Abstract
Purpose: :
Stereoscopic color fundus photography has been the standard imaging modality for evaluating geographic atrophy (GA). Recent reports on fundus autofluorescence (FAF) images have shown that GA can be detected on FAF imaging, seen as areas of decreased autofluorescence (DAF). The objective of this study is to compare evaluation of GA from color photos to FAF images.
Methods: :
Calibrated digital images from the AREDS2 trail were evaluated in ImageNet (Topcon Meditec) software by trained ocular disease evaluators using the definitions described in AREDS Report #6. The area of GA and its proximity to the fovea was documented. FAF images obtained from HRA2 (Heidelberg Eng.) cameras using a standardized protocol were evaluated independently for presence, proximity to the fovea and the area of DAF. DAF was defined as an area that is 90 to 100% as black as the optic disc, greater than or equal to drusen circle I2 (350µm diameter) in size with well defined borders. The sample consisted of eyes which were evaluated for GA on color photos at any visit with corresponding FAF images available.
Results: :
45 eyes had GA at baseline or a follow-up visit on color evaluation. Both the color photo and corresponding FAF image confirmed presence of GA in 40 (88.9%) eyes. The area of GA on the two image types had an intraclass correlation (ICC) of 0.93 with a mean difference of 0.26 ± 0.88 disc areas, FAF areas being larger than color. The fovea was involved in 14 (35.0%) eyes on color evaluation and 19 (47.5%) eyes with FAF. In the remaining eyes with non-foveal involvement, distance from the fovea with the two image types had an ICC of 0.78 with a mean difference of 81.2 ± 264.1µm, FAF measurements being closer to the fovea. The Pearson’s correlation coefficient (r) between visual acuity and distance from the fovea from color evaluation was 0.60 and from FAF evaluation was 0.53.
Conclusions: :
Detection of GA on FAF images is comparable to color photographs. Area of GA on FAF images is slightly larger than color images. Measurement from foveal center can be influenced in FAF images due to the DAF in the center of the fovea caused by the macular pigment. Color photographs are better than FAF images for precise distance measurements from the fovea.
Clinical Trial: :
www.clinicaltrials.gov NCT00345176
Keywords: age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)