Could “Sub-RPE illumination” be a prognostic marker? A prospective dry AMD study

Abstract

Purpose: To evaluate the natural history of dry age-related macular degeneration (AMD) through advanced retinal pigment epithelium (RPE) analysis and sub-RPE illumination (SRI) data and to elucidate their correlation with disease progression. Methods: A total of 82 patients with dry AMD were included in this longitudinal study. Spectral-domain optical coherence tomography (SD-OCT) was utilized to evaluate central macular thickness (CMT), central retinal thickness (CRT), foveal outer nuclear layer (ONL) thickness, and ellipsoid zone (EZ) integrity. Advanced retinal pigment epithelium (RPE) analysis software was used to obtain area and volume data at 3 mm and 5 mm circles, as well as sub-RPE illumination (SRI) assessments within 5 mm circles. Results: After exclusions, the final cohort consisted of 54 eyes of 54 patients (29 female), with a mean age of 74.72 ± 8.38 years and a mean follow-up period of 13.92 ± 1.7 months. Both area (mm2) and volume (mm3) within the 3 mm and 5 mm circles were significantly increased at the final visit (all P < 0.001). From the SRI data, the area within the 5 mm circle (mm2) was also identified as significantly higher at the final visit (P < 0.001). CMT, CRT, and ONL thickness decreased significantly by the final visit (P = 0.014, P < 0.001, and P < 0.001, respectively). Baseline and final LogMAR visual acuity values showed a significant inverse correlation with the distance of SRI from the fovea (P = 0.03, r = –0.347 and P = 0.04, r = –0.382, respectively). Baseline SRI values were higher in patients with EZ disruption at onset [0.8 (0.1–1.19) vs. 0.0 (0–0.1), P = 0.002]. Furthermore, patients with initial EZ disruption had significantly higher final SRI values than those without [1.1 (0.3–2.1) vs. 0.1 (0.1–0.2), P = 0.038]. A significant positive correlation was found between the initial SRI area and final LogMAR visual acuity (P < 0.001, r = 0.645). Conclusion: Initial SRI area may predict the risk of vision loss over a 12-month follow-up period and could serve as a prognostic marker for progression of dry AMD.