Low-concentration atropine (≤0.1%) is widely used in pediatric populations to slow myopia progression. However, the underlying mechanisms of atropine on retinal structure, choroidal thickness, and ocular microvasculature remain incompletely understood, particularly in the short term. Researchers recently evaluated these effects in a recent randomized, double-masked study published in Eye and Vision. They found that low concentrations of atropine (0.01% to 0.1%) did not alter axial length, retinal thickness, or choroidal thickness within 24 hours of a single dose, but a transient, time-dependent reduction in superficial retinal perfusion was observed at 1 hour postinstillation.

The investigation included 20 healthy adults (mean age 25.5 ± 3.4 years; mean refractive error −1.91 ± 2.24 D), following the exclusion of 1 participant due to prolonged pupil dilation after 0.1% atropine exposure. Participants underwent 5 separate sessions, each involving a single instillation of placebo or atropine at concentrations of 0.01%, 0.025%, 0.05%, or 0.1% in the right eye. Measurements were taken at baseline and 1 hour after instillation after participants watched television, and again at 24 hours postinstillation, during which participants went about their usual routines. Key outcome measures included axial length, retinal and choroidal thickness, and optical coherence tomography angiography (OCTA) parameters such as perfusion density and foveal avascular zone (FAZ) area.

Axial length remained stable across conditions, with baseline values around 24.38 mm and negligible variation at 1 hour and 24 hours postinstillation. Similarly, retinal thickness in the central 1.0 mm region remained consistent and averaged approximately 265 µm across all concentrations and time points. Choroidal thickness also showed no significant variation; central values generally ranged from approximately 361 µm to 367 µm.

Regarding the time-dependent effect on superficial retinal perfusion from OCTA analysis, perfusion density in the superficial vascular complex within the 1.0 mm to 2.5 mm annulus decreased significantly over time (P=0.02), with a mean reduction of −1.3% ± 1.2% at 1 hour (P=0.03). This reduction was not sustained at 24 hours (−0.4% ± 0.6%, P=0.28). No significant changes were observed in deep vascular complex perfusion density, choriocapillaris perfusion density, or foveal avascular zone area. Additionally, no dose-dependent effects were identified for perfusion changes, which indicated that the observed microvascular response was related to time rather than atropine concentration.

The results indicate that a single instillation of low-dose atropine does not produce measurable short-term changes in ocular structure but may induce transient alterations in retinal perfusion. These findings suggest that early physiological responses to atropine may occur at the microvascular level rather than through immediate structural changes. “Daily atropine administration may lead to cumulative ocular absorption, producing choroidal changes that differ from those observed following a single instillation,” the researchers wrote, citing a study in which choroidal thickening was observed “following daily 0.01% atropine use for 1 week and 3 months, but choroidal thinning [was observed] after 6 months of continued treatment.”

Study limitations include evaluation of only a single instillation rather than repeated dosing for the purpose of understanding atropine’s acute effects, a small sample size, and inclusion of only young adults rather than pediatric patients, who are the primary population for myopia control. These factors may limit generalizability to clinical practice, particularly in children undergoing long-term atropine therapy, the researchers noted. High myopic patients were not included to avoid possible myopia-related retinal changes.

Reference

1. Lal B, Ostrin LA. Short-term effects of atropine on the retina and choroid in young adults. Eye Vis. 2026;13:8. doi:10.1186/s40662-026-00477-1