Clinical observation of orthokeratology lens on low, moderate myopia correction after 2 years

Objective To observe the clinical effects of orthokeratology lens (orthokeratology,OK) on the correction of myopia,to evaluate the effects and safety of long-term Ortho-K on the myopia control.Methods A retrospective case study.Seventy-three cases (143 eyes) with low,and moderate myopia patients were divided into 2 groups,45 cases (87 eyes) with the Ortho-K contact lens in the experimental group,and 28 cases (56 eyes) wearing spectacles in the control group.The experimental group was subdivided into 2 groups:43 eyes in group A (myopia≤-3.00D),44 eyes in group B (-3.00D＜ myopia ≤-6.00D),based on the diopters.The visual acuity (VA) of the experimental group were taken respectively at pre-wear,1 day (8-10 hours),1 week,1 month,3 months,6 months,1 year,1 and a half years,2 years.The changes of axial length,corneal thickness,corneal endothelial and intraocular pressure within 2 years with the Ortho-K contact lens in the experimental group were compared.Refraction was measured in the control group pre-wearing and after 2 years.Data were analyzed by a paired t test before and after wearing glasses,Data between groups were compared with single factor analysis of variance,A P value of 0.05 or less was considered statistically significant.Results In the experimental group,VA improved significantly after wearing glasses a day.In group A,VA was 1.0 after a week,which decreased after 1 and a half of years,and then needed to test again and replace lenses.In group B,the mean VA was 0.8 after a week,which decreased after 1 and a half of years,and then needed to test again and replace lenses.The vertical and horizontal curvature of cornea in the experimental group became flatter than before,and the difference was statistically significant (P ＜0.05) after 2 years.The myopic degree in the experimental group increased (0.65 ± 0.58) D 2 years later,and the control group with spectacles increased (2.19±0.61) D,which showed statistically significant difference (F=228.64,P ＜0.05).The axial length in group A growth increased 0.45±0.28 mm2 years later,and the difference was statistically significant compared with before (t=9.834,P =0.000,P ＜0.05).The axial length in group B growth increased 0.34±0.33 mm 2 years later,and the difference was statistically significant compared with before (t =2.570,P =0.014,P ＜0.05).The axial length variation of two groups had statistical significance difference after 2 years (F =5.360,P ＜0.05).Ortho-K could control the development of low and moderate myopia,the effect was significantly compared with the moderate myopia.In the experimental group,there were no statistically significance in corneal thickness,corneal endothelial cell density,intraocular pressure after 2 years,compared with which measured before (P ＞0.05).Conclusions Most of the low,moderate myopia patients wearing Ortho-K long-term later can get visible VA more than 0.8,and can keep for about a year,when the visual acuity decrease slightly,lens need to be changed.The control effect of moderate myopia is significantly better than low myopia after Long-term wear,and can not cause the changes of corneal thickness,corneal endothelial cell density and intraocular pressure. Key words: Orthokeratology;  Myopia control;  Visual acuity;  Corneal curvature;  Intraocular pressure