Purpose:
This study aimed to investigate the effect of iris colour on pupil, accommodative and myopia progression outcomes in participants using atropine 0.01% eye drops.
Methods:
Data were pooled from three randomized clinical trials: the Irish Myopia Outcome Study of Atropine in Children (MOSAIC; n=250, age 11.8±2.37 years), the Western Australian Atropine Treatment of Myopia (WA-ATOM, n=153, age 11.51±2.69 years), and the US PEDIG Myopia Treatment Study (n=187, age 10.00±1.78 years). Participants were randomized 2:1 to nightly atropine 0.01% or placebo eye drops for 24 months and underwent 6-monthly assessment of near point of accommodation, ocular biometry and cycloplegic autorefraction. Additionally, photopic and mesopic pupil diameter, and dynamic pupillometry, were measured in MOSAIC and WA-ATOM, respectively. Statistical analysis employed linear mixed models with random intercept terms to account for within-subject correlations.
Results:
The pooled analysis included 590 participants (atropine n=396, placebo n=194). The effect of atropine 0.01% eye drops on near point of accommodation in the pooled sample, and on pupil outcomes in the MOSAIC and WA-ATOM, did not differ significantly by eye colour (all p>0.05). At 24 months, there was a greater treatment effect (p<0.05 for interaction with eye colour) in the not brown iris colour group (spherical equivalent: difference=+0.16D, p=0.003; axial length: difference=-0.09mm, p<0.001), compared to the brown eye group (spherical equivalent: difference=-0.07D, p=0.24; axial length: difference=+0.02mm, p=0.31).
Conclusions:
Eye colour had little impact on pupil and accommodative outcomes with atropine 0.01% eye drops, but treatment outcomes were better among participants with lighter iris colours, compared to brown.