Choroidal Thickness Influences Green Emission Autofluorescence Component Intensity in Eyes with Geographic Atrophy Due to Age-Related Macular degeneration: A Color Fundus Autofluorescence Study

Abstract

Purpose : To study the presence of green-emission autofluorescence component (GEFC) in eyes with geographic atrophy (GA) secondary to non-neovascular age-related macular degeneration (AMD) and its correlation with the choroid thickness (CT).

Methods : We reviewed the clinical records and multimodal imaging data of eyes diagnosed with GA secondary to non-neovascular AMD. Imaging modalities included fundus autofluorescence (FAF), near-infrared reflectance (NIR), spectral-domain optical coherence tomography (SD-OCT) (Heidelberg Engineering, Heidelberg, Germany), and “color” FAF (C-FAF). C-FAF images were obtained by a confocal light emitting diode blue-light fundus autofluorescence (FAF) device (EIDON, CenterVue, Padua, Italy). To evaluate the presence of GEFC within the GA area, the C-FAF images were split into the red and green image, and a subtraction function was applied using ImageJ. On SD-OCT images, the retinal thickness (RT) and the CT were measured by two independent readers in the area of fovea and the GA lesion. Inter-observer agreement for RT and CT was calculated using Intraclass Correlation Coefficient (ICC). Using ImageJ, we calculated the mean grey scale value of GEFC within the fovea and GA area. A linear regression analysis was performed to model the relationship between mean GEFC grey scale value and RT and CT.

Results : Thirteen pseudophakic eyes of 13 patients with a mean age of 84.1 years (SD:±5,4) were included. There was good inter-observer reproducibility of measurement for foveal RT (ICC:0,996), subfoveal CT (ICC:0,997);as well as for RT (ICC: 0,989) and CT in the area of the GA (ICC:0,987). We observed a statistically significant negative correlation between the mean grey intensity of GEFC and the CT in the area of GA (R²:0,560, P:0,003). The mean grey intensity value of GEFC and both foveal RT (P:0.017) and subfoveal CF (P:0.3) did not show any significant relationship with the linear regression analysis; the same finding was observed between mean grey scale value of GEFC in the area of GA and RT in the area of GA (P:0,3).

Conclusions : Variations in choroidal thickness appear to influence GEFC intensity in areas of GA. The increase in intensity of GEFC could be related to the hypertransmission of the light reflected from the underlying sclera in areas of reduced choroidal thickness.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.