Central corneal thickening (CCT) and widening iridocorneal angle (ICA) values have been observed following a single dose of highly selective alpha-2 adrenergic receptor agonist brimonidine 0.15%, according to research results published in Eye and Contact Lens. 

Researchers conducted a prospective, randomized controlled study to evaluate the effects of a single brimonidine 0.15% dose on anterior segment morphology, pupil characteristics, and choroidal blood flow in both treated and untreated eyes of healthy volunteers, compared with results from another group of healthy volunteer research participants. 

The total study cohort included 61 patients, assigned to a study and a control group (n=30 and n=31, respectively). Participants’ eyes were randomly assigned so that only 1 eye received 1 brimonidine tartrate 0.15% drop, and the other received 1 drop of sodium hyaluronate ophthalmic solution. In the control group, both eyes received 1 sodium hyaluronate drop and only the right eye was analyzed. 


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Each participant had a comprehensive eye exam, including testing for best-corrected visual acuity (BCVA), IOP measurements, slit-lamp biomicroscopy, and fundus examination. Participants also underwent anterior segment morphology, pupillometry, and choroidal thickness measurements. Effects of brimonidine dosing were tested 2 hours after administration. 

The 30 patients in the study group included 15 men and 15 women (mean age, 26.4±4.5 years); the control group included 14 men and 17 women (mean age, 25.5±4 years). 

Treated eyes demonstrated a statistically significantly thicker CCT and wider ICA values following brimonidine treatment, while pre- and post-instillation measurements of aqueous depth (AD), anterior chamber volume (ACV), and horizontal anterior chamber diameter (HCAD) were similar in treated eyes. 

Scotopic, mesopic, and photopic pupil diameters (PD) in treated eyes all changed significantly following brimonidine installation; untreated eyes also showed significantly decreased scotopic and photopic pupil diameters after brimonidine therapy. Post-instillation dynamic pupil measurements on studied seconds for treated and untreated eyes were significantly lower compared with measurements taken preinstallation. 

While both treated and untreated eyes demonstrated decreased static and dynamic pupil measurements following brimonidine treatment, decrements were “significantly prominent” for treated eyes. 

Average speed value in affected eyes significantly decreased after brimonidine instillation. However, pre- and post-instillation average speed values were similar on studied seconds for both untreated and control eyes. 

In both study groups, mean foveal, nasal, and temporal choroidal thickness did not change significantly following brimonidine installation. 

Study limitations include the small sample size, the collection of measurements only once 2 hours following dosing and a lack of long-term values, and the limited generalizability due to the cross sectional nature of the research. 

“Single dose of brimonidine 0.15% causes thickening in CCT and widening in ICA values in treated eyes,” according to researchers. “Brimonidine has a significant effect in reducing scotopic, mesopic, photopic, and dynamic PD values in treated and even contralateral eyes, while it has no effect on [choroidal thickness] values.” 

Reference

Cankurtaran V, Tekin K. Effects of a single dose of topical brimonidine 0.15% on anterior segment morphology, pupil characteristics, and choroidal thickness in healthy subjects. Eye Contact Lens. 2021;47(6):323-329. doi:10.1097/ICL.000000000000708