Investigation Of Surgically Induced Astigmatism After Phacoemulsification Cataract Surgery

Objective : To compare the arithmetic mean of surgically induced astigmatism(M-SIA)andthe centroid of surgically induced astigmatism(C-SIA)after standard cataract surgery.Methods : In this study,retrospectively examined 66 cases(101 eyes)with cataract more than 3months after cataract surgery and measured postoperative uncorrected visual acuity,best spectacle-corrected visual acuity,IOL MASTER and corneal topography.A total of 94 eyes were included in the comparison of axial length.And 101 eyes,including 50 right eyes and 51 left eyes included in preoperative corneal biological changes,corneal astigmatism changes before and after operation,total M-SIA and C-SIA comparison.Moreover 35 Patients undergoing bilateral cataract surgery(70 eyes including 35 left and right eyes)were included comparison of corneal astigmatism changes,M-SIA and C-SIA.Three months after operation,according to the type of astigmatism,they were divided into with the rule(WTR)astigmatism group,against the rule(ATR)astigmatism group and oblique astigmatism group(OBL).And divided three groups into mild,moderate and severe astigmatism according to the magnitude of astigmatism to analyze and compare the changes of corneal astigmatism,M-SIA and C-SIA before and after operation.Results: There was no significant difference in preoperative biometrics such as flat corneal keratometry,steep corneal keratometry,mean corneal keratometry,axial length,corneal astigmatism and types of corneal astigmatism between the right eye and the left eye.There was no significant difference in preoperative and postoperative corneal astigmatism in entire study population eyes,in the left and right eyes of entire study population,in the left and right eyes of patients who undergoing bilateral cataract surgery,and in the groups based on types of corneal astigmatism: with the rule、against the rule and oblique astigmatism.However,in the groups based on according to the size of astigmatism: mild,moderate and severe astigmatism,there were significant differences in preoperative and postoperative corneal astigmatism.The M-SIA of the whole eye was 0.69 ±0.53 D,the C-SIA was 0.18 ±0.60 D,at an axis of 33 °.Comparing the M-SIA and C-SIA of the right eye and the left eye of entire study population: the M-SIA of the right eye was 0.62 ±0.38 D,the C-SIA was0.06 D ±0.73 D,at an axis of 42 °.The M-SIA of left eye was 0.77 ±0.64 D and C-SIA was 0.31 ±0.96 D,at an axis of 32 °.There was significant difference between the two groups.Among the patients who undergoing bilateral cataract surgery,the M-SIA of the right eye was 0.68 ±0.40 D,and the C-SIA was 0.10 ±0.27 D,at an axis of 27 °.The M-SIA was 0.73±0.66 D and C-SIA was 0.26 ±0.96 D,at an axis of 26 °.There was significant difference between the two groups.In the groups according to the type of astigmatism: there was no significant difference in M-SIA among the three groups or between the two two groups.In the groups according to the size of astigmatism: there was no significant difference in M-SIA among mild,moderate and severe astigmatism groups.Conclusion: 1.A 2.4 mm temporal clear corneal incision standard cataract surgery induce the M-SIA by ～ 0.7D,the magnitude of the C-SIA largely decreased to approximately 30%(overall),10%(right eye)and 40%(left eye).2.The SIA of the temporal side(right eye)was less than SIA of the nasal side(left eye).3.2.4 mm temporal clear corneal incision had little effect on corneal astigmatism and did not change the type of astigmatism.4.There was no difference in SIA caused by different magnitude of corneal astigmatism < 3.0D.