The long-term use of botulinum toxin for adult strabismus

To characterize patients choosing repeated botulinum toxin injection as a treatment for their strabismus, and assess their demand for it over time (up to 8 years).

Patients who had undergone at least eight injections were identified and their clinical records analyzed for diagnosis, demographic details, and demand for toxin injections with time. To establish any predictive variables, the details for these cases were compared with those of matched controls who had undergone fewer injections. Lastly, a questionnaire was mailed to research patients' views as to the indications and preferences for regular toxin injection as a method of treatment.

Ninety-five patients were identified (34 men, 61 women; median age 37 years), of whom 35 had consecutive exotropia and 16 had secondary exotropia. Other diagnoses represented were residual and primary deviations, restrictive exotropias, and oscillopsias. A trend of fewer injections over the attendance period was seen, and the only complication observed was upper lid ptosis in 1% of injections. Cases exhibited similar demographic composition to matched controls, but were more likely to have consecutive exotropia or secondary esotropia as a diagnosis. Univariate analysis showed evidence (p < 0.001) of an association between the number of previous operations and the odds of being a case. No evidence was found that cases and controls lived at differing distances from our hospital. The questionnaire found that 71% of patients stated appearance as the prime reason for seeking treatment, and 37% stated simplicity of toxin therapy as their reason for reattendance. Twenty-six percent of the patients were disillusioned with the results of previous surgery and preferred toxin therapy as a means of controlling their symptoms.

Botulinum toxin injection is an appropriate long-term treatment for some strabismus patients who choose not to undergo further surgery. A trend toward fewer injections with time was observed, and no adverse effects were associated with long-term treatment.