Wet Age-Related Macular Degeneration

Published on 09/05/2015 by admin

Filed under Opthalmology

Last modified 09/05/2015

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8.1

Wet Age-Related Macular Degeneration

Introduction:

Wet (neovascular, exudative) age-related macular degeneration (AMD) is a leading cause for severe vision loss in the elderly population of developed societies. It represents approximately 10% of all AMD cases.

Clinical Features:

The distinguishing feature is the presence of choroidal neovascularization (CNV) in the setting of a patient over the age of 60 years, virtually always with some manifestations of concurrent or pre-existing dry AMD (drusen, geographic atrophy, RPE abnormalities). CNV results in leakage of fluid and/or hemorrhage within or underneath the neurosenory retina, and/or underneath the RPE detachment visible on examination. On the basis of fluorescein angiography, CNV can be subtyped into classic, occult, or mixed. An anatomic classification divides CNV into type 1 (below the RPE), type 2 (above the RPE) or type 3 (retinal angiomatosis proliferation [RAP]). In the presence of a large pigment epithelial detachment (PED), a tear of the RPE can occur. End-stage wet AMD may results in disciform scar formation.

OCT Features:

The most characteristic findings on OCT in wet AMD are the presence of an irregularly shaped PED with adjacent subretinal hemorrhage and subretinal fluid. An irregularly shaped PED is in contrast to a more smooth-shaped PED typically seen in central serous chorioretinopathy. In wet AMD, especially in type 2 CNV, there is frequently a visible interruption in the RPE layer. There are various key features of wet AMD that can be uniquely identified based on their OCT appearance:

▶ Classic CNV: a classic, or type 2, CNV is present when the abnormal neovascular tissue penetrates the RPE/Bruch’s membrane complex and is present in the subretinal space (Figs 8.1.1 and 8.1.2).

Figure 8.1.1 OCT of a classic choroidal neovascularization (far right). Corresponding thickness map (left) and infrared image (middle) are shown.

Figure 8.1.2 Fluorescein angiography (corresponding to Figure 8.1.1) shows a well-defined region of hyperfluorescence that is visible in the early frames and grows in intensity in the late frames, but does not enlarge in size, characteristic of a classic choroidal neovascularization (red circle).

▶ Occult CNV: an occult, or type 1, CNV is present when the abnormal neovascular tissue remains underneath the RPE (Figs 8.1.3 and 8.1.4).