September 28, 2026
By Kevin Chan, OD, MS, FAAO, FBCLA, IACMM
Clinical Relevance: Why It Matters
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Topical atropine medication has evidently demonstrated a positive dose-response relationship to mitigate axial elongation and thus, myopia progression. Its mechanism, however, remains elusive and controversial, which likely involves a plethora of retinal signaling cascades in lieu of the common accommodation-driven belief. Guinea pigs are a great animal model to study the electrophysiology of myopia.
This study aims to investigate the lesser known aspect of atropine on retinal activities via a full-field electroretinography (ERG), which can help distinguish photoreceptor activity (a-wave) from bipolar-cell activity (b-wave).
Study Objective
Wang et al. examined whether 0.01% or 1% atropine alters retinal functions via electroretinography (ERG) during inhibition of lens-induced myopia progression.
Study Design
Thirty-six 14-day-old guinea pigs received a −10.00D lens over one eye and were assigned to topical 0.01% atropine, 1% atropine or sterile water (vehicle). Refraction and dark- and light-adapted ERG were measured at two, four, six and eight weeks.
Key Findings
- 0.01% and 1% atropine demonstrated retardation of myopia progression in a concentration-dependent manner, which aligned with the hypothesis and the known findings reported previously.
- The use of different atropine concentrations, however, did not significantly show statistically significant changes in photopic and scotopic a-wave amplitudes or scotopic (or dark-adapted) b-wave responses.
- However, photopic b-wave amplitude increased proportionately at week six and eight in atropine-treated eyes (not found in the vehicle group).
- This new finding suggests a delayed effect on retinal signaling driven by the cones, possibly involving bipolar cells, without indication of photoreceptor dysfunction.
- Electroretinogram (ERG) alone, however, was yet able to identify the responsible cell type.
Strengths and Limitation of the Study
- Strengths:
- Robust randomized clinical comparison was conducted between 0.01% and 1% atropine, making the association of atropine-induced retinal responses more pronounced.
- Periodic data collection over eight weeks was shown to be more demonstrative of the delayed functional changes rather than a discrete data observed in an isolated setting.
- Having a vehicle and fellow-eye as controls helped improve statistical confidence that the photopic b-wave finding is indeed associated with treatment rather than normal development or lens wear alone.
- Individual photopic and scotopic ERG testings also helped ascertain that atropine did not cause a generalized disturbance of retinal function within the defined study period.
- Limitations:
- Lacked diversity or heterogeneity by using a single animal model alone. It may not be representative of retinal activities of all species (including humans).
- ERG findings could be subject to species-related variabilities.
- Small sample size (n=36) and dichotomized comparison of only 0.01% and 1% atropine did not necessarily delineate the effects at other clinically used concentrations at which children might respond best.
- Full-field ERG results were unable to localize the response to a specific retinal cell type.
- Yet to establish the association between the observable b-wave amplitude changes and treatment efficacy, predict progression or represent a clinically meaningful signal for full interpretation.
- Additional longitudinal human studies are warranted to further elucidate how retinal functional responses vary with atropine dosing regimen.
Clinical Takeaways
The findings of this study support a plausible atropine effect on cone-driven inner-retinal signaling in the guinea pig model.
While this study is yet to ascertain the role of routine ERG for atropine-treated population at large, it would likely bridge the knowledge gap or further our understanding of the key mechanistic actions of atropine in human eyes. This could further advance the pharmacologic strategies of atropine formulation.
In practice, the application of atropine for children should be shifted from solely “Which one is THE best?” to a more individualized approach based on documented axial length and/or refractive progression, age, tolerability and adherence. Subtle variations of retinal functional activities induced by atropine could potentially be the next surrogate marker of treatment efficacy of myopia control during and post-cessation. Furthermore, potential ERG findings and interpretations could help clinicians predicate proactive interventions for myopia-related retinal pathologies.
Abstract
Electroretinogram response changes in a guinea pig myopia model treated with different atropine concentrations
YongHong Wang, Fang Li, Alex NG. Lap Ki
Purpose
Material and methods
Results
Conclusions
