In vivo imaging of foveal sparing in geographic atrophy secondary to age-related macular degeneration.

Purpose: To investigate morphologic alterations in geographic atrophy caused by age-related macular degeneration (AMD) in the presence of foveal sparing using high-resolution in vivo imaging.
Methods: Simultaneous spectral domain optical coherence tomography (SD-OCT, 870 nm, 40,000 A-scans/s) and confocal scanning laser ophthalmoscopy (cSLO; fundus autofluorescence; excitation, 488 nm; emission, 500-700 nm) were performed in 18 eyes with geographic atrophy and foveal sparing using a combined instrument. Anatomic layers were evaluated, and retinal thickness in the fovea and the peripheral macula were measured and compared with those in controls of similar age.
Results: Fundus autofluorescence imaging showed an inhomogeneously reduced signal at the residual foveal island. SD-OCT scans disclosed mitigation of the foveal pit in the absence of extracellular fluid accumulation and an increased mean central retinal thickness of 248 +/- 28 microm compared with 225 +/- 12 microm in control eyes (P = 0.005). No difference in retinal thickness in the peripheral macula was observed (245 +/- 16 vs. 253 +/- 11 microm; P = 0.6). Subanalysis revealed marked appearance of swelling and widening of visible structures at the central outer nuclear layer (153 +/- 22 microm vs. 127 +/- 12 microm; P = 0.003). Below the external limiting membrane, a broad band of irregular high reflectivity was detected instead of the normal three separate reflective bands.
Conclusions: Thickening at the foveal site may reflect a pre-apoptotic stage of neuronal cellular elements indicating imminent atrophy. Limited structure-function correlation found in our study suggests that future therapeutic intervention may be beneficial in only a subset of AMD patients with foveal sparing.