Short Wavelenght versus Near-Infrared Fundus Autofluorescence in the Diagnosis and Follow-Up of Geographic Atrophy

Abstract

Purpose: : To compare standard short-wavelenght fundus autofluorescence (SW-FAF) versus near infrared-wavelenght fundus autofluorescence (NIR-FAF) in detecting geographic atrophy (GA) secondary to age-related macular degeneration.

Methods: : Twenty-nine consecutive patients (45 eyes) affected by GA secondary to age-related macular degeneration were studied by means of fundus autofluorescence imaging, using both SW-FAF (excitation: 488 nm) and NIR-FAF (excitation: 780 nm). All patients also underwent: 30° stereoscopic color fundus photography, spectral domain OCT and microperimetry. Microperimetry was used to assess fixation characteristics and retinal sensitivity.

Results: : In the extrafoveal region, total hypo-autofluorescent (hypo-AF) area was significantly wider with NIR-FAF versus SW-FAF (8.21 µm² ± 6.78 and 7.62 µm² ± 6.36 respectively; p= 0.023). On the contrary in the foveal area, total hypo-AF area was smaller with NIR-FAF versus SW-FAF (0.19 µm² ± 0.02 and 0.42 µm² ± 0.11 respectively; p= 0.008). When the fovea seemed massively involved by atrophy, foveal sparing was larger at NIR-FAF compared to SW-FAF (p= 0.021). In 9 cases (20%) site of fixation was located in hypo-AF area on SW- FAF, this site had normal NIR-FAF and showed persisting retinal sensitivity.

Conclusions: : Standard SW-FAF may overestimate atrophy in the foveal area, correctly detected by NIR-FAF. In the extrafoveal area SW-FAF underestimates atrophy. Standard SW-FAF should be integrated with NIR FAF when detecting and following geographic atrophy to avoid inconsistent results and misinterpretation, from both a morphological and functional perspective.

Keywords: age-related macular degeneration • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • perimetry