Age-related macular degeneration – exudative

Description

Exudative age-related macular degeneration (AMD) refers to the disease process in AMD whereby choroidal neovascularization (CNV) develops and grows through defects in Bruch’s membrane into the sub-RPE or subretinal spaces. CNV carries the likelihood of leakage, leading to RPE detachment, subretinal hemorrhage or lipid, and ultimately disciform scarring and central blindness. For further description, see Age-relatedmaculardegeneration-classification.

Symptoms

Exudative AMD may cause profound central visual impairment.

Signs and classification

Exudative AMD was classified by the Age Related Eye Disease Study (AREDS) research group as levels 4 and 5 in their classification for AMD:

4. Advanced: choroidalneovascularization, other exudativemaculopathy, or geographic atrophicmaculopathy in one eye but not theother. These forms of AMD carry a highrisk of sudden, severe, central visionloss.
5. The most severe form of AMD isbilateral advanced AMD. In more than 40 per cent of patients with exudative AMD, the condition becomes bilateral within 5 years.

Prevalence

While AMD is the leading cause of visual loss in the developed world, fortunately only 10-15 per cent of patients develop the exudative form of the condition.

Significance

Exudative AMD can lead to profound visual loss due to hemorrhaging and

fibrous tractional sequelae. This form of the condition is responsible for up to 90 per cent of the associated severe visual loss in AMD.

Differential diagnosis

Vascular occlusive disease; diabetic retinopathy.

Management

Refractive correction or low-vision aids may be indicated (see Age-related macular degeneration – dry). Currently, there are no available therapies for AMD that are proven to restore the patient’s visual acuity. However, some strategies are designed to reduce the risk of progression.

Additional tests Fluorescein angiography is used to diagnose CNV and to direct treatment. The composition of a CNV lesion is classified according to the fluorescein angiography appearance as either classic (showing a well demarcated hyperfluorescence in the early phase) or occult (poorly demarcated boundaries with late progressive hyperfluorescence).
Indocyanine green (ICG) angiography is a technique that displays the choroidal
rather than the retinal circulation, and may further assist the retinal specialist in localizing the lesion.

Laser treatment The two establishedtreatments that may stabilize vision and limit severe visual loss in patients with CNV are argon laser photocoagulation and, more recently, verteporfin photodynamic treatment (PDT). Argon laser treatment is used mainly for extrafoveal CNV, as treatment of foveal lesions adversely affects vision. The Macular Photocoagulation Study (MPS) showed a benefit of argon laser treatment for extrafoveal lesions, particularly in eyes with poorer initial visual acuity and smaller lesions. Verteporfin PDT allows treatment at the fovea, increasing the proportion of

patients eligible for treatment to 25-40 per cent. PDT has been shown significantly to decrease visual loss in patients with predominantly classic CNV in the macular area. However, even with laser treatment, there is a high risk of the recurrence of membrane growth and need for retreatment.

Injection Exudative AMD may also be amenable to treatment with drugs that inhibit vascular endothelial growth factor. Anecortave acetate is delivered by periocular injection, and pegaptanib sodium (Macugen) is an intraocular injection, requiring repeated doses. Most recently Ranibizumab (Lucentis) and Bevacizumab (Avastin) have produced improved vision in some patients.