Objective: To determine the appropriate dose of botulinum toxin type A for the treatment of dry eye disease in terms of effectiveness and complications. 

Materials and Methods: Patients with dry eye having a similar degree in both eyes treated with non-preservative artificial tears for at least one month and in whom dry eye symptoms persisted with positive fluorescein corneal staining were enrolled. In each patient, a subcutaneous injection of 3.3 units of botulinum toxin type A was administered in the medial part of the randomly selected lower eyelid, while 2.5 units of the same was administered to the second lower eyelid. Complete subjective and objective evaluations were performed at baseline and 2-, 8-, 12-, and 16-weeks after the intervention.

Results: Eleven patients, with a mean age of 64.63±14.81 years, were included. Dry eye symptoms assessed by the mean of ocular surface disease index (OSDI) score improved significantly after treatment in both the 3.3- and 2.5-units groups. Eight of 11 (72.7%) eyes in both groups had improved OSDI scores. No statistically significant improvements were observed in most objective variables. Comparison of post-treatment OSDI score, Tear film break-up time (TBUT), Schirmer’s test, and modified Oxford grading scheme between the 3.3- and 2.5-units groups showed no significant difference at any time point of the study.

Conclusion: Both 3.3- and 2.5-units botulinum toxin injections into the medial lower eyelid improved dry eye symptoms in up to three-quarters of the patients. Botulinum toxin injection into the medial lower eyelid can be used as an adjunctive treatment for dry eye disease by the initial dose of 2.5 units.

Received 27 February 2024 | Revised 5 June 2024 | Accepted 7 June 2024

DOI: 10.35755/jmedassocthai.2024.8.14019