Effect Of Phacoemulsification With Two Different Corneal Incisions On Low-degree Corneal Astigmatism

Objective:To study the effect of phacoemulsification with steep axis and upper corneal incisions on corneal astigmatism and vision for cataract patients with low-degree corneal astigmatism.Methods:A total of 99 cases（104 eyes）of age-related cataract patients with corneal astigmatism less than 1.0D before surgery were collected,and divided into two groups according to different incision positions.Both groups underwent phacoemulsification and IOL implantation;the incisions were located in the clear cornea and were 3.0 mm in size.The surgical incision in group A was located on the steep axis（main meridian of the maximum corneal power）.According to the preoperative corneal astigmatism size,it was further divided into two groups.Patients with corneal astigmatism less than 0.5D were group A₁,and those with corneal astigmatism between 0.5D and 1.0D were Group A₂.The surgical incision in group B was the commonly used upper incision（about 110⁰axial positions）,which was also divided into two groups according to the preoperative corneal astigmatism.Patients with corneal astigmatism less than 0.5D were group B₁,and patients with corneal astigmatism between 0.5D and 1.0D were Group B₂.The uncorrected visual acuity（UCVA）,corneal astigmatism size and axial position were examined before and after surgery.The surgically induced astigmatism（SIA）was calculated by online calculator（http://www.sia-calculator.com/）.Statistical analysis was performed with statistical software.Result:（1）UCVA:The UCVA in groups A and B improved at 1d,1wk,1mo,and 3mo after operation,the differences were statistically significant（P<0.05）.The UCVA of the two groups was gradually improved with the passage of time.Compared between groups at various time points after operation,the average UCVA of group A₁was better than that of group B₁,and group A₂was better than that of group B₂,but the differences were not statistically significant（P>0.05）.（2）Corneal astigmatism size:The degree of corneal astigmatism in group A₁increased at 1d,1mo,and 3mo after surgery compared with that before surgery,the differences were statistically significant（P<0.05）.Corneal astigmatism also increased1wk after surgery compared with that before surgery,the difference was not statistically significant（P>0.05）.In group B₁,the corneal astigmatism increased at 1d,1wk,1mo,and 3mo after operation,the differences were statistically significant（P<0.05）.At various time points after operation,the corneal astigmatism in group A₁was lower than that in group B₁,the differences were statistically significant（P<0.05）.In group A₂,corneal astigmatism was reduced at 1d after surgery,the difference was not statistically significant（P>0.05）;corneal astigmatism was also reduced at 1wk,1mo,and 3mo after surgery,the differences were statistically significant（P<0.05）.In group B₂,corneal astigmatism was increased at 1d,1wk,1mo,and 3mo after operation,the differences were statistically significant（P<0.05）.At various time points after operation,the corneal astigmatism in group A₂was lower than that in group B₂,the differences were statistically significant（P<0.05）.（3）SIA:Both groups A and B had the largest SIA on the first day after surgery,and then gradually decreased.Compared between groups,the SIA of group A was smaller than that of group B on the first day after surgery,the difference was statistically significant（P<0.05）.1wk,1mo and 3mo after surgery,SIA in group A was smaller than that in group B,the difference was not statistically significant（P>0.05）.SIA at3mo after operation in groups A and B were 0.55±0.31D and 0.64±0.26D.（4）The corneal astigmatism axis position:the number of cases of against-the-rule astigmatism in the A and B groups increased at 3 months after operation compared with before operation,but the proportion of each type of astigmatism was not statistically different from that before operation（P>0.05）.Conclusion:（1）For cataract patients with preoperative corneal astigmatism less than 0.5D,3.0mm transparent corneal phacoemulsification was performed.When the incision was located on a steep axis,although it could not correct preoperative corneal astigmatism,it could relatively reduce the increase of postoperative corneal astigmatism compared with the upper incision.（2）For cataract patients with preoperative corneal astigmatism between 0.5D and1.0D,3.0mm transparent corneal phacoemulsification was performed.When the incision was located on the steep axis,the preoperative corneal astigmatism could be effectively corrected.（3）For cataract patients with low-degree corneal astigmatism（≤1.0D）before surgery,no matter the incision was located on the steep axis or on the upper position,the postoperative UCVA was significantly improved compared with that before surgery.At each time point,the UCVA was better than that of the upper incision on the steep axis,but the difference was not significant.