| Purpose To evaluate the effectiveness of Grand Seiko Ref/Keratometer WAM-5500 compared to Topcon KR8900 autorefractor in detecting refractive error in large scale vision screening for Chinese school age children with the WHO criteria.We present a new method for analyzing relative corneal refractive power(RCRP)in children undergoing orthokeratology and explore its potential association to effective myopic control.Recent studies have shown that the odds of achieving successful myopic control with orthokeratology increase with relative corneal refractive power(RCRP).For wide clinical application,the association between parameters derived from Fourier analysis and existing clinical parameters needs to be elucidated.Methods Epidemiological investigation and prospective,self-controlled study were used.886 childrenwith an average age of 9.49 ± 1.88 years,were enrolled in the eye health screening from Tianjin Dagang district and Taida district.All subjects received autorefraction before and after cycloplegia,with Grand Seiko Ref/Keratometer WAM-5500 and the Topcon KR-800 autorefractor.From January 2016 to March2017,55 patients(aged 8-13 years)who visited Tianjin Medical University Eye Hospital were recruited.Axial length and corneal topography were measured before and after one year orthokeratology.Axial growth < 0.30 mm was defined as clear control group and ≥ 0.30 mm as weak control group.The corneal topography difference map was obtained by Fourier analysis to obtain the maximum relative upward refractive power(m RCRP)and the Fourier analysis was modeled to obtain the components M,F1 and F2.Logistic regression was used to evaluate the predictive effect of this model on the prevention and control of myopia.The corneal topography of the patients(aged 8-16 years)who were admitted to Tianjin Medical University Eye Hospital from February 2016 to March 2018 were measured and the differences were made after 6 months of orthokeratology at the baseline of their initial diagnosis.The lens decentration was calculated from the difference of two measurements.By analyzing the modulation function of RCRP at 360 degrees,Fourier parameters,F1,F2,M,and composite index Vmax were obtained.The correlation between Fourier transform parameters and clinical parameters is analyzed in scalar,directional and vector domains.Statistical analysis using SPSS19.0(IBM,USA).Bland-altman consistency and regression model analysis were used,and the sensitivity and specificity analysis under AUC and ROC curves were used for instrument comparison.Logistic regression model was used to evaluate the effect of myopia control 1 year after orthokeratology.Pearson correlation analysis was used to analyze the correlation between the eccentricity of spherical lens,astigmatism lens and keratoplastic lens and the parameters of Fourier model.P<0.05 was considered statistically significant.ResultsThe mean spherical equivalent(SE)was-0.98 ± 1.81 Diopter(D)and the prevalence of myopia was 48.9% defined by WHO criteria according to the result of cycloplegic autorefraction.The mean SE of un-cycloplegic autorefraction with Topcon and WAM were-1.21 ± 1.65(D)and-1.20 ± 1.68(D).R2 of WAM and cycloplegic autorefraction was 0.8318,showing a strong linear agreement.Bland– Altman plot indicated a moderate agreement between the two approaches.The sensitivity and specificity were 90.52% and 83.51% for hyperopia,95.60% and 90.24% for myopia,79.40% and 90.21% for astigmatism,and 98.16% and 98.91% for high myopia.45 subjects of 55 were effectively controlled,and 10 were weakly controlled after one year orthokeratology.There was no significant difference of M between two groups.MRCRP modulation in the significant control group was significantly higher than that in the weak control group(F1,1.17 vs.0.64 diopters [D],P = 0.02).F2,0.85 V.S.0.35 D,P = 0.03).Through the regulation of m RCRP(p = 0.02),when the peak m RCRP > was 4.5D,the probability of achieving effective control increased,and the subjects had more than 80% chance to achieve effective control.In the multiple regression analysis of Fourier parameters and clinical parameters,M and F1 were significantly correlated with lens eccentricity(P<0.001)and SE(P<0.001).F2 was significantly correlated with CA(P<0.001).Vmax was significantly correlated with lens eccentricity(P<0.01)and SE(P<0.001).Direction analysis showed that Vmax and F1 were significantly correlated with lens removal eccentricity(r = 0.512,P<0.001).R = 0.643,P<0.001),F2 was significantly correlated with corneal astigmatism(r = 0.188,P<0.001).In the vector analysis,the correlation coefficient between F1 and lens eccentricity is 0.7107,the correlation coefficient between F2 and corneal astigmatism is 0.8953,and the correlation coefficient between Vmax and lens eccentricity is 0.2985.Conclusions These results suggest that Grand Seiko can be used for large-scale myopia screening in areas with a high prevalence of myopia in large populations.Meanwhile,in the optimization of myopia prevention and control means,the new method reveals how the combination of SE,corneal asymmetry and corneal astigmatism determines the modulation function of m RCRP.In this model,Fourier parameters were found to be directly correlated to clinical parameters,which provided a strong basis for clinical application. |
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