Beyond motor recovery: subthalamic nucleus deep brain stimulation may improve blinking and dry eye symptoms without restoring tear film homeostasis in Parkinson's disease.

PURPOSE: To investigate the longitudinal effects of subthalamic nucleus deep brain stimulation (STN-DBS) on objective and subjective dry eye parameters in patients with Parkinson's disease (PD).

METHODS

This retrospective observational study included 34 patients with advanced PD who underwent STN-DBS. Comprehensive ophthalmic examinations were performed were performed before surgery and at postoperative week 1, month 1, and month 4. Outcome measures included spontaneous blink rate, tear break-up time (TBUT), Schirmer I test, Oxford corneal staining score, and the Ocular Surface Disease Index (OSDI). Longitudinal changes were analyzed using generalized estimating equations (GEE).

RESULTS

Spontaneous blink rate increased significantly over time, reaching statistical significance at postoperative month 4 compared with baseline (rate ratio 1.19, 95% CI 1.04-1.36; p = 0.014). OSDI scores showed progressive improvement throughout follow-up, with significantly lower scores at postoperative week 1 (p = 0.038), month 1 (p = 0.036), and month 4 (p = 0.002). In contrast, no significant longitudinal changes were observed in TBUT (p = 0.552), Schirmer I test results (p = 0.992) or Oxford corneal staining scores (p = 0.090).

CONCLUSIONS

STN-DBS was associated with increased spontaneous blinking and significant improvement in subjective dry eye symptoms in patients with PD, whereas objective measures of tear film stability, tear production, and ocular surface integrity remained unchanged during short-term follow-up. These findings may suggest that the ocular benefits of STN-DBS may be mediated primarily through modulation of central neural mechanisms governing blink regulation and symptom perception rather than restoration of peripheral tear film homeostasis. Continued ophthalmic evaluation and conventional dry eye management remain important following STN-DBS.