A Comparative Study of Correction of Pre-Existing Corneal Astigmatism Between Incision on the Steepest Meridian and Limbal Relaxing Incisions in Phacoemulsification Surgery – A One Year ranDomized Control Trial at KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi

Abstract

Background and objectives As physiological astigmatism is practically invariable, upto 95% of eyes have some clinically detectable astigmatism. More than 1.0 D of pre-operative corneal astigmatism is seen in approximately 40 % of the patients who undergo cataract surgery. The cataract surgery has evolved from the ancient technique of couching to modern manual SICS and phacoemulsification. Earlier, ECCE induced more postoperative astigmatism due to longer incisions and sutures. With the advent of phacoemulsification through a small clear corneal incision and foldable intraocular lens, the focus has transformed from reduction of surgically induced astigmatism to correction of pre-existing astigmatism, if any present. Various techniques have been described for the correction of astigmatism during the cataract surgery like incision on steep meridian, limbal relaxing incisions, toric intraocular lens and laser vision correction. The purpose of this study is to compare the effect of phacoemulsification incision on the steepest meridian alone and in combination with paired limbal relaxing incisions in reducing the pre-existing corneal astigmatism. 1. To compare the clear corneal phacoemulsification incision on the steepest meridian alone and along with limbal relaxing incisions (LRIs) for the reduction of preexisting corneal astigmatism at the time of cataract surgery. 2. To assess the safety and efficacy of limbal relaxing incisions for the correction of pre-existing corneal astigmatism during phacoemulsification surgery. Methodology The present one - year randomized control trial was conducted in the Department of Ophthalmology, KLES Dr. Prabhakar Kore hospital and Medical Research Centre, Belagavi on patients undergoing cataract surgery during the period of January 2017 – December 2017. The patients with pre-existing astigmatism in the range of 0.5D – 2.5 D were included in the study and underwent either phacoemulsification with incision on the steepest meridian (Group A) or phacoemulsification along with the paired limbal relaxing incisions placed on the steepest meridian (Group B). They were evaluated at 3 weeks and 6 weeks postoperatively. Results In the present study, the mean age in Group A was 61.87 + 10.12 years and Group B was 66.17 ± 8.30 years with majority being in the range of 61-70 years. 57% patients were male and 43 % patients were female in Group A and 63% patients were male and 37% patients were female in Group B. In this study, 37% patients in Group A and 17% patients in Group B had pre-existing astigmatism in the range of 0.5 D – 1 D, 53% in the range of 1D – 1.5D in both groups, 10% in Group A and 13% in Group B in the range of 1.5 D – 2 D and no patient in Group A and 17% in Group B had pre-existing astigmatism in the range of 2 D – 2.5 D. In the present study, majority of the patients in Group A that is 22 (73%) had post-operative astigmatism in the range of 0.0 – 0.5 D, followed by 08 patients that is 27% in the range of 0.5 – 1D. In Group B, 28 patients that is 93% had post-operative astigmatism in the range of 0.0 – 0.5D whereas only 2 patients (7%) had post-operative astigmatism in the range of 0.5 – 1D. In Group A, the mean pre-operative and post-operative astigmatism was 1.01 ± 0.27 D and 0.45 ± 0.28 D respectively which was highly significant statistically (p<0.0001). Similarly, in Group B, the mean pre-operative and postoperative astigmatism was 1.27 ± 0.53 D and 0.34 ± 0.20 D respectively which was highly significant statistically (p<0.001). The magnitude of astigmatic correction was more in the LRI group (0.93 ± 0.33) compared to incision on the steep meridian group (0.56 ± 0.01) as LRI corrected upto 2.5 D of astigmatism. The mean surgically induced astigmatism in Group A was 0.67 with the standard deviation of 0.27 and in Group B the mean surgically induced astigmatism was 1.02 with the standard deviation of 0.46. This comparison of difference of surgically induced astigmatism between the two groups was highly significant statistically (p=0.0007). In this study, the mean correction index in Group A was 0.75 ± 0.4 and in Group B the mean correction index was 0.82 ± 0.26 which was not statistically significant. In the present study, the mean flattening effect in Group A was 0.67 with the standard deviation of 0.27 and the mean flattening effect in Group B was 1.02 with the standard deviation of 0.46. The comparison between the two groups was highly significant statistically (p=0.0007). In this study, by taking the phacoemulsification incision on the steepest meridian on the basis of pre-existing astigmatism, that is in Group A, the mean keratometric difference was 0.95 ± 0.92 which was statistically significant (p<0.001). By placing the paired limbal relaxing incisions on the steepest meridian along with phacoemulsification incision as in Group B, the mean keratometric difference was 1.08 ± 0.96 which was statistically significant (p<0.001) The visual rehabilitation was good. 93% patients in Group A and 97% patients in Group B had UCVA in the range of 6/12 – 6/6 and 97 % patients in Group A and all the patients in group B had BCVA in the range of 6/12 – 6/6. Conclusion and interpretation Clear Corneal phacoemulsification incision placed at the steepest meridian and paired limbal relaxing incisions along with phacoemulsification incision helps in reducing the pre-existing corneal astigmatism. Mild cases of astigmatism can be treated by incision on steepest meridian alone whereas in cases of moderate to severe astigmatism, limbal relaxing incisions provide a better option