In vivo quantification of retinal changes associated with drusen in age-related macular degeneration

Drusen alters retinal architecture in early age-related macular degeneration (AMD). However, abnormalities also may exist in drusen-free areas of the AMD retina. This study examines retinal thickness above drusen relative to drusen-free areas in the same patient and a normal population.

Patients with early to intermediate AMD (n = 122) or no disease (n = 30) were examined at the Center for Eye Health. Spectral domain optical coherence tomography (SD-OCT) scans through single, isolated druse (n = 125) or confluent drusen (n = 54) were obtained. The thickness of individual retinal layers was measured above the druse and in a drusen-free area, 150 μm from the drusen edge.

Intraeye comparisons found total retinal thickness above drusen was 16 ± 0.6% less than drusen-free areas. Thinning was mostly in the retinal pigment epithelium/photoreceptor layer (32 ± 1% reduction) and the outer nuclear layer (22 ± 1% reduction). Confluent drusen showed similar thinning of the outer retina as well as inner retina loss (5%). Thinning was strongly correlated with drusen height, but only modestly correlated with drusen width. When compared to the normal population, retinal thickness above drusen and drusen-free areas were significantly reduced.

We confirm outer retina thinning above drusen in early/intermediate AMD compared to drusen-free areas in the same retina or a normal population. Interestingly, drusen-free areas in AMD patients were not the same as control patients suggesting "normal" areas of the AMD retina are abnormal. The strong correlation between retinal thinning and drusen height, rather than width, suggests current grading systems for AMD may need refinement.