Abstract
Purpose :
To investigate the performance of fundus autofluorescence (AF) imaging using red-excitation light (R-AF) in patients with age-related macular degeneration (AMD) and to compare it with short-wavelength AF (SW-AF).
Methods :
R-AF imaging was performed with a confocal scanning laser ophthalmoscope using red excitation lasers (642 nm, 705 nm). Additional multimodal retinal imaging included SW-AF (486 nm), near-infrared-AF (NIR-AF, 785 nm), optical coherence tomography (OCT), and color fundus photography.
Results :
Early or intermediate AMD was present in 30 eyes, geographic atrophy (GA) in 50 eyes. On SW-AF imaging, soft drusen were either hardly visible or revealed a slightly increased AF signal. At the corresponding retinal location, R-AF images usually showed clearly visible target-like lesions with an area of reduced AF surrounded by a ring of increased AF. Reticular pseudodrusen and basal laminar drusen were visible on SW- and R-AF images, however, the affected area was larger on R-AF images, indicating a higher sensitivity to detect these lesions. On R-AF imaging, areas of atrophy were sharply demarcated and usually showed a more pronounced contrast to surrounding areas when compared to SW-AF. Quantitative assessment of the GA area showed a strong correlation between SW-AF and R-AF images (r2= 0.991, 0.991 and 0.999 for SW-AF vs 642 nm, SW-AF vs 705 m and 642 nm vs 705 nm, respectively). In 6 out of 50 eyes, SW-AF images did not allow to reliably determine the border of atrophy due to an interference with macular pigment and additional imaging modalities (NIR-reflectance; OCT) were required to determine the extent of the atrophic area. We observed overall clearer thresholding of atrophic areas from retinal vessels on histogram analysis due to the larger difference in grey levels between these structures on R-AF images. The AF pattern surrounding patches of atrophy was usually similar on SW- and R-AF images.
Conclusions :
R-AF imaging produces high-quality AF images and appears useful for assessing patients with AMD. R-AF may overcome limitations of SW-AF which include glare discomfort during imaging acquisition, reduced image quality and AF signal intensity in patients with cataract, and limited visualization of the central retina due to absorption of the blue excitation light by macular pigment and melanin.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.