Abstract
Purpose :
Low-concentration atropine alters pupil size through competitive binding of acetylcholine receptors on the iris sphincter pupillae and slows myopia progression through an unknown pathway. This study investigates whether the increase in pupil size with 0.01% atropine eye drop use is associated with myopia control efficacy.
Methods :
Participant data from the baseline and 24-month visits of the Myopia Outcome Study of Atropine in Children(MOSAIC)–a randomized controlled trial of 0.01% atropine vs placebo–was used for this analysis. Axial length(AXL) and pupil diameter(photopic and mesopic lighting conditions) was measured using the Aladdin(Topcon, Tokyo, Japan). Spherical equivalent refraction(SER) was measured 30 minutes after instillation of 1% cyclopentolate using autorefraction. To minimize segmentation errors, pupil diameter>3 standard deviations from the mean were excluded and lateral magnification from the cornea corrected. Using linear mixed model analyses, data from both eyes and a random intercept term for subject to account for within-subject correlation was modelled. The 2-year change in SER or AXL were outcomes and pupil diameter at baseline or 2-year change in pupil diameter were the explanatory variables.
Results :
Of 250 participants enrolled in MOSAIC (mean age 11.8±2.4years, 155[62%]female), 167 and 83 were allocated to atropine 0.01% and placebo, respectively. At baseline, the mesopic and photopic pupil size were 5.0±0.75mm (mean difference=0.09mm, p=0.43) and 4.1±0.65mm (mean difference=0.02mm, p=0.85) respectively. Change in mesopic and photopic pupil size at the 24-month visit was greater in the atropine 0.01% group, compared to the placebo group (mean differences 0.39mm, p<0.001 and 0.38mm, p<0.001, respectively) and no significant interaction between eye color (blue, green or brown). After adjusting for age, sex and baseline SER, 24-month change in pupil size was not associated with the outcomes in either treatment group; SER(placebo:beta=-0.003D/mm, p=0.95;0.01% atropine:beta=-0.02D/mm, p=0.42) and AXL(placebo:beta=-0.006mm/mm, p=0.70; atropine 0.01%:beta=-0.001mm/mm, p=0.88) progression.
Conclusions :
Use of atropine 0.01% eye drops only slightly increased pupil size, but amount of pupil size increase was not associated with 2-year change in SER or AXL irrespective of eye color. Change in pupil size with 0.01% atropine use does not appear to be a biomarker of myopia control efficacy.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.