Subtenon Autologous Platelet-Rich Plasma in Degenerative Retinal Diseases: A Prospective Comparative Pilot Study in Retinitis Pigmentosa and Extensive Macular Atrophy with Pseudodrusen-Like Appearance

Purpose: To evaluate the safety, feasibility, and functional outcomes of subtenon autologous platelet-rich plasma (PRP) in patients with retinitis pigmentosa (RP) and Extensive Macular Atrophy with Pseudodrusen-like Appearance (EMAP), two degenerative retinal diseases sharing convergent inflammatory and neurodegenerative pathways. Methods: This prospective, comparative pilot study included adult patients diagnosed with RP or EMAP who received three subtenon injections of autologous PRP (1.5 mL per injection) administered at baseline (Month 0), Month 2, and Month 4. Functional outcomes were assessed from baseline to Month 6, with primary endpoints including best-corrected visual acuity (BCVA, logMAR) and visual field preservation, evaluated by the Field Preservation Deviation Index (FPDI) and Mean Deviation (MD) using automated perimetry. Secondary outcomes included 30-Hz flicker electroretinography (ERG) amplitude (phase 1), structural retinal parameters on optical coherence tomography (OCT)—central macular thickness and ellipsoid zone integrity—and ocular safety outcomes, including intraocular pressure and adverse events. Paired analyses were performed, with subgroup comparisons between RP and EMAP. Results: Thirteen patients were included in the analysis. In the overall cohort, mean BCVA showed a mild, non-significant improvement from 0.99 ± 0.71 logMAR at baseline to 0.90 ± 0.51 logMAR at Month 6 (p = 0.283). When stratified by diagnosis, patients with RP (n = 6) demonstrated a statistically significant improvement in BCVA (p = 0.048), whereas patients with EMAP (n = 7) showed functional stability without significant change (p = 0.619). Visual field parameters (MD and FPDI/VFI) remained stable in both groups, with a non-significant trend toward functional preservation, particularly in the RP subgroup. Quantitative paired analysis of flicker ERG amplitude was limited by incomplete data; however, descriptive evaluation demonstrated preservation of measurable responses without evidence of electrophysiological deterioration. Two transient and manageable ocular adverse events were observed (one episode of mild anterior uveitis in an RP patient with prior uveitis history and one episode of acute ocular hypertension in an EMAP patient attributed to an angle-closure mechanism). No infectious complications, sustained inflammation, or permanent ocular morbidity were reported. Conclusions: Subtenon autologous PRP demonstrated a favorable ocular safety profile and was associated with a preferential functional benefit in retinitis pigmentosa, while functional stability was observed in patients with EMAP. These findings suggest that PRP-based regenerative and immunomodulatory therapy may be more effective in degenerative retinal diseases where residual viable retinal cells and functional plasticity are present, as observed in retinitis pigmentosa, while primarily providing stabilizing effects in aggressive macular atrophic phenotypes such as EMAP. Larger, controlled studies with longer follow-up are warranted to further define the role of subtenon PRP in degenerative retinal diseases.