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Anterior Segment OCTWhat does it have to offer?

Engy M Mostafa MD, PHD

Assistant Professor of Ophthalmology

Sohag University

EOS 2018

No financial interest to disclose

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UBMSL-OCTAS-OCTScheimflugTopography

USOpticalOpticalOpticalImage Source

SupineSittingSittingSittingPosition

YesNoNoNoContact

HighMediumLowLowOperator Skill

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UBMSL-OCTAS-OCTScheimpflugTpography

Features

NoNoNoYesTopography

NoNoNoYesIOP correction

NoNoNoYesLens densimetry

NoNoNoYesWavefrontanalysis

Imaging capabilitiesUBMSL-OCTAS-OCTScheimpflug

topography

25m<25m18mN/AOptical axial resolution

YesYesYesYesPachymetry

YesYesYesNoAngle Visualization

YesYesYesYesAngle estimation

YesNoNoNoCiliry sulcusvisible

YesYesYesNoOpaquemedia

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Why do we need AS-OCT?

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Quantitative

Qualitative QuantitativeQualitativeDiagnosticProperative

Postoperative

Image through an opaque cornea

Cannot Visualize deeply pigmented lesions.The posterior boundary of heavily-pigmentedlesions greater then 2.5 mm becomes blurred.

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Why Do I Image the Cornea?Deeper look

Cornea Layers

Air-tear interface Tear film EpitheliumEndotheliumStroma

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Measure Corneal Thickness

OCT measurements of Central corneal

thickness have shown good correlation with

ultrasound pachymetry.

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A thickness of 104 µm which the ultrasound

pachymeter did not measure, as it was below

its lower measurement limit.

Reis-Bucklers Dystrophy

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Granular Dystrophy

Is it Terrien’s marginal degeneration???

The absence of peripheral thinning typical of

this entity, and a diagnosis of primary lipid

degeneration

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Peter’s Anomaly

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Pellucid Mardinal Degeneration

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Epithelial thickness map

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(1) I-S (the difference between the average

thickness of the inferior octant and that of

the superior octant) >31 μm

(2) IT-SN (the difference between the

inferotemporal octant and the superonasal

octant) >48 μm

(3) Minimum <492 μm

(4) Minimum-maximum <−63 μm

(5) The thinnest region of the cornea is located

outside the central 2 mm area.

LASIK Flap Thickness

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Diffuse Lamellar Keratopathy

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Epithelial Ingrowth

Interface Fluid Syndrome

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Intracorneal Rings

After Corneal Crosslinking

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Presbyopia Implant

The implant depth averaged 166 μm depth.

The opaque implant caused shadowing

underneath.

DALK

Double Chamber

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Corneal Trauma

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Tear Meniscus

Tear Meniscus

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Anterior Chamber Depth

Why measure it?

• Phakic IOL implantation.

• Detect occludable angles

• Important for IOL calculation as in Theoretical

prediction formula: Haigis

• 0.05 mm ACD error = 0.03 diopter IOL power

error

Phakic IOL

Before phakic IOL surgery it is mandatory

1. AC depth : endothelium safety

2. Crytalline lens rise & IOL vault :to respect

the lens

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Crystalline Lens Rise

A CLR of a 600 or more is a contraindication

for doing a Phakic implantation

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Phakic IOL

Good clearance of the sulcus-based over the

natural crystalline lens.

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Iridocorneal Angle

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•Van Herick technique

assess peripheral ACD in relation to corneal

thickness.

Gonioscopy

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Grading of the angle is subjective.

Gonioscopy has low sensitivity (68.3%)

and high specificity (96.6%).

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Accurate localization of the scleral spur

(reference point) for all the other

quantitative measurements.

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AOD 500

Perpendicular distance measured from the

trabecular meshwork at 500 µm anterior to

the scleral spur to the anterior iris surface.

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TISA 500

Anterior: AOD 500

Posterior: line drawn from

the scleral spur

perpendicular to the plane of

the inner scleral wall to the

opposing iris

Superior: inner corneoscleral

wall

Inferior: by the iris surface.

TIA 500

An angle measured with the

apex in the iris recess and

the arms of the angle

passing through a point on

the trabecular meshwork

500 µm from the scleral

spur and the point on the

iris perpendicularly

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Need multiple scans all around limbus for full

analysis

Angle measurement is influenced by patient’s

age and gender, direction of gaze,

accommodation, room illumination, meridians

scanned.

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Light affects angle configuration

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Complete Angle Closure Glaucoma

Angle closure glaucoma

cornea is noticeably edematous

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Pigmentary Glaucoma

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Peripheral Iridotomy

Successful Bleb

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Failed Bleb

Cystic Bleb

Singh et al. Imaging of Trabeculectomy Blebs Using Anterior Segment Optical Coherence

TomographyOphthalmology 2007;114:47–53

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A cyclodialysis cleft.Disinsertion of the ciliary body from the scleralspur and an associated ciliary body detachment.

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Posterior polar cataract demonstrating an

intact posterior capsule .

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Pre and post Cataract Extraction

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Tilted posterior chamber intraocular lens pushing iris forward

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Corneal-conjunctivalintraepithelial squamous

neoplasia

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Pterygium with

corneal opacity

beneath

Pterygium with

clear cornea

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Pseudopterygium Pinguecula

Conjunctival nevus

cysts and the well-defined posterior limit of

the lesion which are signs of its benign nature

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Iris Cyst

the cyst is anterior to the pigment epithelium

of the iris, it can be visualized.

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Iridoschesis

Accomodationchanges ACD depth by 30 µm for every

1 D

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What is real and what is artifact?

• Corneal Reflex

• Inverted Image (in Spectral Domain)

• Shadowing

• Image Averaging

• Algorithm Failure

–Pachymetry: Corneal surface lines

–Pachymetry: Lids

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Averaging

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Thank You

Seeing is Believing