Relationship of aniseikonia with differences of diopter and axial length in myopia patients

Abstract

Objective To explore the relationship of aniseikonia with differences of diopter and axial length in myopia patients, and the possible factors causing aniseikonia. Methods A total of 322 myopia patients (4~40 years old) were selected from May to August, 2021, who underwent optometry in the Ophthalmology Outpatient Department of the Affiliated Hospital of North Sichuan Medical College. ARK-510A autorefractor and Dk-700 optometry system were used for optometry. IOL-Master 700 was used for the measurement of axial length. Aniseikonia were evaluated by binocular aniseikonia test. Gender, age, diopter (sphericity, cylindricity and spherical equivalent), axial length and range of aniseikonia were recorded. Spearman test, chi-square test and multiple linear regression were used to analyze the aniseikonia with the differences of diopter and axial length. At the same time, receiver operating characteristic (ROC) curve of the differences of diopter and axial length was drawn for aniseikonia. Results A total of 322 patients (159 males and 163 females) were included, at an age of (17.77±7.69) years, and the overall prevalence rate of aniseikonia was 15.22% (49 cases). In univariate analysis, the absolute values of all parameter were included in the analysis, the differences of sphericity (r=0.449, P < 0.001), cylindricity (r=0.596, P < 0.001), spherical equivalent (r=0.479, P < 0.001) and axial length (r=0.417, P < 0.001) were all positively correlated with range of aniseikonia. Multivariate analysis indicated that the difference between cylindricity and spherical equivalent showed greater effect on the range of aniseikonia, and the regression equation was Y=0.009-0.626X1 (cylindrical difference)-0.22 X2 (spherical equivalent difference)(F=159.17, P < 0.001, adjusted R2=0.496). In the analysis of risk factors, when the difference of sphericity was more than -2.00 D, and that of cylindricity and spherical equivalent was more than -1.00 D, the risk of aniseikonia was increased. In the diagnostic analysis, the difference of cylindricity (AUC=0.778; 95%CI: 0.69~0.87; P < 0.001; sensitivity: 53.06%, specificity: 99.63%) had the highest value in the diagnosis of aniseikonia. Conclusion Anisometropia does not necessarily lead to aniseikonia. The difference between cylindricity and spherical equivalent is the key factor for aniseikonia, and great attention should be paid in clinical diagnosis and treatment.

Keywords

• aniseikonia
• anisometropia
• sphericity
• cylindricity
• spherical equivalent