Central corneal thickness and its relationship to Parkinson's disease severity

To investigate the effect of Parkinson's disease (PD) on blink rate (BR), tear breakup time test (TBUT), Schirmer's test, and corneal thickness, and the relationship of these effects with disease severity.

Prospective controlled study.

Fifty-five eyes from 55 patients with PD and 40 eyes from 40 healthy subjects were analyzed in the study.

The patients were divided into 2 groups according to their Hoehn-Yahr (H-Y) scores; patients classified as H-Y 1-2 were designated as the mild group, and those classified as H-Y 3-5 were designated as the moderate group. Subjects were screened for BR, TBUT, and Schirmer's test, and the central corneal thickness (CCT) was measured.

The BR, Schirmer's test, TBUT, and CCT values of the patient group were significantly lower than those of the control group. The BR and TBUT of the mild group were significantly lower than those of the control group, but the decreases in the Schirmer's test values and CCT were not statistically significant. In addition, significant decreases in the BR, TBUT, Schirmer's test scores, and CCT were observed in the patient group as the H-Y score increased.

A reduced BR and poor tear quality in the early stages of PD, as well as decreased tear production as the disease progresses, can result in reduced CCT. The possibility of a thin cornea should be taken into consideration while measuring the intraocular pressure in patients with severe PD.