Differences In Biometric And Optical Properties In Myopic Anisometropia

Purpose:To evaluate the difference of ocular biometric properties such as intraocular pressure,axis length,corneal power,optical properties like contrast sensitivity and higher-order aberrations between the more and less myopic eyes in myopic anisometropia patients.Investigate the possible causes of the differences and explore the underlying factors related to the occurrence and development of myopic anisometropia.Methods:115 patients with myopic anisometropia?spherical equivalent difference between two eyes?1.0D,the best corrected visual acuity of all eyes?0.8?from January 2013 to June 2018 were enrolled in our study.According to the difference of spherical equivalent?SE?between two eyes,115 patients were divided into two groups:31 patients with the difference of SE?2.5D and 84 patients with the difference of SE<2.5D.Detailed ocular examinations including visual acuity and optometry,biometric characteristics like intraocular pressure,A-scan,and corneal topography,optical characteristics like contrast sensitivity?4 spatial frequency?underdifferentilluminationconditions,higher-order aberrations,ocular dominance,Optical transfer function in all eyes were recorded.The paired sample t-test was used to compare the difference between two eyes.the correlations and linear relationship between the difference of ocular parameters and the degree of the anisometropia were evaluated using correlation analysis and linear regression.Results:1.The difference of SE between groups was significant.After comparing the spherical power,cylinder power and SE of more and less myopic eyes in each group,it was found that there were significant differences in spherical power and SE between two eyes?P<0.05?,and there was no significant difference in cylinder power?P>0.05?.2.The anterior chamber volume,vitreous cavity length and eye axis length of more myopic eyes were significantly higher than those of less myopic eyes.In two groups?difference of SE?2.5D and<2.5D?more myopic eyes had deeper anterior chamber and higher intraocular pressure,and the difference was statistically significant?P<0.05?.The was no significant difference in central corneal thickness,white-to-white diameter,lens thickness and mean SimK between any group?P>0.05?.3.In the groups of all patients and high anisometropia,the difference of vitreous cavity length and AL in two eyes was positively correlated with the degree of anisometropia.The difference of 1 mm of axis length was equal to2.554D and 3.488D anisometropia respectively.There was no correlation between the difference of corneal power,intraocular pressure,anterior chamber depth,anterior chamber volume and the degree of anisometropia.and the more myopic eyes had an average ACD 0.80%deeper,VL3.45%and AL 2.51%longer than that of the less myopic eyes.4.Only in the group of 31 patients?>2.5D?at the condition of bright,the contrast sensitivity of AULCSF?1.29±0.13?and 6c/d?1.86±0.17?in more myopic eyes was higher than that in less myopic eyes.?1.24±0.11 t=2.097p=0.044,1.79±0.15 t=2.211 p=0.035?.The difference was statistically significant.There was no significant difference in pupil size and BCVA between two eyes?P>0.05?.5.About 2/3 of the patients had right eye as the ocular dominance,1/3had left eye as the non-dominance,46%had more myopic eye as the ocular dominance,and 54%had less myopic eyesas the non-dominance.6.The difference of PSF and MTF in corneal plane between eyes was not significant(P>0.05.The difference was statistically significant7.In total cases,ocular STrefoil,Z3^-3 and corneal STrefoil,Z3³ were higher in less myopic eyes than those in more myopic eyes,and the difference was statistically significant?P<0.05?;in the group of low anisometropia,ocular SSph,corneal Scoma and Z3^-1 were higher in more myopic eyes,the difference was statistically significant?P<0.05?;in the group of high anisometropia,the ocular Sh,STrefoil,Z3^-3 and the corneal Sh,STrefoil,Z3³were higher in less myopic eyes,the difference was statistically significant?P<0.05?.There was no significant difference in the third and fourth higher-order aberrations?P>0.05?.Conclusions:1.The difference of myopic anisometropia is mainly spherical refraction rather than cylindrical refraction,and mainly axial rather than curvature.2.IOP is higher in the more myopic eye of anisometropes,However,the difference of intraocular pressure between two eyes is much smaller than that allowed by physiological range.It is considered that the axial elongation of the eyeball caused only by intraocular pressure alone is not related to myopic anisometropia,Increased intraocular pressure may contribute to axial growth in the case of scleral weakness.3.The anterior chamber volume and depth is deeper,Length of vitreous cavity and axial length is longer in the more myopic eyes of myopic anisometropic patients.Unbalanced growth is the main cause of anisometropia,The greater the degree of anisometropia,the greater the difference between AL and VL,The difference in ACD compared with VL and AL was not proportionate in both eyes,and the posterior contributes the most,the anterior contributes little to the unbalanced growth of eyes,but the vertical position of ACD in the eyes can not be ignored.It has high Symmetry in lens thickness,corneal power,white-to-white diameter and corneal thickness.4.The visual quality at the condition of bright is better than that in dark and dark with glare condition.The CS of middle spatial frequencies is higher than that of high or low spatial frequency,and generally conforms to the bell distribution.The contrast sensitivity of more myopic eyes was slightly better than that of less myopic eyes in the group with high anisometropia,which may be related to the increase of total higher order aberration of less myopic eyes in this group.The decrease of CS was not related to myopic anisometropia.5.In myopic anisometropia patients,there was no difference in BCVA and pupil diameter between the two eyes.Most of the right eyes were ocular dominance.The proportion of ocular dominance with less myopic eyes was slightly higher than that of the more myopic eyes.6.After controlling the influence of diffraction and aberration,there is no significant difference in the optical properties of corneal plane.7.The corneal total higher order aberrations are higher than those of the ocular,which indicates that the higher order aberrations of the lens compensate for corneal aberrations.The third is greater than the fourth order aberration,the coma aberration is greater than trefoil aberration and spherical aberration.The coma and spherical aberration are the main components of the third and fourth order aberrations respectively.In Zernike polynomials,the higher the order,the farther away from the axis,the smaller the value and the contribution to aberration.8.the composition of aberration was different.The correlation between the reduction of total higher-order aberrations and anisometropia is not valid.Whether the increase of coma and spherical aberration has an effect on anisometropia needs further study and exploration.