Characteristic assessment of longitudinal multi-modal imaging preceding geographic atrophy

Abstract

Purpose : While recent consensus efforts present image-based criteria preceding the development of geographic atrophy (GA), widespread clinical use requires further validation and understanding. This work evaluates images prior to GA detection to identify associations between different multi-modal classifications preceding GA.

Methods : Multi-modal imaging data [optical coherence tomography (OCT), fundus autofluorescence (FAF), infrared, and color fundus] were acquired in a 5-year, prospective, longitudinal study of patients with AMD. 20 eyes that developed GA by the final visit were examined using custom software aligning FAF and OCT images within visits and across time. The GA lesion was contoured at its first appearance and preceding images were graded using proposed schemes based on OCT and FAF characteristics. CAM definitions including cRORA [complete RPE and outer retinal atrophy (ORA)], iRORA (incomplete RORA), cORA (complete ORA), and iORA (incomplete ORA) were used in assessing aligned OCT scans corresponding to area developing atrophy. FAF images were graded in the contoured GA area for hyper-autofluorescence (hyperAF), hypo-AF, and mixed-AF features. Analyses was performed aggregating timepoints relative to the first GA occurrence. Quantitative measurements were derived by computing mean image intensities in FAF and OCT and mean total retina thickness in OCT at initial GA regions.

Results : In the 1^st and 2^nd years preceding GA, 97% (29/30) of OCT images exhibited iRORA [with 3% cORA] while in FAF 80% (24/30) exhibited hypoAF [with 17% mixedAF and 3% hyperAF]. 3-5 years prior to GA development, 65% (13/20) exhibited iRORA [with 20% iORA and 15% cORA] in OCT and 45% (9/20) mixedAF [with 35% hypoAF and 20% hyperAF ] in FAF. Across all years leading up to GA, 60% (30/50) images exhibited iRORA+HypoAF, 24% exhibited iRORA+MixedAF, 8% exhibited cRORA+HyperAF, and 8% exhibited iORA, indicating consistent pattern of precursor multimodal grading combinations. Mean intensity in FAF, mean intensity in 50 µm sub-RPE band in OCT, and total retina thickness exhibited correlation with categorical gradings.

Conclusions : Predominant combinations of OCT and FAF gradings were identified in years preceding GA revealing some consistent patterns on multimodal imaging. Combining grading schemes with quantitative analysis of image features could further strengthen the current understanding of imaging changes leading to GA.

This is a 2020 ARVO Annual Meeting abstract.