Risk factors for development of hyper-reflective foci overlying drusen in eyes with intermediate age-related macular degeneration

Aims: The aim of this study is to assess baseline characteristics of drusen preceding the development of intraretinal hyper-reflective foci (IHRF) in eyes with intermediate age-related macular degeneration (AMD). Methods: In this retrospective case-control study, longitudinal optical coherence tomography (OCT) volume data from eyes with intermediate AMD in a retina clinic population were screened. All drusen that developed overlying IHRF were marked. A random number generator was used to select for further grading three drusen that did not develop IHRF. Results: Ninety eyes (from 72 patients), including 140 drusen with overlying IHRF and 270 IHRF- drusen, were analysed. Greater drusen height, basal drusen width and overlying ellipsoid zone (EZ) and external limiting membrane disruption were associated with a significantly greater risk for IHRF development (p≤0.001). Regression analysis revealed EZ disruption increased these odds by 4.1 (p≤0.001). Each 10-μm increase in drusen height and width increased the odds by 34% (p≤0.001) and 3% (p: 0.005), respectively. Each 100-μm increase in distance from the fovea decreased the odds by 10% (p: 0.013). Conclusions: The presence of overlying EZ disruption and a greater drusen height substantially increased the risk for IHRF development, whereas drusen further from the fovea indicated reduced risk. Given the importance of IHRF as a biomarker for AMD progression, these findings may be of value in defining patient populations for future early intervention trials.