Corneal sensitivity, blink rate, and corneal nerve density in progressive supranuclear palsy and parkinson disease

Purpose: Patients with progressive supranuclear palsy (PSP) and patients with Parkinson disease frequently manifest signs of dry eyes, yet many remain asymptomatic. In this study, we established the relationships between blink rate, corneal sensitivity, and corneal nerve density in patients with ocular surface disease associated with PSP and Parkinson disease. Methods: Fourteen eyes of 7 patients with PSP, 8 eyes of 4 patients with Parkinson disease, and 10 eyes of 5 age-matched controls were examined for meibomian dysfunction, ocular surface staining, and blink rate. Corneal sensitivity was measured with a Cochet-Bonnet esthesiometer, and corneal subbasal nerve density was measured by using confocal microscopy in vivo. Comparisons between variables were assessed by using generalized estimating equation models to account for possible correlation between fellow eyes of the same subject. Results: Abnormal ocular surface staining and meibomian disease were present in most subjects with PSP and Parkinson disease, but in none of the controls. Patients with PSP and Parkinson disease had lower blink rates (P < 0.001) and decreased corneal sensitivity (P < 0.001) compared with controls, whereas subbasal nerve density did not differ between groups. Blink rate was correlated with corneal sensitivity (r = 0.83, P < 0.001), but corneal sensitivity was not correlated with subbasal nerve density (r =-0.16, P = 0.78). Conclusions: Patients with ocular surface disease associated with PSP and Parkinson disease might be asymptomatic because of decreased corneal sensitivity. Decreased corneal sensitivity was not explained by loss of corneal nerves but was associated with decreased blink rate.