Hyper-Reflective Foci in Intermediate Age-Related Macular Degeneration: Spatial Abundance and Impact on Retinal Morphology

PURPOSE: The purpose of this study was to analyze spatially resolved structural changes at retinal locations in presence (+) or absence (−) of hyper-reflective foci (HRF) in eyes with subretinal pigment epithelium (RPE) drusen in intermediate age-related macular degeneration (iAMD). METHODS: Patients with IAMD (n = 40; mean age = 69.7 ± 9.2 [SD] years) and healthy controls (n = 27; 64.2 ± 9.0) underwent spectral-domain optical-coherence-tomography imaging and fundus-controlled perimetry testing. After reviewing retinal layer segmentation, presence of HRF was annotated and retinal layer thicknesses (RLTs) extracted using ImageJ. Localized RLTs were compared between +HRF and −HRF positions. Univariate mixed linear models were used to investigate associations among RLT, HRF presence, and HRF size. RESULTS: In iAMD eyes, a mean of 11.1 ± 12.5 HRF were detected with a peak abundance at 0.5 to 1.5 mm eccentricity to the fovea. At +HRF positions, outer nuclear layer (ONL; P = 0.0013, average difference = −12.4 µm) and retinal pigment epithelium drusen complex (RPEDC; P < 0.0001, +45.6 µm) thicknesses differed significantly compared to −HRF positions, even after correcting for accompanying drusen-related RPEDC layer thickening (P = 0.01). Mixed linear models revealed a significant association between increasing HRF area and decreasing ONL (association score = −0.17, P < 0.0001; 95% confidence interval [CI] = −0.22 to −0.11), and inner photoreceptor segments (IS) layer thicknesses (−0.08, P = 0.005; 95% CI = −0.14 to −0.03). Spearman rank correlation analysis yielded a significant correlation between total HRF area and mesopic (P = 0.015), but not scotopic (P = 0.305) retinal sensitivity losses. CONCLUSIONS: Descriptive analysis of this study demonstrated a predominant distribution of HRF at a foveal eccentricity of 0.5 to 1.5 mm, whereas further refined topographic analysis revealed a significant ONL layer thinning in presence of HRF even after correction for sub-RPE drusen presence compared to lesions in absence of HRF. Longitudinal studies are further needed to analyze the prognostic impact as well as the role of HRF presence in the context of iAMD.