Color vision: A study of essential tremor cases versus normal controls

Background and purpose: Patients with essential tremor (ET) and Parkinson's disease (PD) may exhibit overlapping clinical features. Also, a growing number of non-motor features are being documented in ET. Color vision abnormalities, although well known to occur in PD, have not been studied extensively in ET. We assessed color vision in ET cases and controls. We furthermore assessed subgroups of ET cases with clinical features that might link them to PD (i.e., ET cases with a family history of PD, and ET cases with rest tremor) to determine whether these cases had greater color vision abnormalities than ET cases without those features. Methods: Participants were enrolled in a case-control study at Columbia University Medical Center. Color discrimination testing was performed using the Farnsworth-Munsell 100 Hue test. The total error score (TES) for the hue test was determined. Results: The TES was similar in 55 ET cases and 55 controls (144.6±91.8 vs. 145.6±96.6, P=0.96). ET cases with rest tremor (n=8) were similar to ET cases without rest tremor (n=47) with respect to the TES (117.0±73.4 vs. 149.3±94.4, P=0.36), as were ET cases with a family history of PD (n=9) versus without (n=46) (144.4±57.0 vs. 144.6±97.6, P=0.996). Conclusions: Although a number of links exist between ET and PD, and non-motor features have been described in both, a color vision abnormality does not seem to be a feature of ET.