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Dietary supplements may be an interesting approach to treating retinitis pigmentosa (RP), but according to a report published by the American Academy of Ophthalmology, they do not reduce RP progression.

“No high-quality evidence firmly establishes efficacy of any form of dietary supplementation for individuals with RP,” the organization’s Ophthalmic Technology Assessment Committee members wrote in Ophthalmology.

“In some patients, dietary supplementation may pose health risks, as suggested by clinical trial data on vitamin E supplementation in RP, epidemiologic studies of high-dose vitamin A and β-carotene supplementation and systemic health, and studies raising concerns about the quality of products in the dietary supplement marketplace,” they continued.

To investigate how dietary supplementation affects RP progression, Nieraj Jain, MD, and colleagues searched PubMed for English-language original research papers on dietary supplementation for RP.

All 15 articles that met the researchers’ assessment criteria described single-center studies published between 1993 and 2022. Most primary outcome measures were based on electroretinography or perimetry tests. The oral supplements evaluated included vitamin A, docosahexaenoic acid, lutein, vitamin E, goji berry (Lycium barbarum) extract, and chlorogenic acid, and one study assessed an antioxidant nutrient complex containing folic acid, vitamin B6, vitamin A, zinc, copper, selenium, lutein, and zeaxanthin.

Findings typically involved secondary outcomes, subset evaluations, post hoc analyses, or problematic data interpretation, and whether the outcomes were clinically meaningful was often unclear. No studies reported any prominent safety issues.

Dr. Jain spoke with Physician’s Weekly (PW) about the current state of RP treatment, discussions around dietary supplements, and upcoming related research.

PW: Without formal guidelines on the topic, what do clinicians need to know about dietary supplements for RP?

Nieraj Jain, MD: For decades, clinicians have advised patients with retinitis pigmentosa to take various combinations of dietary supplements to slow disease progression. I have seen a broad spectrum of practice patterns among my mentors and colleagues.

However, the findings of this study, which are approved by the American Academy of Ophthalmology, suggest that there is no high-quality evidence to support dietary supplementation for RP.

PW: Why was it necessary to do this study?

RP, the most common monogenic inherited retinal disease worldwide, has an estimated prevalence of 1 in 4,000. RP progresses from nyctalopia to peripheral visual field loss, to central vision loss, and often to legal blindness. Most forms of RP have no known treatment.

Mutations in around 100 genes may lead to photoreceptor degeneration in RP. However, the only FDA-approved RP therapy is associated with biallelic mutations in the RPE65 gene, which affects fewer than 1% of patients with RP.

It would be great if a dietary supplement could help slow this disease in a gene-agnostic fashion, but supplements are not always completely benign. We wanted to provide clinicians and patients with some evidence-based guidance surrounding this issue.

PW:  Are any strengths or limitations especially noteworthy?

This was a deep dive into the literature on dietary supplementation for RP. To my knowledge, the position stated in this paper is the first Academy-approved position on the topic of dietary supplementation for RP.

PW: What research is needed to move this potential treatment forward?

Some RP genotypes may have more favorable responses to certain supplements.

Inherited retinal disease centers have grown worldwide in recent years. Future studies can leverage enhanced recruitment capabilities from large, multicenter collaborations to power studies with more nuanced eligibility criteria. Such studies could use newer tests of retinal structure and function to assess more sensitive, precise, and clinically meaningful endpoints. High-quality genetic testing could identify specific genotypes that may be likely to benefit from interventions.

PW: What else should clinicians know about dietary supplements for RP?

I wish our results had found strong support for using dietary supplements in RP. However, it is nice to provide some clarity on this question. I remain hopeful that the therapeutic landscape for RP will improve during my career. Several promising treatment modalities are currently in the pipeline.