Brimonidine and apraclonidine as vasoconstrictors in adjustable strabismus surgery

Abstract

Conjunctival and episcleral bleeding can interfere with visualization of anatomic structures during strabismus surgery. In the United Kingdom, dilute adrenaline (epinephrine) is routinely used to induce vasoconstriction at the beginning of strabismus surgery. Because it causes mydriasis and mildly inhibits accommodation, it is relatively contraindicated if early postoperative suture adjustment is planned. To test whether topical alpha(2)-adrenergic agonists (brimonidine 0.2% and apraclonidine 1%) are useful alternatives to topical adrenaline (epinephrine) in adjustable suture strabismus surgery. Prospective observational pilot study. Brimonidine 0.2% or apraclonidine 1% was applied to the medial or lateral conjunctiva of 10 consecutive adult patients undergoing strabismus surgery with adjustable sutures under general anesthesia. Video images were taken before and up to 20 minutes after instillation. The surface area of ocular surface blood vessels on the acquired images was quantified at selected intervals using imaging software. Both agents induced potent transient vasoconstriction of ocular surface vessels. Within 5 minutes of application, brimonidine reduces blood vessel surface area by 69.2% (95% CI, 50.4-88); this effect persists for 20 minutes. Apraclonidine reduces vessel area by 64.6% (95% CI, 57.2%-72%) within 10 minutes and begins to wear off over the following 10 minutes. Both brimonidine and apraclonidine may be useful alternatives to topical adrenaline (epinephrine) in adjustable suture strabismus surgery.