Interpreting an OCT in a patient with a suspected Choroidal Neovascular Membrane (CNV)

- CE credits 3 hours
- COPE code 59397-PD / 116190
- Available until Sep 14, 2021

Introduction

In this Optocase you will be taught how to critically interpret OCTs in a series of patients who presented to our retinal service for assessment of choroidal neovascularization

Case 1

An 85-year-old woman presents with a 2-month history of vision loss. You obtain an OCT.

What abnormalities are noted on the OCT?

The presence of an epiretinal membrane

An epiretinal membrane can be seen in many patients with AMD, but there is no association (both are simply common lesions seen in the elderly). If located, it is seen on the surface of the retina. It may or may not be associated with retinal distortion and macular hole formation.
Hyperreflectivity consistent with exudation

Exudate due to lipoprotenacous material depositing in the retina is very hyperreflective and may be associated with deeper retinal shadowing. This can uncommonly be seen in patients with CNV, but is more commonly seen in patients with diabetic macular edema and retinal vein occlusion.
Choroidal neovascurization

Correct

There is the presence of a thin hyperreflective band anterior to the RPE. This represents a classic CNV (demonstrated on angiography).
A retinal artery occlusion

In a patient with retinal artery occlusion (in the acute phase), there is the presence of inner retinal hyperreflectivity, a middle limiting membrane and deeper retinal shadowing.

Introduction

Before we review this and the other remaining cases, let us review a normal OCT. In the image below, can you identify the following layers:

posterior vitreous face,nerve fiber layer (NFL)
ganglion cell layer (GC)
inner plexiform layer (IPL)
inner nuclear layer (INL)
outer plexiform layer (OPL)
external limiting membrane (ELM)
ellipsoidzone (EZ)
cone outer segment terminal line (COST)
retinal pigment epithelium (RPE)
choriocapillaris (CC)
larger chrodoidal vessels and the sclera

This labeled diagram shows the important retinal layers. Here are some important points to remember:

The posterior vitreous may or may not be visible; if it is detached it may be visible. It may be partially or fully detached. The vitreous may also be more opaque in the setting of a vitreous hemorrhage.
The internal limiting membrane (ILM) is a thin hyperreflective line located at the anterior retina.
The nerve fibre layer (NFL) is a hyperreflective, relatively thick layer located just below the ILM. It gets progressively thicker the as the ganglion cell axons make a right angle turn to exit the eye through the optic nerve (here to the left of the image).
The ganglion cell layer (GC) is a darker layer that lies immediately below the NFL.
The inner plexiform layer (IPL) is a hyperreflective layer that separates the darker (hyporeflective) inner nuclear layer (INL) the GC layer.
The outer plexiform layer (OPL) is a hyperreflective layer separating the inner nuclear from the outer nuclear layer (ONL).
The outer nuclear layer (ONL) is a very thick and hyporeflective layer.
The external limiting membrane (ELM) is a thin hyperreflective layer.
The ellipsoid zone (EZ) – and formerly referred to as the inner/outer segment (IS/OS) junction appears as a thicker white line.
The thin line deep to the EZ is the COST line and represents the cone outer segment terminals. The dark line between the EZ and COST represents the photoreceptor outer segments (POS).
Deep to the COST is the retinal pigment epithelium (RPE). Bruch's membrane may or may not be visible deep to the RPE.
The choriocapillaris (CC) is seen as a vascularity in the inner choroid and the larger choroidal vessels as hyporeflective.
The sclera appears as a hyperreflective line posterior to the choroid.

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