Effects Of Myopic Orthokeratology On Visual Quality And Correlation Analysis Of Influencing Factors

PurposeTo analyze the changes in visual performance and optical quality and the time course of changes in optical quality after orthokeratology(ortho-k),and its correlation with the magnitude of lens decentration and the diameter of treatment zone(TxZ).MethodsThis prospective,self-controlled study was conducted at the Tianjin Medical University Eye Hospital(Tianjin,China)between July 2015 and November 2015.The study evaluated 35 eyes of 35 patients wearing overnight ortho-k.There were 19 males and 16 females and the mean age was 11.46±2.33 years(range,8-16 years).At baseline,the spherical equivalent refractive error(SERE)was-3.39±1.40 D(range,-0.75 D to-5.50 D);with-the-rule astigmatism up to-1.50 D.Corneal topography,contrast sensitivity function(CSF)in photopic condition,mesopic condition without and with glare,the root-mean-square(RMS)of the third-order aberrations,fourth-order aberrations,and total higher-order aberrations,modulation transfer function cutoff(MTF cutoff),Strehl ratio(SR),and objective scattering index(OSI)were measured before and 1 month,6 months and 1year after ortho-k treatment.SERE,astigmatism,the magnitude of lens decentration and the TxZ were collected to analyze the correlation with parameters of optical quality.Data were analyzed using SPSS(version 19.0;IBM,NY).spherical equivalent refractive error,astigmatism,AULCSF(photopic condition,mesopic condition without and with glare),third-order RMS,fourth-order RMS,total higher-order RMS,MTF cutoff,SR,and OSI before and after ortho-k treatment were compared using paired-samples t test.Repeated-measures analysis of variance(ANOVA)were performed for the analysis of the time course of changes in these parameters.The relationship between the change in parameters of optical quality and SERE,astigmatism,change in ALUCSF(photopic condition,mesopic condition without and with glare),third-order RMS,fourth-order RMS,total higher-order RMS,MTF cutoff,SR and OSI were analyzed using Pearson correlation test,respectively.All the factors that affect axial elongation mentioned above were examined using stepwise multiple linear regression analysis(in collinearity diagnostic tests;all Variance Inflation Factors(VIF)were <10,which indicated no multiple collinearities).A p<0.05 was considered to be statistically significant.ResultsAfter ortho-k treatment,the SERE significantly decreased to-0.43±0.32D(p<0.01)at 1 month,and uncorrected visual acuity achieved 20/20 or better in all the subject eyes.Posttreatment data showed no significant fluctuations in SERE until 1-year follow-up visits.AULCSF significantly decreased from 1.324±0.098 to 1.236±0.092,1.261±0.090 to 1.185±0.099 and 1.242±0.095 to 1.176±0.099 in photopic condition,mesopic condition without and with glare,respectively;MTF cutoff and SR significantly decreased from 46.18±5.67 to 39.54±5.39(p<0.01)and from 0.28±0.06 to 0.22±0.04(p<0.01),;the third-order RMS,fourth-order RMS,total higher-order RMS significantly increased from 0.251±0.012?m to 0.673±0.019?m,0.206±0.009?m to 0.946±0.021?m and 0.268±0.07?m to0.596±0.010?m,respectively;and OSI significantly increased from 0.42±0.18 to 0.75±0.22(p<0.01).After 1-year ortho-k treatment,the AULCSF were recovered until 6 months' treatment,MTF cutoff value had a slight recovery than 1-month treatment,but this fluctuation was no statistically significant(p=0.338).Similarly,for third-order RMS,fourth-order RMS,total higher-order RMS,SR and OSI,there were not a statistically significant difference from 1-month to 1-year treatment.The decrease in AULCSF(values after ortho-k significantly correlated with the amount of lens decentration(photopic condition,mesopic condition without and with glare),but not with baseline spherical,astigmatic refractive error,or diameter of TxZ(all P>0.05).The increase in third-order RMS,fourth-order RMS,total higher-order RMS correlated with the initial SERE,the amount of lens decentration()and the diameter of TxZ().For the data collected by OQAS,the decrease in MTF cutoff after ortho-k significantly correlated with the amount of lens decentration(r=0.499,P=0.005)and the diameter of TxZ(R=-0.494,P=0.005).The decrease in SR significantly correlated with the diameter of TxZ(P=-0.434,P=0.024).The increase in OSI did not correlate with any of the potential predictive factors being tested(all P>0.05).ConclusionsVisual performance and optical quality decreases after overnight orthokeratology treatment and would be stable until 1-month treatment,which can be alleviated by a lower SERE,a larger TxZ diameter and a smaller lens decentration.