Tear Osmolarity, Break-up Time and Schirmer's Scores in Parkinson's Disease

Dry eye is an important problem in Parkinson's disease (PD) with a potential to affect life quality. Tear osmolarity, accepted as the gold standard in dry eye diagnosis, has not been studied in this subset of patients so far. Therefore, in this study we aimed to evaluate tear osmolarity, Schirmer's test scores and tear film break-up time (TBUT) in PD patients.

PD patients with a minimum follow-up of 1 year and healthy controls who admitted for refractive abnormalities were enrolled to the study. Subjects using any systemic medication with a possibility to affect tear tests were not included in the study. The presence of any ocular surface disorder, previous ocular surgery, previous dry eye diagnosis, any topical ophthalmic medication or contact lens use were other exclusion criteria. Age, gender, disease duration, and Hoehn and Yahr (H&Y) score for disease severity were noted, and blink rate (BR), Schirmer's test score, TBUT and tear osmolarity of the right eye were measured in both groups.

Thirty-seven PD patients and 37 controls were enrolled to the study. The groups were age and gender matched. The mean disease duration and H&Y score were 5.70±2.64 years and 1.70±0.93, respectively. H&Y staging and disease duration were not correlated to BR, Schirmer's scores, TBUT, or tear osmolarity (p>0.05). The mean BR was 8.54±4.99 blinks/minute in PD patients and 11.97±6.36 blinks/minute in the control group. Mean Schirmer's scores, TBUT and osmolarity values were 9.08±4.46 mm, 11.38±4.05 seconds and 306.43±12.63 mOsm/L in the PD group and 17.16±9.57 mm, 12.81±3.66 seconds and 303.81±16.13 mOsm/L in the control group. The differences were significant only in BR and Schirmer's scores.

BR and Schirmer's scores decreased significantly in PD patients. Although not significant, the demonstrated tear osmolarity increment might be important to document the dry eye and inflammatory process of the ocular surface in PD patients.