Choroidal Neovascular Membranes/Subretinal neovascular membranes
Choroidal neovascular membranes (CNVM) can be described based on its location relative to the fovea, location relative to the retinal pigment epithelium, and fluorescein angiography findings.
Location relative to the fovea:
Subfoveal (underneath the fovea)
Juxtafoveal (1-199 microns from the fovea)
Extrafoveal (behind 200 microns from the fovea)
Location relative to the retinal pigment epithelium:
Type 1 CNVM appears beneath the RPE layer and appear as a fibrovascular or hemorrhagic pigment epithelial detachment.
Type 2 CNVM appears above the RPE layer and adjacent SRF leakage.
Type 3 (RAP)
Fluorescein angiography findings:
Classic appears above the RPE layer and adjacent SRF leakage.
Occult appears beneath the RPE layer and appear as a fibrovascular or hemorrhagic pigment epithelial detachment.
Figure 1. Classic/Type 2 CNVM located above the RPE with SRF adjacent to the lesion. A few exudates are visible on the nasal side of the lesion.
Figure 2. Fibrovascular pigment epithelial detachment secondary to a CNVM. Hyper-reflective material is visible in the PED. Type 1.
Figure 3. Fibrovascular pigment epithelial detachment secondary to a CNVM. Small amount of SRF is visible adjacent to the CNVM. Type 1.
Figure 4. CNVM in false color code. Subretinal fluid and intraretnal fluid is visible. When the CNVM leaks it will start in the subretinal space and may leak into the intraretinal layers.
Other types of occult CNVM includes retinal angiomatous proliferation (RAP) and polypoidal choroidal vasculopathy (PCV).
Retinal angiomatous proliferation (RAP)
RAP is described as type 3 CNVM. RAP involves 3 stages. Stage 1 consist of intraretinal neovascularization and as the intraretinal neovascularization grows it extends posteriorly forming stage II subretinal neovascularization. Finally, in stage III the condition develops into a vascularized PED.
Polypoidal choroidal vasculopathy (PCV)
PCV is a the condition that generally affects darker pigmented individuals and has a higher incidence involving Asians and African Americans. The condition is commonly misdignosed as exudative age-related macular degeneration. The etiology is not well understood but it has been proposed that there are abnormal choroidal vasculature with dilation and aneurysmal formation. Patients will present with subretinal, vascular lesions associated with serous and hemorrhagic PEDs around the peripapillary area.
ICGA is standard for diagnosis of polypoidal lesions. Treatment includes combination therapy of photodynamic therapy (PDT) and anti-VEGF therapy.
For more information on treatment read the EVEREST trial.
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