Researchers at Taipei Medical University, Taiwan have reported on an association of retinal diseases and Parkinson’s disease (PD), including a potential reversal of the risk following dopamine supplementation. The study’s findings showed that patients with pre-diagnostic PD appeared to be at a greater risk of retinal disease, compared to non-PD participants however, the risk reversed after treatment. The researchers commented in their report that, “this discrepancy in the temporal relationship between the two diseases may hint that retinal disease is a premotor manifestation of PD, and the possible effect of dopamine supplements on retina”.
Researchers had established that Parkinson disease (PD) is the second most common neurodegenerative disease worldwide, an estimated incidence of 15–328 per 100,000 individuals and prevalence of 15–12,500 per 100,000 individuals. In addition, the impact on vision were reported at all PD stages, indicating up to 82% of patients on dry eyes, blepharitis, double vision, visual hallucination, while the reduction of dopamine has been associated with retinal degeneration and denervation of the visual cortex. The recent study reviewed data from the National Health Insurance Research Database of Taiwan, with a total of 21,845 patients with newly diagnosed PD. In the results of the analysis, PD was found to be significantly co-morbid with recent and remote retinal disease [recent: ≤ 5 years, aOR: 1.12, 95% confidence interval (CI): 1.03–1.23; remote: > 5 years, aOR: 1.18, 95% CI: 1.04–1.34]. The study also reported no similar association between optic nerve disease or glaucoma with PD. In the cohort study, patients with PD were found to have a low risk of retinal disease in short-term (≤ 5 years, aSHR (adjusted sub-distribution hazard ratio): 0.81, 95% CI: 0.71–0.93) and long-term (> 5 years, aSHR: 0.82, 95% CI: 0.72–0.93) after follow-up.
In summary, the present study showed that patients with PD are at higher risk of retinal disease at the pre-motor PD stage than non-PD controls. However, “the hazard ratio reversed markedly in the follow-up period. This contrasting association was not observed between PD and optic nerve disease or glaucoma, other common age-related ophthalmic diseases”. The authors of the publication also commented that this was “the first study to elucidate an association of retinal disease with PD using a bidirectional approach”, and “the first to identify a discrepancy in risk based on temporal association’.