Association between pupil size and response to atropine therapy in the Atropine Treatment of Myopia study (ATOM2)
In brief
Kids whose pupils dilate at least 2 mm on atropine show better myopia control
In the ATOM2 trial of 400 children, a pupil increase of about 2 mm (at least 2.5 mm in 6-8 year olds) was linked to slower axial-length growth and less myopia progression, whereas little or no dilation did not reliably predict poor outcomes. Change in pupil size was a modest, not definitive, marker of treatment response.
- Journal
- Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie (Q1)
- Published
- 20 July 2026
- Study design
- Randomized controlled trial
- Evidence level
- Level 1, High (CEBM 1b)
- Authors
- Daniel Peh, Bryan Sim, Hla Myint Htoon, Deborah Tan, Audrey Chia
- PMID
- 42474739
- DOI
- 10.1007/s00417-026-07405-y
Why clinicians should know about it
- Picked for Ophthalmology (top studies of the week, 25 October 2026): Pediatric myopia management; evaluates response to atropine therapy
Abstract
PURPOSE: To determine if pupil size at baseline, on treatment, or change in pupil size while on atropine was associated with myopia progression. METHODS: This study utilized data from the ATOM2 study, a prospective, randomized, double-masked trial. 400 children were randomized to receive atropine 0.5%, 0.1%, or 0.01% daily in both eyes in a 2:2:1 ratio. Demographic data, as well as pupil size (PS) under photopic (300 lx) and mesopic (4 lx) conditions, axial length (AL), and spherical equivalent (SE) data at baseline and on follow-up, were collected. RESULTS: At baseline, the mean photopic and mesopic pupil size was 3.96+/-0.63 mm and 4.48+/-0.66 mm, respectively. Pupils on higher doses were more dilated, with eyes with smaller PS at baseline having smaller PS on treatment. Multivariate analysis suggested that changes in axial length (AL) and spherical equivalent (SE) were strongly associated with age and change in PS, while PS on treatment was also associated with change in AL after controlling for sex, race and atropine dose. Receiver operating characteristic analysis, however, suggested that change in PS was a poor predictor of treatment response (area under curve: 0.53-0.69), with sensitivity being better than specificity. So while a larger change in PS (e.g. ≥2.5 mm in 6.0-8.9year old children, or ≥2 mm in older children) was more likely to be associated with a better result; having a smaller PS change did not necessarily suggest a poor result. CONCLUSIONS: A larger change in pupil size on treatment was associated with a better treatment response.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.