dos_nov_2014

5 Editorial Diagnostics

Experts’ Corner 47 Ultrasound B-Scan for Posterior Segment

13 Management of Diabetic Macular Edema Evaluation
Shalini Singh, Manisha Agarwal, Aditya Bansal
Theme: Retina
Miscellaneous
23 A New Drug: Ocriplasmin (Microplasmin)
55 Corneal Changes in Diabetes Mellitus
Atul Kumar, Ravish Kinkhabwala,
Brijesh Takkar, Shorya Vardhan Azad, Koushik Tripathy, Rohan Chawla, Y.R. Sharma,
Sangeeta Roy Pradeep Venkatesh, Rajpal Vohra

27 Bionic Eye Evolution

V.S. Gurunadh, Sandeep Gupta, M.A. Khan, 61 Evolution of Vitreous Substitutes
Ajay Banarji, Khaleel M, Parth Patel,
Shefali Joshi Ravi Bypareddy, Obuli Ramchandran N.,
Koushik Tripathy, Subodh Kumar Singh,
33 Anti VEGF Agents in Retinal Disorders – Harshinder Singh, Rohan Chawla,
Rajpal Vohra, Yog Raj Sharma
Current Scenario
Charu Gupta, Cyrus M. Shroff PG Corner

41 Minimally Invasive Vitrectomy Surgery – 69 Macular Hole

The New Era Supriya Batta Arora, Prateeksha Sharma,
Koushik Tripathy, Pulak Agarwal, Nalini Saxena, Meenakshi Thakar, Basudeb Ghosh
Yog Raj Sharma, Rohan Chawla,
Harsh Inder Singh, Ravi Bypareddy, Tear Sheet
Babulal Kumawat, Rajpal Vohra
77 Hereditary Fundus Dystrophies

Richa Pyare, Supriya Batta Arora

www. dosonline.org l 3

“Education is the most powerful weapon which you can use to
change the world.”

-Nelson Mandela

Respected Seniors & Dear Friends,

DOS winter conference was held on 1st and 2nd November at Manekshaw
Centre, Delhi Cantt. The theme of this year’s conference was “Cases &
Controversies in Ophthalmology” and it rightly captured the essence of
this reality. It was well attended and highly appreciated by one and all. The
popular ophthalmic quiz show “Kaun Banega Champion” was a hit and
there was one champion and a couple of other prize winners and numerous
audience prizes were won by a highly charged up audience.

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6CUJMGPV +V KPENWFGF NKXG UWTIGT[ FGOQPUVTCVKQP CU YGNN CU OCP[ UEKGPVKſE
talks with translators in local language. It was very well attended with packed
house with few delegates standing and listening to all the proceedings.
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a historic moment and the beginning of a new chapter of DOS, which makes
DOS a truly international body.

DOS has planned major ophthalmic events for the year 2015 and what can
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and 11th QH ,CPWCT[ YJKEJ CNUQ KPENWFGU C UMKNN VTCPUHGT RTQITCOOG KP
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hosted by local organizing committee of Delhi Ophthalmological Society.
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The theme of annual conference is “Eyennovation”. We invite different
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OKPWVG XKFGQ KU CNUQ KPXKVGF #U YG FKF KP VJG NCUV #PPWCN EQPHGTGPEG QH &15
there will be subspecialty sessions and the young ophthalmologists (YO)
sessions to encourage the young innovators and presenters. On the whole
we are awaiting a great academic feast in the coming few months on multiple
occasions under the aegis of our society.

Sincerely Yours

Rajesh Sinha
Secretary,
Delhi Ophthalmological Society

www. dosonline.org l 5







































Retina

Figure 6: Epiretinal Prosthesis Retinal Prosthesis

penetrate the optic nerve sheath, it relies on the principle 6JG DCUKU HQT VJG TGVKPCN RTQUVJGUKU KU VJG RQUV OQTVGO
of retinotopic organisation within the optic nerve. OQTRJQOGVTKE CPCN[UKU QH VJG TGVKPC QH RCVKGPVU YKVJ GPF
UVCIG 42 YJKEJ JCU TGXGCNGF VJCV QH KPPGT PWENGCT
Advantages and 29.7% of ganglion layer cells were retained compared
to only 4.9% of photoreceptors. It was also seen in legally
6JG GPVKTG XKUWCN ſGNF KU TGRTGUGPVGF KP C UOCNN CTGC DNKPF PGQXCUEWNCT #/& RCVKGPVU VJCV QH 4)%U YGTG
which can be reached surgically. spared and an increase in inner nuclear layer cells was
noted by 10%10,11. These results imply that theoretically
# XKCDNG CPCVQOKE NQECVKQP HQT CP KORNCPV it is possible to stimulate the remaining retinal neurons
electrically to elicit useful visual perceptions. These initial
Disadvantages observations have led to the development of intraocular
retinal prostheses in various centres.
1. Optic nerve is a densely consolidated neural structure
with approximately 1.2 million axons in a 2 mm These retinal prostheses could be –
diameter cylinder. Surgical manipulation of this area
requires dissection of the dura, with an inherent risk 1. Epiretinal YJGP VJG FGXKEG KU KORNCPVGF KPVQ VJG
QH KPHGEVKQPU CPF RQUUKDN[ KPVGTTWRVKQP QH DNQQF ƀQY VQ vitreous cavity and attached to the inner retinal surface,
the optic nerve. UQ VJG GNGEVTKECN UVKOWNCVKQP OGGVU VJG KPPGT TGVKPC ſTUV

6JG QRVKE PGTXG CPF VJG TGVKPCN ICPINKQP EGNNU
4)% 2. Subretinal VJG FGXKEG KU KORNCPVGF KP VJG RQVGPVKCN
TGRTGUGPV JKIJGT QTFGT UVTWEVWTGU VJCP VJG DKRQNCT EGNNU space between the retinal pigment epithelium and the
VCTIGVGF D[ VJG TGVKPCN RTQUVJGUKU #U UWEJ VJG RTQEGUUKPI neurosensory retina, so the electrical stimulation meets
power of the bipolar, amacrine and horizontal cells is VJG QWVGT TGVKPC ſTUV
lost and therefore much more image processing must
be achieved by the implant rather than relying on intact Epiretinal Prosthesis (Figure 6)
human physiologic pathways.
Epiretinal implants rely on imaging devices such as a
.CUVN[ VJG PGTXG ſDTGU HTQO VJG OCEWNC NKG OQUV camera and then transform this visual information to
centrally within the optic nerve. The cuff electrodes patterns of electrical stimulation to excite remaining viable
CTG VJWU HWTVJGT CYC[ HTQO VJG OCEWNCT ſDTGU CPF retinal neurons.
this will dramatically limit the use of this approach.
Investigators have proposed intraneuronal stimulation Humayun et al, have pioneered research in the development
devices in order to target individual neurons within the QH C FGXKEG ECNNGF VJG KPVTCQEWNCT TGVKPCN RTQUVJGUKU
+42
optic nerve more accurately. 6JKU +42 KPENWFGU DQVJ CP GZVGTPCN YGCTCDNG EQORQPGPV
and an implantable, intraocular component. The external
8GTCCTV GV CN9 published results of an optic nerve prosthesis component consists of a spectacle incorporated with a light
EJTQPKECNN[ KORNCPVGF KP C DNKPF XQNWPVGGT QH 42 YKVJ PQ weight camera, pocket batteries and a visual processing
residual vision. The volunteer underwent performance WPKV 2QYGT CPF FCVC KU UGPV D[ YKTGNGUU NKPM HTQO VJG
evaluation during the course of a training programme. The external unit to the internal portion of the prosthesis. The
results were encouraging in that the blind volunteer was intraocular portion consists of a receiver, stimulating chip
able to interact with the environment adequately while and a microelectrode array including 16 platinum electrodes
demonstrating pattern recognition and a learning effect for of approximately 500 um in diameter. The electrode array
processing time and orientation discrimination. KU CHſZGF VQ VJG GRKTGVKPCN UWTHCEG D[ C TGVKPCN VCEM 6JKU
model captures digital video and translates it to a pixelated
KOCIG GZVGTPCNN[ 6JG ſPCN RTQEGUUGF FCVC CPF RQYGT KU
then transferred to the implanted portion of the prosthesis.
The implanted portion of the device then converts the
transferred visual data into controlled patterns of electrical
pulses to stimulate the remaining retinal neurons. In
preliminary tests in the operating room with temporary
epiretinal devices patients could identify crude forms such
as letters or a box shape.

Based on these results a permanent implant trial was started
in 2002 at Doheney Retina Institute. In this initial phase,
three patients received implants, the 16 electrode model
I implant. These patients were able to discern brighter or

www. dosonline.org l 29

Retina: Bionic Eye

dimmer precepts with varying levels of current, and the Figure 7: Subretinal implant
ability to distinguish the direction of motion of objects13.
hinder this technology from realizing its goal of being
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microelectrode array and require less current, stimulation available photodiode arrays is inadequate to generate
of these cells would require more image processing and it UWHſEKGPV GNGEVTKEKV[ HQT UVKOWNCVKQP QH DKRQNCT EGNNU
would be desirable to stimulate the deeper bipolar cells,
thereby utilise the intact processing capability of inner Chow et al14, have now abandoned the notion that their
TGVKPCN EGNN NC[GTU +V JCU DGGP UJQYP D[ )TGGPDGTI VJCV subretinal implant is a prosthesis, but they claim that the low
by varying the pulse width of the stimulating current the level of current delivered by the implant has a therapeutic
electrodes can be ‘tuned’ to stimulate selectively retinal CPF PGWTQ RTQVGEVKXG GHHGEV QP VJG QVJGTYKUG F[KPI TGVKPCN
DKRQNCT EGNNU TCVJGT VJCP 4)%U 6JG 4)%U TGURQPF VQ UJQTVGT photoreceptors.
pulse duration (less than 0.5ms) while deeper retinal neural
layers responded to longer pulse durations (greater than <TGPPGT GV CN15, have also concluded that a subretinal
0.5ms). This experimental result, if consistently produced implant may act as a replacement for lost photoreceptors.
in the patient, would enable epiretinal prosthesis to employ Detectable activation of the visual cortex was also achieved
the processing from the entire retina as it would initiate in their latest work. They have developed a subretinal
the electrical signal propagation at the level of the retinal RTQUVJGUKU EQPUKUVKPI QH CP /&2# RQYGTGF GKVJGT D[ C
bipolar cell. The histological retinal changes associated laser or telemetry for the replacement of degenerated
with the mechanical effects of epiretinal implantation are photoreceptors in outer retinopathies. They have implanted
also less severe than with subretinal implantation. their subretinal implant in blind patients who have gained a
crude form of vision with an ability to recognise forms like
Advantages a dinner plate and motion16.

1. The vitreous acts as a sink for heat dissipation from the Advantages
microelectronic device.
1. Closer proximity to the next surviving neurons to the
# OKPKOCN PWODGT QH OKETQGNGEVTQPKEU CTG KPEQTRQTCVGF visual pathway (i.e. bipolar cell) and therefore less
into the implantable portion of the device. current requirement

3. The wearable portion of electronics allows for easy 6JG NCEM QH C OGEJCPKECN OGCPU QH ſZCVKQP
upgrades without requiring subsequent surgery.
Disadvantages
4. The electronics allow the user and the doctor full
control over every electrode parameter and digital .KOKVGF UWDTGVKPCN URCEG VQ RNCEG GNGEVTQPKEU
signal processing involved in imaging objects, allowing
the implant to be customised for each patient. 2. Close proximity of the retina to the electronics which
would increase the risk of thermal injury to the neurons.
Disadvantages

1. Requirement of technology to provide prolonged
adhesion of the device to the inner retina.

2. Increased current requirement due to greater distance
of the target bipolar cells from epiretinal device than
with the subretinal device.

Subretinal Prosthesis (Figure 7)

The subretinal approach to the retinal prosthesis involves
KORNCPVKPI C OKETQRJQVQFKQFG CTTC[
/2&# DGVYGGP VJG
bipolar cell layer and retinal pigment epithelium. This is
accomplished surgically either via an intraocular approach
through a retinotomy site (ab interno) or a transscleral
approach (ab externo).

The subretinal prosthesis, uses microphotodiodes (solar
cells) alone as a powering mechanism, which offers an
attractive solution to enhance the vision of patients affected
D[ 42 CPF #/& *QYGXGT UGXGTCN NKOKVCVKQPU EWTTGPVN[

30 l DOS Times - Vol. 20, No. 5 November, 2014

Retina

Figure 8: Argus II the devices are indeed electrically conducting and posses
potential to be used in patients to detect light or even
Electrotherapeutics distinguish between objects such as cup or plate. The device
is basically meant to take place of photoreceptors. While
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site of implantation of the Chow device is subretinal, it which would further help in providing higher resolution
will require viable photoreceptors to be present to function images. The new device is approximately one quarter the
properly. Chow et al have reported improvement in visual size of original device, reducing surgery and recovery
function of their patients, which cannot be attributed to times.
a therapeutic effect of low level chronic electric current,
but possibly through a yet unknown indirect effect of the #TIWU ++ 4GVKPCN 2TQUVJGUKU 5[UVGO YCU (&# CRRTQXGF HQT
implant rather than from a direct activation of neurons. WUG KP CFXCPEGF 42 KP (GDTWCT[
+V TGEGKXGF VJG
Chow et al reported results of their 10 implanted patients, European CE mark in 2011.)
with 9 to 36 months of follow up. There, were no implant
related complications. The improvement in visual function 6JG #TIWU ++ KU CP GRKTGVKPCN UVKOWNCVKPI FGXKEG FGUKIPGF VQ
NKMG KORTQXGF EQPVTCUV UGPUKVKXKV[ CPF XKUWCN ſGNFU JCXG improve visual functioning in people who are blind—or,
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effect caused by the mere presence of the implant. 42 VJG CDKNKV[ VQ RGTEGKXG DNCEM CPF YJKVG KOCIGU CPF
motion.
The Argus II (Figure 8)
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6JG #TIWU ++ KU VJG UGEQPF IGPGTCVKQP QH CP GNGEVTQPKE 7PKVGF 5VCVGU QVJGTU CTG RTGUUKPI HQTYCTF KP FGXGNQROGPV
retinal implant designed for the treatment of blindness OQUV PQVCDN[ VJG #NRJC +/5 OCPWHCEVWTGF D[ 4GVKPC
FWG VQ 4GVKPKVKU RKIOGPVQUC 6JG ſTUV RJCUG QH VJG KORNCPV +ORNCPV #) KP )GTOCP[18.
study began in 2002 which was followed by successful
implantation in six patients in the trial, it was found that Other Devices in Development

+P CFFKVKQP VQ 5GEQPF 5KIJVŏU RQUVOCTMGVKPI VTKCNU QH #TIWU
three companies have devices in human studies, currently
either recruiting or under way, as registered at www.
ClinicalTrials.gov. These include a subretinal implant from
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subretinal device in pigs and is preparing for human testing.

Alpha IMS

#RCTV HTQO #TIWU VJG #NRJC +/5 HTQO 4GVKPC +ORNCPV #)
is the farthest along in development and is the only retinal
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+P ,WN[ KV TGEGKXGF VJG %' OCTM KP 'WTQRG

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mounted camera. Rather, it uses a wireless subretinal chip,
which moves with the eye, containing 1,500 electrodes,
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6JGUG UKIPCNU CHVGT RCUUKPI VJTQWIJ CP CORNKſECVKQP EKTEWKV
stimulate intact retinal cells to induce visual perceptions.

Earlier this year, clinical trial results were reported from
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dependent signal generation” in all nine subjects over a
VJTGG VQ PKPG OQPVJ RGTKQF

www. dosonline.org l 31





































Diagnostics: Ultrasound B-Scan for Posterior Segment Evaluation

(a) (b)

Figure 14a: +LJK UHÁHFWLYH JOREXODU HFKR V R GLVORFDWHG OHQV UHG DUURZ Figure 14b: Dislocated IOL in
posterior vitreous (blue arrow).

Figure 15: +LJK UHÁHFWLYH HFKR ZKLWH DUURZ Figure 16: Open globe injury showing vitreous
with reverberation (red arrow) also with acoustic haemorrhage (red arrow) and posterior globe

shadowing (blue arrow) suggestive of IOFB. dehiscence (blue arrow).

(a) (b)

Figure 17a: (FKRJUDP VKRZV GLIIXVH GRW DQG FOXPS HFKRHV RI ORZ WR PRGHUDWH UHÁHFWLYLW\ UHG DUURZ LQ YLWUHRXV ZLWK LQFUHDVHG
FKRURLGDO WKLFNQHVV EOXH DUURZ V R RI (QGRSKWKDOPLWLV Figure 17b: (FKRJUDP VKRZLQJ 7 VLJQ V R SDQRSKWKDOPLWLV

52 l DOS Times - Vol. 20, No. 5 November, 2014