New Findings on Visual Dysfunction in Parkinson's Disease

A 2026 report in MDPI Brain Sciences describes differences in visual function in people with Parkinson's disease (PD) versus age-matched controls across two domains: sensory color discrimination and binocular/vergence performance.

Using computerized color testing alongside standard clinical binocular measures, investigators compared group-level performance and examined whether these visual metrics were associated with motor severity as assessed by UPDRS scores.

The single-center cohort study compared 19 participants with PD with 12 healthy controls and reported results from a comprehensive eye exam that included ocular motility testing and computerized color-vision assessment. Color discrimination was evaluated with the Cambridge Color Test Ellipse Test, which derives thresholds across multiple contrast vectors to fit a discrimination (MacAdam) ellipse and summarize performance via ellipse characteristics. Binocular vision was assessed with near point of convergence testing (using a RAF ruler), an alternating prism cover test at near to quantify deviation in prism diopters, and Titmus stereopsis testing with log-adjusted values in analysis. To reduce potential motor-related confounds in the color task, participants verbally indicated the Landolt “C” orientation while a clinical researcher entered the response, keeping the sequence centered on perceptual discrimination and standard binocular metrics.

For the color-vision component, investigators reported between-group differences in discrimination-ellipse characteristics on the Cambridge Color Test Ellipse Test. Compared with controls, PD participants had a larger ellipse area (p=0.012) and an increased short-axis length (p=0.009), while the distribution of ellipse-angle orientations also differed between groups (chi-square p=0.03). In discussion, the authors characterized these results as “non-specific” changes in color discrimination in this dataset, with ellipse metrics suggesting broader rather than narrowly axis-specific differences at the group level. Overall, the reported color-testing results indicated measurable alterations in discrimination-ellipse properties among PD participants versus controls in this cohort.

Binocular and vergence measures also differed between groups, with PD participants showing a more remote near point of convergence (17.1±6.1 cm vs 9.1±4.0 cm; p<0.001), a larger mean near-angle deviation on alternate cover prism testing (7.7±6.4 vs 1.5±1.2 prism diopters; p=0.001), and worse stereoacuity (2.3±0.79 vs 1.7±0.24 log arcsec; p=0.006). When the authors examined whether visual performance related to motor severity, they reported no significant correlations between UPDRS motor scores and the color-discrimination ellipse metrics or the binocular/vergence outcomes.

Key Takeaways:

• Investigators reported group-level differences on computerized color testing in PD versus controls, described as non-specific changes in color discrimination based on discrimination-ellipse characteristics.
• Clinical binocular testing found between-group differences, including altered near vergence/alignment and reduced stereopsis in PD compared with controls.
• Across analyses, the authors reported that UPDRS motor scores were not significantly correlated with either the color-vision metrics or the binocular/vergence measures assessed.