To assess changes in outer retinal layer (ORL) thickness before the development of exudative macular neovascularization (MNV) in eyes with age-related macular degeneration.

Retrospective observational case series.

Eyes with age-related macular degeneration that eventually developed exudative MNV followed with sequential optical coherence tomography for ≥2 years before the exudation occurred were enrolled. The ORL thickness was automatically calculated by the optical coherence tomography software for each sector of the early treatment diabetic retinopathy study map at each follow-up visit. The ORL thickness change from baseline to the day when the exudative MNV developed was compared between sectors that eventually developed exudative MNV and those that did not.

Forty-seven eyes (47 patients) were included. At baseline (24 ± 3 months before exudative MNV), mean (standard deviation) ORL thickness of sectors that eventually developed exudative MNV was similar to that of sectors that did not (85.2 [8.2] µm vs 86.8 [5.7] µm, P = .08). ORL thickness significantly increased in sectors that developed exudative MNV compared with those that did not (+5.8 [10.4] µm vs −2.8 [3.6] µm, P < .01). The regression model based on these data predicted an increase in ORL thickness from baseline of +4.2% 55 days and +11.1% 30 days before exudative MNV was detected. The ORL thickness of areas that did not develop exudative MNV did not change.

Thickening of the ORL begins in the area where exudative MNV will develop long before the exudation, accelerating significantly in the last 2 months. The occurrence of exudative MNV could be predicted by 2 months using this simple analysis.