Accuracy of the ratio of axial length to corneal radius in the assessment of myopia in children and adolescents / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To explore the accuracy of the ratio of axial length(AL)to the average corneal radius(CR)(AL/CR value, i.e., axial ratio)in assessing myopia in children and adolescents.METHOD:Cross-sectional study. A total of 340 cases(680 eyes)of children and adolescents aged 4-16 years old were collected from the ophthalmology clinic of Shangyu People's Hospital of Shaoxing between January 2022 and October 2022. All patients were subjected to optometry after cycloplegia to obtain spherical equivalent(SE), check and record the patient's AL, average CR, and calculate the AL/CR value.RESULTS:All subjects in this study underwent optometry after cycloplegia, and a total of 609 eyes(89.6%)were found to have myopia(SE≤-0.50 D), 58 eyes(8.5%)with hyperopia(SE≥+0.50 D)and 13 eyes(1.9%)with emmetropia(-0.50 D>SE>+0.50 D). There was a statistically significant difference in SE, AL and AL/CR values among different refractive states(P<0.01), but there was no difference in CR(P>0.05). All subjects have refractive parameters: SE +8.75--8.75(average -2.25±2.38)D; AL 19.91-27.54(average 24.41±1.22)mm; CR 7.17-8.71(average 7.83±0.27); AL/CR values range from 2.50-3.50(average 3.12±0.14), correlation analysis showed a relative strong negative correlation between SE and AL/CR and AL(r=-0.891, P<0.01; r=-0.758, P<0.01), but no significant correlation between SE and CR(r=0.067, P>0.05), there was a positive correlation between AL and CR(r=0.483, P<0.01). The linear relationships between SE and AL/CR, AL were SE=45.026-15.162×AL/CR, R2=0.794, SE=33.741-1.474×AL, R2=0.574, respectively. The gold standard was based on the optometric results of cycloplegia, the sensitivity, specificity, misdiagnosis rate and missed diagnosis rate of AL/CR value for myopia were 0.962, 0.839, 0.169, 0.038, respectively, and the accuracy was 94.85%, the Kappa coefficient was 0.742, and the area under the ROC curve was 0.972.CONCLUSION:With high qualitative diagnostic value for myopia and a certain clinical significance for myopia monitoring, AL/CR value can be used to guide myopia prevention and control and other related ophthalmic clinical work.

Analysis of refractive parameters and theirs correlation with spherical equivalent in preschool children aged 3 to 6 years / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To investigate the distribution of refractive parameters and theirs correlation with spherical equivalent(SE)in preschool children aged 3 to 6 years, and evaluate the accuracy of each screening index in diagnosing refractive errors.METHODS: Cross-sectional study. A total of 791 preschool children, ranging from 3 to 6 years old, who consented to undergo mydriatic refraction were selected. Axial length(AL), corneal refractive power(K), and SE were measured after microcoria optometry and mydriatic optometry. Additionally, the corneal radius of curvature(CR)and the axial length/corneal radius of curvature(AL/CR)ratio were calculated.RESULTS: A total of 791 students participated in the study, out of which 400(50.6%)were male and 391(49.4%)were female. The mean values for AL, CR, AL/CR, and SE were 22.62±0.94mm, 7.81±0.29mm, 2.90±0.09, and +1.95±1.31D, respectively. AL, CR, and AL/CR increased with age. AL and CR were significantly higher in males than in females(all P<0.001), while there was no statistically significant difference between AL/CR and SE in males and females(P=0.82, 0.19). The correlation coefficients of SE and AL/CR, AL and CR were -0.86, -0.50 and 0.16, respectively. The results of multiple linear regression analysis indicate that for each unit increase in AL/CR, there was a corresponding shift of 10.91 towards myopia in SE. The sensitivity of AL/CR in screening for myopia was 94.44%, with a specificity of 90.46% and a Youden index of 0.84. For screening myopia under microcoria optometry, the sensitivity was 100%, with a specificity of 66.09% and a Youden index of 0.66. The area under the curve was 0.967 and 0.809 when the ROC curves were plotted using AL/CR and AL as indicators for screening myopia, respectively.CONCLUSION: For large group screening activities where mydriatic optometry is not feasible, AL/CR is better for evaluating refractive status and identifying children with myopia and hyperopia reserve that are lower than normal for their age, compared to AL and microcoria optometry.

Changes of corneal parameters in different areas after cataract surgery / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the distribution characteristics of axial sagittal front power(ASF), true net power(TNP), total corneal refractive power(TCRP)and the difference in back-front corneal radius ratio(B/F ratio)after cataract surgery.METHODS: A prospective study. A total of 156 patients(156 eyes)with age-related cataract who attend Weifang Eye Hospital for cataract surgery from December 2020 to May 2021 were collected. Pentacam was performed before operation and 3mo after operation to collect ASF, TNP and TCRP on 2, 4 and 6mm diameters rings and areas on the corneal apex and pupil-centered, as well as B/F ratio.RESULTS: 3mo after operation, there was no statistical difference in ASF on the 2mm diameters ring and area centered on the corneal apex compared with preoperative values(all P>0.05), however, the ASF values on the 4 and 6mm diameters rings and areas were significantly different from those before surgery(all P<0.05); There was no statistical difference in ASF on the 2mm diameters rings and areas centered on the pupil compared with preoperative values(all P>0.05). The postoperative values of TNP and TCRP on the 2, 4 and 6mm diameters rings and areas centered on the corneal apex and centered on the pupil were statistically different before surgery(all P<0.05). Preoperative, TCRP values were different between 2mm and 6mm and between 4mm and 6mm on both corneal apex and pupil-centered rings(all P<0.0167), TCRP values were all different between 2mm and 6mm diameters areas on corneal apex and pupil-centered(all P<0.0167); 3mo after operation, TCRP values were different on corneal apex and pupil-centered rings between 2mm and 6mm and between 4mm and 6mm diameters(all P<0.0167). While TCRP values on the corneal apex and pupil-centered areas were only different between 2mm and 6mm diameters(all P<0.0167). The preoperative B/F ratio of patients was 81.79%±1.87%, and the postoperative B/ F ratio of patients was 80.68%±2.23%(P<0.001).CONCLUSION: Corneal parameters of different diameters of rings and areas centered on the corneal apex and pupil before and after cataract surgery may change and differ, which should be taken into account when selecting the K value for intraocular lens calculation and individualizing the selection of IOLs based on corneal characteristics.

Clinical exploration based on cost analysis: costs among different screening methods for myopia in school-aged children / 中华医学科研管理杂志

To explore an easily executive and conveniently generalized method with effectiveness and low costing for myopia screening at the early stage.Research was performed to testify the reasonability of using axial length/corneal radius (AL/CR) for myopia screening in children by comparing the cost between AL/CR plus vision acuity (VA) and simple VA examination.Chinese school-aged children in Yangfang school district,Beijing (n=1427,aged 6～12 years old) were randomly grouped for either pure VA examination or for VA plus AL/CR examination.Those suspicious myopic children were informed for further refractive examination.Finally,the cost from screening to definite diagnosis of refractive error was calculated.Generally,compared with VA examination,the total cost was reduced by 15.12％ and by 12.34％,respectively,in the elder group using VA plus AL/CR examination.VA plus AL/CR examination is an economical and reasonable method for screening suspicious myopia in Chinese school-aged children compared with pure VA examination.

Change in Ocular Dimensions with Age in Patients with Emmetropia

PURPOSE: We evaluated changes in ocular dimensions according to age in patients with emmetropia. METHODS: We examined the refraction, corneal curvature, and biometry in 150 subjects from 5 to 75 years old with spherical equivalent refractions under +/-0.75 diopter (D). Ocular dimensions were measured by A-scan ultrasonography and keratometry. We analysed the distribution and change of ocular dimensions according to age (1: 0~19-year-old group, 2: 20~39-year-old group, 3: 40~59-year-old group, 4: 60~79-year-old group). RESULTS: The values for corneal radius (CR), vitreous chamber depth (VCD) and axial length (AL) were highest in group 2. Lens thickness (LT) increased with increasing age, whereas anterior chamber depth (ACD)decreased with increasing age (P<0.05). CR, VCD, AL (P<0.05) and ACD (P=0.10) seem to have higher values in males, while LT seems to have a higher value in females (P=0.06). CONCLUSIONS: Axial length increases with increasing age in subjects aged 0 to 39 years in emmetropia. In subjects aged 40 years or older, axial length becomes smaller with age. In each age group compensational changes to achieve emmetropia according to AL change are shown in ocular dimensions like CR, VCD, ACD, LT.

Corneal radius of curvature in emmetropic Thai people.

The corneal radius of curvature of 110 emmetropic Thai people from the out-patient section, Department of Ophthlmology was measured by keratometer, male 37, female 73, age 14-58 years, the mean corneal radius of curvature right eye in the vertical meridian = 7.612+0.264 mm., in the horizontal meridian = 7.726+0.257 mm., left eye in the vertical meridian = 7.610+0.269 mm., in the horizontal meridian = 7.733+0.269 mm. These corneal curvature value in Thai people were more curve than that of the European and American eye. This assume that the dimension of the Thai eye are smaller than those of the European and American eye.