Western Australia Atropine for the Treatment of Myopia: corneal biometry analysis and a case of incidental keratoconus

The human eye is a complex optical instrument, and for millions of children around the world, its shape is changing in a way that leads to blurry distance vision. This condition, known as myopia, typically begins in childhood and progresses as the eye grows too long from front to back. While the primary driver of this change is the elongation of the eyeball itself, the front window of the eye—the cornea—also plays a significant role in focusing light. Because the cornea accounts for roughly two-thirds of the eye's total focusing power, scientists have long wondered if treatments designed to slow down the growth of the eye might also subtly alter the shape or strength of this front surface.

To manage the rapid rise of myopia, doctors often prescribe low-concentration atropine eye drops. These drops work by blocking specific chemical signals in the eye, effectively slowing the elongation process. However, because the cornea contains the same chemical receptors that the drops target, a lingering question has remained: could these drops inadvertently change the cornea's shape or weaken its structure over time? This concern is particularly relevant because a weakened cornea can lead to a condition called keratoconus, where the eye bulges outward into a cone shape, causing significant vision problems. Understanding whether a common treatment for one eye problem might trigger another is a critical safety question for parents and doctors alike.

Researchers in Western Australia decided to investigate this directly using a large group of children. They conducted a rigorous study involving 153 participants aged six to sixteen, all of whom had progressive myopia. The children were randomly assigned to receive either nightly drops containing 0.01% atropine or a placebo solution that looked and felt exactly the same but contained no active medicine. This double-blind setup ensured that neither the families nor the doctors knew who was receiving the real treatment until the data was analyzed. The study ran for two years of treatment, followed by a one-year period where no drops were used at all, allowing the team to observe long-term effects. Throughout this three-year period, the researchers used a specialized camera system to take high-resolution, three-dimensional images of the corneas, measuring their thickness, curvature, and overall structural integrity with extreme precision.

During the course of the study, a single, unexpected event occurred that drew immediate attention. One child in the treatment group, a nine-year-old boy, began to show signs of increasing astigmatism, a condition where the eye is shaped more like a football than a basketball. By the two-year mark, his corneal measurements had shifted in a way that raised concerns for early ectasia, a weakening of the corneal tissue. Further imaging confirmed that the cornea was steepening and thinning, leading to a diagnosis of keratoconus. This diagnosis came as a surprise because the child had no family history of the condition, no known allergies, and did not engage in excessive eye rubbing, which are common risk factors. The medical team referred him to a specialist, and he successfully underwent a procedure to strengthen the cornea, allowing him to continue with his daily life and vision correction.

The presence of this single case naturally prompted a deeper look at the entire group to see if the treatment had caused a broader pattern of corneal weakening. The researchers compared the corneal measurements of the children who received the atropine drops against those who received the placebo. They analyzed specific indices designed to detect early signs of corneal instability, looking for any statistical difference between the two groups. The results were reassuring. Across the entire cohort, the children who used the atropine drops did not show a higher risk of corneal weakening or ectasia compared to the placebo group. In fact, the data suggested that the group using the drops had slightly better stability scores on the primary safety index than the placebo group, a finding that held true even after the treatment stopped.

While the overall safety profile was positive, the researchers did observe one specific, isolated change in the shape of the cornea. By the end of the three-year period, the group using atropine showed a slightly greater steepening of the maximum curvature on the front surface of the eye compared to the placebo group. However, this change was small and did not translate into a change in the overall focusing power of the cornea or an increase in astigmatism for the group as a whole. The thickness of the cornea and the curvature of its back surface remained stable and indistinguishable between the two groups. The single case of keratoconus was determined to be consistent with the natural, random occurrence of the disease in the general population, rather than a result of the medication.

The study also examined how the treatment affected the astigmatism of the children, measuring the direction and magnitude of the irregularity in their vision. The analysis showed that the drops did not alter the natural progression of astigmatism. The children in both groups experienced similar, gradual shifts in their vision over time, mirroring the typical patterns seen in growing eyes. This suggests that the mechanism by which atropine slows the growth of the eye does not involve a significant reshaping of the cornea's front surface. The findings align with previous large-scale studies that found the cornea remains largely stable during low-concentration atropine therapy, reinforcing the idea that the drug's primary effect is on the length of the eye rather than its front window.

Ultimately, the research provides a clear answer to the safety concerns regarding corneal structure. The use of 0.01% atropine eye drops does not appear to increase the risk of developing keratoconus or other forms of corneal weakening in children. While the single case of keratoconus in the treatment group was a serious medical event, the statistical analysis indicates it was an incidental occurrence, not a side effect of the treatment. The study concludes that for the vast majority of children, these drops are a safe option for managing myopia without compromising the structural integrity of the cornea. The findings offer peace of mind to families and clinicians, confirming that the treatment targets the eye's growth without destabilizing its front surface.