Quantitative Fundus Autofluorescence in Early Dry AMD Using ImageJ: Near-Perfect Interobserver Agreement and Pattern-Specific Intensity Characterization
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Purpose
To assess the feasibility of quantitative fundus autofluorescence (FAF) measurement in early age-related macular degeneration (AMD) using the freely available ImageJ software, to characterize signal intensity across FAF patterns, and to evaluate interobserver reproducibility in pattern classification.
Methods
Single-center, non-blinded, retrospective, consecutive-case analytical study. FAF images acquired with Spectralis OCT+HRA (Heidelberg Engineering) from patients with early dry AMD seen at a tertiary referral center between January 2010 and September 2016 were analyzed. A standardized 300×300-pixel region of interest (ROI) centered on the fovea was evaluated in ImageJ v2.0.0-rc54/1.51h (Fiji distribution). Mean, minimum, and maximum autofluorescence (AF) pixel intensity were recorded. Each image was independently classified according to the Bindewald classification system by two graders; a third senior grader adjudicated discordances. Cohen’s kappa (κ) was used to assess interobserver agreement.
Results
Of 423 patients with available FAF studies, 107 had dry AMD; 45 met quality and diagnostic criteria for early AMD and were included in the quantitative analysis. Mean age was 73.47 ± 8.1 years; 62.2% were female. Mean FAF intensity was 120.26 (range 74.76–160.79); mean minimum was 32.07 (range 3–63) and mean maximum was 205.80 (range 125–255). Seven of eight Bindewald patterns were identified; the “stippled” pattern was absent. The most frequent pattern was minimal changes (31.1%), followed by increased focal (24.4%) and patchy (15.6%). Reticular pattern showed the highest mean AF (143.8), while lacelike pattern showed the lowest (88.4). Interobserver agreement for Bindewald pattern classification was almost perfect (κ = 0.969; 95% CI, 0.908–1.000; p < 0.001). Agreement for lesion extent was moderate (κ = 0.531) and for foveal involvement was substantial (κ = 0.622).
Conclusions
Quantitative FAF evaluation of early AMD using ImageJ is feasible and reproducible. ImageJ represents a cost-free alternative for multimodal retinal image analysis, with potential for automated screening applications in resource-limited settings.
