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-mu m increase in drusen height and width increased the odds by 34% (p <= 0.001) and 3% (p: 0.005), respectively. Each 100-mu m 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.