One-year efficacy and tolerability of 0.05% atropine for myopia control in Estonia: a prospective cohort study

This prospective cohort study demonstrates that 0.05% atropine is an effective and well-tolerated treatment for myopia control in patients with light irises, with early axial length changes serving as a predictive marker for long-term treatment response.

The Gist

Imagine your child's eyes are like a growing balloon. For many kids, this balloon grows too fast, stretching the eye out and causing nearsightedness (myopia). If the balloon gets too big, it can become fragile and prone to popping (serious eye problems later in life).

Doctors have a special "deflator" called atropine eye drops that helps slow down this growth. But there's a catch: the stronger the deflator, the more it might annoy the balloon (causing side effects like sensitivity to light).

This study is like a report card from a real-world classroom in Estonia, testing a specific strength of these drops (0.05% atropine) on a group of kids who have light-colored eyes (blue, green, or gray).

Here is the story of what they found, broken down simply:

1. The "Light-Eyed" Concern

For a long time, doctors worried that kids with light eyes might react too strongly to these drops. Think of light irises like a thin, clear curtain, while dark irises are like a thick, heavy velvet curtain. The "light curtain" lets more light in, so doctors thought the drops might make the pupil (the hole in the center of the eye) open too wide, causing too much glare and trouble reading.

The Verdict: The study found this worry was mostly unfounded. Even though the kids had light eyes, the drops worked beautifully and were much more comfortable than expected.

2. The "Speed Bump" Effect (Side Effects)

When the kids first started using the drops, it was a bit like jumping into a cold pool.

• The Splash: About half the kids felt a bit of glare (photophobia) or had trouble reading up close (near-work difficulties) in the first week.
• The Adjustment: But here's the good news: the kids' eyes got used to it very quickly. By the third month, the "splash" was almost gone. The side effects were like a temporary headache after a new workout—they happened at first but faded away as the body adjusted.
• The Result: Almost no one had to stop using the drops or buy special sunglasses. They just kept going.

3. The "Brake" Performance (Efficacy)

Did the drops actually stop the balloon from growing? Yes, and very well.

• Over the course of a year, the kids' eyes grew very, very little.
• Imagine if you expected a balloon to grow 1 inch, but it only grew the width of a human hair. That is how well the drops worked.
• Nearly 9 out of 10 kids had their eye growth slowed down to a near-halt.

4. The "Crystal Ball" Discovery (Predicting the Future)

This is the most exciting part of the study. The researchers asked: "Can we tell if the treatment is working after just a few weeks, instead of waiting a whole year?"

They found a surprising pattern: The eye's reaction in the first few weeks is a crystal ball for the whole year.

• If the eye showed a tiny bit of "shrinkage" or very slow growth in the first month or three months, it was a very strong sign that the eye would stay small for the whole year.
• It's like checking the weather forecast on a Tuesday; if the clouds look right, you can predict it will be sunny all weekend. This means doctors might be able to spot kids who aren't responding well very early on and switch their treatment plan before the eye grows too much.

The Bottom Line

This study is like a reassuring thumbs-up for parents and doctors.

1. It works: 0.05% atropine is a powerful tool to stop nearsightedness from getting worse.
2. It's safe: Even for kids with light eyes, the side effects are usually just a temporary annoyance that fades away.
3. It's smart: We might be able to predict how well the treatment will work just by looking at the eye's growth in the first few months, allowing for faster, smarter decisions.

In short: The "deflator" works great, the "cold pool" splash is brief, and we have a new way to peek into the future of a child's vision.

Technical Summary

1. Problem Statement

While low-concentration atropine (specifically 0.05%) is established as an effective intervention for slowing myopia progression, significant uncertainties remain regarding its real-world application, particularly in specific demographic subgroups.

• Light Iris Pigmentation: There is clinical concern that patients with lighter irises (common in European populations) may experience higher rates of atropine-induced side effects (e.g., photophobia, near-work difficulties) due to greater pupil dilation susceptibility.
• Predictive Monitoring: Clinicians lack validated early biomarkers to predict long-term treatment response. Currently, treatment adjustments often rely on observing progression over 6–12 months, potentially delaying effective management for non-responders.
• Real-World vs. Clinical Trials: There is a need to validate the efficacy and tolerability of 0.05% atropine outside controlled trial settings, specifically in routine clinical practice.

2. Methodology

• Study Design: Prospective cohort study conducted at East Tallinn Central Hospital, Estonia.
• Participants: 33 patients (median age 11.97 years; 48.5% male) with moderate to high myopia.
  • Inclusion Criteria: Baseline axial length (AL) ≥75th percentile (Dutch growth chart) and/or myopia progression ≥0.50 D/year.
  • Demographics: 82% of participants had light irises (Seddon scale grades 1 and 2).
• Intervention:
  • Drug: 0.05% atropine eye drops (preservative-free, compounded single-dose units).
  • Regimen: One drop in each eye, Monday through Friday, in the evening.
  • Adaptation: Two patients temporarily switched to lower concentrations (0.01% or 0.025%) due to intolerance but resumed 0.05% by months 6 and 9.
• Outcome Measures:
  • Primary Efficacy: Change in Cycloplegic Spherical Equivalent Refraction (SER) and Axial Length (AL) over 12 months.
  • Biometrics: Photopic pupil diameter and accommodation amplitude measured at 1 week, 1 month, and 3, 6, 9, 12 months using Topcon MYAH.
  • Tolerability: Systematic recording of side effects (photophobia, near-work difficulty, etc.) with severity ratings (0–10 scale).
  • Predictive Analysis: Linear regression models were used to determine if early AL changes (1 week to 6 months) predicted 12-month AL outcomes, adjusting for age, sex, and baseline AL.
• Statistical Analysis: Linear mixed-effects models for longitudinal data; linear regression for predictive modeling.

3. Key Contributions

• Real-World Evidence in Light-Iris Populations: Provides robust data confirming that 0.05% atropine is effective and tolerable in a predominantly light-iris cohort, addressing a specific gap in the literature regarding iris pigmentation and drug susceptibility.
• Early Predictive Biomarkers: Identifies that early changes in Axial Length (AL) are strong predictors of 12-month treatment outcomes. This suggests that clinicians can assess treatment efficacy much earlier than the traditional 6–12 month window.
• Tolerability Trajectory: Characterizes the temporal pattern of side effects, demonstrating that while initial side effects are common, they are transient and rarely require permanent treatment modification.

4. Key Results

• Efficacy:
  • SER Change: Mean change of –0.078 ± 0.349 D over 12 months.
  • AL Change: Mean elongation of 0.052 ± 0.115 mm.
  • Success Rates: 87.9% of participants had SER progression <0.5 D, and 90.9% had AL elongation <0.2 mm.
  • Comparison: Results were comparable to or better than other major studies (e.g., MOSAIC2, LAMP), despite the cohort having light irises.
• Tolerability:
  • Initial Side Effects: High incidence at 1 week (Enlarged pupils: 69.7%; Photophobia: 48.5%; Near-work difficulty: 42.4%).
  • Resolution: Incidence dropped sharply by 3 months (Photophobia and near-work difficulty fell to 12.1%).
  • Severity: Median severity scores decreased from 4–5/10 at 1 week to 2/10 at 3 months.
  • Discontinuation: No participants discontinued treatment permanently; only two required temporary dose reduction. No systemic side effects were reported.
• Predictive Modeling:
  • Early AL changes significantly predicted 12-month outcomes ($P < 0.05$ for all time points).
  • Predictive Power: The model's explanatory power ($R^2$) increased over time:
    • 1 week: $R^2 = 0.27$
    • 3 months: $R^2 = 0.40$
    • 6 months: $R^2 = 0.66$ (Strong association, $\beta = 0.95$, approaching a 1:1 relationship).
  • This indicates that AL measurements at 3–6 months can reliably forecast the full-year outcome.

5. Significance

• Clinical Practice: The study supports the widespread implementation of 0.05% atropine as a first-line therapy for myopia control, even in populations with light irises where tolerability was previously a concern.
• Management Strategy: The findings advocate for a shift in monitoring protocols. Clinicians can utilize early biometric monitoring (specifically AL at 3–6 months) to identify non-responders early. This allows for timely interventions (e.g., dose escalation or combination therapy) rather than waiting for significant myopic progression to occur.
• Patient Counseling: The data provides evidence to reassure patients and parents that while initial side effects are common, they are typically mild and self-limiting, improving adherence rates.

Limitations: The study had a modest sample size ($N=33$), lacked an untreated control group (relying on historical/natural progression data for comparison), and had a 12-month follow-up, limiting insights into long-term rebound effects.