Comparison of cycloplegia at 20- and 30-minutes following proxymetacaine and cyclopentolate instillation in white 12-13-year-olds

Clinical Relevance: Reducing the time between drop instillation and refraction reduces the time paediatric patients and young adults spend in practice, facilitating more eye examinations daily. Background: The current procedure for paediatric cycloplegic refraction is to wait for at least 30-minutes post-instillation of a cycloplegic before measuring spherical equivalent refraction. This study compared cycloplegia at 20- and 30-minutes following 0.5% proxymetacaine and 1.0% cyclopentolate in 12-13-year-olds. Methods: Participants were 99 white 12-13-year-olds. One drop of proxymetacaine hydrochloride (Minims, 0.5% w/v, Bausch & Lomb, UK) followed by one drop of cyclopentolate hydrochloride (Minims, 1.0% w/v, Bausch & Lomb, UK) was instilled into both eyes. Spherical equivalent refraction was measured by autorefraction (Dong Yang Rekto ORK-11 Auto Ref-Keratometer) at 20- and 30-minutes post-instillation. Data were analysed through paired t-testing, correlations, and linear regression analysis. Results: There was no significant difference in level of cycloplegia achieved at 20- (Mean spherical equivalent refraction (standard deviation) 0.438 (1.404) D) and 30-minutes (0.487 (1.420) D) post-eyedrop instillation (t (98) = 1.667, p = 0.099). The mean spherical equivalent refraction difference between time points was small (0.049 (0.294) D, 95% confidence interval =-0.108 ̶ 0.009D). Agreement indices: Accuracy = 0.999, Precision = 0.973, Concordance = 0.972. Spherical equivalent refraction at 20- and 30-minutes differed by ≤0.50D in 92% of eyes, and by <1.00D in 95%. Conclusions: There was no clinically significant difference in spherical equivalent refraction or level of cycloplegia at 20- and 30-minutes post-eyedrop instillation. The latent time between drop instillation and measurement of refractive error may be reduced to 20 minutes in White 12-13-year-olds and young adults. Further studies must determine if these results persist in younger children and non-White populations.