Objective: To evaluate time of maximum cycloplegia in myopic children with brown irises and to study differences between refractive error after maximum cycloplegia measured by retinoscopy and autorefraction.

Materials and Methods: The present study was a prospective descriptive study included myopic children with brown irises aged 5 to 14 years. Cycloplegic refraction was performed using cyclopentolate 1%, three times, ten minutes apart. Refractive error was measured by autorefraction before and at 30, 40, 50, 60, 70, and 80 minutes after the first instillation of cyclopentolate. Finally, retinoscopy was performed by a single examiner at 80 minutes. Time of maximum cycloplegia was determined from the time point at which the 95% confidence interval of the differences between the mean spherical equivalent (SE) at each point and its final value at 80 minutes was reached and remained within the equivalence limit (±0.25 D). Difference between SE of retinoscopy and autorefraction was evaluated.

Results: Sixty-eight children were recruited. The mean age was 10.5 years (SD 2.4). Thirty-seven children were male (54%). The time of maximum cycloplegia was 30 minutes after the first instillation of cyclopentolate. At 80 minutes, the degree of myopia measured by autorefraction was significantly higher compared to those measured by retinoscopy (p<0.001, mean difference 0.26 D).

Conclusion: Time of maximum cycloplegia in myopic children with brown irises was 30 minutes after the first instillation of cyclopentolate. Even when the maximum cycloplegia was reached, the degree of myopia measured by autorefraction was higher than that measured by retinoscopy.

Keywords: Cycloplegic refraction, Cyclopentolate, Cycloplegia, Myopia, Myopia in children, Retinoscopy, Autorefraction

DOI: doi.org/10.35755/jmedassocthai.2021.03.11414

Received 14 May 2020 | Revised 23 October 2020 | Accepted 29 October 2020