatt D. Re-evaluation of monocular cataracts in children. Am J Ophthalmol 1973;76:381-88. 30. Reese AB. Persistent hyperplastic primary vitreous. The Edward Jackson Memorial Lecture. Am J Ophthalmol 1955;40:317-31. 31. Lundvall A, Kugelberg U. Outcome after treatment of congenital unilateral cataract. Acta Ophthalmol Scand 2002;80:588092. 32. Day AC, MacLaren RE, Bruce C, et al. Outcomes of phacoemulsification and intraocular lens implantation in microphthalmos and nanophthalmos. J Cataract Refract Surg 2013;39:87-96. 33. Infant Aphakia Treatment Study Group. Comparison of contact lens and intraocular lens correction of monocular aphakia during infancy: a randomized clinical trial of HOTV optotype acuity at age 4.5 years and clinical findings at 5 years. JAMA Ophthalmol 2014;132:676-82. 34. Solebo AL, Russell-Eggitt I, Cumberland PM, Rahi JS. British Isles Congenital Cataract interest group. Risks and outcomes associated with primary intraocular lens implantation in children under 2 years of age : the IoLunder2 cohort study. Br J Ophthalmol 2015;99:1471-6. 35. Lambert SR, Lynn M, Drews-Botsch C, et al. Optotype acuity and re-operation rate after unilateral cataract surgery within the first 6 months of life with or without IOL implantation. Br J Ophthalmol 2004;88:1387-90. 36. Kumar P, Lambert SR. Evaluating the evidence for and against the use of IOLs in infants and young children. Expert Rev Med Devices 2016;13:381-9. 37. Magli A, Forte R, Carrelli R, et al. Longterm outcomes of primary intraocular lens implantation for unilateral congenital cataracts. Semin ophthalmol 2015;21:1-6. 38. Vasavada AR, Vasavada V, Shah SK, et al. Five-Year Postoperative Outcomes of Bilateral Aphakia and Pseudophakia in Children up to 2 Years of Age : A Randomized Clinical Trial. Am J Ophthalmol 2018;193:33-44. 39. Gupta A, Kekunnaya R, Ramappa M, Vaddavalli PK. Br J Ophthalmol 2011;95:477-80. 40. Struck MC. Long-term results of pediatric cataract surgery and primary intraocular lens implantation from 7 to 22 months of life. JAMA Ophthalmol 2015;133:1180-3. 41. Wilson ME Jr, Trivedi RH. Eye growth after pediatric cataract surgery. Am J Ophthalmol 2004;138:1039-40. 42. Fan DS, Rao SK, Yu CB, et al. Changes in refraction and ocular dimensions after cataract surgery and primary intraocular lens implantation in infants. J Cataract Refract Surg 2006;32:1104-08. 43. Nihalani BR, VanderVeen DK. Comparison of intraocular lens power calculation formulae in pediatric eyes. Ophthalmology;117(8):1493-1499. 44. Vanderveen DK, Nizam A, Lynn MJ, et al. Predictability of intraocular lens power calculation and early refractive status : the Infant Aphakia Treatment Study. Arch Ophthalmol 2012;130:293-99. 45. Vanderveen DK, Trivedi RH, Nizam A, et al. Predictability of intraocular lens power calculation formulae in infantile eyes with unilateral congenital cataract: Results from the Infant Aphakia Treatment Study. Am J Ophthalmol 2013;156:1252-1260. 46. Trivedi RH, Wilson ME, Reardon W. Accuracy of the Holladay 2 intraocular lens for pediatric eyes in the absence of preoperative refraction. J Cataract Refract Surg 2011;37:1239-1243. 47. Vasavada V, Shah SK, Vasavada VA, et al. Comparison of IOL power calculation formulae for pediatric eyes. Eye 2016;30:1242-50. 48. Lambert SR, Lynn MJ, Hartmann EE, et al. Comparison of contact lens and intraocular lens correction of monocular aphakia during infancy : a randomized clinical trial of HOTV optotype acuity at age 4.5 years and clinical findings at age 5 years. JAMA Ophthalmol 2014;132:676-82. 49. Hoffman RS, Vasavada AR, Allen QB, et al for the ASCRS Cataract Clinical Committee, Challenging/Complicated Cataract Surgery Subcommittee. Cataract surgery in the small eye. J Cataract Refract Surg 2015;41:2565-75. 50. Lambert SR, Buckley EG, Drews-Botsch CD, et al. Infant Aphakia Treatment Study Group. The infant aphakia treatment study: design and clinical measures at enrolment. Arch Ophthalmol 2010;128:21-7. 51. Plager DA, Yang S, Neely D, Sprunger D, Sondhi N. Complications in the first year following cataract surgery with and without IOL in infants and older children. J AAPOS 2002; 6:9–14. 51. Trivedi RH, Wilson ME Jr, Bartholomew LR, Lal G, Peterseim MM. Opacification of the visual axis after cataract surgery and single acrylic intraocular lens implantation in the first year of life. J AAPOS 2004; 8:156–164. 52. Lambert SR, Lynn M, Drews-Botsch C, Loupe D, Plager DA, Medow NB, Wilson ME, Buckley EG, Drack AV, Fawcett SL. A comparison of grating visual acuity, strabismus, and reoperation outcomes among children with aphakia and pseudophakia after unilateral cataract surgery during the first six months of life. J AAPOS 2001; 5:70–75. 53. BenEzra D, Cohen E. Posterior capsulectomy in pediatric cataract surgery; the necessity of a choice. Ophthalmology 1997; 104:2168– 2174. 54. Apple DJ, Solomon KD, Tetz MR, et al. Posterior capsule opacification. Surv Ophthalmol 1992; 37:73–116. 55. Koch DD, Kohnen T. A retrospective comparison of techniques to prevent secondary cataract formation following posterior chamber intraocular lens implantation in infants and children. Trans Am Ophthalmol Soc 1997; 95:351–360. 56. McDonnell PJ, Zarbin MA, Green WR. Posterior capsule opacification cification in pseudophakic eyes. Ophthalmology 1983; 90:1548–1553. 57. Gimbel HV. Posterior continuous curvilinear capsulorhexis and optic capture of the intraocular lens to prevent secondary opacification in pediatric cataract surgery. J Cataract Refract Surg 1997; 23:652–656. 58. Vasavada AR, Vasavada V, Shah SK, et al. Postoperative outcomes of intraocular lens implantation in the bag versus posterior optic capture in pediatric cataract surgery. J Cataract Refract Surg. 2017 Sep;43:1177-1183. 59. Ram J, Singh R, Gupta R, et al. Toric intraocular lens implantation in children with developmental cataract and preexisting corneal astigmatism. Acta Ophthalmologica 2017;95:e95-e100. Subspecialty - Cataract

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 14 15 60. Gimbel HV, Camoriano GD, Aman-Ullah M. Bilateral Implantation of Scleral-Fixated Cionni Endocapsular Rings and Toric Intraocular Lenses in a Pediatric Patient with Marfan’s Syndrome. Case Rep Ophthalmol. 2012;3:16-23. 61. Vasavada AR, Raj SM, Karve S, et al. Retrospective ultrasound biomicroscopic analysis of single-piece sulcus-fixated acrylic intraocular lenses. J Cataract Refract Surg 2010;36:771-7. 62. Nihalani B, Vanderween DK. Secondary intraocular lens implantation after pediatric aphakia. J AAPOS 2011;15:435-40. 63. Wilson ME, Hafez GA, Trivedi RH. Secondary in-the-bag-intraocular lens implantation in children who have been aphakic since early infancy. JAAPOS 2011;15 : 162-166. Dr. Shail Vasavada, DO, DNB, FICO, FRCS Raghudeep Eye Hospital, Gurukul Road, Ahmedabad, India. Corresponding Author: Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 14 15 Shallow Anterior Chamber Post Cataract Surgery: Causes and Management Swati Singh, MS, Pranita Sahay, MD, FRCS, FRCOphth, FICO, FAICO, DNB, Surbi Taneja, MBBS, DNB, Mansi Johri, MBBS, DNB Centre for Sight, New Delhi. Cataract extraction is the most commonly performed ophthalmic surgery all over the world. The transition of cataract surgery from intracapsular cataract extraction (ICCE) and extracapsular cataract extraction (ECCE) to small incision cataract surgery (SICS) and Phacoemulsification has reduced the rate of intraoperative and postoperative complications along with improved visual outcomes. However, despite the use of best technology by a skilled surgeon, certain complications can still occur in the postoperative period which can jeopardize the success of the surgery. Shallowing of the anterior chamber in immediate or early postoperative period is one such complication which requires urgent medical or surgical intervention based on the etiology. An inappropriate wound construction with a leaky tunnel, capsular block syndrome with fluid entrapment in the bag and anterior shift of PCIOL, pupillary block with fibrinous exudates/membrane/air bubble or adhesions between iris and anterior capsular rim/intraocular lens, aqueous misdirection syndrome and serous choroidal effusion are some uncommon reasons for a postoperative shallowing of anterior chamber. We describe 5 cases who presented with shallow anterior chambers caused by different etiologies in immediate or early postoperative period after an uneventful phacoemulsification and their management. Case 1: Wound Leak 55-year-old woman had uncomplicated phacoemulsification surgery in her right eye. On the first post-operative day, unaided vision in right eye (RE) was 6/12 and intraocular pressure (IOP) with non-contact tonometer, 2 mm Hg. The anterior chamber (AC) was shallow in periphery and centre. Siedel’s test was conducted, and profuse wound leak was noticed from the corneal tunnel (Figure-1). The eye was patched, and frequency of steroids was reduced to 4 hourly dosage. Timolol 0.5% eye drop was advised 12 hourly to reduce aqueous secretion. After 48 hours of patching the wound leak subsided and anterior chamber depth became normal. IOP was 10 mm and unaided vision 6/6 in RE. Case 2: Acute Secondary Angle Closure and Shallow AC Caused by Air Bubble Migrating Behind the Iris 72-year-old woman underwent phacoemulsification with PCIOL implantation for hard mature cataract in her left eye (LE). An air bubble was injected in anterior chamber (AC) in view of a small Descemet’s membrane detachment at the incision site. On the first post operative day, the unaided vision in LE was counting fingers close to face and IOP, 50 mm Hg. Slit lamp examination showed a flat anterior chamber with irido-corneal contact superiorly and slit like AC inferiorly. The pupil was 2.5 mm in size and no air was seen in AC (Figure-2A). However, the miosed pupil was completely occluded by the air bubble which had moved into the posterior chamber and had pushed the iris anteriorly causing a secondary angle closure glaucoma with acute elevation of IOP. She was given oral acetazolamide 500 mg and cycloplegic eyedrop and was made to lie in supine position. An hour later the pupil was fully dilated, and air bubble had moved out into the anterior chamber (Figure-2B). Left eye vision improved to 6/18 and IOP came down to 32 mm Hg. She was discharged on tablet acetazolamide 250 mg 12 hourly for 2 days, brimonidine-timolol combination with homatropine eyedrop six hourly along with routine steroid antibiotic eyedrops. Follow-up after 3 days showed normal IOP and unaided vision of 6/9. Case 3: Aqueous misdirection syndrome 68-year-old man underwent sequential phacoemulsification in RE followed by LE within a gap of 7 days. On postop day one, RE vision was 6/9. However, on the first postoperative day of LE, the unaided vision was 6/18 in RE and 6/9 in LE. An axial shallowing of anterior chamber with anterior shift of IOL was Figure 1: Tcase 1 Right eye showing profuse leak from main corneal entry wound on slit lamp examination after fluorescein staining under cobalt blue filter. Subspecialty - Cataract

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 16 17 noted in RE without any iris bombe’ (Figure-3). There was no wound leak and the posterior capsule was in approximation with the posterior surface of IOL. AC depth was 2.79 mm/ 3.62 mm and IOP was 24 mm/16 mm in right and left eyes respectively. RE corrected distance vision was 6/6 with -1.50 DS and fundus examination was unremarkable. Aqueous misdirection syndrome was suspected, and we started timolol 0.5% eyedrop 12 hourly and atropine 1% eyedrop 4 hourly in RE. Patient responded to treatment and AC was reformed in a week. Atropine and timolol eyedrops were slowly withdrawn in a month and no recurrence was noted in RE afterwards. At 3 months post-op follow-up, both eyes were quiet with unaided vision of 6/6 and normal IOP. Figure 2A: Case 2 Left eye showing small pupil with air bubble behind the iris filling the pupillary area. Figure 3: Case 3 right eye on oblique slit illumination showing axial shallowing of AC and anterior shift of IOL. Figure 2B: Case 2 left eye slit lamp examination showing the air bubble in front of iris filling half of the anterior chamber after dilation.. Case 4: Pseudophakic Pupillary Block A 68-year-old man had uneventful phacoemulsification surgery for mature cataract in LE. He was on steroid-antibiotic and homatropine eyedrop for post-operative corneal edema and inflammation. On the 18th post-operative day, he presented with pain and heaviness in left eye with blurred vision. On examination, IOP was 44 mm in LE and anterior chamber was shallow in periphery with irido-corneal contact and iris bombe’ formation. The entire margin of the mid-dilated pupil was adhering to the anterior capsulotomy rim causing pupillary block (Figure-4). He was given intravenous injection mannitol 20%, 1 gm/kg and tablet acetazolamide 500 mg and YAG laser peripheral iridotomy was done which caused resolution of iris bombe’ and opening of the anterior chamber angle. Case 5: Capsular Block Syndrome 60-year-old woman presented with unexpected myopia of -2.5 D with shallow anterior chamber and IOP of 18 mm Hg on first postoperative day after an uneventful phacoemulsification surgery in RE. Examination revealed a distended capsular bag with entrapped fluid causing an anterior shift of the IOL and shallow AC (Figure-5). Patient was managed conservatively but as no improvement was observed at one week follow-up, a YAG laser opening was created in peripheral anterior capsule inferiorly which released the fluid and restored the AC depth to normal level. Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 16 17 Figure 4: Case 4 left eye on oblique illumination showing peripheral AC shallowing with iris bombe’ formation. Figure 5: Case 5 right eye oblique slit beam examination showing a shallow AC with increased space between the IOL and posterior capsule (green arrow) indicating a distended capsular bag with trapped fluid. Discussion The intraocular pressure plays a significant role in making the clinical diagnosis in a patient presenting with shallow anterior chamber in the post operative period as shown in the flow chart. Mild changes in AC depth may be missed initially but a comparison with the fellow eye may be helpful in patients with bilateral pseudophakia. The clinician should carefully examine all cases with unplanned myopic shift in refraction and a serial monitoring of AC depth on IOL master can be done with close follow-up when no obvious pathology is detected. An early diagnosis and prompt management directed to the specific etiology saves the patient from vision threatening complications like endophthalmitis, hypotony, permanent peripheral anterior synechiae formation with intractable secondary glaucoma and corneal decompensation. References 1. Reddy MK. Complications of cataract surgery. Indian J Ophthalmol. 1995 Dec;43(4):201-9. PMID: 8655202. 2. Grzybowski A, Kanclerz P. Acute and chronic fluid misdirection syndrome: pathophysiology and treatment. Graefes Arch Clin Exp Ophthalmol. 2018 Jan;256(1):135-154. Doi: 10.1007/s00417-017- 3837-0. Epub 2017 Nov 6. PMID: 29110086; PMCID: PMC5748435. 3. Mancino R, Varesi C, Cerulli A, Aiello F, Nucci C. Acute bilateral angle-closure glaucoma and choroidal effusion associated with acetazolamide administration after cataract surgery. J Cataract Refract Surg 2011;37415-7. 4. Gaton DD, Mimouni K, Lusky M, Ehrlich R, Weinberger D. Pupillary block following posterior chamber intraocular lens implantation in adults. Br J Ophthalmol. 2003 Sep;87(9):1109-11. doi: 10.1136/ bjo.87.9.1109. PMID: 12928277; PMCID: PMC1771845. Subspecialty - Cataract

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 18 19 5. Durak I, Ozbek Z, Ferliel ST, Oner FH, Söylev M. Early postoperative capsular block syndrome. J Cataract Refract Surg. 2001 Apr;27(4):555- 9. doi: 10.1016/s0886-3350(00)00689-1. PMID: 11311623. Dr. Swati Singh, MS Consultant, Cataract and Glaucoma Department Centre for Sight, New Delhi Corresponding Author: Subspecialty - Cataract

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 18 19 Insights into Role of ASOCT in Strabismus Vaishali Tomar, MBBS, MS, Subhash Dadeya, MD, MNAMS, FIMSA Guru Nanak Eye Center, New Delhi, Maulana Azad Medical College. Introduction Imaging techniques have a very important role in not only understanding the etiology of strabismus but also in planning the surgery. The knowledge of exact limbal insertion distance of rectus muscle helps in calculation of the surgical amount to be performed. Since the insertion is invisible in routine examination such as slit lamp biomicroscopy, a preoperative technique is required to improve the surgical plan and prevent resurgeries. Earlier, more oftenly CT and high resolution MRI[1] were used for similar purpose. These conventional modalities have the risk of radiation exposure. Furthermore, they also prove to be more costly with no additional benefit over current modalities. Those techniques were unable to identify exact extraocular muscle(EOM) insertion and the distance from the limbus. Ultrasonography allows us to visualise the EOMs and measure their distance from limbus but its accuracy is questionable due to low image resolution. Ultrasound biomicroscopy(UBM)[2-4] have proved to be more accurate in measuring limbal insertion distance before strabismus surgery, for both primary surgeries and resurgeries. However, it is difficult to perform in children due to technical difficulty such as placing a water filled cup on the ocular surface. Also, significant measurement errors are often induced due to unintentional pressing of eyeball with the UBM cup. Hence, there comes the role of newly developed anterior segment optical coherence tomography(ASOCT). With the wavelength of 1310nm, it generates a two dimensional image of high resolution from a reflected beam of light. It has qualities of faster scanning, minimum motion artifact, low scattering and high penetration into turbid tissues such as opaque corneas, sclera, iris and angle. Morever, it is a non contact examination and hence suitable for children and post operative assessment. Role of ASOCT in Resurgery Resurgeries are of special concern in the field of strabismology. Whenever we encounter a case of undercorrection or overcorrection post strabismus surgery,we need to take detailed history and investigate the patient thoroughly. This includes previous surgical details if available, amount of residual or consecutive deviation, extraocular movements and the evidence of conjunctival scarring along the operated muscles. Thereafter, we decide the plan on whether to operate in the same eye or the other eye depending on the status of unoperated muscles and other clinical factors. It becomes difficult to plan a surgery when the previous surgical details are unavailable. If we are planning an exploratory surgery, that is, operating on the same eye, we can apply our basic knowledge like conjunctival scarring, muscle site and patient recalling abilities. It is obviously easy to plan other eye if it is assumed optimal surgery has already been done in the other eye. But again there lies risk of overcorrection or undercorrection even if we operate the fresh eye and hence, such situation can be more challenging. So to circumvent all these problems, if we can reliably get the information on the type and the approximate amount of surgery done, then the whole situation becomes more predictable and scientific. Hence, in a nutshell, to solve all these issues, knowing aboout the exact muscle location and the probable type of surgery done (recession or resection) can provide great relief to the treating surgeon and the associated patient. Earlier models of OCT’s have limited penetration and narrow area of scanning which limit our desired information. To improve on these limitations swept source ASOCT (SS-ASOCT)[5] has additional advantages. Identification of Muscles In unoperated eyes, the muscle begins as curved, thin and hypoechoic structure at a fixed distance from the angle. This corresponds to the initial tendinous part of the muscle which when traced posteriorly, the corresponding hypoechoic area occupies progressively larger space which further corresponds to the muscle belly. The identification of transition from tendon to belly might be difficult but muscle can be identified with certainity in almost all the subjects. While tracing the boundaries, the outer surface of ocular coat has a smooth convex contour with uniform thickness throughout and no significant irregularities. Figure 1: Showing insertion of LR from the angle in unoperated eye. Subspecialty - Squint

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 20 21 Figure 2: Showing insertion of MR from the angle in unoperated eye. Figure 3: Showing resected MR (note the increased thickness at insertion site). Combined with the longitudinal scanning, the addition of cross-sectional scanning can further ease our understanding on muscle anatomy. The cross-sectional scanning is nothing but a simultaneously acquired scan at 90 degrees to it. In general, the longitudinal scan provides the lengthwise details and the cross- sectional scan the widthwise details. Hence, the combined scanning is more productive than the isolated scan. In recessed medial rectus muscle, the anterior ocular coat contour can be unremarkable and the posterior ocular coat contour can show variable thinning. In resected medial rectus muscle, the posterior ocular coat might appear thicker and irregular with variable conjunctival folds. There is increase in thickness due to presence of muscle belly at the original insertion site. The identification of lateral rectus muscle is easy as compared to medial rectus due to more working space and absence of plica semilunaris and caruncle whose shadow hinders the visibility of structures. A recessed lateral rectus muscle shows well maintained anterior ocular coat and disturbed posterior ocular coat. In resected lateral rectus muscle, bulky insertion site can be noted. Use in Post Traumatic Strabismus In strabismic eyes with a previous history of trauma, the routine MRI and CT are only be able to identify the muscle belly and the surrounding bony changes, however, the identification of muscle location on sclera is difficult. In these cases, the ASOCT can help to identify the location to a noticeable extent. This ASOCT knowledge can be used in surgical exploration, planning and as a prognostic indicator. Use in Thyroid Eye Disease In sthyroid eye disease, the cross-sectional images has the potential to show changes along muscle tendon as well as belly. Till now, the B scan ultrasound, CT, and MRI have been used to characterize the muscle size, however, the ASOCT in presence of axially protruded globe is specially useful in visualizing the anterior portion of the muscle. The proptosis exposed a large scleral area, hence, the scanning is easy and quick in these eyes (provided restrictions is less). The thickened muscle belly and its tendon can be clearly visualized in patients with thyroid eye disease, nevertheless, the thickness measurements can be used to monitor the patients who are on treatment. Use in Staphylomatous Eyes The other important indication is imaging in ocular coat ectatic disorder or staphylomatous eyes. If in such cases, patients develop sensory squint, there can be risk of uveal tissue prolapse due to critical location of ectasia. The ASOCT guided safe evaluation and the reaffirmation of negotiable ocular coat status can help in positive surgical planning and execution in such cases. Errors in Muscle Identification 1. Postoperatively, the muscle imaging needs to be cautiously judged till 4 weeks. Because the muscle space often erroneously appears as large hypointense layer, which settles over a period with the resolution of edema and tenoconjunctival flattening. 2. The large caliber conjunctival vessels can erroneously be judged as muscle areas. This can be avoided by carefully observing the muscle-specific characteristics. 3. In presence of dense conjunctival folds or scars (more so along the medial rectus), the muscle-specific identities can be misleading. Hence, here only a presumption can be made, and more definite conclusions are better avoided. 4. The identification of thin tendon/belly can be difficult sometimes, hence, in these cases, a co-relational scan between the longitudinal and the horizontal scans can be considered for better clarity. 5. Naïve surgeons can falsely label the subconjunctival dark areas as muscle which can be avoided by examining them more clearly by noticing the focal and discontinuous nature of the artifacts. Discussion The extraocular muscle insertion site is treated as reference point in the calculation of the amount of strabismus surgery. Since the prior strabismus surgery can alter the insertion points of muscle, a careful preoperative evaluation is mandatory especially in Subspecialty - Squint

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 20 21 cases of resurgeries. The ASOCT helps to design a surgical plan by localisation of displaced EOM insertion. In a study by Liu et al[6], 37 muscles of the 16 patients were studied including 18 medial rectus and 19 lateral rectus muscles. The Bland Altman plots showed that a total of 17 of 18 (94%) and 18 of 19 (95%) ASOCT-caliper differences,were found in the medial rectus and lateral rectus group respectively, to be within 95% confidence interval of the mean difference. In addition 92% of the measured values were within the predefined level (1.0 mm) of agreement between the two methods. In another study by Ngo et al[7], a total of 65 muscles were evaluated including 9 muscles undergoing resurgeries. Of all these, 62 muscles were successfully imaged. The ASOCT measurements were within 1mm of the intraoperative measurements in all reoperated eyes. Overall, 89.7% of the measurements were within 1mm difference considered clinically acceptable. Also, they were able to image a previously recessed as far posterior from the limbus as 13.5mm. John et al[8] did a study on 25 patients (mean age 17.9 ± 9.4 years) in 2017 on 35 muscles of which 12 were re-operated. The study was done with Visante OCT. Totally 88.6% of the measurements were within 1mm difference which was considered clinically acceptable. De-Pablo-Gomez-de-Liano et al[9] did a study in 2016 on 22 muscles for the agreement between direct intraoperative measurement and OCT measurements and got an intraclass correlation coefficient with a good agreement (0.931; 95% confidence interval [95% CI]: 0.839–0.972; p<0.001). This study included another set of 35 muscles for the agreement between trans-conjunctival intraopera- tive measurement and OCT. The study conducted by Pihlblad et al[10] in 2019 included pre, intra and postoperative muscle insertion measurements. The different OCT machines used were Bioptigen, Inc. (Leica Microsystems Inc., Buffalo Grove, IL, USA), Spectralis HRA+OCT with Anterior Segment Module (Heidelberg Engineering, Heidelberg, Germany), Visante (Carl Zeiss, Oberkochen, Germany), and Zeiss Rescan 700 (Carl Zeiss, Oberkochen, Germany). Measurements were compared to the handheld caliper distance measured during the strabismus surgery prior to disinsertion of EOM and also after reattachment of EOM to the sclera following surgery. But their result of 61% (62/102) of imaged muscles being at 1mm difference was not as successful as previous studies. Further they assumed that the rectus muscle insertion did not change over a period of 1 month postoperatively, which was a major limitation of the study. In another study by Amar Pujari et al[11] on the role of SS-ASOCT in strabismus re-operation with lost surgical details, 10 patients with a mean age of 23.7±5.75 years, were taken. Seven were male and three were female. The mean pre-operative SS-ASOCT measured distance from angle to insertion was 8.90±1.85mm and the mean intraoperative distance was 9.12±2.14mm. A mean difference of 0.21±1.31mm was noted, and this difference was statistically insignificant (paired t test, p = 0.57). In addition, SS-ASOCT unraveled novel signs to differentiate operated eyes from the un-operated eyes, and recessed muscle from the resected muscle. Based on these findings they concluded that pre-operative SS-ASOCT can provide reliable muscle details with respect to its type of surgery and amount surgery. In a study by Savleen Kaur et al[4],thirteen previously operated muscles of 6 subjects (age 20.3±4.4 years; range, 11-25) were imaged. The muscle insertion could be identified in 12 cases on AS-OCT and 10 cases on UBM. The difference between the imaging result and the caliper reading was ≤1 mm in 9 cases on AS-OCT and 5 cases on the UBM (69% vs 38%; P = 0.03). The maximum insertion distance on AS-OCT was 13.8mm; on UBM, 10.4mm. AS-OCT had a higher grade than UBM for patient comfort (P = 0.0005) and speed (P = 0.001). Moreover, as many clinicians use OCT for management of various posterior segment disorders, this equipment is easily available in most of the institutes. Hence, it is readily available for pre-operative measurements of EOM without additional expense and can be performed even by an adequately trained technician well-versed with the procedure. Conclusion To conclude, the SS-ASOCT with its advanced scanning abilities can be used to locate the extra ocular muscles locally. In normal eyes, in operated eyes with or without surgical details, in posttraumatic eyes, in thyroid eye disease, in ocular coat disease, and in other conditions where muscle details were essential they were imaged using ASOCT, to get the reasonable information with respect to its presence or absence and its measurements. Thus, in future, this cross-sectional imaging tool can reliably be used as an interrogative tool or a surgical guide while planning surgery in routine as well as complex case scenarios. References 1. Chaudhuri Z, Demer JL. Magnetic resonance imaging in strabismus. Delhi J Ophthalmol 2014; 24:188–191. 2. Thakur N, Singh R, Kaur S, et al. Ultrasound Biomicroscopy in Strabismus Surgery: Efficacy in Postoperative Assessment of Horizontal Muscle Insertions. Strabismus 2015; 23:73–79. 3. Khan HA, Smith DR, Kraft SP. Localizing rectus muscle insertions using high frequency wide-field ultrasound biomicroscopy. Br J Ophthalmol 201296:683–687. 4. Kaur S, Sukhija J, Korla S, Sachdeva K, Chaurasia S, Raj S. Comparison of the swept-source anterior segment optical coherence tomography and wide-field ultrasound biomicroscopy for imaging previously operated horizontal extraocular muscles.JAAPOS. 2021 Aug;25(4):212.e1-212.e6. doi: 10.1016/j.jaapos.2021.03.007. Epub 2021 Jul 9. PMID: 34246760. 5. Ramos JLB, Li Y, Huang D. Clinical and research applications of anterior segment optical coherence tomography – a review. Clin Exp Ophthalmol. 2009;37:81–89. 6. Liu X, Wang F, Xiao Y, et al. Measurement of the limbus-insertion distance in adult strabismus patients with anterior segment optical coherence tomography. Invest Ophthalmol Vis Sci 2011; 52:8370– 8373. 7. Ngo CS, Smith D, Kraft SP. The accuracy of anterior segment optical Subspecialty - Squint

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 22 23 coherence tomography (AS-OCT) in localizing extraocular rectus muscles insertions. JAAPOS 2015; 19:233–236. 8. John J, Joseph EK, Meena CK, et al. Clinical utility of anterior segment optical coherence tomography in strabismus surgery: prospective observational study. Kerala J Ophthalmol 2017; 29: 112. 9. De-Pablo-Gomez-de-Liano L, Fernandez-Vigo JI, Ventura-Abreu N, Morales-Fernandez L, Garcia-Feijoo J, Gomez-de-Liano R. Agreement between intraoperative measurements and optical coherence tomography of the limbus-insertion distance of the extraocular muscles. 10. Pihlblad MS, Reynolds JD. Anterior Segment Optical Coherence Tomography of Previously Operated Extraocular Muscles. Am Orthopt J. 2017 Jan;67(1):61-66. doi: 10.3368/aoj.67.1.61. PMID: 28904216. 11. Pujari A, Modaboyina S, Das D, Mahajan A, Thangavel R, Phuljhele S, Saxena R, Sharma N, Sharma P. Clinical Role of Swept Source Anterior Segment Optical Coherence Tomography in Strabismus ReOperation with Lost Surgical Details. Clin Ophthalmol. 2021 Aug 25;15:3581-3591. doi: 10.2147/OPTH.S328215. PMID: 34471343; PMCID: PMC8403674. Prof. Subhash C Dadeya, MD, MNAMS, FIMSA Director Professor, Guru Nanak Eye Center, New Delhi, Maulana Azad Medical College Corresponding Author: Subspecialty - Squint

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 22 23 Role of Scleral Contact Lenses in Keratoconus Tanveer Alam Khan, MBBS, MD, Sneha Aggarwal, M Optom, Murugesan Vanathi, MBBS, MD Cornea, Cataract and Refractive Surgery Services, Dr. R. P. Centre for Ophthalmic Sciences, AIIMS, New Delhi, India. Abstract: Scleral contact lenses (ScCL) provide a good therapeutic option in patients of moderate to advanced keratoconus where vision cannot be improved with rigid corneal contact lenses, either because of poor lens centration or inability to fit such a lens. One advantage of these lenses is that they are supported by the sclera and therefore can be fitted on eyes with markedly irregular corneas. Secondly, there is a constant aqueous reservoir between the lens and the cornea which neutralizes most of the irregular astigmatism and plays protective role too. These lenses may also delay the need for keratoplasty in patients who have exhausted other options for visual correction. Keywords: Keratoconus; Scleral contact lens; Keratoplasty, corneal ectasia, visual rehabilitation Introduction Keratoconus is a bilateral, progressive but self-limiting corneal disorder characterized by protrusion, distortion, thinning, and sometimes corneal scarring, which reduces optical clarity and decreases vision.[1] Spectacles are useful in the early stages of keratoconus when the astigmatism is mild. With advanced keratoconus, spectacles play a very limited role and contact lenses become necessary for improving the vision and play a major role. Various options for contact lenses are available and one can use any one of these as a starting lens, depending on the severity of the cone and associated conditions.[2-5] Some of these options include rigid gas-permeable (RGP) lenses, piggyback lens systems, hybrid lenses, and scleral lenses.[6] Contact lenses are estimated to manage 75% of keratoconus cases successfully.[7] Scleral contact lenses are indicated for corneal gas-permeable lens intolerance, improved comfort, and lens centration.[8] Koppen et al[9] reported that scleral lenses mitigated the need for corneal transplant in 80% of those with severe keratoconus. Although lamellar or full-thickness keratoplasty improves visual acuity in eyes with corneal scarring, it must be noted that scleral lenses may still be necessary to reach the bestcorrected post-surgical visual acuity.[10-13] Discussion Scleral contact lenses rest on the sclera and do not touch the cornea and limbus, leaving a clear area between the contact lens and the cornea. There is renewed interest over the last few years because of the availability of high Dk material and newer designs.[7,14-16] These lenses are indicated when all other contact lenses fail to improve the vision or because of inability to get an optimal fit with RGP lenses, RGP intolerance, 3 and 9 O’ clock staining of the cornea, vascularization, advanced keratoconus or scarring in the cornea.[14-17] Even associated diseases such as vernal keratoconjunctivitis (VKC) should not deter one from trying these lenses. The contraindications are presence of corneal oedema, acute hydrops and post filtration surgery. The fitting of the lens can be resumed after the hydrops heals.[18] The other indication for these lenses is prior to penetrating keratoplasty in order to delay the surgery.[17] Slit lamp biomicroscopy aids in assessing the two main parameters of scleral lens fitting: haptic and vault. An acceptable fit is characterized by an adequate corneal clearance (no touch) with no air bubble in the fluid (Figure-1), thick and thin tear vault is depicted in (Figure-2) and no impingement i.e. no compression of conjunctival vessels or edge lift (Figure-3). Details of Scleral CL fitting in advanced KC is depicted in Figure 4-8. Management of corneal ectasia with scleral contact lenses has been described in several studies.[17,19-22] Pullum and Buckley[14] reported a 60% overall success rate in a group of 530 patients fit with scleral lenses for a variety of diagnoses, more than half of which had keratoconus. Segal et al[17] fitted 48 patients (66 eyes), of whom 75% had keratoconus, with an overall success rate of 90%. Visser et al[22] described the use of the ProCornea lens and reported that 50% of patients fitted with that particular sclera design had keratoconus. Corneal rigid gas-permeable lenses have long been assumed to provide the best possible visual acuity in patients with keratoconus. In severe keratoconus, the irregularity of the anterior corneal surface can make it difficult to achieve reasonable lens centration and stability with corneal lenses. A retrospective study by Salam et al[23] indicated that scleral contact lenses provide visual acuity that was comparable with that attained with corneal lenses in patients with moderate to severe keratoconus. Significant improvement in visual acuity was reported with scleral lenses in patients with keratoconus in the study by Visser et al[24] and Segal et al.[17] The wide variety of corneal lens options allow for adequate management of most cases of keratoconus, however, some patients with keratoconus do not achieve adequate vision or comfort with corneal contact lenses. Furthermore, some patients may experience recurrent apical erosions with corneal lenses. In situations such as this, scleral lenses may be advantageous because they vault the cornea and allow the entire corneal epithelium to be Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 24 25 bathed with fluid. Corneal contact lens intolerance is one of the primary indications for keratoplasty in patients with keratoconus.[1] The option of fitting scleral lenses may defer the need for keratoplasty in patients who are intolerant to traditional contact lens designs and who do not have visually significant corneal scarring.[15] Little is known about the rates of adverse events in contemporary scleral contact lenses, and many of the adverse events previously reported are from PMMA or first-generation gas-permeable designs.[25] Common physiological complications include hypoxia leading to corneal edema (7.4%),[25] neovascularization (1.1 to 13.3%),[25] corneal abrasion (3.1%),[25] and infection, inflammation, and solution toxicity.[25-30] Other lens-related adverse events are midday fogging (20 to 46%),[28,31] mechanical irritation (12.6%),[25] Figure 1: Posterior surface of Scleral Contact Lens fitted over anterior corneal surface depicting optimal Tear Vault. Figure 2: Thick and Very thin tear vault in scleral contact lens fitting. protein deposits (3.5%),[25] giant papillary conjunctivitis (1.7%),[25] and poor lens fit due to disease progression.[25-31] The medical applications of scleral lenses encompass both visual and therapeutic indications for a range of complicated corneal and ocular surface conditions for which treatment by other methods is either unsuitable or less effective. A combination of the high oxygen transmissibility of the lens material and tear exchange that is obtained by a fitting technique with apical and limbal clearance may be responsible for maintaining a normal corneal physiology with the use of scleral lenses.[32] In the study by Romero-Rangel et al,[33] 92% of the patients reported improvement in quality of life as reflected by improvement in their ability to perform daily activities. Subspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 24 25 Figure 4: Scleral Contact Lens fitting in an advanced keratoconus. Figure 3: Edges of scleral contact lens are well aligned with sclera and no impingement of vessels are seen. Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 26 27 Figure 5: Scleral Contact Lens fitted in a very advanced Keratoconus with pathological Myopia for visual rehabilitation mitigating the need for corneal transplantation. Figure 6: Scleral Contact Lens fitted for advanced KC with Healed Uveitis and ASOCT image well depicting the tear lens vault over cornea. Figure 7: Scleral Contact Lenses can be seen in an ASOCT image to understand lens alignment on sclera in order to avoid lens edge related complications. Subspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 26 27 Figure 8: An ASOCT image beautifully captures the Scleral Contact Lens in a case of advanced corneal ectasia. Conclusion To conclude, scleral contact lenses can provide successful and safe visual and therapeutic solution for certain cases of keratoconus in which spectacles and conventional contact lenses have failed, and surgery is undesirable or contraindicated. Financial Support and Sponsorship None Conflicts of Interest There are no conflicts of interest. References 1. Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42:297-319. 2. Mandathara Sudharman P, Rathi V, Dumapati S. Rose K lenses for keratoconus-An Indian experience. Eye Contact Lens 2010;36:220-2. 3. Kok JH, van Mil C. Piggyback lenses in keratoconus. Cornea 1993;12:60-4. 4. Jain AK, Sukhija J. Rose-K contact lens for keratoconus. Indian J Ophthalmol 2007;55:121-5. 5. Ozbek Z, Cohen EJ. Use of intralimbal rigid gas-permeable lenses for pellucid marginal degeneration, keratoconus, and after penetrating keratoplasty. Eye Contact Lens 2006;32:33-6. 6. Bennett ES, Henry VA. Clinical Manual of Contact Lenses. 5th ed. Philadelphia, PA: Wolters Kluwer; 2019. 7. Barnett M, Mannis MJ. Contact Lenses in the Management of Keratoconus. Cornea 2011;30:1510–6. 8. Pullum K. Rigid Gas Permeable Scleral Lenses: There Has to Be a Bearing Surface Somewhere. Cont Lens Anterior Eye 2018;41:S29– 30. 9. Koppen C, Kreps EO, Anthonissen L, et al. Scleral Lenses Reduce the Need for Corneal Transplants in Severe Keratoconus. Am J Ophthalmol 2018;185:43–7. 10. Pecego M, Barnett M, Mannis MJ, et al. Jupiter Scleral Lenses: The UC Davis Eye Center Experience. Eye Contact Lens 2012;38:179–82. 11. Pullum KW, Whiting MA, Buckley RJ. Scleral Contact Lenses: The Expanding Role. Cornea 2005;24:269–77. 12. Severinsky B, Millodot M. Current Applications and Efficacy of Scleral Contact Lenses—A Retrospective Study. J Optom 2010;3:158–63. 13. Parker JS, van Dijk K, Melles GRJ. Treatment Options for Advanced Keratoconus: A Review. Surv Ophthalmol 2015;60:459–80. 14. Pullum KW, Buckley RJ. A study of 530 patients referred for rigid gas permeable scleral contact lens assessment. Cornea 1997;16:612-22. 15. Schornack MM, Patel SV. Scleral lenses in the management of keratoconus. Eye Contact Lens 2010;36:39-44. 16. Rathi VM, Mandathara PS, Dumpati S, Vaddavalli PK, Sangwan VS. Boston ocular surface prosthesis: An Indian experience. Indian J Ophthalmol 2011;59:279-81. 17. Segal O, Barkana Y, Hourovitz D, Behrman S, Kamun Y, Avni I, et al. Scleral contact lenses may help where other modalities fail. Cornea 2003;22:308-10. 18. Rathi VM, Sudharman Mandathara P, Vaddavalli PK, Dumpati S, Chakrabarti T, Sangwan VS. Fluid-filled scleral contact lenses in vernal keratoconjunctivitis. Eye Contact Lens 2012;38:203-6. 19. Schein OD, Rosenthal P, Ducharme C. A gas-permeable scleral contact lens for visual rehabilitation. Am J Ophthalmol 1990;109:318 –322. 20. Rosenthal P, Croteau A. Fluid-ventilated, gas-permeable scleral contact lens is an effective option for managing severe ocular surface Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 28 29 disease and many corneal disorders that would otherwise require penetrating keratoplasty. Eye Contact Lens 2005;31:130 –134. 21. Pullum KW. The unique role of scleral lenses in contact lens practice. Cont Lens Anterior Eye 1999;22(suppl 1):S26 –S34. 22. Visser ES, Visser R, van Lier HJ, et al. Modern scleral lenses. I. Clinical features. Eye Contact Lens 2007;33:13–20. 23. Salam A, Melia B, Singh AJ. Scleral contact lenses are not optically inferior to corneal lenses. Br J Ophthalmol 2005;89:1662–1663. 24. Visser ES, Visser R, van Lier HJ, et al. Modern scleral lenses. II. Patient satisfaction. Eye Contact Lens 2007;33:21–25. 25. Tan DT, Pullum KW, Buckley RJ. Medical Applications of Scleral Contact Lenses: 1. A Retrospective Analysis of 343 Cases. Cornea 1995;14:121–9. 26. Walker MK, Bergmanson JP, MillerWL, et al. Complications and Fitting Challenges Associated with Scleral Contact Lenses: A Review. Cont Lens Anterior Eye 2016; 39:88–96. 27. Van der Worp E, Bornman D, Ferreira DL, et al.Modern Scleral Contact Lenses: A Review. Cont Lens Anterior Eye 2014;37:240–50. 28. Bruce AS, Nguyen LM. Acute Red Eye (Non-ulcerative Keratitis) Associated with Mini-scleral Contact Lens Wear for Keratoconus. Clin Exp Optom 2013;96:245–8. 29. Walker MK. Scleral Lenses: Clearing the Fog. I-site Newsletter; 2014. Available at: http://www.netherlens.com/october_2014. Accessed December 27, 2022. 30. Barnett M, Johns LK. Contemporary Scleral Lenses: Theory and Application. Sharjah, UAE: Bentham Science Publishers; 2017. 31. Schornack MM, Fogt J, Harthan J, et al. Factors Associated with Patient-reported Midday Fogging in Established Scleral Lens Wearers [published online March 20, 2020]. Cont Lens Anterior Eye. 2020. 32. Kok JH, Visser R. Treatment of ocular surface disorders and dry eyes with high gas-permeable scleral lenses. Cornea 1992;11:518–22. 33. Romero-Rangel T, Stavrou P, Cotter J, et al. Gas-permeable sclera contact lens therapy in ocular surface disease. Am J Ophthalmol 2000; 130:25–32. Prof. Murugesan Vanathi, MBBS, MD Cornea, Cataract and Refractive Surgery Services, Dr. R. P. Centre for Ophthalmic Sciences, AIIMS, New Delhi, India Corresponding Author: Subspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 28 29 Descemet Membrane Detachment: An Overview Jatinder Singh Bhalla, MS, DNB, MNAMS, Neha Yadav, MBBS, Ridhima Sakhuja, MBBS, MS, DNB, FPOS, Yogesh Kumar, MBBS, Ashish Kumar Sain, DO, Sec DNB Department of Ophthalmology, DDU Hospital, Hari Nagar, New Delhi. The Descemet membrane is the basement membrane of the corneal endothelial cells that has a major role in maintaining layer integrity and maintaining cornea transparency. History - Detachment of Descemet membrane (DMD) was first described in 1927 by Weve[1], and the first systematic description and classification was given by Bernard Samuels in 1928.[2] In 1964, Scheie[3] identified it as a potential vision-threatening complication after cataract extraction. Incidence of DMD has been almost 43% of cases after cataract surgery.[4] The incidence of visually significant DMD after Preoperative Intraoperative Postoperative • age over 65 years • preexisting endothelial diseases like Fuchs dystrophy, and intrinsic DSI abnormal- ities. • mature or dense cataract, • uncooperative patient • lack of sufficient anaesthesia • previous history of ocular trauma like chemical injuries.[8,9,10] • clear corneal incisions creating lateral traction • use of blunt blades for creating incisions • inadvertent insertion of instruments between the stroma and DM • entry into the anterior chamber in a soft globe • tight or small incisions, shelved or oblique incision • direct engagement of the DM after a small detachment into the phacoemulsification or irrigation/ aspiration probe • Inadvertent injection of substances like saline, air, antibiotics, or viscoelastic.[8,10] • total ultrasound time over 60 seconds.[11] • familial and genetic causes of weak adhesion between DM and posterior corneal stroma[9] • preexisting endothelial abnormalities. extracapsular surgery and phacoemulsification is reported to be 2.6% and 0.5%, respectively[5]; however, the most recent reports establish an incidence of 0.044% to 0.52% after phacoemulsification surgery.[6,7] DMD has also been associated with various ocular surgeries such as iridectomy, corneal transplantation, vitrectomy, trabeculectomy, holmium laser sclerostomy, hydrogen peroxide injury, alkali burn, and viscocanalostomy.[4] Risk Factors Clinical Features Symptoms- Persistent poor visual acuity after cataract surgery or diminution of vision in cases with delayed presentation. Signs- DMD is seen as a translucent membrane in the anterior chamber at the site of corneal incision. It presents early as localized or diffuse corneal edema over the area of DMD and later progresses to persistent corneal edema (>2 weeks). A double anterior chamber might also be seen in cases with central and extensive DMDs. Diagnosis 1. Slit Lamp Biomicroscopy- DMDs at the main incision or side port may be observed by slit lamp post operatively.[12,13,14] In early period, it present as localized or diffuse corneal edema usually beginning over the area of detachment. In case of Persistent corneal edema (>2 weeks), a hazy cornea can also be seen. 2. Gonioscopy- Improves accuracy of diagnosis of small and peripheral DMDs.[15,16,17] Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 30 31 3. Confocal Microscopy- Descemet membrane and endothelium microstructural changes can be assessed.[18,19] 4. Ultrasound Biomicroscopy (UBM)- It is used to visualize, locate, and guide surgical repair of DMDs, particularly if hazy media interfare with visualisation.[19,20,21,22] Major limitations include requirement of a skilled technician, a cooperative patient, and it is a time-consuming procedure. 5. Anterior Segment Optical Coherence Tomography Classification DMD has been classified based on its configuration, height, extent, length, and position with respect to pupil. 1. Samuel Classification:- DMDs was classified into 3 types namely, active (pushed back), passive (pulled back or torn away), and detachments because of difference in elasticity between the parenchyma and the glass membrane causing DM to roll on itself or form folds.[23] Mild Moderate Severe • <25% of the cornea • peripheral • 25-50% cornea • peripheral • >50% of the cornea • central cornea (ASOCT)- The principle is based on the optical scattering of different ocular tissue structures, using low coherence interferometry for ocular structures imaging. It provides high-resolution cross- sectional images of the anterior segment even through a relatively opaque cornea, and minimal experience is required for image acquisition, hence making it an indispensable tool in corneal disorders. 2. Mackool Classification:- DMDs was classified into 2 types, planar and nonplanar.[24] When the separation between Descemet membrane from its overlying stroma is less than 1mm in all areas, it is called planar, whereas when the separation is more than 1 mm in any area, it is considered as nonplanar. 3. Jain Classification:- DMDs was classified into three groups based on the extension of detachment.[25] Figure 1: showing clinical DMD with ASOCT picture showing associated DMD. 4. Jacob Classification:- DMD was classified based on the etiology, clinical features, ASOCT findings, intra- operative features, and management protocol.[26] Subspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 30 31 Rhegmatogenous Tractional Bullous Complex secondary to tear, hole, or dialysis of Descemet membrane at Schwalbe’s line. traction and foreshortening of Descemet membrane secondary to inflammation, fibrosis, or incarceration in any of several locations: graft - host junction, peripheral anterior synechiae, or suture with subsequent contraction. smooth bulge of Descemet membrane into the anterior chamber in the absence of any Descemet membrane break or with a small needle puncture. Descemet membrane macrofolds, rolls or scrolled edges as well as combinations of other variants of DMD. Table of Original Article Management There is no gold standard for the treatment of DMDs. Management varies from conservative treatments like observation, topical steroids and hyperosmotic agents to surgical interventions like intracameral air or expandable gases injection descemetopexy, viscoelastic injection, transcorneal suturing, endothelial keratoplasty, and conventional penetrating keratoplasty. Conservative Treatment In small, peripheral, planar DMD with nonscrolled edges,[24] Spontaneous reattachment of DMDs can occur providing good visual outcome post surgery. Prolonged DMDs can lead to visual loss because of corneal opacification due to Descemet membrane fibrosis, scars, contractions, and folds.[28,29] However, conservative treatment and waiting for spontaneous reattachment avoids surgery and perioperative risks. Conservative treatment can be done either through observation or medication in the form of topical steroids and hyperosmotic agents. Topical steroid like prednisolone 1% eye drops, topical dexamethasone 0.1% eye drops, topical betamethasone 0.1% eye drops and hyperosmotic agents like sodium chloride 5% eye drops, or/and sodium chloride 6% eye ointment are used in case of DMD. Mackool and Holtz[24] suggested that spontaneous reattachment of nonplanar DMDs was infrequent and required surgery, whereas planar DMDs showed spontaneous reattachment and a better prognosis with conservative treatment. However, Assia et al[17] reported spontaneous reattachment in nonplanar nonscrolled DMDs suggesting that a nonscrolled detachment would reattach even if the separation between the Descemet membrane and stroma was greater than 1mm. Spontaneous reattachment has been observed through a wide timeframe (some weeks to several months) [17,36,60-62]. In the HELP protocol described by Kumar et al.[27] DMDs less than 1.0mm long and less than 100mm high in any zone, DMDs 1.0 to 2.0mm long and 100 to 300mm high in zones 2 and 3 and DMDs longer than 2.0mm and higher than 300mm in zone 3 were treated with medication and a 4-week observation period for signs of spontaneous reattachment were given; they observed reattachment in 96.9% of eyes, with 92.3% reaching a corrected distance visual acuity of 20/40 or better. Surgical Management Indication:- • Nonplanar DMD • Scrolled edge • Length of DMD >2 mm • Involving the central cornea • Nonresolving DMD with conservative or medical management 5. Help algorithm[27]:- Based on height, extent(zone), length and relation to pupil. The cornea is classified into 3 zones to analyze the extent of detachment, zone 1 (central): 5mm, zone 2 (paracentral): 5-8mm, and zone 3 (peripheral): >8mm. 6. ASOCT- Based classification – by Sharma and coworkers.[4] Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 32 33 Mackool and coworkers suggested the need for surgical intervention in cases of nonplanar DMD.[24] Kumar and coworkers in the HELP algorithm[27] suggested surgical management in cases of DMD with length 1-2mm and height 100-300 micron in the central 5mm of the cornea, and length >2mm and height >300 micron in the central 8mm of the cornea at presentation.[43] surgical management should also be done in all cases of nonresolving DMD at 4-week follow-up. A. Descemetopexy The term “descemetopexy” was introduced by Sparks and coworkers in 1967 to describe the surgical reattachment of detached DM with injection of air into the anterior chamber in DMD.[30] With use of 100% air, there is rapid absorption of air seen from the anterior chamber which led to use of isoexpansile gases like 14% perfluoropropane (C3F8) and 14-20% sulfur hexafluoride (SF6) that would stay in the anterior chamber for a longer time (14% C3F8: 6 weeks; 20% SF6: 2 weeks).[32,33,34] Thus reducing the need for repeat injections. The site of entry chosen should be opposite to or away from the area of the DMD where the DM is attached. A complete gas-filled chamber is maintained for at least 15-20 minutes.[31] Followed by release of 1/3rd bubble and the size of gas is then reduced to two-third of anterior chamber or 8mm bubble size to avoid postoperative pupillary block. An inferior peripheral iridectomy should be done if a complete bubble is left in anterior chamber. It is important for the patient to maintain supine position after the procedure. An increased risk of raised intra- ocular pressure and pupillary block glaucoma (11.6%) is seen with descemetopexy.[25,27] Descemetopexy involving injection of large amount of air or gas can lead to compression of iris against the lens surface leading to iris ischemia and subsequent Urrets-Zavalia syndrome.[35] An inferior peripheral iridectomy during descemetopexy can prevent this complication. Sharma et al.[4] described an algorithm based on AS-OCT where planar DMDs located in the superior half of the cornea were managed using intracameral air, and those with scrolled edges present superiorly or located inferiorly (scolled and planar edges both) were managed using intracameral 14% C3F8; all DMDs resolved successfully within 6-32 days. B. Mechanical Tamponade Donzis and coworkers in 1986 first reported the surgical repair of DMD with intracameral injection of VISCOELASTIC (Healon!).[36] The authors reported that the viscoelastic property of sodium hyaluronate helps to move the DM to its appropriate position after intracameral injection. Generally, viscoelastic tamponade is applied with recurrence of detachment after air or gas injection. However, Sharma et al.[4] reported a mixed method with the injection of viscoelastic immediately when detachment is detected intraoperatively, followed by air descemetopexy at the end of surgery. Post operative treatment with topical or oral intraocular-pressure-lowering drugs was done to control raised IOP. Intracameral injection of perfluoro-n-octane has also been described for management of persistent DMD.[37] C. Suture Fixation The use of 10-0 monofilament nylon suture for transcorneal suture fixation of DMD has been tried with variable success.[8,9] It is usually combined with intra-cameral injection of air or gas. It is associated with the risk of tenting of the Descemet membran. Also, there is risk of progression of the DMD, as the leading edge is not secured. Therefore, this procedure is preferred in cases of large and intractable DMD. D. Manual Repositioning Manual repositioning of the DM in cases of DMD is now considered an obsolete procedure with limited reports in literature to support its use. E. Descemetotomy Lowenstein and co-workers in 1993 TERMED DESCEMETOTOMY for the management of postkeratoplasty cases with retained host Descemet membrane.[38,39] It consists of either surgical removal of the membrane or creation of breaks in the host DM with the help of Nd-YAG laser.[40,41] Jacob and co-workers described the technique of “ab externo relaxing descemetotomy” for bullous DMD.[42] In this technique, a clear corneal incision, close to the limbus, is made with a keratome, which is carefully advanced inwards into the anterior chamber to incise the taut DM. This is followed by pneumodescemetopexy to allow internal drainage of the supraDescemetic fluid into the anterior chamber. it is important to note that the procedure of relaxing descemetotomy can be associated with the risk of corneal endothelial damage and hence should be avoided in asymptomatic cases with small peripheral DMD. F. Interface Drainage Drainage of interface fluid or supra-Descemetic fluid is usually performed in combination with pneumodescemetopexy in cases with primary failure of pneumodescemetopexy. The use of 20-gauge microvitreoretinal blade, 23-gauge needle, and curved needle of 10-0 mono-filament suture for draining the supraDescemetic fluid from the interface has been tried with good outcomes.[43,44,45,46] G. Keratoplasty Keratoplasty is the last treatment option reserved for cases of recalcitrant DMD wherein other treatment options have failed. Endothelial keratoplasty in the form of DSAEK and Descemet membrane endothelial transplant is preferred for the management of cases of corneal edema with DMD.[31] However, long-standing cases of DMD with corneal edema and scarring often require penetrating keratoplasty for visual rehabilitation. Conclusion There is no gold standard for the treatment of DMDs. ManageSubspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 32 33 ment varies from conservative treatments like observation, topical steroids and hyperosmotic agents to surgical interventions like intracameral air or expandable gases injection descemetopexy, viscoelastic injection, transcorneal suturing, with keratoplasty being the last treatment option reserved for cases where other treatment options have failed. Pneumatic descemetopexy is the gold standard treatment for management of most of the cases. To conclude, a case-based approach is required for the management of cases with DMD. Good visual outcome can be obtained with early intervention in these cases. References 1. Weve H. Loslating der membraan van Descemet na lensextractie [Separation of the membrane of Descemet after extraction of the lens]. Ned Tijdschr Geneeskd 1927; 71:398–400. 2. Samuels B. Detachment of Descemet’s membrane. Trans Am Ophthalmol Soc 1928; 26:427–437. 3. Scheie HG. Stripping of Descemet’s membrane in cataract extraction. Trans Am Ophthalmol Soc 1964; 62:140–152. 4. Sharma N, Gupta S, Maharana P, Shanmugam P, Nagpal R, Vajpayee RB. Anterior segment optical coherence tomography-guided management algorithm for Descemet membrane detachment after intraocular surgery. Cornea. 2015;34(9):1170e4. 5. Najjar DM, Rapuano CJ, Cohen EJ. Descemet membrane detachment with hemorrhage after alkali burn to the cornea. Am J Ophthalmol. 2004;137(1):185e7. 6. Kremer I, Stiebel H, Yassur Y, Weinberger D. Sulfur hexafluoride injection for Descemet’s membrane detachment in cataract surgery. J Cataract Refract Surg. 1997;23(10):1449e53. 7. Suda T, Nishida T, Ohashi Y, Nakagawa S, Manabe R. Fibronectin appears at the site of corneal stromal wound in rabbits. Curr Eye Res. 1981;1(9):553e6. 8. Benatti CA, Tsao JZ, Afshari NA. Descemet membrane detachment during cataract surgery: etiology and management. Curr Opin Ophthalmol. 2017;28(1):35e41. 9. Chow VWS, Agarwal T, Vajpayee RB, Jhanji V. Update on diagnosis and management of Descemet’s membrane detachment. Curr Opin Ophthalmol. 2013;24(4):356e61. 10. Guo P, Pan Y, Zhang Y, et al. Study on the classification of Descemet membrane detachment after cataract surgery with AS-OCT. Int J Med Sci. 2018;15(11):1092e7. 11. Sharma N, Aron N, Kakkar P, Titiyal JS. Continuous intraoperative OCT guided management of post-deep anterior lamellar keratoplasty descemet’s membrane detachment. Saudi J Ophthalmol. 2016;30(2):133e6. 12. Bhatia HK, Gupta R. Delayed-onset descemet membrane detachment after uneventful cataract surgery treated by corneal venting incision with air tamponade: a case report. BMC Ophthalmol 2016; 16:35. 13. Sharma N, Bandivadekar P, Agarwal T, et al. Incision-site descemet mem- & brane detachment during and after phacoemulsification: risk factors and management. Eye Contact Lens 2015; 41:273–276. 14. Shalchi Z, O’Brart DP, Ilari L. Bilateral descemet membrane detachment following cataract surgery. JAMA Ophthalmol 2013; 131:533–535. 15. Monroe WM. Gonioscopy after cataract extraction. South Med J 1971; 64:1122 – 1124. 16. Anderson CJ. Gonioscopy in no-stitch cataract incisions. JCataractRefract Surg 1993; 19:620–621. 17. Assia EI, Levkovich-Verbin H, Blumenthal M. Management of Descemet’s membrane detachment. J Cataract Refract Surg 1995; 21:714–717. 18. PatelSV, McLarenJW, HodgeDO, BourneW.Confocalmicroscopyinvivo in corneas of long-term contact lens wearers. Invest Ophthalmol Vis Sci 2002; 43:995-1003. 19. Zhang Z. Corneal cross-linking for the treatment of fungal keratitis. Cornea 2013; 32:217–218. 20. MorinelliEN, NajacRD, SpeakerMG, etal. Repair of Descemet’s membrane detachment with the assistance of intraoperative ultrasound biomicroscopy. Am J Ophthalmol 1996; 121:718–720. 21. Al-Mezaine HS. Descemet’s membrane detachment after cataract extraction surgery. Int Ophthalmol 2010; 30:391–396. 22. Winn BJ, Lin SC, Hee MR, Chiu CS. Repair of descemet membrane detachments with the assistance of anterior segment optical coherence tomography. Arch Ophthalmol 2008; 126:730–732. 23. Samuels B. Detachment of Descemet’s membrane. Trans Am Ophthalmol Soc. 1928;26:427e37. 24. Mackool RJ, Holtz SJ. Descemet membrane detachment. Arch Ophthalmol. 1977;95(3):459e63. 25. Jain R, Murthy SI, Basu S, Ali MH, Sangwan VS. Anatomic and visual outcomes of Descemetopexy in post-cataract surgery Descemet’s membrane detachment. Ophthalmology. 2013;120(7):1366e72. 26. Jacob S, Agarwal A, Chaudhry P, Narasimhan S, Chaudhry VN. A new clinico-tomographic classification and management algorithm for Descemet’s membrane detachment. Contact Lens Anterior Eye. 2015;38(5):327e33. 27. Kumar DA, Agarwal A, Sivanganam S, Chandrasekar R. Height-, extent-, length-, and pupil-based (HELP) algorithm to manage postphacoemulsification Descemet membrane detachment. J Cataract Refract Surg. 2015;41(9):1945e53. 28. MarconAS, RapuanoCJ, JonesMR, etal. Descemet’s membrane detachment after cataract surgery: management and outcome. Ophthalmology 2002; 109:2325 – 2330. 29. Mahmood MA, Teichmann KD, Tomey KF, al-Rashed D. Detachment of Descemet’s membrane. J Cataract Refract Surg 1998; 24:827 – 833. 30. Sparks GM. Descemetopexy. Surgical reattachment of stripped Descemet’s membrane. Arch Ophthalmol. 1967;78(1):31e4. 31. Odayappan A, Shivananda N, Ramakrishnan S, Krishnan T, Nachiappan S, Krishnamurthy S. A retrospective study on the incidence of post-cataract surgery Descemet’s membrane detachment and outcome of air descemetopexy. Br J Ophthalmol. 2018;102(2):182e6. 32. Ellis DR, Cohen KL. Sulfur hexafluoride gas in the repair of Descemet’s membrane detachment. Cornea. 1995;14(4):436e7. 33. Kremer I, Stiebel H, Yassur Y, Weinberger D. Sulfur hexafluoride injection for Descemet’s membrane detachment in cataract surgery. J Cataract Refract Surg. 1997;23(10):1449e53. 34. Sharma A, Singh SK, Bhutia PL, Pant R. Perfluoropropane (C3F8) injection for Descemet’s membrane detachment in cataract surgery. Nepal J Ophthalmol. 2015;7(1):74e8. 35. Maurino V, Allan BDS, Stevens JD, Tuft SJ. Fixed dilated pupil Subspecialty - Cornea

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 34 35 (Urrets-Zavalia syndrome) after air/gas injection after deep lamellar keratoplasty for keratoconus. Am J Ophthalmol. 2002;133(2):266e8 36. Donzis PB, Karcioglu ZA, Insler MS. Sodium hyaluronate (Healon) in the surgical repair of Descemet’s membrane detachment. Ophthalmic Surg. 1986;17(11):735e7 37. Kumar MA, Vaithianathan V. Descemet’s membrane detachment managed with perfluro-n-octane liquid. Indian J Ophthalmol. 2012;60(1):71e2. 38. Loewenstein A, Geyer O, Lazar M. Descemetotomy. J Cataract Refract Surg. 1996;22(6):652. 39. Loewenstein A, Geyer O, Lazar M. Intentional retention of Descemet’s membrane in keratoplasty for the surgical treatment of bullous keratopathy. Acta Ophthalmol (Copenh). 1993;71(2):280e2. 40. Chen Y-P, Lai PCC, Chen PYF, Lin K-K, Hsiao C-H. Retained Descemet’s membrane after penetrating keratoplasty. J Cataract Refract Surg. 2003;29(9):1842e4. 41. Masket S, Tennen DG. Neodymium: YAG laser optical opening for retained Descemet’s membrane after penetrating keratoplasty. J Cataract Refract Surg. 1996;22(1):139e41. 42. Jacob S, Agarwal A, Agarwal A, Ai S. Recognizing and managing Bullous Descemet detachment secondary to accidental hydroseparation during phacoemulsification/ cataract surgery by relaxing descemetotomy. Cornea. 2018;37(3):394e9. 43. Bhatia HK, Gupta R. Delayed-onset descemet membrane detachment after uneventful cataract surgery treated by corneal venting incision with air tamponade: a case report. BMC Ophthalmol. 2016;16:35. 44. Ghaffariyeh A, Honarpisheh N, Chamacham T. Supra- Descemet’s fluid drainage with simultaneous air injection: an alternative treatment for Descemet’s membrane detachment. Middle East Afr J Ophthalmol. 2011;18(2):189e91. 45. Singh A, Vanathi M, Sahu S, Devi S. Intraoperative OCT assisted descemetopexy with stromal vent incisions and intracameral gas injection for case of non-resolving Descemet’s membrane detachment. BMJ Case Rep. 2017;2017. bcr2016217268. 46. Weng Y, Ren Y-P, Zhang L, Huang X-D, Shen-Tu X-C. An alternative technique for Descemet’s membrane detachment following phacoemulsification: case report and review of literature. BMC Ophthalmol. 2017;17(1):109. Dr. Neha Yadav, MBBS DNB Resident, DDU Hospital, New Delhi. Corresponding Author: Subspecialty - Cornea

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 34 35 Phacoemulsification in Eyes with Operated Glaucoma Filtering Surgery Dewang Angmo, MD, DNB, FRCS, FICO, MNAMS, Anand Bukke, MD Dr Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi, India. The problem of cataract management in the patients of glaucoma who have undergone previous filtering surgery is a challenging proposition for anterior segment surgeon, as the surgery can lead to several complications in such already compromised eyes. Cataract surgery may be required after filtering surgery either because of a pre-existing cataract or due to cataract progression/ development post trabeculectomy. As glaucoma requires lifelong management, the development of cataract is a significant concern because its treatment may lead to loss of IOP control. According to the Collaborative Initial Glaucoma Treatment Study (CIGTS), the risk of cataract extraction at 5 years in the trabeculectomy group was 17.3% versus 6.2% in the medical group.[1] Globally, the reported incidence of cataract progression after filtering surgery varies greatly, from 2% to 53%.[2] All morphological types of cataract formation are increased whether it is cortical, nuclear, or posterior subcapsular type.[3] The postoperative course following the filtration procedure determines the formation and rate of progression of cataract from visually insignificant to visually incapacitating. A flat anterior chamber (AC) and post operative inflammation after filtration surgery are major risk factors for cataract formation. The Advanced Glaucoma Intervention Study (AGIS) data has itself shown that these two complications following filtration surgery increase the risk of cataract formation by 14%.[3] Other variables like initial surgery, older age, a more negative spherical equivalent, and pseudo-exfoliative glaucoma confer a higher risk of cataract extraction.[4,5] Progression of cataract after trabeculectomy must be properly identified since lens opacification may alter retinal sensitivity and therefore the visual field,[6] and lens growth may modify the irido-corneal angle. Moreover, when cataract extraction is indicated, specific problems can be encountered, resulting from previous glaucoma surgery. In cases with pre-existing cataract, trabeculectomy is usually performed first to be followed by cataract surgery at a later date in a staged manner in cases where glaucoma is significantly advanced or fluctuation in IOP during the course of cataract surgery may be detrimental to the optic nerve health.[4] Following a filtering surgery, cataract surgery may be required at an early stage in these patients as the determination of glaucoma progression becomes increasingly difficult with the use of functional tests in the form of Humphrey visual fields. The cataract leads to declining performance on visual field testing by the patient. On the other hand, cataract surgery in the patients with previous trabeculectomy is considered to have an adverse effect on long term survival of the filtering bleb and thus may require special consideration.[7-20] The main objectives of the surgery are to restore optimal visual function without compromising the functioning of the bleb. The following factors need to be kept in mind while operating on eyes which may have previously undergone a trabeculectomy: • Low endothelial cell count • Poor pupillary dilatation (sphincter atrophy or posterior synechiae) • Floppy iris • Shallow anterior chamber • Hypotony • Pre-existing zonular weakness • Extra caution to prevent posterior capsule rupture and vitreous loss • Post-operative uveitis • Post-operative bleb failure • Enhanced need for anti-glaucoma medications post surgery Amongst these, the most important factor is the loss of IOP control in an eye which previously had attained target IOP. Phacoemulsification may significantly increase IOP and thereby the need for glaucoma medication in eye with pre-existing functioning filtering blebs. Most blebs fail soon after the cataract surgery, usually within 1 month.[17,20] Several factors are associated with an increased risk of loss of IOP control: • Eyes with higher IOP before phacoemulsification tend to have worse post-operative IOP control and bleb failure.[21] • Age: Controversial evidence exists as to age is a good or bad prognostic factor for success of filtering blebs. Some studies observe that age of 50 years[21] or younger is a bad prognostic factor while some state that > 60 years of age impart a higher risk of failure.[19] • Intraoperative iris manipulation[21] • Early IOP spikes: More than 25mm Hg or >19 mmHg within 2 weeks[21] • PC rupture with vitreous loss[21,22] • Short interval between trabeculectomy and cataract: With most studies agreeing at duration less than 6 months to be unsafe.[22] Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 36 37 • Cataract surgery by means of Extracapsular cataract extraction has worse prognosis on the filtering bleb compared with phacoemulsification.[22,12,23-25] • Use of preoperative glaucoma medications • Eyes with intra or post operative complications[12] Preoperative Evaluation Preoperative evaluation should include a thorough clinical examination and investigations to evaluate and prognosticate the case individually (Figure-1a). Important aspects of the evaluation include: • Evaluation of bleb function can be done using Slit lamp biomicroscopy. (Figure-1) Blebs should also be graded preoperatively based on bleb grading systems like Moorfields or Indiana Bleb Grading systems which helps in following up the blebs with regards to change in vascularity and height over time.[26] Other modalities like ASOCT (Anterior Segment Optical Coherence Tomography) and Ultrasound Biomicroscopy (UBM) can also be sought to evaluate bleb morphology and ostium patency. (Figure-2)[26-28] These investigations are also useful to follow up the changes in bleb morphology over time. Figure 1: Clinical photograph showing slit-lamp evaluation of bleb morphology and cataract. A&B) Through Diffuse and slit illumination Bleb height, vascularity and surface area can be assessed. C) Slit-lamp evaluation of pre-operative anterior chamber depth and cataract. Figure 2: A) Thin cystic avascular bleb on slit-lamp examination, B) ASOCT to shows bleb morphology and thinnest area of the bleb which helps in plan of management. Subspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 36 37 • IOP measurement (diurnal control/ diurnal variation). • Gonioscopy must be done to determine the patency of internal ostium of trabeculectomy and determine the extent of peripheral anterior synechiae. • Extent of optic nerve damage as assessed by optic disc and field changes over time. • Corneal endothelial specular count should be performed, as these eyes tend to have a low specular count due to previous surgery and raised IOP. • Keratometry, corneal topography should be obtained in order to plan proper incision placement with respect to astigmatic considerations. In case of regular astigmatism with a steep horizontal meridian, temporal clear corneal incision with or without opposite clear corneal incision can be planned. In case of significant astigmatism at a site different from horizontal meridian, toric IOL can be planned because incision placement in operated superior trabeculectomy is not feasible. In cases with irregular astigmatism, astigmatism correction procedures should be best avoided.[12,22-24] • Assessment of maximal pupillary dilation which may be limited secondary to synechiae, long term miotic use, pseudo-exfoliation, or sphincter atrophy in cases of angle closure glaucoma. In case of poorly dilating pupils, iris hooks/pupil stretch devices should be kept ready during surgery. • Evaluation of the type of cataract and lens density. • In eyes with advanced cataract where fundus evaluation and fields are not possible, B scan USG may be used to estimate the cupping of the optic nerve head. • Any evidence of zonular weakness and pseudo-exfoliation must be looked for if the pupil dilates well. In cases of non dilating pupils, pre-operative evaluation for zonular sufficiency can be done by performing a UBM. In case any zonular insufficiency is suspected, endo-capsular rings should be kept ready during surgery. • The interval between two surgeries is very crucial for bleb survival. If possible, it is better to delay the surgery as far as possible or until the patient can maintain daily activities with his best available correction. At least a 6-month interval should be taken for cataract extraction for best outcomes.[22] However, there may be special situations wherein early cataract surgery may be required before a stipulated 6 month. These are: • Development of dense cataract in one eyed patient. • Neovascular glaucoma: Where media clarity is prerequisite for fundus evaluation and therapeutic laser photocoagulation. • IOP is uncontrolled after filtering trabeculectomy where cause of non-control is deemed to be increased lens thickness/shallow anterior chamber. • Traumatic glaucoma with subluxation causing fluctuating IOP even after trabeculectomy. Intraoperative Measures • Surgery should be performed with special precautions to prevent any inadvertent bleb trauma and incite minimum inflammation. Thin cystic high blebs are especially prone to bleb rupture. (Figure-3) • Superpinky or Honan balloon should be avoided as it can result in gross hypotony because of micro-rupture and leak of the bleb with subsequent shallowing of the anterior chamber. Instead, an intermittent massage is a better option in the presence of a filtering bleb to avoid hypotony prior to the commencement of the cataract surgery. • Phacoemulsification in eyes with a functional filtering bleb should be performed via a clear corneal site away from the filtering bleb.[29] Since filtering bleb is usually superior in location, a temporal or slightly inferotemporal clear corneal incision should be made as phacoemulsification main port so that paracentesis port is also placed away from bleb site. Clear corneal or near-clear corneal (in front of the vascular arcades) incisions are preferred as they incite lesser inflammation compared to the scleral or limbal incisions. Large incision surgery like ECCE is not recommended in these eyes as they confer a significantly higher risk of trabeculectomy failure compared to phacoemulsification over time.[12,22-24] • Incision size is guided by the diameter of phaco tip and size of the IOL used. Smaller the incision size, lesser will be the postoperative inflammation and lesser would be anterior chamber collapse and endothelial cell loss intra-operatively. One should be little cautious while doing paracentesis as many of these eyes have a shallow AC and there is a risk of damaging the iris or the anterior capsule. Bimanual microincision cataract surgery (Phakonit) via two side ports is another viable option in these eyes.[30] • Pupillary miosis is very commonly encountered in these cases, due to either posterior synechiae or atrophy/ sclerosis of the iris stroma, chronic miotic usage, previous angle closure Figure 3: A) Thin cystic bleb which is prone to trauma from occult trauma and frequent eye rubbing, B) Thin cystic bleb showing leak after fluorescein staining on cobalt blue filter. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 38 39 attack, tissue aging or pseudo-exfoliation. Synechiolysis, injection of high molecular weight viscoelastics, stripping of pupillary membranes are performed as necessary. The pupil is then dilated with the aid of iris hooks, Malyugin ring or other mechanical means (stretch pupilloplasty or multiple small sphincterotomies) if required. Essentially, minimal iris handling should be performed as iris manipulation may lead to poor IOP control by disrupting the blood-aqueous barrier and inciting a severe inflammatory reaction.[22] • The already compromised corneal endothelium should be protected with the use of a dispersive viscoelastic such as chondroitin sulphate or a visco-adaptive such as 2.3% sodium hyaluronate (Healon5) to minimize endothelial cell loss. Arshinoff soft shell technique can also be performed. • Chilled BSS plus is the ideal irrigating fluid to use in these eyes because of its protective action on endothelial cell loss. • While staining the anterior capsule with dye during capsulorhexis, one can also see the staining of conjunctiva overlying the bleb through the sclerostomy ostium as described by the author.[31,32] This can provide an intraoperative assessment of bleb function and help one in deciding whether to perform a simultaneous internal revision of bleb during phacoemulsification. • After performing capsulorhexis, one must remove the capsular flap to prevent its potential migration into the fistula leading to bleb failure. • The dynamics of anterior chamber depth and bottle height are more complex compared to routine phacoemulsification. These eyes tend to have shallow chamber due to additional outflow of irrigating fluid through the sclera ostium. Therefore, the height of infusion bottle should be increased to prevent collapse of anterior chamber. The vacuum setting should also be kept on lower side and phacoemulsification performed in the capsular bag by standard stop and chop or phaco chop nucleotomy. • Every effort should be made to remove all nuclear and cortical remnants to prevent blockage of sclerostomy opening by nucleo-cortical remnants. Any retained cortical matter can excite inflammation and lead to bleb failure. • Square edge single piece foldable hydro acrylic IOLs perform the best; are inserted via a 2.2/2.75 mm incision. Enlarging the incision should be avoided to prevent anterior chamber collapse at any stage. In case of posterior capsular rupture, sulcus implantation is performed with a multipiece (3 piece) hydrophobic acrylic IOL. Acrylic single piece lenses if put in sulcus, induce severe iris chaffing which may produce pigment dispersion glaucoma and should not be performed.[33] Aspheric IOLs should also be preferred over non-aspheric lenses as they may produce less wavefront aberration which may help in preserving visual function in already compromised glaucomatous eyes which have decreased contrast sensitivity.[34] Multifocal IOLs are generally not recommended in these eyes as they result in decrease in contrast sensitivity.[34] However, in a study by Kamath et al where they compared visual functions after implanting multifocal IOLs in eyes with glaucoma or ocular hypertension with monofocal IOLs, no difference could be discerned in visual outcomes between the two groups; rather the patients benefitted from the distance and near visual acuity from the multifocality of IOL.[34] • IOP increase after cataract surgery, most pronounced in eyes with hypotony, may increase the axial length by an average of 0.275 mm, and affect anterior chamber depth and lens position, which all in turn affect the predictability of the postoperative refractive power. However, taking pretrabeculectomy axial length may not be accurate either as post operative IOP increase may not be predicted. Therefore, surgeon should be wary that post operative refractive surprises may occur in eyes with operated trabeculectomy and account for myopia in a patient planned for post operative emmetropia. No difference was found in the predicted and final refractive outcomes between the eyes with previously operated trabeculectomy and medically treated glaucoma undergoing phacoemulsification.[35] Lower pre-phacoemulsification intraocular pressure is weakly correlated with a myopic shift in final refraction.[16] • After IOL insertion, a thorough viscoelastic removal is mandatory and may be performed in the entire circumference using a bimanual I/A hand. Viscoelastic must also be removed from beneath IOL. After aspiration of viscoelastics, function is assessed by injection of BSS into anterior chamber. If bleb is not formed with BSS injection, internal revision is performed by passing a cyclodialysis spatula through the wound or paracentesis port to the sclerostomy fistula and then to subtenon space. Circular movements are performed to open the sclera flap. Goniolens may be used to visualize the ostium. At the end of surgery, if there is a tendency for bleb failure and one need to give post operative massage, then at least one suture should be applied even to the phaco port. Subconjunctival injection of 5FU (5mg/0.1ml) or mitomycin C drops (0.2-0.4mg/ml) may be considered if there is a tendency of bleb failure. Sharma et al in their study suggested that 5FU has a protective effect on the functioning bleb and may be used routinely at the end of phacoemulsification in such cases. They observed that worsening of IOP after 12 months was more in patients who did not receive 5FU at end of surgery.[36] Post Operative Considerations In early post operative period, intraocular pressure spikes are frequently observed after cataract surgery in glaucomatous eyes and considerable fluctuation in pressure can occur during the first post operative month.[21] Close follow-up is mandatory for monitoring IOP and bleb integrity. If bleb functioning is in question, gentle digital massage should be performed, especially in the early post-operative period. One should also cover with anti-glaucoma medications as necessary in the immediate postoperative period. In cases when increased IOP spike may Subspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 38 39 prove to be detrimental to optic nerve head function, then one can even use systemic carbonic anhydrase inhibitors in the immediate post operative period on a short term basis to blunt such spikes. Vigorous use of topical steroids is indicated to decrease post operative inflammation, which may subsequently lead to bleb failure. The investigator should pay attention on corkscrew vessels and bleb encapsulation as signs of imminent scar formation. If there is an increase in bleb vascularisation or fibrosis, repeated subconjunctival 5FU (5mg) injections can be given. Evidence suggests that intraoperative subconjunctival 5-fluorouracil (5-FU) may be protective, and repeated postoperative 5-FU injections may have a role in high-risk individuals along with aggressive anti-inflammatory treatment. Bleb Morphology Bleb might undergo a decrease in surface as well as height following uneventful phacoemulsification, an effect most pronounced in the immediate post-operative period.[14,18] In eyes that have undergone trabeculectomy only, this change in bleb morphology is more gradual in comparison to those eyes which have undergone as subsequent phacoemulsification also. Though the reasons for this are not completely understood, the possible etiology for this bleb failure could be decrease outflow through the uveoscleral route, due to an inflammatory process by an increase in the permeability of blood-aqueous humour barrier induced by the phacoemulsification procedure. This change in bleb morphology may be visible in 18-77.6% of operated patients.[9,14,18,21,37] Influence of Cataract Extraction on the Outcome of Hypotony Following Trabeculectomy Cataract surgery has also been advocated to treat post filtering surgery hypotony maculopathy and chronic choroidal detachment in those patients with co-existing cataract. Sibayan et al reported that cataract extraction can be beneficial in the management of postfiltration hypotony maculopathy.[38] In the similar study, Doyle et al tried modified technique of phacoemusification leaving viscoelastic in eyes at the conclusion of the surgery. The authors observed that this helped in decreasing initial aqueous flow through the bleb and thereafter, minimizing topical steroid use resulted in increased inflammation and the associated decrease in bleb size and function to resolve hypotony after trabeculectomy.[39] Conclusions The wide variation in the results from various parts of the world lead us to the conclusion that taking decision about cataract surgery in an operated trabeculectomy patient is a very tricky situation and utmost care should be taken to avoid potential postoperative complication, the most important of which is the failure of the existing bleb. Due care given at each step as mentioned above can give good results with no detrimental changes in postoperative IOP and bleb status as evident from the published literature. Patients should be maintained on long term follow up with regular check up of IOP and visual fields to detect any change in the bleb function as well as functional deterioration. Keypoints 1. Delay cataract surgery until the bleb has matured (at least 6 months). 2. Assess bleb function before surgery. 3. Evaluate pupillary dilation. 4. Minimize conjunctival trauma. 5. Utilize a small clear corneal incision far away from the bleb (temporal if possible). 6. Assess bleb function upon completion of the cataract surgery and revise if needed. 7. Aggressively treat postoperative inflammation and IOP spikes. References 1. Lichter PR, Musch DC, Gillespie BW, et al. Interim clinical outcomes in the Collaborative Initial Glaucoma Treatment Study comparing initial treatment randomised to medications or surgery. Ophthalmology 2001; 108: 1943-1953. 2. Liebmann JM, Ritch B. Complications of glaucoma filtering surgery. Glaucomas. St Louis: Mosby: 1703-1736; 1996. 3. The AGIS Investigators. Advanced Glaucoma Intervention Study (AGIS): 8. Risk of cataract formation after trabeculectomy. Arch Ophthalmol. 2001;119(12):1771-9. 4. Musch DC, Gillespie BW, Niziol LM, et al; Collaborative Initial Glaucoma Treatment Study Group. Cataract extraction in the collaborative initial glaucoma treatment study: incidence, risk factors, and the effect of cataract progression and extraction on clinical and quality-of-life outcomes. Arch Ophthalmol. 2006;124(12):1694-700. 5. Ehrnrooth P, Lehto I, Puska P, Laatikainen L. Phacoemulsification in trabeculectomized eyes. Acta Ophthalmol Scand. 2005;83(5):561-6. 6. The AGIS Investigators. Advanced Glaucoma Intervention Study (AGIS), 6: Effect of Cataract on Visual Field and Visual Acuity. Arch Ophthalmol. 2000;118(12):1639-1652. 7. Chen PP, Weaver YK, Budenz DL, et al: Trabeculectomy function after cataract extraction. Ophthalmology 105: 1928-35, 1998. 8. Crichton AC, Kirker AW: Intraocular pressure and medication control after clear corneal phacoemulsification and AcrySof posterior chamber intraocular lens implantation in patients with filtering blebs. J Glaucoma 10: 38-46, 2001. 9. Derbolav A, Vass C, Menapace R, et al: Long-term effect of phacoemulsification on intraocular pressure after trabeculectomy. J Cataract Refract Surg 28: 425-30, 2002. 10. Rebolleda G, Muñoz-Negrete FJ: Phacoemulsification in eyes with functioning filtering blebs: a prospective study. Ophthalmology 109: 2248-55, 2002. 11. Shingleton BJ, O’Donoghue MW, Hall PE: Results of phacoemulsification in eyes with preexisting glaucoma filters. J Cataract Refract Surg 29: 1093-6, 2003. 12. Swamynathan K, Capistrano AP, Cantor LB, et al: Effect of temporal corneal phacoemulsification on intraocular pressure in eyes with prior trabeculectomy with an anti-metabolite. Ophthalmology 111: 674-8, 2004. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 40 41 13. Chiseliţă D, Antohi I, Medvichi R, et al. The influence of cataract surgery on the efficacy of trabeculectomy in patients with open-angle glaucoma. Oftalmologia. 2004;48(2):71-80. 14. Ehrnrooth P, Lehto I, Puska P, Laatikainen L. Phacoemulsification in trabeculectomized eyes. Acta Ophthalmol Scand. 2005;83(5):561-6. 15. Inal A, Bayraktar S, Inal B, et al. Intraocular pressure control after clear corneal phacoemulsification in eyes with previous trabeculectomy: a controlled study. Acta Ophthalmol Scand. 2005;83(5):554-60. 16. Husain R, Liang S, Foster PJ, et al. Cataract surgery after trabeculectomy: the effect on trabeculectomy function. Arch Ophthalmol. 2012;130(2):165-170. 17. Zhang N, Tsai PL, Catoira-Boyle YP, et al. The effect of prior trabeculectomy on refractive outcomes of cataract surgery. Am J Ophthalmol. 2013;155(5):858-63. 18. Nguyen DQ, Niyadurupola N, Tapp RJ,et al. Effect of phacoemulsification on trabeculectomy function. Clin Experiment Ophthalmol. 2013 Oct 29. doi: 10.1111/ceo.12254. 19. M Sałaga-Pylak, M Kowal and T Żarnowski. Deterioration of filtering bleb morphology and function after phacoemulsification. BMC Ophthalmol 2013,13:17. 20. Mandal AK, Chelerkar V, Jain SS, Nutheti R. Outcome of cataract extraction and posterior chamber intraocular lens implantation following glaucoma filtration surgery. Eye (Lond). 2005;19(9):1000-8. 21. Seah SK, Jap A, Prata JA Jr, et al. Cataract surgery after trabeculectomy. Ophthalmic Surg Lasers. 1996;27(7):587-94. 22. Law SK, Riddle J. Management of cataracts in patients with glaucoma. Int Ophthalmol Clin. 2011 Summer;51(3):1-18. 23. The complicated cataract: the Massachusetts eye and ear infirmary phacoemulsification practice handbook. edited by Roberto Pineda II, Alejandro Espaillat, Victor L. Perez, and Susannah G. Rowe. SLACK, 2001. 24. Casson R, Rahman R, Salmon JF: Phacoemulsification with intraocular lens implantation after trabeculectomy. J Glaucoma 11: 429-33, 2002. 25. Halikiopoulos D, Moster MR, Azuara-Blanco A, et al. The outcome of the functioning filter after subsequent cataract extraction.2001;32(2):108-17. 26. Wells AP, Ashraff NN, Hall RC, Purdie G. Comparison of two clinical Bleb grading systems. Ophthalmology. 2006;113(1):77-83. 27. Aptel F, Dumas S, Denis P. Ultrasound biomicroscopy and optical coherence tomography imaging of filtering blebs after deep sclerectomy with new collagen implant. Eur J Ophthalmol. 2009;19(2):223-30. 28. Singh M, Chew PT, Friedman DS, et al. Imaging of trabeculectomy blebs using anterior segment optical coherence tomography. Ophthalmology. 2007;114(1):47-53. 29. Wang X, Zhang H, Li S, et al. The effects of phacoemulsification on intraocular pressure and ultrasound biomicroscopic image of filtering bleb in eyes with cataract and functioning filtering blebs. Eye (Lond)2009;23:112–16. 30. Park HJ, Kwon YH, Weitzman M, et al: Temporal corneal phacoemulsification in patients with filtered glaucoma. Arch Ophthalmol 115: 1375-80, 1997. 31. Dada T, Muralidhar R and Sethi HS. Insertion of a foldable hydrophobic IOL through the trabeculectomy fistula in cases with Microincision cataract surgery combined with trabeculectomy. BMC Ophthalmology 2006, 6:14. 32. Dada T, Muralidhar R, Sethi HS. Staining of filtering bleb with trypan blue during phacoemulsification. Eye (2006) 20, 858–859. 33. Hong Y, Sun YX, Qi H, et al. Pigment dispersion glaucoma induced by the chafing effect of intraocular lens haptics in Asian eyes. Curr Eye Res. 2013;38(3):358-62. 34. Kamath GG, Prasad S, Danson A, Phillips RP. Visual outcome with the array multifocal intraocular lens in patients with concurrent eye disease. J Cataract Refract Surg. 2000;26(4):576-81. 35. Muallem MS, Nelson GA, Osmanovic S, et al. Predicted refraction versus refraction outcome in cataract surgery after trabeculectomy. J Glaucoma. 2009;18(4):284-7. 36. Sharma TK, Arora S, Corridan PG. Phacoemulsification in patients with previous trabeculectomy: role of 5-fluorouracil. .Eye (2007) 21, 780–783. 37. Yamagami S, Araie M, Mori M, Mishima K. Posterior chamber IOL implantation in filtered or nonfiltered glaucoma eyes. Jpn J Ophthalmol 1994;38:71-9. 38. Sibayan SA, Igarashi S, Kasahara N, et al. Cataract extraction as a means of treating post filtration hypotony maculopathy. Ophthalmic Surg Lasers 1997;28:241-3. 39. Doyle JW, Smith MF. Effect of phacoemulsification surgery on hypotony following trabeculectomy surgery. Arch Ophthalmol. 2000;118(6):763-765. Dr. Dewang Angmo, MD, DNB, FRCS, FICO, MNAMS Associate Professor of Ophthalmology Dr Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi, India. Corresponding Author: Subspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 40 41 Single Site vs Double Site for Combined Phaco-Trabeculectomy Vinita Ramnani, MS, Sakshi Ramnani, MBBS 1. Head of the Department, Eye Department, Bansal Hospital, Bhopal. 2. Junior Resident, Department of Ophthalmology, JSS Medical College, Mysore. Coexistent glaucoma and cataract is a challenging to diagnose and manage. Glaucoma is the second major cause of blindness after cataract and hence poses a significant global health problem with a prevalence of 0.5 to 9%. Risk of blindness in unilateral and bilateral treated glaucoma eyes is 27% and 9% respectively. Coexistent glaucoma and cataract can influence each other’s management strategies with various treatment options available: 1. Cataract surgery alone. 2. Cataract surgery with continuation of anti-hypertensive drugs postoperatively. 3. Two separate surgeries: Trabeculectomy followed by cataract surgery or vice versa. 4. Combined glaucoma and cataract surgery techniques like: • Extracapsular cataract surgery (ECCS), Small incision cataract surgery (SICS) or Phacoemulsification with trabeculectomy by single site or two separate sites. • Minimally invasive cataract surgery (MICS) and Trabeculectomy • Phacoemulsification with nonpenetrating glaucoma surgeries (NPGS) • Phacoemulsification with shunts and valve glaucoma surgeries • Phacoemulsification with Microinvasive Glaucoma surgeries (MIGS) • Phacoemulsification with Diode laser cyclophotocoagulation (DCPC) Combined Phacotrabeculectomy (Phacotrab) Cataract and glaucoma commonly coexist, especially amongst the elderly population.[1] The goal of the treatment plan in coexisting glaucoma with cataract is to achieve an adequate long-term intraocular pressure (IOP) control, with optimal visual rehabilitation to improve the quality of life of the patient and to avoid IOP spikes in the postoperative period which are deleterious to the health of the optic nerve head.[2] The other important factors to be remembered are minimal surgical trauma and risk, and ensuring that the procedure is cost effective. Careful assessment of the risk-benefit ratio associated with each surgical procedure, patient’s preferences and their visual requirements, severity of glaucoma, cost-benefit analysis, as well as the experience and skill of the surgeon are determining factors to choose the most appropriate management procedures in such cases. Combined phacoemulsification with trabeculectomy is the best surgical approach in concurrent cataract and glaucoma.[3] Recently there has been a widespread shift towards the use of combined Phacotrabeculectomy as the treatment of choice for such patients.[4] Combined Phacotrabeculectomy is as safe and effective in controlling IOP as trabeculectomy alone.[5] It is a convenient and economical method and also provides early visual rehabilitation. Combined surgery is advised for glaucomatous eyes with visually significant cataract to prevent early hypertensive crisis, achieve a better visual acuity with a well-controlled IOP on least medication. However, these benefits must be critically weighed against a higher rate of operative and postoperative complications like bleeding, hypotony, choroidal detachment and shallow anterior chamber (AC) as compared to phacoemulsification alone.[6] Phacotrabeculectomy can be done via a single site, where both phacoemulsification and trabeculectomy are performed from the same incision with rigid or foldable intraocular lens (IOL) implantation. The second option is a two sites procedure: a temporal clear corneal phacoemulsification with a superior trabeculectomy. Indications of Combined Phacotrab • Visually significant cataract with uncontrolled IOP. • Advanced glaucoma with risk of optic nerve damage due to post-operative IOP spikes (Snuff out phenomenon). • Moderate to severe glaucoma, with a controlled IOP with urgent need for visual recovery. • Failure of medication due to non-compliance, drug allergies or side-effects, and financial constraints. Advantages of Combined Phacotrab • Enhanced postoperative visual rehabilitation and reduced follow-ups. • Reduced morbidity of two successive operations • Concurrent visual recovery and IOP control specially in elderly or patients with multiple comorbidities. • Comfortable, convenient and cost effective • Prevention of postoperative IOP spikes that often occur in glaucoma patients after a cataract surgery. • Decreased risk of bleb fibrosis and dysfunction with subsequent cataract surgery. • Gratifying results with no untoward side effects. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 42 43 Disadvantages of Combined Phacotrab • Increased intra-operative manipulation, time and complications like vitreous loss, corneal endothelial damage and post-operative inflammation and hyphema. • Higher risk of endophthalmitis. • Relavitely lesser long-term reduction in IOP and bleb success as compared to trabeculectomy.[7] Single Site Combined Phacotrab Procedure • Patients can be operated under peribulbar, subtenon or topical anaesthesia. • A fornix-based conjunctival flap is made and the vessels over sclera are treated with light surface cautery. • A triangular 4 mm x 3.5 mm scleral incision is made at the limbus and a ¾ th partial thickness scleral flap is created with a 15-no. blade or crescent knife to reach 1 mm further into the clear cornea from the gray-blue transition zone. • If Mitomycin C (MMC) use is planned, it has to be done before entry into the AC. 0.02 or 0.04 mg MMC is applied for 2 to 4 minutes using 2-5 soaked pledgets to cover a wider area of sclera without touching the conjunctiva. Thorough wash is important to protect the eye and ear. • A paracentesis is made into the clear cornea with a side port or MVR Blade with a slightly oblique insertion, with or without an AC maintainer. • A 2.2 mm or smaller keratome is used to enter the AC at the corneal side of the scleral tunnel through which phacoemulsification is performed using any of the preferred nucleus chopping techniques. • Following irrigation-aspiration and foldable IOL implantation, a 1.5 mm × 2.5 mm rectangular deep block of scleral tissue is excised with Vanna’ scissors or Kelly’s punch and peripheral iridectomy is performed. Thorough aspiration of viscoelastic is ensured and cyclopentolate drops are instilled. • The external scleral incision needs to be secured with three 10-0 nylon sutures, one at apex and two at the base of the triangle on both sides with or without 1-2 releasable sutures. • The conjunctiva is reopposed at the limbus using a 10-0 vicryl suture at both ends taking sub scleral bites to secure the conjunctiva tightly to prevent any retraction or leaks. An additional central horizontal matrix conjunctival suture can be put to prevent bleb leak. • Balanced salt solution is injected via the paracentesis, AC is formed and patency of the passage is ensured by a nicely elevated bleb at the end. • Sub-conjunctival injection of dexamethasone and gentamycin is given in the inferior fornix. • Postoperative medications include prednisolone acetate and moxifloxacin combination eye drops to be tapered over 3 to 6 weeks and cyclopentolate eye drops once or twice a day for one week. • Regular follow-ups with visual acuity, IOP by applanation tonometry, optic disc and fields assessment should be conducted. • This method is useful for all types of glaucoma like primary angle closure or open angle, secondary, complicated, traumatic or post vitrectomy glaucoma. Advantages of Single Site Phacotrab • Left over conjunctival space for future procedures. • Fornix based flap with superior single site phacotrab is easier to perform, similar to a phacoemulsification scleral tunnel. • Saves time. • Single surgical wound. • No need for the surgeon to change his/her position and the microscope. Disadvantages of Single Site Phacotrab • Higher rate of intra and post-operative complications like bleeding, inflammation, hypotony, choroidal detachment and shallow chambers. • Excessive conjunctival manipulation • Longer visual recovery • The window for subconjunctival drainage of trabeculectomy is same as the phacoemulsification incision, therefore wound is not water tight. • Accidental antimetabolite spillage into the AC after scleral flap creation can have adverse effects. • Increased risk of surgically induced astigmatism. • Increased risk of conjunctival scarring. • Some studies show relatively poor results in terms of IOP control. Two Separate Site Phacotrab: Advantages • Improved exposure for cataract surgery via a temporal clear corneal approach especially in deep set eyes or a narrow palpebral fissure. • Lesser manipulation of the conjunctiva with reduced inflammation superiorly enhances bleb survival and facilitates rapid visual recovery. Two Separate Site Phacotrab: Disadvantages • Increased surgical time. • Surgeon needs to change position from temporal to superior. Conclusion One Site Vs Two Sites Both techniques yield similar results with respect to final best corrected visual acuity and IOP reduction. The two-site phacotrab patients have lesser induced astigmatism and a better postoperative IOP control with reduced anti-glaucoma medication requirement postoperatively as compared to the onesite procedure. Two site phacotrab has two separate incisions with lesser wound trauma and scarring of the scleral flap and conjunctiva that results in better filtration.[8] However the twoSubspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 42 43 site approach generally requires greater intra-operative time and may be associated with lower endothelial cell count.[9,10] Despite intense research on the subject, there is very little evidence that a two-site phacotrab approach for combined surgery may achieve a better IOP control.[11-20] In absence of strong evidence in support of a specific method for Phacotrabeculectomy, surgeons’ preference and experience are the deciding factors. Each technique has its own merits and demerits, it’s better to individualize the management of each eye for the best results as per the patient’s requirement. References 1. Chandrasekaran S, Cumming RG, Rochtchina E, Mitchell P. Associations between elevated intraocular pressure and glaucoma, use of glaucoma medications, and 5-year incident cataract: the blue mountains eye study. Ophthalmology. 2006;113(3):417-24. 2. Krupin T, Feitl ME, Bishop KI. Postoperative intraocular pressure rises in open angle glaucoma patients after cataract or combined cataract-filtration surgery. Ophthalmology. 1989; 96:579-84. 3. Stewart WC, Crinkley CM, Carlson AN. Results of combined phacoemulsification and trabeculectomy in patients with elevated preoperative intraocular pressures. J Glaucoma. 1995;4(3):164-9. 4. Casson RJ, Salmon JF. Combined surgery in the treatment of patients with cataract and primary open-angle glaucoma. J Cataract Refract Surg. 2001; 27:1854-63. 5. Wedrich A, Menapace R, Radax U, Papapanos P. Long-term results of combined trabeculectomy and small incision cataract surgery. J Cataract Refract Surg. 1995;21(1):49-54. 6. Shingleton BJ, Wooler KB, Bourne CI, O’Donoghue MW. Combined cataract and trabeculectomy surgery in eyes with pseudoexfoliation glaucoma. J Cataract Refract Surg. 2011;37(11):1961-70. 7. Jiang N, Zhao GQ, Lin J, Hu LT, Che CY, Wang Q, Xu Q, Li C, Zhang Figure 1: Angle closure glaucoma with Nuclear cataract, mid dilated pupil and iris atrophic patches. Figure 3: Inner window of trabeculectomy made with Kelly’s Punch. Figure 2: Triangular scleral flap for trabeculectomy and Pseudophakia. Figure 4: Final photo on table of Combined Single Site Phacotrabeculectomy. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 44 45 J. Meta- analysis of the efficacy and safety of combined surgery in the management of eyes with coexisting cataract and open angle glaucoma. International journal of ophthalmology. 2018; 11:279. 8. Vass C, Menapace R, Surgical strategies in patients with combined cataract and glaucoma, Curr Opin Ophthalmol, 2004;15(1):61–6. 9. Buys YM, Chipman ML, Zack B, et al., Prospective randomized comparison of one- versus two-site Phacotrabeculectomy two-year results, Ophthalmology, 2008;115(7):1130–33. 10. Nassiri N, Nassiri N, Rahnavardi M, et al., A comparison of corneal endothelial cell changes after 1-site and 2-site Phacotrabeculectomy, Cornea, 2008;27(8):889–94. 11. Gdih GA, Yuen D, Yan P, et al., Meta-analysis of 1- versus 2-Site Phacotrabeculectomy, Ophthalmology, 2011;118(1):71–6. 36. Zhao LQ, Zhu H, Phacotrabeculectomy meta-analysis, Ophthalmology, 2011;118(6): 1216.e1–2. 12. Nassiri N, Nassiri N, Mohammadi B, et al., Comparison of 2 surgical techniques in Phacotrabeculectomy: 1 site versus 2 sites, Eur J Ophthalmol, 2010;20(2):316–26. 13. Cotran PR, Roh S, McGwin G, Randomized comparison of 1-Site and 2-Site Phacotrabeculectomy with 3-year follow-up, Ophthalmology, 2008;115(3):447–54. 14. Shingleton BJ, Price RS, O’Donoghue MW, et al., Comparison of 1-site versus 2-site Phacotrabeculectomy, J Cataract Refract Surg, 2006;32(5):799–802. 15. Jampel HD, Friedman DS, Lubomski LH, et al., Effect of technique on intraocular pressure after combined cataract and glaucoma surgery: An evidence-based review, Ophthalmology, 2002;109(12):2215–24. 16. Borggrefe J, Lieb W, Grehn F, A prospective randomized comparison of two techniques of combined cataract glaucoma surgery, Graefes Arch Clin Exp Ophthalmol, 1999;237(11):887–92. 17. Sayyad F, Helal M, el-Maghraby A, et al., One-site versus 2-site Phacotrabeculectomy: a randomized study, J Cataract Refract Surg, 1999;25(1):77–82. 18. Wyse T, Meyer M, Ruderman JM, et al., Combined trabeculectomy and phacoemulsification: a one-site vs a two-site approach, Am J Ophthalmol, 1998;125(3):334–9. 19. Kozobolis VP, Siganos CS, Christodoulakis EV, et al., Two-site Phacotrabeculectomy with intraoperative mitomycin-C: fornixversus limbus-based conjunctival opening in fellow eyes, J Cataract Refract Surg, 2002;28(10):1758–62. 20. Shingleton BJ, Chaudhry IM, O’Donoghue MW, et al., Phacotrabeculectomy: limbus-based versus fornix-based conjunctival flaps in fellow eyes, Ophthalmology, 1999;106(6):1152–5. Dr. Vinita Ramnani, MS Head of the Department, Eye Department, Bansal Hospital, Bhopal. Corresponding Author: Subspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 44 45 Tonometry and Recent Advances Talvir Sidhu, MBBS, MD, DNB, Vishu Bansal, MBBS, Chiman Lal, MBBS, MS, Mohit Goyal, MBBS, MS Department of Ophthalmology, Government Medical College and Rajindra Hospital, Patiala, Punjab. Introduction Tonometry is an essential part of ophthalmic examination. It measures the intraocular pressure, which is the key modifiable factor in development and progression of glaucoma. Intraocular pressure measurement requires a calibrated and standardized measuring instrument which is readily available at ophthalmology centres. A measurement taken by any instrument should be accurate and precise. Accuracy is the closeness of the measurement to its true value and precision is reproducibility/ repeatability of the value in same eye. An accurate and precise IOP measurement allows comparison and monitoring of intraocular pressure for facilitating better treatment to patients. The first tonometer was developed by von Graefe in 1863. Since then, various instruments have been devised to measure IOP. These are of mainly two types: (1) applanation tonometers; (2) indentation tonometers. Goldmann Applanation Tonometry Principle Goldmann Applanation Tonometer (GAT) was first introduced by Hans Goldmann and Theo Schmidt in 1957. Goldmann based his tonometer on The Imbert-Fick law.[1] This law states that an external force (W) applied against a perfectly dry, flexible and infinitely thin perfect sphere equals the pressure in the sphere (Pt ) multiplied by the area flattened (A) by the external force. (Figure-1) W=Pt x A Figure 1: The Imbert-Fick law (W=Pt x A). Figure 3: Parts of Goldmann Applanation Tonometer. Figure 2: The Modified Imbert-Fick law (W + S=Pt A1 + B). But, since cornea is aspherical, wet, neither perfectly flexible nor infinitely thin, the above law could not be used. So, a Modified Imbert-Fick Law was devised. The tears create a surface tension (S), and a force (B) is required to bend the cornea due to the lack of flexibility. As the cornea is approximately 550 µm thick at the centre, the outer flattened area (A) is not the same as the inner area (A1 ). The Modified Imbert-Fick Law equation was: W+S=Pt A1 + B When A1 equals 7.35 mm2 , the corneal surface tension (S) balances the force (B) required to bend the cornea. This area A1 is obtained when the diameter of external applanated area is 3.06 mm. (Figure-2) Parts – Figure-3 1. Measuring prism. 2. Feeler arm. 3. Insert for Control Weight. 4. Housing. 5. Revolving knob. 6. Measuring drum. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 46 47 Procedure The patient is seated comfortably with his chin on the chin rest of slit lamp. A topical anaesthetic (Proparacaine 0.5%) is instilled into the conjunctival sac followed by staining with Fluorescein strip. The illumination arm is adjusted to illuminate the Cornea and biprism with Cobalt Blue light. The revolving knob is kept at low settings, approximately 1 (10 mmHg). The biprism is gently brought in contact with the corneal surface and 2 semicircular bright green colour mires are observed through the eyepiece of the slitlamp.(Figure-4) The mire thickness should be 1/10th of total diameter of applanated area. The rotating knob is then turned to align the mires in such a way that their inner edges are in contact. At this point, the reading on the measuring drum is noted and multiplied by 10(ten) to obtain the Intra ocular Pressure. Goldmann and Theo Schmidt found that in astigmatic corneas, the mires reached the ned point sooner than actual IOP reading in the flat meridian as compared to the steep meridian. It was found that three dioptre astigmatism can lead to one mmHg change in IOP. Therefore, to overcome this problem in patients with regular astigmatism, an angle of 43o is marked on the prism holder as a red line. At this angle, the applanated area of an ellipse will be exactly 7.354 mm2 to give accurate reading of the IOP. Alternatively, IOP reading can be taken in flat and steep meridian and averaged.[2] Figure 4: The position of the mires as seen in GAT prism after fluorescein staining. Table 1: Sources of Error with Goldmann Tonometry. Earlier, Fluorescein solution was used to stain the conjunctiva. But now Fluorescein strips are used as the solution might get contaminated with Pseudomonas or Staphylococcus bacteria. Central corneal thickness (CCT) and corneal curvature • Thicker cornea-falsely higher IOP • Thinner cornea-falsely lower IOP[3] (For every 10 microns, change of 0.7 mm Hg) • Steeper cornea-overestimation[4] Corneal oedema Underestimation Amount of fluorescein • Wider menisci-overestimation • Narrower menisci-underestimation • Improper vertical alignment (one semicircle larger than the other)- overestimation Astigmatism • With-the-rule astigmatismunderestimation • Against-the-rule astigmatismoverestimation Repeated readings in short duration Slight underestimation due to massaging effect on the globe Incorrect calibration Should be calibrated at least once in a month Contraindications of GAT 1. Ruptured globe: Contact tonometry is avoided when ruptured globe is suspected in a patient as it may lead to extrusion of aqueous or vitreous humour. 2. Infection: GAT is avoided in cases of infected corneal surface as in Keratoconjunctivitis. If necessary, then the apparatus should be disinfected and thoroughly cleaned after use. 3. Active Corneal ulcer, corneal scars: Contact tonometry can further aggravate these conditions. 4. Allergic to Topical anaesthetic agent (Proparacaine) or Fluorescein dye. 5. Inability to sit upright as in bed ridden patients.[5] Calibration of GAT 1. Ideally GAT must be calibrated on monthly basis. 2. Calibration is done at dial positions 0, 2, and 6 (equivalent to 0, 20, and 60 mmHg, respectively). (Figure-5) 3. At dial position 0, the feeler arm should be in free movement once the prism has been inserted. When the measuring drum is rotated forward slightly ahead of ‘0’ (towards 1), the prism arm should move forward. Similarly, when the measuring drum is rotated backwards slightly behind ‘0’ (less than 0), the prism arm should move backward. 4. To check the positions at 2 and 6, a check weight in the Subspecialty - Glaucoma

www.dosonline.org/dos-times DOS Times - Volume 29, Number 2, March-April 2023 46 47 shape of a rod is inserted into the holder. The weight should be heavier opposite to the prism (towards the ophthalmologist). When the weight is aligned at the reading ‘2’, the prism moves to and fro freely at the reading ‘2’ of the moving drum/IOP. When the weight is aligned at the reading ‘6’, the prism moves to and fro freely at the reading ‘6’ of the moving drum /IOP.[6] Figure 5: Calibration of GAT. Figure 6: Parts of Perkins Tonometer. Cleaning of Prism • Soaking the applanation tip for 5 to 15 minutes in diluted sodium hypochlorite (1:10 household bleach), 3% hydrogen peroxide, or 70% isopropyl alcohol • Wiping the applanation tip with 70% isopropyl alcohol, 3% hydrogen peroxide, iodophor (povidone- iodine), or 1:1000 Merthiolate.[7] Perkins Tonometer The Perkins tonometer (Clement Clarke, Haag-Streit, UK) is based on the same principle as Goldmann Applanation Tonometer. It is a portable tonometer with inbuilt cobalt blue filter light and can be used in supine patients/in children during anaesthesia/bedside. (Figure-6) Non-Contact Tonometry Air Puff Tonometer Non-contact air puff tonometry was developed in 1970s by Grolman. It uses an air column with gradually increasing intensity to applanate the cornea. The air column stops after achieving the desired level of corneal flattening. The intensity of air puff required to flatten the cornea is measured and converted to pressure reading in mmHg. Principle The instrument consists of a central air plenum and light emitter along with detector on the sides. The central air plenum creates an air-jet at a constantly increasing force to deform the cornea. This deformation/applanation of cornea is detected by the optoelectrical system using a collimated light beam at the central cornea. When the central cornea is flattened to 3.6 mm, maximum number of reflected light is detected and recorded as peak intensity. The air jet intensity at this level is recorded as intraocular pressure in mmHg. (Figure-7) There is no direct contact between the device and the eye surface, hence topical anaesthesia is not required. Subspecialty - Glaucoma

DOS Times - Volume 29, Number 2, March-April 2023 www.dosonline.org/dos-times 48 49 Figure 7: Principle of Non-contact tonometer. Figure 8: IOP measurement by Ocular response analyser. The green curve represents the air jet pressure and the red line represents the two peaks of corneal deformation. The first red peak P1 is similar to the NCT applanation of the cornea when the cornea is deformed inwards (inward applanation) and the second red peak P2 is the outward applanation, when the cornea returns to its normal position as the air jet pressure decreases. Due to elasticity and resistance of the cornea, there is a delay between the two peaks P1 & P2.[9] Principle The patient is seated with the chin on the machine chin-rest to check the IOP. The patient must be warned about the air puff, and is instructed to look straight ahead. Although the machine has an auto-stop to avoid corneal touch, it is important that the distance between the machine air plenum is slowly reduced to avoid trauma to cornea. The patient is asked to stop blinking momentarily when the machine is aligned with the eye and is ready to measure intraocular pressure. A minimum of 3 readings should be averaged to estimate the mean IOP as IOP varies during the cardiac cycle. Since there is no touch with the eye, theoretically there is no need to sterilize the instrument, however the air-jet may cause tear-film aerosol production, which maybe potentially infectious especially in people having viral infections. Accuracy Non-contact tonometer has a fair agreement with Goldmann Applanation Tonometry; it tends to overestimate the IOP for pressures lower than 10 mm Hg and underestimate the IOP for pressures more than 19 mm Hg. Advantages Disadvantages • Corneal anaesthesia/ fluorescein dye is not required • Minimal training is required • Can be used as a screening tool • It is accurate over a certain range of IOP beyond which, there may be over or underestimation. • Limited role in poor corneal surface or dry eyes Table 2: Advantages and disadvantages of NCT. Ocular Response Analyser ORA [Reichert Technologies, Depew, NY, USA] is a modified version of non-contact tonometry developed in 2005. Principle A continuous air jet is used to deform the anterior corneal surface, similar to that in NCT. ORA measures the air jet force required to applanate the cornea and measures the recovery of cornea from deformed to normal state, thus measuring intraocular pressure and corneal hysteresis, respectively. It gives two readings of IOP- a Goldmann-correlated IOP and a corneal compensated IOP (IOPcc). Additionally, it also measures a corneal resistance factor. (Figure-8) Goldmann-correlated IOP (IOPg) is the average of the inward (P1) and outward (P2) applanation pressures and closely corresponds to Goldmann IOP. Corneal-compensated IOP (IOPcc) is derived by using both IOP and corneal biomechanical factors. Corneal biomechanical factors: Corneal Hysteresis (CH) represents the elastic nature of the cornea or its ‘viscous-damping’ capacity. The cornea absorbs the air pressure energy when it is applanated the first time, this causes the second applanation pressure measurement to be lower than the first measurement. The difference between these two pressures (P1-P2) is corneal hysteresis. It is associated with eyes potential to buffer the negative effects of high IOP fluctuations. A lower corneal hysteresis is associated with glaucoma and its progression.[8] Corneal Resistance Factor (CRF) is a measurement of corneal resistance. It is derived from the formula (P1-kP2). k is the constant determined from an empirical analysis of the relationship between both P1 and P2 and CCT.[9] CRF is significantly less in normal tension glaucoma and maximum in open angle glaucoma.[8] Subspecialty - Glaucoma