Background: Subfoveal neovascular membranes cause significant visual loss in age-related macular degeneration (AMD) and the ocular histoplasmosis syndrome. The frequency of post-laser treatment persistence or recurrence of subfoveal membranes in AMD is as high as 51%. The reason for the high incidence of failure after laser treatment is unknown. The authors performed a histopathologic study of subfoveal membranes to determine the distribution of blood vessels within the neovascular complex, and to see if the blood vessel pattern would provide insight into the reason for laser treatment failure.
Methods: The authors used light microscopy to examine serial sections of subfoveal membranes from six patients (4 with AMD, 2 with the ocular histoplasmosis syndrome). The data from this examination were used to create detailed two-dimensional vascular maps of each membrane.
Results: The authors found that subfoveal membranes from patients with AMD and the ocular histoplasmosis syndrome, whether occurring de novo or after laser treatment, have a nonuniform distribution of blood vessels, and that large areas which include the membrane margin may be avascular.
Conclusions: Using current laser treatment protocols, it is likely that avascular or poorly perfused peripheral areas of the neovascular complex would be left untreated after laser photocoagulation. Partial treatment of the neovascular complex may contribute to the high rate of post-laser treatment persistence or recurrence of subfoveal membranes.