China: In a study published in Graefe's Archive for Clinical and Experimental Ophthalmology, entitled "Effect of low-dose atropine eyedrops on pupil metrics: results after half a year of treatment and cessation" by Wei-Ling Bai and colleagues, researchers have found that pupil size and the constriction ratio return to pre-atropine levels after cessation. A once-nightly dose of 0.01% atropine eyedrops increased pupil diameter and decreased constriction ratio but did not influence the Pupillary Light Reflex or PLR.
Low-concentration atropine eyedrops are used for myopia treatment. The effects for controlling myopia development could be better with a higher concentration of atropine eyedrops but with a risk of adverse effects and a more obvious rebound after drug cessation. However, there needs to be more data on ideal atropine concentration.
Researchers evaluated the effect of low-dose atropine eyedrops on pupil metrics in mainland China's double-masked, placebo-controlled, and crossover trial.
In phase 1, subjects received 0.01% atropine or placebo once nightly. After one year, the atropine group switched to placebo (atropine-placebo group), and the placebo group switched to atropine (placebo-atropine group).
Researchers measured ocular parameters at the crossover time point (12th month) and the 18th month.
The results of the study are:
One hundred five subjects completed the study.
The atropine-placebo and placebo-atropine groups had 48 and 57 children, respectively.
There was a decrease in the photopic pupil diameter (PD) and mesopic PD and an increase in constriction ratio (CR, %) than values at the crossover time point of the atropine-placebo group (after cessation).
There was no difference in pupil metrics of the atropine-placebo group from the values at the crossover time point of the placebo-atropine group.
There was an increase in the photopic PD, and the mesopic PD increased and decreased in the CR after six months of treatment, compared with values at the crossover time point of the placebo-atropine group.
During 0.01% atropine treatment, pupil metrics and myopia progression had no association.
They concluded that Pupil metrics and the CR could return to pre-atropine levels following cessation. During treatment, Pupil metrics had no significant effect on myopia progression.
The study's limitations were the lack of baseline measurement of pupil metrics for the atropine-placebo group before atropine treatment, failure to measure the pupil metrics at the beginning of the first year and higher drop-out rate.
Further research is warranted for analysing different atropine concentrations and longer follow-ups in validating the specific long-term effects of atropine on pupil metrics.
Further reading:
Bai, WL., Gan, JH., Wei, S. et al. Effect of low-dose atropine eyedrops on pupil metrics: results after half a year of treatment and cessation. Graefes Arch Clin Exp Ophthalmol 261, 1177–1186 (2023). https://doi.org/10.1007/s00417-022-05863-8