Subtenon Autologous Platelet-Rich Plasma in Inherited and Degenerative Retinal Diseases

Retinitis pigmentosa (RP) is a genetically and phenotypically heterogeneous group of inherited retinal dystrophies characterized by progressive degeneration of photoreceptors, typically initiating with rod dysfunction and followed by secondary cone involvement. This process leads to nyctalopia, progressive constriction of the visual field, and, in advanced stages, impairment of central vision. Although recent advances in gene-specific and cell-based therapies have expanded treatment possibilities for selected subgroups, the majority of patients with RP still lack broadly applicable therapeutic approaches capable of modifying disease progression.

Extensive Macular Atrophy with Pseudodrusen-like Appearance (EMAP) is a distinct degenerative macular phenotype characterized by early-onset bilateral macular atrophy associated with pseudodrusen-like deposits, progressive loss of the outer retina and retinal pigment epithelium, and marked chorioretinal thinning. Despite its phenotypic differences from classical inherited retinal dystrophies, EMAP shares several pathobiological mechanisms with RP, including photoreceptor degeneration, outer retinal ischemia, chronic para-inflammatory activity, microglial activation, and progressive macular atrophy, ultimately resulting in severe central vision loss.

Accumulating experimental and clinical evidence suggests that both RP and EMAP are driven not only by primary degenerative mechanisms but also by sustained para-inflammatory processes at the level of the outer retina, retinal pigment epithelium, and choroid. Dysregulation of microglial activity, oxidative stress, complement activation, and chronic release of inflammatory mediators may contribute to secondary neuronal damage and accelerate structural and functional decline. These shared biological pathways provide a rationale for exploring therapeutic strategies with combined neurotrophic, anti-inflammatory, and tissue-supportive effects.

Autologous platelet-rich plasma (PRP) has emerged as a potential multimodal biologic therapy due to its high concentration of endogenous growth factors and cytokines, including platelet-derived growth factor, transforming growth factor-beta, insulin-like growth factor-1, basic fibroblast growth factor, and other bioactive mediators. These factors may support retinal homeostasis by modulating inflammatory signaling, enhancing chorioretinal perfusion, and promoting cellular survival pathways within the neuroretina and retinal pigment epithelium.

The subtenon route of administration was selected to enable gradual diffusion of PRP-derived bioactive factors toward the posterior segment while minimizing risks associated with intravitreal delivery. This approach is particularly suited for chronic degenerative retinal diseases, where safety, repeatability, and long-term tolerability are essential considerations.

This prospective pilot study was designed to assess the feasibility and ocular safety of repeated subtenon administration of autologous PRP in patients with RP and EMAP, while exploring functional and structural signals over a defined follow-up period. By integrating multimodal functional and imaging assessments, the study aims to generate preliminary data to inform the design of future controlled clinical trials evaluating regenerative and immunomodulatory strategies for inherited and degenerative retinal disorders characterized by progressive photoreceptor loss and macular atrophy.

Inclusion criteria

• Age ≥ 18 years.
• Clinical diagnosis of retinitis pigmentosa (RP) or EMAP (Extensive Macular Atrophy with Pseudodrusen-like Appearance), confirmed by multimodal evaluation.
• Best-corrected visual acuity (BCVA) ≥ counting fingers at 1 meter (approximately ≤ 1.9 logMAR) in the study eye.
• Measurable visual field on iCare COMPASS (10-2 or 24-2) with acceptable reliability indices.
• Clear ocular media adequate for safe intravitreal injection and high-quality optical coherence tomography (OCT) imaging.
• Ability and willingness to provide written informed consent.
• Ability to comply with scheduled study visits, including:

• Baseline (M0)
• Day 7-14 after injections
• Month 2 (M2), Day 7-14
• Month 4 (M4), Day 7-14
• Month 6 (M6)
• For ERG subset only:

o Presence of a recordable baseline 30-Hz flicker electroretinogram (ERG) response, defined as a signal-to-noise ratio ≥ 3:1 and amplitude ≥ 3.0 μV.

• Note: Absence of a measurable flicker ERG response does not exclude participation in the main study.

Exclusion criteria

• Active ocular inflammation (anterior, intermediate, or posterior uveitis) or active infectious ocular disease in the study eye.
• Active choroidal neovascularization or other macular diseases unrelated to RP or EMAP.
• Uncontrolled glaucoma (intraocular pressure > 21 mmHg despite therapy) or optic neuropathies not related to RP or EMAP.
• Significant media opacity that may impair imaging quality or compromise the safety of intravitreal injection.
• Recent ocular interventions that may confound study outcomes, including:

• Intravitreal therapy within 3 months prior to enrollment.
• Periocular corticosteroid injection within 3 months prior to enrollment.
• Major intraocular surgery within 3 months prior to enrollment.
• Known hypersensitivity to adalimumab, povidone-iodine, local anesthetics, or any component of the study formulations.
• Coagulopathy or contraindications to ocular injections, including:

• Platelet count < 100,000/μL, or
• INR > 1.5 unless adequately corrected.
• Pregnancy or breastfeeding.
• Women of childbearing potential unwilling to use effective contraception during the study period.
• Uncontrolled systemic disease that, in the investigator's judgment, increases risk or interferes with study participation or completion.
• Participation in another interventional clinical trial within 3 months prior to enrollment.