Impact of pupil diameter on controlling the development of myopia in orthokeratology

Objective To evaluate the impact of diameter on controlling the development of myopia in orthokeratology.Methods Forty-nine children aged 7 to 14 years were enrolled in this prospective clinical study.Orthokeratology was performed to correct the refractive errors of these children after measurements of refraction,pupil diameter and axial length.Axial length (AL) and diameter were measured 24 months after lens wearing.The average diameter was calculated and was used as the criterion for dividing the children into pupil size above averagevs pupil size below average.Data were analyzed by a paired t-test,an independent t-test,repeated measured ANOVAs and Pearson correlation analysis.Results AL increased significantly throughout the 24-month observation period (F=67.182,P＜0.01).The axial growth of subjects with below average sizes and those with above average sizes was 0.43±0.28 mm and 0.24±0.27 mm,indicating a statistically significant difference (t=2.379,P＜0.05).AL change in subjects with above average diameters was 55.81％ of that for subjects with below average diameters.Baseline diameter was negatively correlated with axial growth at the 24-month visit (r=-0.361,P＜0.05).Linear regression analysis was used between baseline diameter and 2-year axial growth:Axial growth=-0.161× baseline diameter +0.987 (F=7.048,P＜0.05).The average diameter for subjects with above average sizes and those with below average sizes after 2 years was 3.72±0.53 mm and 3.51±0.37 mm,indicating no statistically significant difference (t=2.543,P＞0.05).Conclusion The effect of orthokeratology to control myopia would be more beneficial for children with larger diameters than for children with smaller diameters.This may be due to the enhancement of the myopic shift in the peripheral retina. Key words: Orthokeratology ;  Axial length ;  Refractive, ocular peripheral;  Pupil diameter