Axial Length/Corneal Radius Of Curvature Ratio To The Detection Of Cycloplegic Refractive States In Preschool Children

Introduction: In China,the prevalence of refractive errors is high,and the onset of myopia is early.For children and teenagers,their refractive errors should be detected,diagnosed and intervened early.Cycloplegic optometry is the gold standard for measuring refractive status internationally,but this diagnostic method is affected by external conditions,or cooperation and compliance of subjects.With children accompanying by more than three weeks of vision loss and photophobia after cycloplegia,it is necessary to search for other methods to replace the cycloplegic optometry in large-scale vision screening.This study aimed to evaluate the axial length/corneal radius of the curvature ratio on the cycloplegic refractive status and to provide a reference cut-off value for the estimation of refractive state.Methods: A total of 270 preschool children aged 3 to 7 years with the suspected refractive error were selected from the ophthalmology clinic of the Second Hospital of Dalian Medical University.After excluding other eye diseases,axial length(AL),and corneal radius of curvature(CRC)were identified,cycloplegic optometry was conducted and the degree of spherical equivalent(SE)of the right eyes was recorded.Subjects were divided into four groups according to SE grades: Group A,SE ≤-0.50D;Group B,-0.50 D < SE ≤ +1.25D;Group C,+1.25 D < SE ≤ +3.00D;Group D,SE >+3.00 D.One-way ANOVA was performed according to age and SE grades grouping to compare the differences between groups of various refractive factors.The relationship between each element was examined from the overall and grouping aspects,and the regression curve was fitted.The ROC curves were drawn and the area under the ROC curves was calculated,and different diagnostic thresholds were output according to the needs.Results: SE was negatively associated with age.Children with small SE had a longer axial length and a greater AL/CRC ratio.There was no significant difference in the refractive elements of the eyes of children aged 3 to 5 years old.The progress of children’s emmetropia was accelerated after the age of 5 years old.The refractive states of children approached to the pre-myopia or reached myopia at the age of 6 to 7 years old.The correlation between AL/CRC and cycloplegic SE was much stronger(r =-0.914,P<0.001).The linear regression was SE = 40.95-1.76 × AL and SE = 43.5-14.46 × AL/CRC.After grouping by age and SE,the correlation between AL/CRC ratio and SE was still stronger than that between AL and SE.ROC curves showed that AL/CRC was better than AL for detecting refractive error.The diagnostic threshold of myopia in AL/CRC was 3.00,the threshold for diagnosis of hyperopia less than +1.25 D was AL/CRC greater than 2.93,and the threshold of diagnosing hyperopia greater than+3.00 D was AL/CRC less than 2.83,with the maximum Youden index.Conclusion: Axial length/corneal radius of curvature ratio can well represent the equilibrium of the ocular tissues.AL/CRC has higher sensitivity and specificity than any single ocular element as a new refractive state diagnostic method.