Influence Of Angle Alpha On Visual Quality After Implantation Of Intraocular Lenses

Objective:To obtain the Alpha Angle after IOL implantation using iTrace function analyzer,and to study the effect of this Angle on the visual quality of patients after IOL implantation.Methods:31 cases(56 eyes)who underwent phacoemulsification combined with IOL implantation in our hospital from January 2021 to December2022 were collected.All patients’ eyes were divided into four groups according to Axial Length of the eye: Group A: axial length < 26mm(AL),group B :26mm≤AL < 28 mm,group C 28mm≤AL < 30 mm,and group D ≥30mmAL.According to the different results of the IOL Alpha Angle comparison among the four groups,we divided the Axial Length into two groups: Group a: < 30 mmAL;Group b: ≥30mmAL.Finally,the≥30mmAL group were divided into two groups according to whether or not they were implanted in the Capsular tension ring.Group b1: Group without capsular tension ring implantation.Group b2: Capsular tension ring was implanted in the group.Angle Alpha(Alpha Angle of cornea)was detected by iTrace before surgery.Distance,intermediate,and near visual acuities were recorded 3 months postoperatively.iTrace was used to measure Angle Alpha(Alpha Angle of cornea),modulation transfer function average height(MTF AH),point spread function(PSF),Spherical aberration(SA),Coma aberration(Coma)Higher order aberration(HOA).And after full dilation of pupil,the Angle Alpha(Alpha Angle of IOL),which reflects the centralization of the IOL,is depicted manually by iTrace.Results:1.There was a statistically significant difference between the Alpha Angle of cornea and the Alpha Angle of IOL in all patients three months after surgery(P < 0.05).2.Comparing the IOL Alpha Angle of patients with different axial length,there were statistical differences between the ≥ 30 mmAL group and the other three groups.3.The objective visual quality parameters of ≤30mmAL group and≥30mmAL group were statistically different in MTF AH(P=0.001),PSF(P=0.0005)and coma(P=0.0079).SA(P=0.34)and HOA(P=0.06)had no significant difference.There were statistically significant differences in UCDVA(P < 0.0001),BCDVA(P < 0.0001)and UCIVA(P=0.04),while there were no statistically significant differences in UCNVA(P=0.98).4.The Alpha Angle of IOL after the implantation of capsular tension ring(CTR)was lower than that of the patients without capsular tension ring implantation when the axial length is larger than 30 mm.Conclusion:1.There is a difference between the Alpha Angle of IOL and the Alpha Angle of cornea.The Alpha Angle obtained by the new method can reflect the neutrality of IOL well.2.When the axial length of the eye is more than 30 mm,the Alpha Angle of the IOL is generally larger,indicating that the intraocular lens is decentered largerly.When the axial length of the eye was between 26-30 mm,the Alpha Angle of IOL did not increase significantly,and the intraocular lens had no large decentration,suggesting that some patients with high myopia also had conditions for multifocal intraocular lens implantation.3.The decentration of intraocular lens in the ≥30mmAL group is too large,which leads to the degradation of subjective and objective visual quality.4.Capsular tension ring implantation can improve IOL decentration and increase IOL neutrality in patients with long axial length.