<b>COMPARISON OF TEAR FILM PARAMETERS IN PATIENTS WITH MULTIPLE SCLEROSIS AND PARKINSON’S DISEASE</b>

Background: Dry eye disease is a common ocular manifestation of neurodegenerative disorders and may adversely affect visual function and quality of life. However, limited evidence is available comparing tear film parameters between patients with Multiple Sclerosis (MS) and Parkinson's Disease (PD). Objective: To evaluate and compare tear film function and dry eye parameters in patients with Multiple Sclerosis and Parkinson's Disease. Materials and Methods: A comparative cross-sectional study was conducted at the Department of Ophthalmology, Mayo Hospital, Lahore, in collaboration with the Department of Neurology. Fifty-eight participants were enrolled, including 29 patients with MS and 29 with PD. Dry eye symptoms were assessed using the Ocular Surface Disease Index (OSDI), tear film stability was evaluated by Tear Break-Up Time (TBUT), and tear secretion was measured using the Schirmer I test. Data were analyzed using IBM SPSS Statistics version 26.0. Independent samples t-test was used for normally distributed variables, while the Mann–Whitney U test was applied for non-normally distributed data. Statistical significance was set at p < 0.05. Results: Patients with Parkinson's disease had significantly higher OSDI scores than patients with Multiple Sclerosis (61.93 ± 6.60 vs. 36.71 ± 7.30; p < 0.001). Mean TBUT was significantly lower in the PD group for both the right eye (6.27 ± 0.99 vs. 9.05 ± 1.25 seconds; p < 0.001) and left eye (6.30 ± 1.17 vs. 9.19 ± 1.30 seconds; p < 0.001). Schirmer test values were lower in PD patients; however, a statistically significant difference was observed only for the left eye (p = 0.045), while the right eye showed no significant difference (p = 0.394). Effect size analysis demonstrated very large differences between the two groups for OSDI (Cohen's d = 3.63), right-eye TBUT (d = 2.47), and left-eye TBUT (d = 2.33). Conclusion: Patients with Parkinson's disease exhibited significantly greater dry eye symptoms and poorer tear film stability than patients with Multiple Sclerosis. Routine ocular surface assessment should be considered in patients with neurodegenerative disorders, particularly those with Parkinson's disease, to facilitate early diagnosis and management of dry eye disease.