DJO Oct- Dec 2022 Vol 32 issue (2)

DJO Vol. 32, No. 2, October-December 2021

filling of retinal veins • Hard exudates, soft exudates
• Early phase – Laminar flow • Melanin- choroidal nevus
• Late phase – entire retinal lumen fills • Xanthophyll-RPE hypertrophy
Venous Phase (d) (15-20s) • Lipofuscin
• Veins completely fills over the next 10 seconds
• Fluorescence decreases in arteries and increases in veins Hyper fluorescence
• Maximal vessel fluorescence occurs 25-30seconds after • Hyper fluorescence can be due to increase in fluorescein

the injection content of the tissue- leak, pooling and staining
• Perifoveal capillary network best visualised at the peak • Or due to better visibility of normal fluorescein

venous phase density- Window defect (transmitted fluorescence).
Recirculation Phase (e) (20-30s)
1. Leak: Early hyper fluorescence which increases in size
• During this phase – intensity of fluorescence slowly and intensity with time. This is due to extravasation
diminishes as they are eliminated from the kidneys of dye from leaky blood vessels due to disruption of
inner BRB. This may be due to dysfunction or loss of
Late Phase (Elimination phase) (f) (upto 5 minutes) existing vascular endothelial tight junctions as in DR,
• Gradual elimination of the dye from retinal and venous occlusions, cystoid macular edema (CME) etc.
choroidal vasculature (5-10 minutes ) (Figure 2)
• Staining of the optic disc occurs
• Any other area of hyper flourescence indicates 2. Pooling: A pooling in an anatomical space is
extravascular hyper fluorescence. characterised by a hyper fluorescence which increases
in intensity with time, however, the size of fluorescence
Abnormal fluorescence on FFA remains fairly same and well defined throughout the
Hypofluorescence angiogram. This occurs due to breakdown of outer
BRB. The dye is collected in a defined anatomic space,
It is usually seen due to less dye in vasculature (inadequate either subretinal e.g CSCR (Figure 3) or sub-RPE space
perfusion/filling of vessels) or could be due to poor visibility e.g Pigment epithelial detachment (PED).
of dye (Blocked fluorescence)
Non perfusion/filling defects 3. Staining: Some structures retain the dye in their tissue
and show hyper fluorescence in the later stages of the
• Ischemic retinal vascular disease angiography. e,g optic disc, exposed sclera etc.
• Ophthalmic artery occlusion
• Giant cell arteritis 4. Transmitted fluorescence (Window defect): Healthy
• Hypertensive choroidopathy - choroidal infarcts RPE blocks choroidal fluorescence. In cases with
• Loss of vascular bed as in myopic degeneration and atrophy of RPE, visibility of underlying choroidal
fluorescence is enhanced. This fluorescence follows
choroidemia the same pattern as flow of dye through normal ocular
Blocked Fluorescence circulation. It appears early and peaks early during
1. Masking of retinal fluorescence- choroidal filling phase. It is of the same shape as that
of pigment epithelium atrophy. Therefore, it doesn’t
• Pre retinal lesions – pre retinal bleed (vitreous increase in size or shape with time. The fluorescence
haemorrhage, subhyaloid haemorrhage, sub inner fades as and when dye washes out of choroidal
limiting membrane haemorrhage) (Figure 2).

2. Masking of background choroidal fluorescence-
• Intra retinal / Subretinal bleed

Figure 2: (A) Fundus photo showing CRVO. (B) FFA image showing hypo fluorescence corresponding to hemorrhages (*) and Capillary non perfusion (CNP) areas
(#) and pin point Hyper fluorescence in areas of dilated capillary bed and early collaterals formation (circle). Source: Guru Nanak eye centre, New Delhi.

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DJO Vol. 32, No. 2, October-December 2021

circulation. which increase in late phase. Also the level of bleed (pre
retinal/intra retinal or sub retinal) can be ascertained in
Pre Injection Hyper Fluorescence FFA.
d. Diabetic Maculopathy- It can be focal or diffuse
1. Autofluorescence – depending upon pattern of macular leakage. A typical
It is an inherent property of a lesion to spontaneously petalloid pattern or honey coomb appearance is seen in
fluoresce even in the absence of dye. e.g Optic disc drusen, chronic macular edema.
astrocytic hamartoma, etc. e. Ischaemic Maculopathy- Normally foveal avascular
zone (FAZ) is regular in size, almost circular in shape,
2. Pseudofluorescence - dark and non-fluorescent. In Ischaemic maculopathy,
It occurs due to the mismatched filters. e.g if green-yellow FAZ becomes distorted and irregular with broken
light penetrates the original blue filter, it will pass through the margins.
entire system or if blue light reflected from non-fluorescent 2. Hypertensive retinopathy (HR) - Retina, choroid and
fundus structures penetrates the green-yellow filter, pseudo optic nerve, all three may be involved. The FFA features
fluorescence will occur. include arteriovenous crossing changes, arteriolar
constriction, blocked fluorescence due to haemorrhages
Salient FFA features in different ocular pathologies and exudates. Disc edema may also be seen in stage four
1. Diabetic retinopathy5- HR.
a. Mild to moderate non proliferative diabetic retinopathy 3. Vascular Occlusions-
a. Venous Occlusions- Branch retinal venous occlusions
(NPDR) - Microaneurysms appear as hyper fluorescent (BRVOs) and Central venous vascular occlusion
dots that may leak in later phases. Blocked fluorescence (CRVOs). The FFA features are blocked fluorescence
may be seen corresponding to superficial flame shaped due to haemorrhages, capillary dilatation, venous
and deeper dot and blot haemorrhages. tortuosity, delayed filling in veins, CNP areas, NVEs
b. Severe NPDR- As per Early treatment of diabetic with or without macular leakage. Collaterals may
retinopathy study (ETDRS) definition, 4-2-1 rule of also be seen at posterior pole or in periphery, in close
Davis Murphy, microaneurysms and haemorrhages association with CNP areas.
in all 4 quadrants, venous abnormalities in 2 or more b. Arterial occlusions- Branch retinal arterial occlusion
quadrants & Intra retinal micro vascular abnormalities (BRAOs) and Central retinal arterial occlusion
(IRMAs) in at least 1 quadrant. If 2/3 criteria are present: (CRAOs). The typical FFA findings include delayed arm
severe NPDR and if 3/3 are present, very severe NPDR. retina time with poor choroidal flush and non-filling
FFA findings include hypofluorsecnce corresponding to of arteries. Box carring (Cattle trucking) can be seen
Capillary non perfusion areas (CNP), IRMAs, Venous in form of break or discontinuation of blood column.
abnormalities (Venous dilatation, beading and looping), A cilioretinal artery (15-20% population) can be seen
Blocked fluorescence due to hard and soft exudates arising out of choroidal circulation.
or haemorrhages and hyper fluorescence due to leaky 4. Dry age related macular degeneration (ARMD) - Dry
microaneurysms.
c. PDR- Neovascularisation of disc (NVD) and
neovascularisation elsewhere (NVEs) leak profusely

Figure 3: Smoke stack appearance in CSCR. Source: Guru Nanak eye centre, New Delhi.

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ARMD shows drusen and geographical atrophy in later All the findings must be correlated clinically, remembering
stages. Hard drusen (smaller drusen) appear as hyper the fact that FFA is just a diagnostic tool to supplement the
fluorescent dots which later fade away, while the larger
soft drusen show early hyper fluorescence followed clinical findings. References
by staining. Geographical atrophy is suggestive of
RPE atrophy which reflects as window defect hyper 1. Marmor M. Fluorescein Angiography. Archives of
fluorescence. Focal hyper pigmentation of RPE may Ophthalmology. 2011;129(7):943.
show a mottled appearance.
5. Wet ARMD- 2. Novotny H, Alvis D. A Method of Photographing Fluorescence
a. Classical Choroidal neovascularisation membrane in Circulating Blood in the Human Retina. Circulation.
(CNVM)- FFA shows a well outlined lacy pattern of 1961;24(1):82-86.
hyper fluorescent area corresponding to CNVM patch
which leaks in early phase and increase in size and 3. Wolfe DR: Fluorescein angiography basic science and
intensity in the later phases of the angiogram. engineering. Ophthalmology 1986; 93:1617–1620.
b. Occult CNVM- It may present as Fibrovascular PED
or Late leakage of undetermined source (LLUS). FFA 4. Hayreh S. The Ophthalmic artery: III. BRANCHES. British
shows ill-defined area of leakage which does not Journal of Ophthalmology. 1962;46(4):212-247.
correspond to the area of CNVM patch.
6. Pigment Epithelial Detachment (PED) - FFA shows 5. Shukla U, Tripathy K. Diabetic Retinopathy [Internet]. Ncbi.nlm.
pooling of dye in well-defined space which gradually nih.gov. 2021. Available from: https://www.ncbi.nlm.nih.gov/
increase in intensity but not in size or extent. Long books/NBK560805/
standing cases show irregular hypo and hyper
fluorescence within PED because of pigment migration. Cite This Article as: Priyadarshi Gupta, Ekta Shaw, Fundus
Notching, irregular and slow filling is suggestive of an Fluorescein Angiography. Delhi J Ophthalmol 2021 32 (2) 97 -101.
underlying Wet ARMD/ CNVM. Acknowledgments: Nil
7. Central serous chorioretinopathy- FFA shows an ink Conflict of interest: None declared
blot appearance or smoke stack appearance. Source of Funding: None
8. CME- Typical petalloid pattern or honeycomb pattern Date of Submission 11 Nov 2021
around the fovea may be seen. Also, leakage at the Date of Acceptance: 29 Dec 2021
fovea and peri-foveal areas is suggestive of a global
breakdown of inner BRB. Address for correspondence
9. Choroidal melanoma- Depending upon the size of the Priyadarshi Gupta
tumor, FFA shows double circulation in larger choroidal
tumors (both retinal and tumor blood vessels fill up) Senior Resident
while smaller tumors show mottled hyper fluorescence Department of Ophthalmology,
with late staining. Retina and Uvea services,
10. Choroidal folds- FFA shows alternating band of hyper Guru Nanak eye centre,
and hypo fluorescence corresponding to crests (widely New Delhi, India.
spaced and thinned out RPE) and troughs (crowding of Email: [email protected]
RPE) respectively.
Quick Response Code
FFA reading is an art and requires practice. Most of the FFA
can be reported in this basic prototype

1. Arm to Retina time (normal/delayed)
2. AV transit time (normal/delayed)
3. FAZ – shape and size (enlarged/broken)
4. Abnormal Fluorescence areas (Hypo or hyper) and

their course in the late phase (like capillary non-
perfusion areas, microaneurysms, etc.)
5. Late phase findings: leakage/ staining especially of the
disc.

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Theam article

Oct Angiography: The Basics

Abstract Khushboo Chawla

Department of Ophthalmology, Guru Nanak Eye Centre, New Delhi, India.

OCT angiography is a new imaging technology that provides volumetric analysis of retina, choroid, and optic nerve.
It helps to delineate early hemodynamic alteration in the vasculature of retina and choroid. Being non-invasive,
OCT A is employed over standard angiographic techniques of fundus fluorescein angiography (FFA) and indocyanine
green angiography (ICGA) which study changes in retinal superficial layers and choroid respectively. It gives a high
specificity and sensitivity in diagnosis and follow-up of vascular diseases such as diabetic retinopathy, vascular
occlusion, and macular degeneration. This article seeks to detail the principle and techniques of OCTA.

Delhi J Ophthalmol 2021; 32; 102-106; Doi http://dx.doi.org/10.7869/djo.729

Keywords:OCT Angiography, Retinal Vasculature, Multimodal Imaging

Introduction Ocular Blood Supply

OCTA is one of the breakthroughs in the advancing field of The vascular network of human retina is divided into
ophthalmic imaging. It is a useful clinical tool to evaluate different capillary plexuses. Each capillary plexus has

structural vascular anatomy of retina, choroid and optic nerve characteristic morphometric features and are linked by

head. interconnecting vessels.

From the anterior most layer i.e. internal limiting membrane

A non-invasive in-vivo imaging modality combining both (ILM) to posterior most axial locations, four distinct plexuses

quantitative and qualitative assessment of vasculature seen on are :

standard angiography, OCTA is an emerging technology for 1. Radial peripapillary/Nerve fibre capillary plexus

evaluation and follow-up of conditions like diabetic retinopathy, (NFLCP)

retinal vascular occlusive diseases, uveitis, inherited diseases, 2. Superficial capillary plexus (SCP)

age-related macular degeneration and optic nerve disorders. 3. Intermediate capillary plexus (ICP) and the deep

capillary plexus (DCP)

4. Choroid (Figure 1)

Figure 1: Diagram showing the retinal circulation. The ICP and DCP receive the supply from the SVC arterioles and drain into the SVC venules. Anastomosis
occurs between plexus from different level from both the arterial and venular side. Source- Drawings by Dave Schumick from Anand-Apte and Hollyfield (2009)

Encyclopedia of the Eye

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DJO Vol. 32, No. 2, October-December 2021

Principle 3. Outer retinal slab- This slab extends from 70µm below
IPL to 30µm below RPE reference line. This region has
OCT- A is based on low coherence interferometry principle. no retinal vasculature and is thus, seen as an empty space
Sequential B-scans are taken over time positioned at the in a normal eye. Any abnormality is useful to identify
same retinal location and subjected to analysis for changes type 2 choroidal neovascular membrane (subretinal)
in amplitude or phase of image captured by device. The
reflected beams are detected as high flow slow flow or no (Figure 5).
flow zone. Movement is suspected in case of any change
detected in intensity, amplitude, phase or both. The 4. Choriocapillaris- Extends 30µm below RPE reference
movement is due to the flow of erythrocytes in the vessels. to 60µm below RPE reference. It incorporates
The obtained signal can then be amplified X- number of choriocapillaris and allows detection of early type 1
times (incorporated software eg SSADA— split spectrum CNVM (sub-RPE).
amplitude-decorrelation angiography) and digitally
processed to provide an en face view of the vasculature at Foveal avascular zone (FAZ): is a complete avascular zone
different predetermined slabs1-3 (Figure 2). with variable dimensions in normal healthy individuals. The

Figure 2: A schematic flowchart of OCTA working [3]. Repeated B scans labelled N1, N2, N3 are repeatedly captured from the location line L1 in the diagram. The
difference between successive B scans N1- N2 and N2-N3 is derived (Line L2). Line L3 is from the combined data. The procedure is repeated at different location

to form a volumetric cube data. Source- A practical guide to optical coherence tomography angiography interpretation. by Greig, E., Duker, J., & Waheed, N.

Spectral-domain (SD-OCT) or Swept-source (SS-OCT)
project light of wavelength of 800nm or 1050nm respectively.

The procedure is repeated at different locations to form a Figure 3: Inner retinal slab: a) OCTA image similar to that of FFA. b) Superficial
volumetric cube data. retinal plexus. Source- A practical guide to optical coherence tomography
The important terminologies in the sequence used are
angiography interpretation. by Greig, E., Duker, J., & Waheed, N.
• Ts- Acquisition time for each B scan.
• Tf- time taken for beam to rapidly return back to initial

position called ‘Fly back time’.
• ΔT/ interscan time- Difference between two B scans.

(sum of Ts and Tf).

Commercially available software’s on OCTA splits the
volume cube up into following four slabs:
1. Inner retinal slab- Contains large retinal blood vessels,

extending from 3µm below ILM to 15µm below inner
plexiform layer (IPL). It corresponds to superficial retinal
vascular plexus. This is generally visible on FFA
(Figur 3).

2. Middle retinal slab- Extends 15µm below IPL to Figure 4: Middle Retinal slab. a) OCTA image showing the deeper dense
70µm below IPL. It contains small retinal blood vessels retinal plexus b) anatomical depiction of the deep retinal plexus. Source- A
corresponding to DCP. This plexus is not clearly practical guide to optical coherence tomography angiography interpretation.
visible on FFA therefore OCTA helps in diagnosis of
pathologies like parafoveal telangiectasia (PFT) type 2b, by Greig, E., Duker, J., & Waheed, N.
paracentral acute middle maculopathy (PAMM), and
retinal angiomatous proliferation (RAP) (Figure 4).

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SVP, present in ganglion cell layer (GCL), terminates slightly be visualised in the inner retinal slab.
away from foveal centre than deep vascular layer. Outer retina and choriocapillaris (ORCC) slab may be
combined as one: useful in cases of wet AMD.
Interpretation
Segmentation lines
Sequence of steps to be followed in reading and The predetermined slabs are recognised automatically and
interpreting scan (Figure 6) are: demarcating segmentation lines are set. After selection of
Image the correct area →See the en-face OCTA image to be read, segmentation line needs to be checked
images→Check segmentation lines→ Look at the B scan with for correct identification of retinal boundaries. In a normal
flow overlay→evaluate enface intensity images(Figure 7) healthy individual, it is accurately detected. However, it may
En face OCT images- -The superficial slab captures SCP and be misread in pathological conditions with haemorrhage
part of radial peripapillary capillary plexus. The SCP along or,fluid.4
with the DCP delineates the FAZ. In diabetic retinopathy,
FAZ alter microaneurysms and early vascular changes will

Figure 5: Outer retinal slab: (a) No vascularity seen in OCTA, (b) anatomical zone seen in outer retinal slab-IPL to RPE Source- A practical guide to optical
coherence tomography angiography interpretation. by Greig, E., Duker, J., & Waheed, N.

Figure 6: showing the OCTA scan report: (a) enface retinal image, (b) cross-sectional image with segmentation into slabs- superficial(red-green), deep(green-
blue), avascular(blue-yellow). (c, d, e) angiogram images of the superficial, deep and avascular slab, (f) OCTA image of the whole retinal layers encoded in false
colours. Source: Hormel TT, Jia Y,et al. Plexus-specific retinal vascular anatomy and pathologies as seen by projection-resolved optical coherence tomographic

angiography

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Figure 7: Step by step interpretation sequence of an OCTA scan. Source: A practical guide to optical coherence tomography angiography interpretation. by Greig,

E., Duker, J., & Waheed, N.

Enface intensity images through 3D cube. The algorithms automatically detects

The structural and angiography projection for a given retinal retinal boundaries based on reflectivity and texture.

slab should be examined. Various pathological findings Pathologies such as fluid in DME, drusens in AMD

such as edema, fluid and haemorrhages may cause lower may alter boundary detection and lead to altered slab

signal strength and thus a false low intensity. These may formation resulting in segmentation errors.

be misinterpreted as low flow and are thus called shadow 5. Shadow artifact- Any structural aberration obstructs the
artifacts. If the structural en face image shows good signal visualization of deeper/outer layers due to reflectance of
intensity and angiogram shows reduced flow in the same the beam. Obstruction is caused by hemorrhage, drusens,
area, this can be interpreted as a true reduction in flow. etc.1

Various pitfalls in OCT interpretations due to artifacts Abnormalities Seen in OCTA
created by technique or software are as follows:
1. Abnormal flow- neovascularization

1. Signal strength- Signal is information derived from 2. Abnormal/anomalous vasculature- aneurysms and
tissue being imaged. Noise is spurious, unwanted dilated vessels, or
information generated through image acquisition and
3. No flow/dropout areas, as seen in nonperfusion3

processing. Low signal and high noise may give a poor Clinical Application ofOCTA
image quality.
1. Diabetic retinopathy: FFA is indicated for vascular
2. Motion artifacts- Any kind of movements such as head changes in DR. OCTA detects early changes in DR
or eyes creates a ‘bulk motion’. The OCTA detects any with vascular losses. Commonly noted changes are:
movement as flow of RBC’s. , thereby misinterpreting FAZ enlargement with DR progression,(Figure 8)
bulk motion as changes in the blood flow. microaneurysms (seen as small capillary dilatations) and

3. Projection artifact- OCT beam travelling through retina Capillary dropouts.

layers, strike SCP and is reflected back and captured. The High-resolution 3D structural reconstruction aids in
rest of beams travel deeper and are reflected by RPE. studying detailed pathophysiology of DR progression.
Sometimes, light beam reflected by RPE is influenced by
flow and erroneously depicts SCP in the deeper layers. 2. Age-related macular degeneration:
This misinterpretation of flow is the most important OCTA is useful for diagnosis of wet AMD. Three types
artifact in OCTA.
of wet AMD: Type 1 - below RPE, type 2 - between
4. Segmentation artifacts- Each slab is generated by an RPE and retina, and type 3 - arises from superficial
upper and lower boundary that slices horizontally retinal vasculature and growing downwards toward the
neurosensory retina and eventually choriocapillaris.

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Figure 8: OCTA image showing (a) Normal and (b) Distorted FAZ. Source- Guru Nanak eye centre, New Delhi.

OCTA identifies, localizes subclinical CNVM and helps Cite This Article as: Khushboo Chawla, OCT Angiography:
to moniter regression post antiVEGF injection.5 Delhi J Ophthalmol 2021 32 (2) 102 -106

3. Retinal vascular occlusions: to assess the non-perfused Acknowledgments: Nil
areas and development of collaterals.

4. Retinal pathologies like macular telangiectasias, retinal Conflict of interest: None declared
inflammatory disease, retinal tumors and retinal Source of Funding: None
hereditary dystrophies. Date of Submission 26 July 2021
Date of Acceptance: 29 Dec 2021
Summary Points
Address for correspondence
• OCTA images flow in retinal and choroidal vasculature. Khushboo Chawla, MBBS, DNB
• It has a steep learning curve.
• It is important to evaluate the correct slab such as Senior Resident Ophthalmology
Department of Ophthalmology, Guru
Superficial and deep plexus in vascular diseases, ORCC Nanak eye centre,
in CNVM. New Delhi, India.
• Artifacts may lead to misinterpretation. Email: [email protected]

Reference

1. Chow D, Oliveira P. OCT Angiography. 1st ed. Beijing: Thieme; Quick Response Code
2017.

2. Hormel TT, Jia Y, Jian Y, Hwang TS, Bailey ST, Pennesi ME, Wilson
DJ, Morrison JC, Huang D. Plexus-specific retinal vascular anatomy
and pathologies as seen by projection-resolved optical coherence
tomographic angiography. Prog Retin Eye Res. 2021 Jan;80:100878.

3. Greig, E., Duker, J., & Waheed, N. (2020). A practical guide to
optical coherence tomography angiography interpretation.
International Journal Of Retina And Vitreous, 6(1).

4. Spaide RF, Fujimoto JG, Waheed NK, Sadda SR, Staurenghi G.
Optical coherence tomography angiography. Prog Retin Eye Res.
2018;64:1-55.

5. Rocholz R, Corvi F, Weichsel J, et al. OCT Angiography (OCTA)
in Retinal Diagnostics. 2019 Aug 14. In: Bille JF, editor. High
Resolution Imaging in Microscopy and Ophthalmology: New
Frontiers in Biomedical Optics [Internet]. Cham (CH): Springer;
2019. Chapter 6.

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DJO Vol. 32, No. 2, October-December 2021

Theme Article

Cross-Sectional Imaging In Ocular And Orbital Lesions

A Review

Apoorva Sehgal1, Alpana Manchanda1, Jyoti Kumar1, Ruchi Goel2, R K Saran3, Ayush Jain1

1Department of Radiodiagnosis, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi
2Department of Ophthalmology, Maulana Azad Medical College and Guru Nanak Eye Centre, New Delhi

3Department of Pathology, Maulana Azad Medical College and G.I.P.M.E.R, New Delhi

Orbit is the site for a heterogeneous group of tumors and tumor-like conditions which often overlap in their clinical presentation

and examination findings. Thus, a detailed imaging evaluation is warranted to reach a definitive diagnosis or narrow the list

Abstract of differentials in challenging cases. Magnetic Resonance Imaging (MRI) with its exquisite soft tissue contrast resolution is the
modality of choice with Computed Tomography and Ultrasound, reserved for specific indications. This review highlights the role

of various imaging modalities in evaluating non-traumatic orbital lesions with a detailed account on imaging features of the

commonly encountered lesions and their clinical relevance.

Delhi J Ophthalmol 2021;32;107-118; Doi http://dx.doi.org/10.7869/djo.730

Keywords: Orbit, Magnetic Resonance Imaging, Ultrasound, Computed Tomography

Introduction Computed Tomography (CT) offers quick multi-planar

The orbit is the site of a large number of pathologies imaging with lack of sensitivity to eyeball motion. It is the

of diverse etiologies such as congenital, inflammatory, modality of choice for subtle calcifications, bony erosions/

infectious, vascular, traumatic and neoplastic. Imaging has hyperostosis associated with mass lesions and for imaging

to be tailored to the symptoms and clinical findings which primary osseous lesions in the orbit. Its main pitfalls are

are often non-specific and overlapping.1 radiation exposure to the lens and poor characterization of

Tissue diagnosis, either by open biopsy or fine needle soft tissue lesions and their intracranial extension.5

aspiration is the gold standard in diagnosis. However, tissue Magnetic Resonance Imaging (MRI) with its exquisite
sampling may not always be feasible especially in highly soft tissue contrast resolution, multiplanar capability and
vascular lesions and lesions involving the posterior orbit. absence of ionizing radiation is the imaging modality of
Cross-sectional imaging plays a vital role in the diagnosis choice in evaluating ocular and orbital pathologies and
and management of these lesions.2 delineating their extent.5

Imaging Modalities Functional MR techniques of Diffusion weighted Magnetic
Resonance Imaging (DWMRI) and Dynamic contrast-
Plain radiography has limited role in the characterization of enhanced MRI (DCE-MRI) allow insight into tissue
orbital masses. It can help depict calcifications/phleboliths cellularity and vascularity respectively and have been used
and bony erosions associated with orbital lesions. as problem solving tools for pre-operative evaluation of
Ultrasonography (USG) is generally performed for initial space occupying lesions of the orbit in case of overlapping
evaluation of suspected intraocular pathology. The morphologic features on conventional MR sequences.6,7
superficial location and cystic composition of the globe 18-Fluoro-deoxyglucose Positron Emission Tomography
make USG ideal for its imaging especially in the presence CT/MRI provide useful physiologic information which
of opaque light conducting media.3 It is a non-ionizing, cost- complement the morphologic details derived from the above
effective and widely available real-time imaging modality mentioned imaging modalities and is useful in assessing
providing detailed cross-sectional anatomy of the globe. tumor grade, therapeutic response, recurrence, distant
It can be easily performed in children without requiring metastasis from orbital tumors and metastasis to the orbit.8
sedation. However, in addition to being operator dependent, Indications of various imaging modalities are summarized
USG has limited role in assessing retrobulbar pathologies, in Table 1.
painful lesions and bony abnormalities.4 Color Doppler
Imaging (CDI) helps in assessing the vascularity of lesions.1

Table 1: Indications Of Various Imaging Modalities In Non-Traumatic Orbital Lesions

Plain radiography Ultrasonography Computed Tomography Magnetic Resonance
Imaging
Depiction of : • Excellent for intraocular Modality of choice for depiction
• intralesional calcifications/ pathologies including of : Imaging modality of choice
for characterization and
phleboliths membrane detachments, • intralesional calcifications/ delineation of extent of all
• bare orbit in sphenoid wing cysticercosis and phleboliths; orbital lesions

dysplasia in NF-1 intraocular neoplasms like • bone changes associated with
• bony erosions/hyperostosis/ retinoblastoma, choroidal orbital masses;

primary bone lesions involving hemangioma etc. • primary osseous masses
the orbit like osteoma, fibrous • Can be used for preseptal
dysplasia etc. (however, CT is
space lesions
superior in this regard

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Anatomic Consideration Doppler helps in detecting and quantifying blood flow and
in surgical planning. Venous malformations typically appear
The orbit is divided into the ocular compartment or globe, as well circumscribed, round or ovoid, homogeneously
muscle cone, intraconal, extraconal and preseptal spaces. The hyperdense lesions with occasional phleboliths and
contents of various orbital compartments are enumerated in expansion of orbital walls on CT. They may displace adjacent
Table 2. Localizing lesions to particular orbital compartments structures but do not invade them. The lesions usually
helps to demystify the diagnostic approach and narrow appear isointense on T1 and hyperintense to muscle on T2-
down the list of differentials.8 The commonly encountered weighted MR images.9,10 On dynamic contrast-enhanced CT/
pathologies in each of these compartments are listed in Table MRI, these malformations show poor enhancement on early
3. The normal cross sectional anatomy of the orbit is depicted arterial phase with gradually progressive centripetal fill in of
in Figures 1 and 2. contrast.9,11 (Figure 3)

Table 2: Contents Of Orbital Compartments Orbital varices

Intraconal Compartment These uncommon venous malformations are the most
common cause of spontaneous orbital hemorrhage. They
Optic nerve sheath complex affect males and females equally in the second or third
Ophthalmic artery and Superior ophthalmic vein decade.9 Most patients present with intermittent proptosis
Other cranial nerves (oculomotor, nasociliary branch of ophthalmic that increases on bending forward or coughing. However,
some may have a small communication with the venous
nerve, abducens nerve) system and present with a more sustained painful proptosis
Ciliary ganglion due to thrombosis and hemorrhage. Varices appear as a
Orbital fat smooth, triangular, or segmentally dilated, tangled tuft
of vessels. These appear hypo- to hyperintense on T1,
Extraconal Compartment hyperintense on T2-weighted MR images and usually
enhance intensely on post contrast scans.9 Prone scanning is
Cranial nerves (lacrimal and frontal branches of ophthalmic nerve, recommended to demonstrate lesion distensibility. (Figure
trochlear nerve, anterior and posterior ethmoidal branches of 4)

nasociliary nerve, zygomatic and infraorbital branches of maxillary Lymphatic Malformation
nerve)
Previously known as lymphangioma, these lesions usually
Lacrimal Gland manifest in infancy or childhood and affect males and
Superior and inferior ophthalmic veins females equally.9 They are slow growing lesions, may enlarge
Muscles (superior oblique, inferior oblique, levator palpebrae abruptly due to hemorrhage. They are unencapsulated,
multicompartmental lesions often insinuating between
superioris) normal orbital structures.12 Imaging features can be variable
Orbital fat

Preseptal Compartment

Skin
Eyelids
Superior, inferior tarsi and muscles (orbicularis oculi, corrugator
supercilli, depressor supercilli)
Lacrimal gland and nasolacrimal drainage apparatus

Table 3: Compartment Based Approach To Orbital Lesions

Intraocular Intraconal Extraconal Multicompartmental

• Retinoblastoma • Optic nerve sheath complex lesions- • Dermoid/epidermoid • Lymphatic
• Uveal melanoma optic nerve glioma, optic nerve sheath • Schwannoma of branches of malformations
• Choroidal hemangioma meningioma, lymphoma, leukemia
• Choroidal metastasis trigeminal nerve • Lymphoma
• Hemangioblastoma • Retrobulbar fat lesions-venous • Rhabdomyosarcoma • Rhabdomyosarcoma
malformation, schwannoma of III, IV • Lacrimal gland-epithelial • Plexiform neurofibroma
and VI cranial nerves • Metastasis
neoplasms, leukemia, • OIS
• Muscle cone lesions-thyroid lymphoma, OIS, sarcoidosis • IgG4 related disease
ophthalmopathy, OIS, IgG4 related • Metastasis, multiple myeloma
disease • Osseous lesions

Etiological Classification Of Orbital Masses depending on the presence/absence and age of intralesional
(I) Vascular Lesions hemorrhage. These lesions are cystic and appear hypo/iso/
hyperintense on T1 and T2 weighted images with absence
Venous Malformation of contrast enhancement. Venous component, if present may
demonstrate phleboliths and minimal enhancement on late
Venous malformations, formerly known as cavernous venous phase images. The presence of fluid-fluid levels due
hemangioma are the most common benign orbital lesions to hemorrhage is almost pathognomonic.9,12 (Figure 5)
in adults. They occur most often in females, 18-72 years
of age.9 Common clinical manifestations include painless Carotid-cavernous fistula
progressive proptosis and less often pain, diplopia, lid
swelling, palpable lump and diminished vision.10 They Carotid cavernous fistulas result from abnormal
are usually located in the lateral intraconal space. Bone communication between the cavernous sinus and internal or
remodelling and intralesional calcification may be seen. external carotid artery. They may result from trauma, surgery
Imaging features seen on USG include well-defined margins or may occur spontaneously in patients with Ehlers-Danlos
owing to its fibrous pseudocapsule with honeycomb-like syndrome and osteogenesis imperfecta. Classic clinical triad
structure and moderate to high internal reflectivity. Color includes pulsatile exophthalmos, conjunctival chemosis

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Figure 1: NORMAL ORBITAL ANATOMY- Coronal T1W MR images of right orbit (a, b) show extraocular muscles (levator palpebrae superioris-1, superior rectus-2,
lateral rectus-3, superior oblique-4, medial rectus-5, inferior rectus-6), optic nerve (7) and lacrimal gland (8).

Axial T1W image with color overlay (c) shows the various orbital compartments (red- extraconal, yellow- intraconal, blue- preseptal and green- intraocular
compartment).

Figure 2: ORBITAL FORAMEN- Axial (a, b, c) and coronal (d, e, f) CT images in bone window depict superior orbital fissure (SOF), optic canal (OC), inferior

orbital fissure (IOF) and infraorbital foramen (IF).

and auscultatory bruit. Imaging findings on CT and MRI early arterial and venous phase enhancement followed by

are proptosis, congestive extraocular muscle enlargement, rapid washout of contrast on dynamic contrast enhanced

superior ophthalmic vein distension and cavernous sinus MRI, a feature which helps differentiate these lesions from

dilatation. Conventional catheter angiography is usually venous malformations.9

required for lesion classification and treatment planning.9 (II) Congenital/Developmental Lesions
Dermoid
Solitary fibrous tumor

Patients with this rare neoplasm present in the fifth decade Dermoids are the most common congenital orbital lesions.

with no gender predilection. They can be slow growing They are typically located in the superotemporal extraconal

benign lesions or frankly malignant with lung being the space owing to their origin from epithelial sequestration,

commonest site for metastasis. On imaging, these lesions usually at the zygomaticofrontal and frontoethmoidal

are frequently lobulated, well circumscribed, extraconal in sutures.8 Orbital dermoids are well circumscribed

location adjacent to paranasal sinuses. They are isointense encapsulated lesions with variable echogenicity/density of

to grey matter on T1 and T2 weighted images with marked its contents on USG and CT respectively. This heterogeneous

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Figure 3: VENOUS MALFORMATION IN A 45 YEAR OLD MALE WITH RIGHT EYE FULLNESS- Axial T2W MR image (a) shows an encapsulated homogeneously
hyperintense lesion in right intraconal space with mass effect. The lesion shows heterogeneous contrast enhancement on early post contrast T1 fat suppressed

image (b) with progressive filling in of contrast on delayed post contrast scan (c) and persistent pattern of time intensity curve (d) on DCE-MRI.

Figure 4: ORBITAL VARIX IN A 50 YEAR OLD FEMALE WITH INTERMITTENT PROPTOSIS OF LEFT EYE- Axial T1W MR image (a) depicts an irregular hypointense
lesion in posterior intraconal and extraconal space of left orbit. The lesion could not be appreciated on post contrast T1 fat suppressed image which was

obtained about 30 minutes after the patient laid supine in the MR scanner (b). However, on prone scan (c) the lesion showed marked enlargement reaching till
the orbital apex with intense homogeneous contrast enhancement.

Figure 5: LYMPHATIC MALFORMATION IN A 7 YEAR OLD MALE CHILD WITH RIGHT SIDED PROPTOSIS- Sagittal (a)and coronal (b) T2W MR images show a
septated multicompartmental lesion in extraconal and intraconal space of right orbit with blood-fluid level within (arrow in a).

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Figure 6: ORBITAL DERMOID IN A 15 YEAR OLD FEMALE WITH SWELLING IN LEFT EYE- Axial T1W MR image (a) demonstrates a well circumscribed heterogeneously
hyperintense lesion in lateral extraconal space of left orbit with central signal suppression on T1 fat suppressed image (b) due to macroscopic fat..

Figure 7: THYROID OPHTHALMOPATHY IN A 50 YEAR OLD FEMALE WITH BILATERAL EXOPHTHALMOS- Axial (a) and Coronal (b) NCCT images show fusiform

enlargement of all four recti muscles with resultant exophthalmos. There is characteristic sparing of the anterior tendons giving the ‘coca cola bottle’ appearance
of the involved muscles. The relative sparing of bilateral superior oblique muscles can be appreciated in the coronal image..

appearance can be attributed to soft tissue/fat/fluid finding, although asymmetrical muscle involvement
components either or all of which may be present in the can occur. Unilateral orbital involvement is uncommon,
same lesion. Fat-fluid levels and calcifications may be seen. occurring in only 6 to 10% of patients.15 The muscles most
Pressure effect may cause bony scalloping of the lacrimal frequently affected are the inferior, medial and superior recti
fossa. On MRI, dermoids appear hyperintense on T1 and T2 (Figure 7). Orbital fat enlargement, bone changes, especially
weighted images with signal suppression on fat saturated bowing of the lamina papyracea resulting from muscle
images. The presence of macroscopic fat is diagnostic (Figure pressure, lacrimal gland displacement and enlargement,
6). Rim enhancement is rare.8,13 exophthalmos, anterior soft tissue swelling and superior

Colobomatous Cyst ophthalmic vein dilatation are non-specific findings. Disease
activity can be evaluated on MRI as edema points towards
Colobomatous cysts are rare malformations, usually active disease while fibrotic changes with fatty replacement
associated with microphthalmia and present as a protruding correspond to chronic stage.15,16
mass in the inferior orbit. The cysts appear hypodense on
CT, hypointense on T1 and hyperintense on T2 weighted Orbital Inflammatory Syndrome (OIS)
MR images, communicate with the vitreous cavity. Bilateral
lesions may be associated with other systemic congenital OIS, also known as non-specific orbital inflammation/
malformations.14 idiopathic orbital inflammation/orbital pseudotumor is
usually a diagnosis of exclusion.17 The clinical features,

(III) Infectious/Inflammatory Lesions imaging findings and differential diagnosis depend on the
Thyroid eye disease site of involvement and phase of disease. Dacryoadenitis
usually presents with diffuse enlargement of the lacrimal
This is the most common extrathyroidal manifestation of gland. Myositis appears as diffuse thickening of the extra-
Graves disease, occurring in 25-50% of the patients with ocular muscles often involving the surrounding fat, tendon
hyperthyroidism.15 Rarely, it may also occur in hypothyroid/ and myo-tendinous junction, a feature that helps distinguish
euthyroid patients. The active inflammatory phase is OIS from thyroid orbitopathy that produces bilateral
followed by a chronic fibrotic phase. The diagnosis is usually extraocular muscle enlargement, sparing the myotendinous
based on clinical and laboratory findings. Dysthyroid optic junction.18 Inflammatory cellulitis is inflammation of
neuropathy is the most dreaded complication and results preseptal or postsetpal fat which appears as poorly defined
from the mechanical compression of the optic nerve at the fat stranding and enhancement. Infectious cellulitis shares
orbital apex by enlarged extraocular muscles.16 Symmetrical, similar imaging features, and can be differentiated on the
fusiform multiple extraocular muscle enlargement involving basis of clinical features. Presence of an abscess is a clear
its non-tendinous portion is the most common imaging

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Figure 8: TUBERCULAR ORBITAL ABSCESS IN A 5 YEAR OLD MALE WITH LEFT SIDED PROPTOSIS AND PERIORBITAL SWELLING- Post coronal T1 fat suppressed
image (a) depicts a peripherally enhancing collection in the superior extraconal space of left orbit with periorbital extension, mass effect and associated left
ethmoid and maxillary sinusitis. Proven to be tubercular abscess on microbiological analysis of the aspirate. Follow up scan (b) after 2 months of anti-tubercular

treatment reveals marked reduction in the size of the abscess.

indicator of infectious etiology.18 Optic perineuritis is collection appearing hypointense on T1, hyperintense on

inflammation of the optic nerve sheath and presents with soft T2 weighted MR images with central diffusion restriction

tissue thickening and ill-defined enhancement surrounding owing to its thick viscous contents.22 Bony orbital walls

the optic nerve. Since the nerve per se is usually unaffected, and adjacent sinuses particularly ethmoid sinus need to be

patients present with pain rather than vision loss. Other carefully evaluated (Figure 8). In case of fungal infections, the

manifestations of OIS include periscleritis, focal mass and disease may spread into the pterygopalatine, infratemporal

diffuse involvement. The mass in OIS appears hypointense fossa and brain. Imaging findings of endophthalmitis are

on T2 weighted images, iso to slightly hyperintense on T1- periocular inflammation, thickening and enhancement of the

weighted images with prominent post contrast enhancement. ocular wall, hyperattenuation on CT, and abnormal increased

Globe deformity may be appreciated in the fibrotic phase. signal intensity on FLAIR MR images of the affected vitreous

Rarely, the disease may involve the orbital apex or may humor. Post-infectious optic neuropathy may occur in

extend further into the cavernous sinus causing Tolosa-Hunt pediatric population. On imaging, the involved optic nerve

syndrome.17,18,19 is enlarged with T2/STIR hyperintensity and post contrast

IgG4 related disease enhancement. A serious complication of orbital infection is
orbital compartment syndrome which is usually diagnosed
IgG4 related disease is an idiopathic systemic fibro- clinically. On imaging, it should be suspected in cases of
inflammatory disorder characterized by tissue infiltration severe proptosis, deformation of the posterior globe giving
by IgG4 plasma cells. Autoimmune pancreatitis is its most
common manifestation. In the orbit, bilateral extraocular the ‘guitar-pick’ sign and stretching of the optic nerve.21
muscle and lacrimal gland enlargement along with
intraorbital inflammation, infraorbital nerve enlargement Cysticercosis
and sinus disease are the commonly described imaging
Orbital cysticercosis, caused by the parasite Cysticercus
cellulosae, larval form of Taenia solium is a preventable

findings. Sometimes, it may present as an orbital mass

extending posteriorly into the orbital apex and/or cavernous

sinus. A few studies have described sparing of the tendon

in IgG4 related disease similar to thyroid eye disease. Early

involvement of lateral rectus muscle is seen in IgG4 related

disease compared to thyroid ophthalmopathy. Another

differential is OIS which characteristically causes unilateral

enlargement of the entire muscle, including its tendon.

The pattern of extraocular muscle enlargement is slightly

different with OIS involving the medial rectus, followed by

superior and lateral recti muscles. Both OIS and IgG4 related

disease show dramatic response to corticosteroids.20

Infection

Orbital infections are usually bacterial in etiology with fungal Figure 9: ORBITAL MYOCYSTICERCOSIS IN A 30 YEAR OLD MALE WITH
infections seen almost exclusively in immunocompromised RESTRICTED OCULAR MOTILITY- Coronal CECT image shows a peripherally
hosts.21 Orbital infections may manifest as pre-septal and/ enhancing hypodense cystic lesion with an eccenteric hyperdensity
or post septal cellulitis, abscess or endopthalmitis. Orbital
abscess typically appears as a peripherally enhancing fluid representing the scolex in left superior rectus muscle

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Figure 10: ORBITAL LYMPHOMA IN A 68 YEAR OLD MALE WITH RIGHT ORBITAL MASS- Coronal T2W MR image shows a homogeneous mass lesion in the lateral

extraconal space of right orbit with homogeneous mild contrast enhancement on post contrast scan (b). Axial diffusion weighted image (c) shows marked

hyperintensity of lesion with signal drop on corresponding ADC map (d) suggestive of diffusion restriction with a low mean ADC value.

cause of blindness endemic in India. The extraocular muscles of pseudotumor. Patient’s clinical history is often useful,
are the commonest site of involvement (Figure 9). Globe, since patients with pseudotumor present with acute pain
subconjunctival space, eyelid, optic nerve and retro-orbital and those with lymphoma usually have no pain. However,
space are other common sites. Lacrimal sac cysticercosis, biopsy may be required for diagnosis.25,26
though uncommon has also been reported.23 CT and MRI
of the orbits reveal a cystic lesion with a central scolex. (V) Neoplastic Lesions

Adjacent soft-tissue inflammation may be present. The scolex A) Lacrimal Gland Masses

may not be visible if the cyst is dead or ruptured and has They are further divided into epithelial and non-epithelial

surrounding inflammation. Concurrent neurocysticercosis origin masses.

and myocysticercosis should be excluded.23,24 Epithelial lesions comprise 40%–50% of lacrimal masses

(IV) Lymphoproliferative Lesions and are largely neoplastic. Nonepithelial lesions could
be either inflammatory (dacryoadenitis) or neoplastic

Lymphoproliferative lesions are the most common primary (lymphoproliferative disease) processes.25

orbital masses in adults ≥60 years of age. These lesions Epithelial Lesions
represent a spectrum of disorders including lymphoid Pleomorphic adenomas are benign mixed tumors, consisting
hyperplasia, atypical lymphoid hyperplasia and lymphoma of both mesenchymal and epithelial elements. They are the
with the latter being the commonest.25 Orbital lymphoma most common benign lacrimal gland tumors and mostly
may be a manifestation of systemic lymphoma or arise present as painless masses in adults over 30 years of age.25
primarily in the orbit. B-cell Non-Hodgkin lymphoma,

specifically the mucosa-associated lymphoid tissue (MALT) On imaging, these appear as well - circumscribed,

subtype is the most common primary orbital lymphoma.25 homogeneous enhancing masses in the superotemporal

Patients usually present with a painless palpable mass, orbit. They can be heterogeneous secondary to cystic

proptosis, and restricted ocular motility. Majority of the degeneration, haemorrhage or necrosis. Bone remodelling

lesions are unilateral and often extraconal. Lacrimal gland may be associated owing to their slow growth. Lesions appear

is involved in about 40% of cases. Optic nerve and globe hypointense on T1 weighted images and hyperintense on T2

are uncommon sites of involvement.8,25 Approximately half weighted images. Bone erosion, nodularity or infiltrative

of the lesions are diffuse and ill defined, with the other borders should raise suspicion for malignancy.27

half appearing as a circumscribed mass on imaging. T2 Treatment consists of en-bloc removal of the tumor without

hypointensity, uniform enhancement, molding around biopsy, with excellent prognosis. Incomplete excision or

normal orbital structures and diffusion restriction are the rupture of the tumor may lead to recurrence or malignant

characteristic MR findings (Figure 10). Bone erosion is rare.26 transformation to pleomorphic adenocarcinoma.25

Differentiation of orbital lymphoma from pseudotumor Adenoid cystic carcinomas are the most common epithelial
is challenging. DWI often proves helpful in this regard lacrimal gland malignancy mostly presenting in the 4th
with lymphomas exhibiting marked diffusion restriction decade. Owing to their strong propensity for perineural
and lower ADC values than pseudotumor. The findings of spread, proptosis may be minimal and patients commonly
infiltration or thickening of ocular muscles favor a diagnosis present with pain, which is a strong indicator of malignancy.

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Figure 11: OPTIC NERVE GLIOMA IN A 3 YEAR OLD MALE WITH RIGHT SIDED PROPTOSIS AND DIMINISHED VISION- Axial T2W MR image (a) shows fusiform
enlargement and heterogeneous hyperintense signal of the intraorbital segment of right optic nerve with resultant proptosis and mass effect. Axial post contrast

image (b) shows heterogeneous marked enhancement of the lesion.

Figure 12: OPTIC NERVE SHEATH MENINGIOMA IN A 20 YEAR OLD FEMALE WITH DIMINISHED VISION IN LEFT EYE- Axial T2W MR image (a) shows a markedly
hypointense intraconal lesion with mass effect on the muscle cone. The lesion surrounding the left optic nerve shows mild enhancement on post contrast T1 fat

suppressed MR image giving ‘tram-track appearance’ (b). Marked T2 hypointensity can be attributed to calcification which was confirmed on CT (c).

Prognosis is generally poor.25 and hypothalamus. The lesions are isointense on T1 and iso-
Early lesions may be indistinguishable from pleomorphic to hyperintense on T2-weighted images with heterogeneous
adenoma on imaging. Irregular margins with distortion enhancement (Figure 11). Cystic spaces and calcification
of globe and orbital contents are usually seen in patients may be seen.30 A rim of hyperintensity may be appreciated
with advanced disease. Bone erosion and calcification at tumor periphery on T2 weighted images, that may mimic
point towards the presence of malignancy. Cranial nerves, an enlarged subarachnoid space. However, this corresponds
especially the lacrimal branch of ophthalmic nerve, should to leptomeningeal infiltration and proliferation (arachnoidal
be carefully examined for perineural invasion.28 gliomatosis) on pathology.25 In patients with NF-1, the optic
nerve often appears tortuous, kinked and diffusely enlarged.
Non - epithelial Lesions In comparison, the lesions are fusiform in patients without
About half of the nonepithelial lacrimal lesions are NF-1. Chiasmal involvement is more likely in the absence
lymphoproliferative disorders 25 which have been described of neurofibromatosis. The optic nerve cannot be identified
above. separately from the tumor, a finding that is useful for
differentiating glioma from meningioma.25,29
B) Optic Nerve And Meningeal Lesions
Optic Nerve Sheath Meningioma
Optic Nerve Glioma
Optic nerve sheath meningiomas derive from the arachnoid
Gliomas are the most common primary tumor of the sheath around the optic nerve. Cross-sectional imaging
optic nerve. They may occur anywhere along the optic features are characteristic with biopsy usually not warranted.
tract and manifest in children less than 8 years of Patients, usually females present in the 5th decade of life.25
age.25 Histopathologically, these are juvenile pilocytic These tumors are rare in children except in cases of NF-2. A
astrocytomas. Gliomas are associated with neurofibromatosis ‘tram-track’ configuration is often observed on axial contrast-
type 1 (NF-1) and bilateral disease is pathognomonic for enhanced CT or MRI because the nerve substance is spared.
NF-1.29 Malignant optic nerve gliomas are extremely rare On coronal images, this configuration appears similar to a
aggressive lesions, classified as anaplastic astrocytoma or ‘donut’ or ‘target sign’.25,30 Meningiomas may manifest as
glioblastoma multiforme on histology. They may occur fusiform or eccentric masses. On CT, associated hyperostosis
in adults and are not associated with NF-1. The imaging and intralesional calcification may be appreciated (Figure
appearance is characteristic so biopsy is rarely required.25 12). A primary optic nerve sheath meningioma may extend
MRI is the modality of choice, especially for assessing intracranially to involve the contralateral optic nerve.
involvement of the orbital apex, optic chiasm, optic tracts

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C) Peripheral Nerve Sheath Lesions in the orbit. Plexiform neurofibromas are the most common
type and are essentially pathognomonic for NF-1.25
Schwannoma
Like schwannomas, neurofibromas are commonly
Schwannomas (also called neurilemomas) are encapsulated, extraconal, owing to their frequent origin from branches
benign tumors arising from Schwann cells. They most of the trigeminal nerve.25 Plexiform neurofibromas
commonly arise from the branches of trigeminal nerve; appear as heterogeneously enhancing serpentine masses,
however, they may arise from any cranial, sympathetic or hyperintense on T2-weighted images giving ‘target sign’
parasympathetic nerve supplying the orbit.25 Two distinct and heterogeneous on T1-weighted images.33 The lesions
patterns are seen at microscopy- Antoni A pattern is cellular, may cross tissue planes and involve the periorbital region
composed of spindle cells that may form Verocay bodies and face. Their appearance is often compared with that
and Antoni B pattern is a loose arrangement of stellate cells of a “bag of worms.” Clinical and imaging features of
in a mucoid stroma. Both patterns often coexist in the same solitary neurofibroma are largely indistinguishable from
lesion.31 those of schwannoma and the distinction is often made
On imaging, schwannomas are typically located in the on histopathology. However, because of lack of capsule,
superior extraconal space, owing to their frequent origin solitary neurofibromas may be less well circumscribed than
from the frontal branch of the ophthalmic nerve.25 The lesions schwannoma. Cystic components and T2 heterogeneity
often abut orbital foramen, assuming a cone or dumbbell favor the diagnosis of schwannoma over neurofibroma.
shape. These are well circumscribed masses, isointense on Neurofibromas are the hallmark lesion of NF-1 and
T1, heterogeneously hyperintense on T2 weighted images, a schwannomas are more characteristic of NF-2.25 The primary
feature that differentiates it from the relatively homogeneous reason for attempting to distinguish between these lesions
venous malformation. This heterogeneity likely reflects the on imaging is that malignant transformation, although rare
mixed solid-cystic component and Antoni A and B patterns is relatively more common with neurofibromas.25
on microscopy. Both schwannoma and venous malformation
show progressive enhancement on DCE-MRI, contrast Malignant Peripheral Nerve Sheath lesions
spread pattern has been used to differentiate the two entities
in some studies with contrast enhancement beginning from Malignant peripheral nerve sheath tumors may arise de novo
a point in venous malformation in comparison to a wide or from preexisting peripheral nerve sheath tumors. Patients
area in schwannoma.32 with NF-1 carry a 10% lifetime risk of developing malignant
peripheral nerve sheath tumors, which most commonly
Neurofibroma arise from plexiform neurofibromas. Rapid growth and
soft-tissue or bone destruction should raise the suspicion of
Neurofibromas are benign unencapsulated peripheral nerve malignancy.25
tumors. Localized, diffuse, and plexiform forms may occur

Figure 13: : RETINOBLASTOMA IN A 3 YEAR OLD FEMALE WITH LEFT SIDED LEUKOCORIA- Axial NCCT image (a) depicts marked intraocular calcification in left
globe. T2W MR image (b) shows a hypointense (due to calcification) intraocular lesion involving the lens and intraorbital left optic nerve (arrowhead in b) with
resultant retinal detachment (arrow in b). The lesion along with the involved optic nerve appear hyperintense on axial diffusion weighted image (c) with signal

drop on corresponding ADC map (d) suggestive of diffusion restriction with a low mean ADC value.

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Figure 14 BILATERAL ORBITAL AND DURAL METASTASIS IN A 3 YEAR OLD MALE WITH NEUROBLASTOMA- Coronal CECT images in soft tissue (a) and bone

window (b) show homogeneously enhancing metastatic deposits in superior extraconal spaces of bilateral orbits, dural based deposits in bilateral frontal lobes,

associated permeative lytic destruction and spiculated periosteal reaction of the involved calvarium and bony orbital walls.

D) Primary Melanocytic Neoplasms The tumor is slightly hyperintense on T1W images,
Malignant uveal melanomas are the most common primary hypointense on T2W images compared to vitreous humor on
intraocular tumor in adults, their incidence being highest MRI with diffusion restriction on DWI. ADC values can be
in Caucasians. They mostly arise from the choroid.8 The used for monitoring treatment response in retinoblastoma34
diagnosis is usually made on ophthalmoscopy and USG, (Figure 13). Differential diagnosis include Coat’s disease,
cross-sectional imaging is necessary in case of opaque persistent primary hyperplastic vitreous and toxocariasis,
lens or significant subretinal effusion. Poor prognostic all of which usually lack calcifications. Retinopathy of
factors include age>60 years, large tumor size, anterior prematurity rarely shows calcifications, it may be bilateral
uveal location and heavy tumor pigmentation.25 Systemic and history of prematurity is usually present.8
metastases to liver, lungs and brain are common. CT shows
a well-circumscribed, hyperdense, mushroom-shaped mass F) Rhabdomyosarcoma (RMS)
with a broad choroidal base and marked post contrast RMS is the most common malignant mesenchymal tumor
enhancement. Calcification is rare. On MRI, the lesions show of childhood, seen between 5-10 years of age with slight
characteristic hyperintense signal on T1 and hypointense male predilection. The orbit is the most common location
signal on T2W MR images owing to their melanin content. in head and neck. RMS typically arises in the extraconal
Imaging differentials include choroidal hemangioma, space; however, intraconal extension may be seen.12 It is an
choroidal detachment, retinoblastoma and uveal metastases. aggressive tumor with infiltration into adjacent structures
Ocular melanomas show marked diffusion restriction with and hematogenous dissemination to lungs being common.
a low mean ADC value. FDG-PET CT has the potential to Histopathologically, it can be divided into embryonal,
detect recurrence, regional and distant metastases.8,25 pleomorphic, alveolar and botryoid subtypes. The alveolar
subtype is the most anaplastic variant.8 RMS appear
isodense to muscle on NCCT and usually show significant

E) Retinoblastoma post contrast enhancement. CT depicts the bony erosions

Retinoblastomas are the most common intraocular tumor well. It appears iso-intense to muscle on T1W images, hypo

of childhood, mostly seen in less than 5 years of age. They or hyperintense on T2W images and shows marked contrast

can be hereditary (40 %) or sporadic (60 %). Hereditary enhancement. Necrosis and calcification are uncommon.8,12

retinoblastomas are associated with early onset of disease The presence of unilateral, rapidly progressive proptosis

and ultrasound and MRI have recently been recommended in a child must always raise suspicion of RMS. PET CT/

for antenatal screening.8 About half of the patients present MRI is a valuable adjunct for grading and staging of RMS.

with leukocoria. 40% patients have bilateral disease.34 Differential diagnosis include hemangioma, orbital cellulitis,

Ophthalmoscopy and USG form the basis of initial lymphoma, Langerhans cell histiocytosis, metastasis from

diagnosis,with cross-sectional imaging mandatory to assess neuroblastoma etc.8

disease extent and prognosis. Trilateral Retinoblastoma refers G) Metastasis
to bilateral disease in association with a pinealoblastoma. Metastatic breast cancer is the most common type to
CECT demonstrates a markedly enhancing intraocular mass metastasize to the orbit, followed by metastatic prostate
with intratumoral calcification and necrosis. Calcification carcinoma, melanoma and lung cancer. In children, metastasis
is seen in about 90% cases.8 MRI brain should always from round cell tumors particularly neuroblastoma can be
be performed to determine extraocular and intracranial found (Figure 14). Intraocular metastases most frequently
extension as well as to rule out an associated pinealoblastoma. involve the choroid, with metastatic lung cancer being most

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DJO Vol. 32, No. 2, October-December 2021

commonly implicated.25 16. Siakallis LC, Uddin JM, Miszkiel KA. Imaging investigation
of thyroid eye disease. Ophthalmic Plastic & Reconstructive
H) Lid Tumors With Orbital Extension Surgery. 2018 Jul;34(4S):S41-51.

Common malignant neoplasms of the eyelid include 17. Lee EJ, Jung SL, Kim BS, Ahn KJ, Kim YJ, Jung AK et al.
MR Imaging of Orbital Inflammatory Pseudotumors with
squamous cell carcinoma, basal cell carcinoma, melanoma, Extraorbital Extension. Korean J Radiol. 2005 Jun;6(2):82-8.

sebaceous cell carcinoma, and lymphoma. These tumors are 18. Pakdaman MN, Sepahdari AR, Elkhamary SM. Orbital
inflammatory disease: Pictorial review and differential
often highly aggressive and show contiguous invasion of diagnosis. World J Radiol. 2014 Apr 28;6(4):106-15.

orbital structures.8 Conclusion 19. Ferreira T, Saraiva P, Genders S, Buchem M, Luyten G, Beenakker
J. CT and MR imaging of orbital inflammation. Neuroradiology.
Evaluation of orbital lesions requires a multimodality 2018 Dec;60(12):1253-66.

approach to balance the strengths and weaknesses of each 20. Tiegs-Heiden CA, Eckel LJ, Hunt CH, Diehn FE, Schwartz KM,
Kallmes DF et al. Immunoglobulin G4-related disease of the
modality. The use of clinical information and information orbit: imaging features in 27 patients. AJNR Am J Neuroradiol.
2014 Jul;35(7):1393-7.
obtained from imaging helps to obtain the best results.
21. Nguyen VD, Singh AK, Altmeyer WB, Tantiwongkosi
Precise description of lesion location, compartments B. Demystifying orbital emergencies: a pictorial review.
Radiographics. 2017 May;37(3):947-62.
involved, orbital apex, perineural and associated intracranial
22. Sepahdari A, Aakalu V, Kapur R, Michals E, Saran N, French
extension provides information beyond what can be seen A et al. MRI of Orbital Cellulitis and Orbital Abscess: The
Role of Diffusion-Weighted Imaging. Am J Roentgenol. 2009
at fundoscopy and facilitate appropriate management and Sep;193(3):W244-50.

prognostication. 23. Dhiman R, Devi S, Duraipandi K, Chandra P, Vanathi M, Tandon
R et al. Cysticercosis of the eye. Int J Ophthalmol. 2017;10(8):1319-
References 24.

1. Hande P, Talwar I. Multimodality imaging of the orbit. Indian J 24. Bodh SA, Kamal S, Kumar S, Goel R, Nagpal S, Aditya K. Orbital
Radiol Imaging. 2012 Jul;22(3):227–39. Cysticercosis. DJO. 2012 Dec;23(2):99-103.

2. Ben Simon GJ, Annunziata CC, Fink J, Villablanca P, McCann 25. Tailor TD, Gupta D, Dalley RW, Keene CD, Anzai Y. Orbital
JD, Goldberg RA. Rethinking orbital imaging: establishing neoplasms in adults: clinical, radiologic, and pathologic review.
guidelines for interpreting orbital imaging studies and Radiographics. 2013 Oct;33(6):1739-58.
evaluating their predictive value in patients with orbital tumors.
Ophthalmology. 2005 Dec;112(12):2196-207. 26. Priego G, Majos C, Climent F, Muntane A. Orbital lymphoma:
imaging features and differential diagnosis. Insights into
3. Nagaraju RM, Gurushankar G, Bhimarao, Kadakola B. imaging. 2012 Aug;3(4):337-44.
Efficacy of High Frequency Ultrasound in Localization and
Characterization of Orbital Lesions. J Clin Diagn Res. 2015 27. Clarós P, Choffor-Nchinda E, Lopez-Fortuny M, Zofia
Sep;9(9):TC01-6. Sobolewska A, Clarós A. Lacrimal gland pleomorphic adenoma:
a review of 52 cases, 15-year experience. Acta oto-laryngologica.
4. Vijayvargiya R, Shukla AK. Role of MRI in Evaluation of Orbital 2019 Jan;139(1):100-4.
Mass Lesions with Ultrasonographic and Histopathological
Correlation. Int J Med Res Prof. 2017 Mar;3(2):156-68. 28. Qin W, Chong R, Huang X, Liu M, Yin ZQ. Adenoid cystic
carcinoma of the lacrimal gland: CT and MRI findings. European
5. Thust SC, Miszkiel K, Davagnanam I. Orbit. Grainger & Allison's journal of ophthalmology. 2012 May;22(3):316-9.
Diagnostic Radiology. 6th ed. China: Elsevier Limited; 2015.
29. Avery RA, Fisher MJ, Liu GT. Optic pathway glio¬mas. J
6. Xu XQ, Qian W, Ma G, Hu H, Su GY, Liu H et al. Combined Neuroophthalmol 2011;31(3):269–278.
diffusion-weighted imaging and dynamic contrast-enhanced
MRI for differentiating radiologically indeterminate malignant 30. Becker M, Masterson K, Delavelle J, Viallon M, Vargas MI, Becker
from benign orbital masses. Clin Radiol. 2017 Oct;72(10):903. CD. Imaging of the optic nerve. European journal of radiology.
2010 May;74(2):299-313.
7. Sun B, Song L. Orbital malignant lesions in adults:
multiparametric MR imaging. Jpn J Radiol. 2017 Aug;35(8):454- 31. Pointdujour-Lim R, Lally SE, Shields JA, Eagle Jr RC, Shields
62. CL. Orbital schwannoma: radiographic and histopathologic
correlation in 15 cases. Ophthalmic Plastic & Reconstructive
8. Purohit BS, Vargas MI, Ailianou A, Merlini L, Poletti PA, Platon Surgery. 2018 Mar;34(2):162-7.
A et al. Orbital tumours and tumour-like lesions: exploring the
armamentarium of multiparametric imaging. Insights Imaging. 32. Tanaka A, Mihara F, Yoshiura T, Togao O, Kuwabara Y,
2016 Feb;7(1):43-68. Natori Y et al. Differentiation of Cavernous Hemangioma
from Schwannoma of the Orbit: A Dynamic MRI Study. Am J
9. Smoker WR, Gentry LR, Yee NK, Reede DL, Nerad JA. Vascular Roentgenol. 2004 Dec;183(6):1799-804.
Lesions of the Orbit: More than Meets the Eye. RadioGraphics.
2008 Jan;28(1):185-204. 33. Lim R, Jaramillo D, Poussaint TY, Chang Y, Korf B. Superficial
Neurofibroma: A Lesion with Unique MRI Characteristics in
10. Ansari SA, Mafee MF. Orbital cavernous hemangioma: role of Patients with Neurofibromatosis Type 1. Am J Roentgenol. 2005
imaging. Neuroimaging Clin N Am 2005;15:137–158. Mar;184(3):962-8.

11. Rootman J. Vascular malformations of the orbit: hemodynamic 34. Rauschecker AM, Patel CV, Yeom KW, Eisenhut CA, Gawande
concepts. Orbit 2003;22:103–120. RS, O’Brien JM et al. High-resolution MR imaging of the
orbit in patients with retinoblastoma. Radiographics. 2012
12. Khan SN, Sepahdari AR. Orbital masses: CT and MRI of Sep;32(5):1307-26.
common vascular lesions, benign tumors, and malignancies.
Saudi J Ophthalmol. 2012 Oct;26(4):373-83.

13. Shields JA, Shields CL. Orbital cysts of childhood—classification,
clinical features, and management. SurvOphthalmol. 2004
May;49(3):281-99.

14. Timalsina BR, Shrestha GB, Thapa M. Congenital Microphthalmia
with Intraorbital Cyst: A Rare Case Report. Case reports in
ophthalmological medicine. 2019 Dec; 2019:1-3.

15. Gonçalves AC, Gebrim EM, Monteiro ML. Imaging studies
for diagnosing Graves' orbitopathy and dysthyroid optic
neuropathy. Clinics (Sao Paulo). 2012 Nov;67(11):1327-34.

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DJO Vol. 32, No. 2, October-December 2021

Cite This Article as: Apoorva Sehgal, Alpana Manchanda,
Jyoti Kumar, Ruchi Goel, R K Saran, Ayush Jain. Cross-
Sectional Imaging In Ocular And Orbital Lesions – A
Review. Delhi J Ophthalmol 2021; 32 (2), 107-118.
Acknowledgments: Nil
Conflict of interest: None declared
Source of Funding: None
Date of Submission: 19 Mar 2021
Date of Acceptance: 16 Apr 2021

Address for correspondence
Apoorva Sehgal Senior Resident

Department of Radiodiagnosis,
Maulana Azad Medical College and
Lok Nayak Hospital, New Delhi,India
Email:[email protected]

Quick Response Code

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DJO Vol. 32, No. 2, October-December 2021

Instrument Focus

Corneal Topography: Sirius

Jigyasa Sahu

Department of Ophthalmology, Guru Nanak Eye Centre and Maulana Azad Medical College, New Delhi, India.

Abstract Present-day corneal tomography analysis has improved accuracy of corneal contour detection and is considered extremely
valuable in the diagnosis of subclinical keratoconus. Sirius (Costruzione Strumenti Oftalmici, Florence, Italy) based on a single
Scheimpflug camera with Placido imaging, is one of the commonly used corneal tomography systems. It creates 3-D imaging
of the anterior segment and provides details of the anterior and posterior corneal contour, pachymetry, anterior chamber
depth, and pupil diameter. This article will help the clinician understand different indices of topography scan and will guide the
practicing clinician by giving practical tips for decision-making in the diagnosis and management of keratoconus.

Delhi J Ophthalmol 2021;32;119-124; Doi http://dx.doi.org/10.7869/djo.731

Keywords: Corneal Tomography; Refractive Surgery Screening; Keratoconus

Introduction plane on which the object and image lie, the planes would
intersect at a point, producing better image resolution. There
Anterior segment imaging system has undergone many are two types of devices operating with either one camera
advances in the past years. Older machines based on (e.g., Pentacam, Sirius) or with two cameras (e.g., Galilei Dual
Placido principle were solely dependent on information Scheimpflug Analyzer). Two cameras allow measurements
acquired from anterior surface of the cornea, therefore to be averaged and minimize decentration, such as in the
referred to as “corneal topography” system. On the other case of involuntary eye movement, and theoretically provide
hand, Scheimpflug devices provide actual information more accurate measurements. Sirius uses a blue light (UV-
about both anterior and posterior surface of cornea and free) of 475 nm to illuminate the eye along with a rotating
hence are referred to as “corneal tomography” system.1 Scheimpflug camera which is a custom-designed digital
Scheimpflug based devices are - Pentacam (Oculus, charge-coupled device (CCD) with synchronous pixel
Wetzlar, Germany), Sirius (CSO Florence, Italy), Galilei sampling. There is a single rotating Scheimpflug camera
(Ziemer, Port, Switzerland) and TMS-5 (Tomey, Nagoya, based on Scheimpflug law that states “To get a higher depth
Japan).2 Sirius Scheimpflug analyzer is based on Placido of focus, movement of three planes is needed and picture
disc and a mono rotating Scheimpflug system for corneal plane, objective plane, and film plane need to intersect”. The
photography. All biometric measurements of the anterior machine has 22 Placido rings which enhance anterior surface
chamber are calculated using up to 100 high-resolution (HR) measurements, analyses>100 000 points, and cover 12mm
corneal sections. Measurement speed reduces effect of eye zone of cornea. Around 25 Scheimpflug images and 1 Placido
movement producing a high-quality accurate measurement. disc image are acquired in less than 1 sec. The machine
In addition to clinical diagnosis of the anterior segment, it is merges data by Arc-Step (Placido disk) reconstruction to
used in refractive and cataract surgery, IOL calculation and the ones by Scheimpflug image, taken at the same time by 2
meibography. Objective examinations provide an accurate different cameras. Integration of the two technologies allows
measurement of pupil diameter in scotopic, mesopic, and accurate measurement in elevations, curvature, and power
photopic conditions. terms for the entire cornea.

Principle

Corneal topography uses three of the following principles: The Sirius captures 21632 elevation points on front surface
Placido disc reflection, Scanning slit technology or and 16000 on the posterior surface covering 12mm of corneal
Scheimpflug photography. Placido disc is a device made diameter. The slit images captured by the rotating camera
of concentric rings drawn on a device of a different color are photographed from 0 to 180 degrees angles to avoid
(generally white rings on a black background). The first shadows from nose. The machine automatically corrects for
refracting surface of cornea (more accurately, the tear small eye movements. Scan is conducted in a dark room and
film –air interface and not epithelium) also acts as convex the patient is asked to fixate on the center of the machine.
mirror and reflects back light in a pattern dependent on the

corneal pattern. In Orbscan, 40 slits (20 each from nasal Interpretation of Sirius scan
and temporal side) are projected on the cornea to assess 240
points on each slit. The triangulation between the reference Detailed information about anterior segment parameters
slit beam surface and the reflected beam captured by the include the anterior as well as posterior corneal contour
camera can be used to analyse the anterior and posterior and elevation, pachymetry, astigmatism, pupil size, anterior
corneal curvature and the pachymetry. One limitation of slit- chamber depth, aberometric map, pupillography and
scanning topography is that the peripheral measurement of meibography. (Figure 1)

the cornea loses its accuracy because the object, light, and The details visualized on the Sirius map are discussed in
image planes are no longer parallel. This issue was addressed detail below-
by taking into account the Scheimpflug principle. First used 1. Patient information details
in photography, Scheimpflug noted that by extrapolating the The box on the top right corner (Figure 1: black star) contains

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DJO Vol. 32, No. 2, October-December 2021

Figure 1: A typical Sirius topography printout.. f. Other data- Iridocorneal angle, Horizontal anterior
chamber diameter which is measured as the distance
information about the patient which includes name of between vertices of iridocorneal angles, lens rise and corneal
patient, examined eye, identification code, date of scan and volume are also mentioned in summary indices.
time, and date of birth.
4. Keratometry readings (Figure 1: b)-This section mentions
2. Acquisition Quality steep and flat K readings, average keratometry, and effective
The acquisition quality of the scan (Figure 1:black arrow) cylinder in 3mm, 5mm, and 7mm zone on anterior and
is given by the amount of coverage in terms of percentage posterior surface.
of coverage of scheimpflug camera (SC) and percentage of
placido (P) coverage. The centration is also mentioned in 5. Shape indices (Figure 1: c)- Parameters that define the
percentage. asphero-toric surface which best approximates samples
of the measured corneal surface within the chosen zone.
3. Summary indices (Figure 1: a) Consists of steep radius of curvature (rs), flat radius of
a. HVID (Horizontal visible iris diameter) Indicates curvature (rf), asphericity, and RMS/area for different pupil
horizontal limbus size (in mm) and is derived from the diameters and anterior and posterior surfaces.
keratoscopic image rf: Flat Radius of curvature- This is apical radius (in mm or
in D) of the flattest meridian of asphero-toric surface which
b. Pupil (topographic) Diameter of pupil as well as best approximates measured surface within the chosen
coordinates of pupil center location; x,y diameter.
rs: Steep Radius of curvature- This is apical radius (in mm or
c. Thinnest location-The x and y coordinates of the thinnest in D) of the steepest meridian of asphero-toric surface which
corneal location on the pachymetry map are mentioned with best approximates the measured surface within the chosen
thickness. diameter.
RMS (Root Mean Square)- This represents deviation of
d. Apex- Indicates the value and location of steepest point in surface being examined from the asphero-toric best-fit
the tangential map. Location and value of corneal thickness surface. The higher the RMS, the more irregular the corneal
for this point are shown.. surface.

e. Anterior Chamber- It mentions central corneal thickness, 6. Refractive analysis (Figure 1: d)- It is calculated from
aqueous depth and total anterior chamber volume. corneal wavefront related to an entrance pupil located in
the position of patient’s pupil. The Mean Pupil Power is
equivalent corneal power (in diopters). Cyl being corneal
cylinder (in diopters). LSA being corneal Longitudinal
Spherical Aberration (in diopters).

7. Keratoconus screening combines the topographic indices
of Sirius and employs an algorithm for classification as
normal, keratoconus, suspect keratoconus, and abnormal.

8. Topographic indices of Sirius (Figure 1: e)
1. Root mean square (RMS) is calculated as deviation
in regularity/aberrations (characterized rf, rs, asphericity,
and axis) of the corneal surface being examined from the
best fit asphero-toric surface. RMS/A is the root mean square
per area of cornea being examined. Low RMS in the area
signifies that the surface of the cornea is regular and high
values denote irregular corneal surfaces. RMSf/A (μm/mm2)
calculated on front or anterior surface of the cornea. Cut-off
values for keratoconus suspect is 0.088 and for keratoconus
is 0.13. RMSb/A (μm/mm2) calculated on back surface of the
cornea. Cut-off values for keratoconus suspect is 0.212 and
for keratoconus is 0.269.3

2. Symmetry index of curvature It is defined as
difference of mean anterior tangential curvature (in
diopters) of two circular zones centered on the vertical axis
in inferior and superior hemispheres. The two circular zones
are centered in (x = 0 mm, y = ±1.5 mm) and their radius is

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DJO Vol. 32, No. 2, October-December 2021

1.5 mm. SIf is an index which measures vertical asymmetry: irregularities. It is also useful for determining morphologic
positive values indicate an inferior hemisphere steeper patterns of the cone in ectatic corneal disorders. (Figure 3
than superior one, vice versa negative values indicate a showing different patterns on curvature maps). It also
superior hemisphere steeper than the inferior one. SIb is also highlights peripheral corneal irregularities.
expressed in diopters.
Steep areas are denoted by hot colours (red and orange); flat
3. Keratoconus Vertex front and back (KVf and KVb)- areas by cold colours (green and blue). Red segments signify
Anterior & Posterior keratoconus vertex: Highest point of steep meridians and blue segments signify flat meridians.
ectasia on anterior and posterior elevation maps of anterior The normal pattern is symmetric bowtie (SB). Normally, the
and posterior corneal surface respectively. inferior (I) point has a higher value than the superior (S) one,
and the I-S difference should be < 1.5 D. The superior point
4. Baiocchi-Calossi-Versaci front and back index may rarely have a higher value than the inferior one; in this
(BCVf) and (BCVb) evaluates the presence of an ectasia case, the S-I difference should be < 2.5 D.
through analysis of the coma and trefoil components of
Zernike's decomposition of elevations in the zones where 3. Pachymetry Map: It can be in the form of-
keratoconus statistically arises. Based on the presumption
that ectasia statistically develops in a preferential direction
(infero-temporal) and it mainly manifests in coma, trefoil,
spherical aberration. The index BCV or vectorial BCV is the
vectorial sum of BCVf and BCVb.3

Maps

1. Colour coding : Topographic maps are color coded
in three kinds of colors. Hot colors (red,orange) signify
steep portion, neutral colors (green), and cooler colors (blue,
purple) which signify flat portion. There are two kinds of
color scales. (Figure 2)

ABSOLUTE SCALE - It has same dioptric step power on Figure 2: Color coding of a keratometry map
every map and allows direct comparison of 2 different maps.
Its advantage is that it allows rapid pattern recognition of 1. Five values: A central value representing central
topographic maps. However, since there are large steps, they thickness, and four values around the 5 mm central
do not show subtle changes. circle.

Normalized Scale- In this diopteric power steps are based 2. Distributed values all over the cornea: The distributed
on the patient's cornea. Since there are small steps, it shows pattern is more important and valuable.
more detailed changes. Its disadvantage being that 2 different
maps cannot be compared directly. The main elements are three locations that appear on
main page: the thinnest location, the corneal apex and
2. Curvature Map: pupil center.
The axial/sagittal map: It is routinely used and shows areas
of flattening and steepening. Abnormal shapes can be
Tangential map: This map helps in describing corneal a. Horizontal displacement of the thinnest location
b. Dome shape. The thinnest location is vertically displaced
c. Bell shape. There is a thin band in inferior part of

the cornea. It is a hallmark for Pellucid Marginal

Table 1: Differences between different topography systems and few salient points.

Orbscan Pentacam Sirius
Based on a combination of Placido rings and scheimpflug
Based on slit scanning Based on scheimpflug camera imaging
technology. camera imaging
Gives true elevation points as elevation data is Also gives true elevation points.
Does not give true more accurately given by 3D analysis. Reference
elevation points. Employs an internal algorithm for classification of patients into
best fit sphere is taken for comparison normal, suspect, abnormal or keratoconus compatible.
Does not incorporate
special indices for Gives detailed Belin Ambrosio enhanced ectasia Allows more accurate detection of anterior surface parameters
display for easy detection of keratoconus. because of placido incorporation with scheimpflug camera
keratoconus detection.
Also gives special thickness profiles unique to
pentacam

Obtains corneal Obtains corneal thickness from 8-10mm of Obtains full corneal thickness
thickness from 8-10mm cornea

of cornea

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DJO Vol. 32, No. 2, October-December 2021

Degeneration (PMD) pachymetry map and corneal altimetric data, Sirius helps in
d. Keratoglobus. A generalized thinning reaches the corneal intrastromal ring segment placement for correction
of refractive errors and keratoconic corneas. (Figure 4)
limbus .
3. Glaucoma screening- Sirius also gives iridocorneal
4. Elevation Maps: Described with respect to reference angle measurements and pachymetry data, which are useful
body types .4 parameters for glaucoma specialists.

a. Toric Ellipsoid Body - There are two perpendicular axes, 4. Pupillography- Sirius has inbuilt pupillography
one is steeper than the other. Its advantage is the ability measurement software. The measurement of pupil can be
to study real course of astigmatic corneal surfaces. done in scotopic, mesopic and photopic conditions and even
in dynamic mode. Knowing the center and diameter of the
b. Spherical Body -It is better than previous bodies in pupil is essential for refractive procedures.
highlighting corneal irregularities since the normal
cornea has a toric ellipsoid shape. 5. Intraocular lens(IOL) calculation module- This is
based on ray tracing techniques regardless of the state of
The normal shape of a cornea with regular astigmatism is the cornea (untreated or treated for refractive error) and
symmetric hourglass. Vertical steeper meridians are shown provides IOL power calculation for spherical or toric power
as depressions negative value. of IOLs.
Abnormal shapes are Skewed hourglass which can normally
also be seen with a large Kappa angle and misalignment 6. Corneal aberrometry analysis- Offers a complete
during capture, otherwise it indicates an abnormal distorted overview of the corneal aberrations. It is possible to select
cornea. Tongue-like extension and irregular hourglass which the contribution of anterior, posterior, or total cornea for
are seen in abnormally distorted corneas. Isolated island is different pupil diameters. The Optical Path Difference (OPD)/
encountered in abnormally distorted corneas with central or Wavefront error (WFE) maps and the visual simulations
paracentral protrusion. (point spread function (PSF)/ modulation transfer function
(MTF)/ image convolution with optotype) can help clinicians
Uses of Sirius topography in understanding patients' visual problems. The OPD
specifically detects the total refractive error (in diopters) in
1. Keratoconus and other ectatic disorder screening- the eye, including aberrations in the cornea, lens and other
With its keratoconus screening indices, Sirius topography structures.
classifies candidates into normal, suspects, keratoconus, or 7. Tear film analysis- because of the incorporation of
abnormal. This feature helps even novice clinicians not to
miss forme fruste or pre-clinical cases. The comparison of
sirius with other topography systems is discussed in
(Table 1).
2. Intrastromal rings placement- On the basis of

Figure 3: Various patterns as seen on curvature/keratometry maps.

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DJO Vol. 32, No. 2, October-December 2021

Figure 4: Intracorneal ring segment planning in a keratoconic cornea with the help of Sirius.

E-ISSN: 2454-2784  P-ISSN: 0972-0200 Figure 5: Meibomian gland analysis in Sirius. Delhi Journal of Ophthalmology

123

DJO Vol. 32, No. 2, October-December 2021

Placido discs in Sirius, it allows the measurement of Non- Cite This Article as: Jigyasa Sahu. Corneal Topography:
invasive tear break up time (NI-TBUT). Sirius Delhi J Ophthalmol 2021; 32 (2), 119-124.
Acknowledgments: Nil
8. Meibography- meibomian glands can be viewed Conflict of interest: None declared
in infrared light and after the image is captured, software Source of Funding: None
can be used to measure the area of gland dropout and the Date of Submission: 03 Mar 2020
condition of glands can be assessed. (Figure 5) Date of Acceptance: 13 Mar 2020

Conclusion Address for correspondence

The Sirius is a new topographic device based on the principles Jigyasa Sahu
of Scheimpflug photography. It consists of a combination
of single rotating Scheimpflug camera and a Placido disk, MBBS, MS (Ophtha), FICO, MRCS(Ed) Ophth
and allows full analysis of the topography and elevation of Senior Resident Ophthalmology
the anterior and posterior corneal surface and full corneal
thickness. Additionally abberometry data and non invasive Department of Ophthalmology,
meibomian gland assessment are advantageous. Guru Nanak Eye Centre and Maulana
Azad Medical College, New Delhi, India
References [email protected]

1. Mazen Sinjab. Reading Pentacam Topography (Basics and Case Quick Response Code
Study Series). 2nd ed. JAYPEE; 6,9-11,20-48.

2. Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk
assessment for ectasia after corneal refractive surgery.
Ophthalmology. 2008;115(1):37–50.

3. Doctor Kumar, Vunnava Krishna Poojita, Shroff Rushad et al.
Simplifying and understanding various topographic indices
for keratoconus using Scheimpflug based topographers, Indian
Journal of Ophthalmology, 2020, 68(12):2732-2743. doi: 10.4103/
ijo.IJO_2111_20

4. Upadhyaya A, Khan S, Sahay P, Goel S, Kumawat DPentacam –
A Corneal Tomography System.DJO 2020;31:90-95

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