Intraocular pressure changes by orthokeratology in myopic children

Objective To evaluate the changes of intraocular pressure (IOP) in myopic children undergoing overnight orthokeratology treatment.Methods It was a retrospective case-series study.Orthokeratology was performed to correct the refractive errors of 303 eyes of 303 teenagers.The patients were divided into 3 groups:low-myopia,moderate-myopia,and high-myopia,based on the diopters.IOP,corneal curvature and refraction were taken respectively at pre-wear,1 day and 7,30,90 days after orthokeratology.Data were analyzed by repeated-measures ANOVA tests.LSD corrections were performed to compare the differences in I0P if significant differences were found.Results The change of IOP became stable after 1-week orthokeratology treatment,and were significant decrease in IOP after treatment (F=51.75,P＜0.01).Moderate and high myopia had an increase of 1.04 mmHg (t=-4.81,P＜0.01) and 0.58 mmHg (t=-2.65,P＜0.05) respectively in IOP at 1-day visit,and low myopia only showed a downward trend at the same time (t=0.57,P＞0.05).Furthermore,the changes in diopters were positively correlated with those in IOP (r=0.131,P＜0.05)3 months post-treatment.The changes of IOP resulted by one unit change in diopter were significantly different among different degree of myopic group (F=3.57,P＜0.05).With one unit change in diopter,the low-myopia teenagers showed significantly more reduction in IOP at 0.50 mmHg than moderate-myopia teenagers (t=-2.57,P＜0.01).No significant differences were observed between low-and high-myopia groups (t=-1.86,P＞0.05),moderate-and high-myopia groups (t=0.68,P＞0.05).Conclusion Orthokeratology results a decrease in IOP measurements.The observed patterns of IOP changes may be caused cooperatively by the changes in corneal morphology and eye accommodation function. Key words: Intraocular pressure;  Noncontact tonometer;  Orthokeratology;  Corneal curvature; Refraction