Quantitative Fundus Autofluorescence in Geographic Atrophy Secondary to AMD: Comparison With Stargardt Disease, PRPH2-Associated Retinal Dystrophies, and Healthy Controls.

PURPOSE: To analyze differences in quantitative fundus autofluorescence (qAF) between geographic atrophy (GA) secondary to age-related macular degeneration (AMD) and other diseases associated with macular atrophy including Stargardt disease (STGD), and autosomal-dominant PRPH2-associated retinal dystrophies (PRPH2).

METHODS

Patients with GA, STGD, PRPH2, and healthy subjects were included in this cross-sectional study. The qAF was assessed using a confocal scanning laser ophthalmoscope equipped with an internal fluorescent reference. Mean qAF values were obtained using the standardized qAF Delori pattern (qAF8). Care was taken to remove areas of atrophy within the qAF8 pattern. Mixed models were calculated to compare disease groups, correcting for age, and evaluate possible associations between qAF8 and macular atrophy size.

RESULTS

Two hundred eight eyes from 118 patients (87 GA, 22 STGD, 10 PRPH2, 89 healthy controls) were analyzed. There were significant differences in qAF8 between the groups (P < 0.001). GA patients showed significantly reduced qAF8 values compared to healthy controls (P < 0.001), STGD patients (P < 0.001), and PRPH2 patients (P < 0.001). STGD patients demonstrated significantly elevated qAF8 values compared to healthy controls (P < 0.001). PRPH2 patients did not differ from healthy controls (P = 0.3). GA and PRPH2 demonstrated nominal inverse correlations with increasing atrophy area, whereas STGD showed a significant positive correlation. Lens status was confounded completely with disease group and thus could not be tested as an independent covariate. Univariately, lens status was associated with qAF8 (P < 0.001), whereas age was not significant in the final model (P = 0.4).

CONCLUSIONS

The qAF8 varies significantly between eyes with macular atrophy due to GA secondary to AMD, STGD and PRPH2-associated retinal dystrophy. Although age was included as covariate, residual confounding cannot entirely be excluded due to the partial overlap in age distributions of cohorts. Lens status could not be adjusted for because it was completely confounded with disease group. This noninvasive, objectively acquired data may serve as an adjunctive biomarker to support diagnosis, prognosis, counselling and management in these degenerative disorders, pending further validation in balanced cohorts.