Quantitative Autofluorescence Illuminates 2 Geographic Atrophy Pathways in AMD

Geographic atrophy (GA) appears to occur in 2 different pathways, originating from soft drusen and subretinal drusenoid deposits (SDDs), according to research published in Eye. Lower quantitative autofluorescence (qAF) values reflect a soft drusen pathway, while higher qAF values may indicate the SDD pathway, according to the report. 

Researchers included 18 patients (eyes, 23; mean age, 85 years) with age-related macular degeneration (AMD) and GA who underwent spectral-domain optical coherence tomography (SD-OCT) and quantitative autofluorescence (qAF) imaging in the analysis. The research team selected 52 GA regions-of-interest (ROIs), or clusters of adjacent lesions, and the ROIs were divided into groups based on the dominant intermediate AMD precursors using serial tracked SD-OCT scans. The average follow-up time was 5.5 years (range, 1.2-10 years).

Group 1 lesions (soft drusen/pigment epithelial detachment precursors, 18/52) were isolated and had a lower mean qAF (35.88 units). Group 2 lesions (mixed precursors, 22/52) had intermediate qAF (58.13 units), and group 3 lesions (SDD precursors, 12/52) were multilobular and had significantly higher mean qAF (71.62 units) compared with group 1 and 2 lesions (P <.05), according to the report.   

A significantly higher prevalence of split retinal pigment epithelium and Bruch’s membrane complex was found in SDD-associated GA, suggesting that basal laminar deposits, not drusen-associated lesions, structurally differentiated it from group 1 lesions. 

“In conclusion, there are potentially two different pathways to GA that are associated with the two characteristic [intermediate] AMD phenotypes of drusen and SDD, and that can be differentiated by the surrogate marker of qAF in their outcomes. The source of the greater autofluorescence in SDD-associated GA appears to be [basal laminar deposits],” according to the researchers. “Quantitative autofluorescence and individual consideration of the two SDD- and drusen-associated pathways might improve the interpretation of research on GA mechanisms, treatments and prognostic factors for disease progression.”

This study was limited by the small sample size.