The Research Of The Correction Of Astigmatism By The Composite Corneal Incision In Cataract Surgery

[Background information and Objective] Cataract is a worldwide major blindness-causing eye disease. Recently combined phacoemulsification and intraocular lens implantation surgery has become the main surgical treatment for cataract. With the progressing of the cataract surgical technology and the increasing requirements of the postoperative visual quality from the patients, the cataract surgery has been gradually transited to the refractive surgery from emersion surgery. The corneal astigmatism after the cataract surgery is an important factor that affects the patients’ vision and comfort. Thus, it has been a relentless pursuit goal of the ophthalmologist to alleviate corneal astigmatism after the cataract surgery. Normally, the human corneal is in the state of tension equilibrium, maintains fixed corneal shape and refractive stability. The equilibrium of this tension will be broken when an incision is made, the corneal refractive pattern will be changed,and there will be a redistribution of the refractive of the corneal. Therefore, it is possible to correct the astigmatism by the composite corneal incision. According to published reports, the releasing corneal incision through the maximum corneal curvature radial axis can effectively reduce the astigmatism. The purpose of this research is to study the efficiency of the correction of the corneal astigmatism pre-cataract-surgery by making the main and the auxiliary corneal incision through the maximum corneal curvature radial axis.[Methods] It is a forward-looking research. All the subjects including44patients (47eyes) who came from the Jinan central hospital affiliated to Shandong University. All of them were diagnosed as age-related cataract and the value of the preoperative corneal astigmatism were greater than1.5D. The patients were registered by the order and randomly divided into2groups:experimental group (composite clear corneal incision-both the main and the auxiliary corneal incision are on the maximum corneal curvature radial axis,the orientation of the main and the auxiliary corneal incision is180°) with26eyes and control group (top right clear corneal incision-the main incision is located in the10:30o’clock position, the auxiliary incision is located at3:00o’clock, the maximum corneal curvature radial axis is random) with21eyes. Diseases affecting vision were excluded preoperative. All patients had combined phacoemulsification and intraocular lens implantation surgery through a3.2mm clear corneal incision. The corneal astigmatism, uncorrected visual acuity, best visual acuity of the two groups were measured at pre-surgery, one week,one month and three months after surgery. Then we assessed the effects of the correction of the corneal astigmatism by these2kinds of incision. Besides, the experimental group is compared with the study that using the on-axis clear corneal incision(OCCI) reported in the literature.[Results] The vision of the patients of the both groups got improved after the surgeries. The uncorrected vision of the experimental group was better than that of control group at1week and3months after the surgeries, and there were statistical significances of the differences(P<0.05). However, there were no statistical significances differences of the best visual acuity between the two groups at3months after the surgeries(P>0.05). The average corneal astigmatisms of the experimental group at1week,1month,3months after the surgeries were1.24±0.66D、1.58±0.71D、1.54±0.71D. On the contrast, they were3.32±1.89D、2.65±1.08D、2.59±1.02D of the control group. The corneal astigmatisms of the experimental group were smaller than that of control group at1week,1month and3months after the surgeries, and there were statistical significances of the differences(P<0.05). The corneal astigmatisms of the control group at1week,1month and3months after the surgeries were greater than that of the group before the surgeries, and there were statistical significances of the differences(P<0.05); there were statistical significances of the differences(P<0.05) between the corneal astigmatisms at1week and1months,3months after the surgeries; there were no statistical significances of the differences(P>0.05) between the corneal astigmatisms at1month and3months after the surgeries. In the experimental group, the corneal astigmatisms at1week,1month and3months after the surgeries were smaller than that of the group before the surgeries, and there were statistical significances of the differences(P<0.05); there were statistical significances of the differences(P<0.05) between the corneal astigmatisms at1week and1months,3months after the surgeries; there were no statistical significances of the differences(P>0.05) between the corneal astigmatisms at1month and3months after the surgeries. Compared with the study using on-axis clear corneal incision(OCCI),the composite clear corneal incision is more effective on corneal astigmatism correction.[Conclusion] In the Phacoemulsification cataract surgery, making the main and the auxiliary corneal incision through the maximum corneal curvature radial axis(the orientation of the main and the auxiliary corneal incision is180°) is more effective on the correction of the corneal astigmatism from pre-cataract-surgery. During1week later to3months later of the surgery, with incision gradually healed,the edema at the incision had gone, and the tissue restored, corneal refraction gradually achieved a steady state, the corneal astigmatism had a certain back. Precision3.2mm clear corneal incision can enter the Refractive steady state in advance (1month after the surgery).