Comparative study of refractive errors between patients with Parkinson’s disease versus age- and sex-matched healthy controls

To compare refractive errors between patients with Parkinson’s disease (PD) and age- and sex-matched healthy controls. In this cross-sectional comparative study, individuals diagnosed with PD were chosen from Qaem Hospital in Mashhad (Iran) through convenience sampling, while healthy individuals were randomly selected from a population without PD. Following the application of inclusion and exclusion criteria, optometric examinations were conducted, which included measurements of uncorrected and best-corrected visual acuity, objective and subjective refraction, and binocular vision assessments. Myopia and hyperopia were classified as having a spherical equivalent (SE) worse than 0.50 diopters (D), and astigmatism was defined as a cylinder power exceeding 0.50 D. In this study, 41 normal individuals and 42 PD patients were examined. The average age of the control group was 54.9 ± 9.8 years, while the PD group had an average age of 55.3 ± 9.6 years (P = 0.866). The mean SE for PD patients was 0.52 ± 1.22 D, compared to 0.09 ± 1.03 D in healthy subjects (P = 0.092). The mean cylinder power for PD patients was − 0.94 ± 0.55 D, compared to -0.59 ± 0.44 D for normal subjects (P = 0.002). The prevalence of hyperopia was found to be 45.2%(95%CI: 29.8–60.7) in the PD group and 26.8%(95%CI: 12.9–40.8) in the normal group (OR: 2.78, 95%CI: 0.94–8.19, P = 0.064). Additionally, 14.3%(95%CI: 3.4–25.2) of PD patients and 22.0%(95%CI: 8.9–35.0) of healthy subjects were identified as myopic (OR = 0.57, 95%CI: 0.16–1.99, P = 0.380). Lastly, astigmatism was present in 29.3%(95%CI: 15-43.6) of normal subjects and 69.0%(95%CI: 54.7–83.4) of PD patients (OR = 5.84, 95%CI: 2.19–15.51, P < 0.001). Astigmatism is notably prevalent among individuals with PD. Given the visual symptoms associated with astigmatism, it is essential to focus on its correction in these patients. Moreover, monitoring astigmatism, along with hyperopic shifts, could function as a predictive marker for PD screening in optometric practice.