Pupillometry Study of Brimonidine Tartrate 0.2% and Apraclonidine 0.5%

Abstract

This study investigated possible effects of brimonidine tartrate 0.2% and apraclonidine 0.5% on pupil diameter. Ten subjects between 20 and 40 years of age participated. A Colvard pupillometer (Oasis Medical) was used to measure pupil diameter. Baseline and serial measurements were obtained at 3 luminance levels (>6.4, <0.82-0.4, and <0.2-0.02 cd/m(2)) during a 4-hour interval following instillation of 1 drop of brimonidine tartrate 0.2% or apraclonidine 0.5% in one eye versus a placebo in the contralateral eye. The measurements for each drug were obtained on different days. A nested random effects model controlling for subject's age, race, and sex was used for statistical analysis. A maximum reduction in pupil diameter was observed at 90 minutes from instillation (1.40 mm at >6.4 cd/m(2), 1.69 mm at <0.82-0.4 cd/m(2), and 1.55 mm at <0.2-0.02 cd/m(2)) for brimonidine tartrate 0.2%. At all time intervals and illumination levels, miosis (P < .01) occurred. Apraclonidine 0.5% did not produce a significant effect on pupil diameter. Brimonidine tartrate 0.2% produced a moderate miotic effect. No effect was observed for apraclonidine 0.5%. A predominant agonistic effect on α-2 receptors of the iris dilator may explain this behavior.

Studying the Effect of Iris Mechanics on the Pupillary Light Reflex Using Brimonidine-Induced Anisocoria

“…In this study, an average reduction in resting pupil size of 1.78 mm was observed in brimonidine-treated eyes, which is consistent with the results observed in the other studies. 32,36,37 The relationship between log stimulus intensity and pupil contraction amplitude will vary depending on the area of retina being illuminated, in addition to stimulus brightness. The Ganzfeld bowl light stimulus used in this study will undoubtedly produce a greater pupil response than a smaller-sized light stimulus, although scatter of bright light across the retina even with a smaller-sized light tends to recruit larger areas of retina at brighter lights.…”

“…Brimonidine exerts most of its pharmacologic effect through a2adrenoreceptor-mediated downregulation of norepinephrine release. [44][45][46][47][48][49][50][51] At present, there is no evidence that the a2 agonist activity of brimonidine exerts a modulatory effect on the iris sphincter and its a1 biological activity has been found to be insignificant. 47 CONCLUSIONS Iris mechanics start to limit the excursion of the pupil, on average, when pupil size reaches 3.3 mm in diameter among subjects.…”

Effects of mydriasis and miosis on kinetic perimetry findings in normal participants

“…Therefore, less attention is now paid to pupil diameter. Interestingly, among the different glaucoma therapeutics, it has been reported that 0.15 % [21,22] and 0.2 % [23,24] brimonidine has a miotic effect in addition to an intraocular pressure-lowering effect, constricting the pupil from 5-6 to 3-4 mm. It is known that a pupil size of around 3.5 mm is associated with the best visual performance because the effect of aberration and diffraction are the lowest.…”

Neuro-ophthalmology Annual Review

“…This highlights the importance of concentration when using apraclonidine since the previously mentioned study by Cambron et al 4 demonstrated a miotic effect using apraclonidine 1%. 5 The dissimilar responses of the pupil to 0.5% and 1% apraclonidine could limit the ability of the clinician to appreciate a reversal of the anisocoria in the HS if they are not aware of these differences.…”