Functional and Structural Outcomes of Photobiomodulation Therapy in Dry Age-Related Macular Degeneration: A Single-Center Experience

Purpose: To evaluate the anatomical and functional efficacy of photobiomodulation (PBM) therapy in patients with dry age-related macular degeneration (AMD) and to investigate structural predictors of visual response. Methods: This retrospective study included 47 eyes of 30 patients with dry AMD treated with PBM. Best-corrected visual acuity (BCVA) was recorded as Early Treatment Diabetic Retinopathy Study (ETDRS) letter score, and visual change (ΔBCVA) was calculated. Spectral-domain optical coherence tomography parameters—central retinal thickness (CRT), central macular volume (ETDRS 9-subfield central zone), and photoreceptor layer integrity (external limiting membrane [ELM], ellipsoid zone [EZ], and interdigitation zone [IZ])—were assessed pre- and post-treatment. Age-Related Eye Disease Study (AREDS) stage was graded per eye. Because both eyes from some patients were included, generalized estimating equation (GEE) models with patient-level clustering were used to account for inter-eye correlation. Effect estimates were reported as unstandardized coefficients with 95% confidence intervals. Results: Visual acuity improved following PBM therapy, with mean ETDRS letter scores increasing from 75.0 ± 14.1 to 78.0 ± 12.1 letters. In the GEE model accounting for patient-level clustering, the estimated mean gain was 2.97 ETDRS letters (95% CI: 1.15 to 4.79; p = 0.001). Mean CRT showed no significant change following PBM therapy (210.32 ± 48.61 µm vs. 211.23 ± 50.27 µm; GEE estimate: +0.91 µm; 95% CI: −5.52 to 7.35; p = 0.780). Central macular volume likewise remained stable (0.1913 ± 0.030 vs. 0.1919 ± 0.033 mm3; GEE estimate: +0.0006 mm3; 95% CI: −0.0054 to 0.0067; p = 0.836). Photoreceptor layer integrity demonstrated limited structural change, with no significant time effect for EZ or IZ integrity in binary GEE models and no observed pre–post change in ELM integrity. In multivariable GEE analysis, baseline BCVA (p < 0.001), ELM integrity (p < 0.001) and central macular volume (p = 0.041) were associated with change in ETDRS letter score, whereas AREDS category, EZ integrity, and IZ integrity were not. Conclusions: PBM therapy demonstrated limited short-term anatomical change but variable functional outcomes in dry AMD. Baseline BCVA emerged as the primary determinant of visual response, suggesting that treatment benefit may be influenced predominantly by pre-treatment functional reserve.