Choroidal Thickness Influences Near-Infrared Reflectance Intensity in Eyes With Geographic Atrophy Due To Age-Related Macular Degeneration

PURPOSE. To evaluate the effects of retinal and choroidal thickness on near-infrared reflectance (NIR) scanning laser ophthalmoscopy in eyes with geographic atrophy (GA) secondary to non-neovascular age-related macular degeneration (AMD). METHODS. This was a cross-sectional review of the clinical records and multimodal imaging data of eyes diagnosed with GA secondary to non-neovascular AMD. Imaging modalities included color fundus photography, fundus autofluorescence, NIR, and structural spectral-domain optical coherence tomography (SD-OCT). On SD-OCT images, the foveal retina thickness and the subfoveal choroidal thickness were measured by two independent readers. Near-infrared reflectance intensity within areas of GA was subjectively graded as hyperreflective, isoreflective, or hyporeflective and objectively estimated by using ImageJ to calculate the mean gray scale value within each GA area. A linear regression analysis was performed to model the relationship between mean NIR gray scale value and retinal and choroidal thickness. RESULTS. One hundred four eyes of 104 patients with a mean age of 81.3 years (SD: +/- 8.3) were included. The area of GA was hyperreflective on NIR in 88 eyes (85%), isoreflective in 13 eyes (12%), and hyporeflective in 3 eyes (3%). The mean foveal retinal thickness was 101.5 mu m (SD: +/- 54) showing no significant relationship with mean NIR (P = 0.464); and the mean subfoveal choroidal thickness was 172.6 mu m (SD: +/- 114.7) showing a statistically significant relationship with mean NIR intensity in the linear regression analysis (r = 0.590; r(2) = 0.348; P < 0.00001). CONCLUSIONS. Variations in choroidal thickness appear to influence NIR intensity in areas of GA and have the potential to affect image interpretation. The recognition of this relationship may provide useful information regarding choroidal thickness.