Longitudinal evaluation of the distribution of intraretinal hyper-reflective foci in eyes with intermediate age-related macular degeneration.

Abstract

Purpose : Intraretinal hyper-reflective foci (IHRF) are a well-established optical coherence tomography (OCT) risk factor for progression of age-related macular degeneration (AMD). In this study we assess the change in the number and distribution of IHRF over two years in eyes with intermediate AMD (iAMD).

Methods : En-face Cirrus OCT images (512x128 macular cube; 6x6 mm) were collected in eyes with iAMD as a part of the Amish Eye Study at baseline and 24 months later. To quantify the axial distribution of IHRF across the neurosensory retina, a series of 5 sequential equidistant retinal slabs were generated between the outer border of the internal limiting membrane (ILM) and the inner border of retinal pigment epithelium (RPE), with slab 1 just above the RPE, and slab 5 just below the ILM (Figure 1). Following thresholding, binarization, and removal of artifacts, IHRF were quantified in each retinal slab using ImageJ. The change in IHRF number in each slab between baseline and month 24 was calculated.

Results : Fifty-two eyes showed evidence of IHRF at baseline, and all continued to show evidence of IHRF at 24 months (M24). The total IHRF count increased significantly from 240 (mean/eye ± standard deviation, 4.62 ± 0.63) at baseline to 604 (11.62 ± 13.86, p<0.001) at M24 with a mean increase of 364 (range: - 9 to + 60). Overall, at M24, 80.7% eyes showed an increase in IHRF whereas 15.4% of eyes showed a decrease (two eyes (3.8%) showed no change). The number of IHRF in individuals slabs at baseline and M24 are shown in Table 1, demonstrating a greater number of IHRF and a greater increase in IHRF over 24 months in the outer slabs.

Conclusions : IHRF are most common in the outer retinal layers and tend to increase in number over time. The changes, however, are not uniform with some eyes demonstrating a decrease. The impact of the distribution and frequency of these IHRF on the overall progression of AMD requires further study.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Representative OCT B-scan image depicting the position of the five consecutive slabs used for quantification of hyperreflective foci. Corresponding en-face images are shown depicting the number of hyper-reflective foci in each slab (image A corresponds to slab 5, and image E corresponds to slab 1)