A Longitudinal Study To Evaluate The Effect Of Manual Sics Sclerocorneal Tunnel Incision Placed In The Steepest Meridian On Pre-Existing Astigmatism And Surgically Induced Astigmatism By This Incision On Eyes Undergoing Cataract Surgery At KLES Hospital, Belagavi

Abstract

Cataract (47.9%) remains the leading cause of visual impairment in all areas of the world, except for developed countries. The spectrum of cataract surgery has evolved greatly from the days to Extra-Capsular Cataract Extraction (ECCE) to phacoemulsification and Manual SICS now-a-days. Phacoemulsification is predominantly done in developed countries, but is difficult to perform in developing countries due to the constraints of higher cost and the need for high-end machines. Manual SICS is the hence the affordable and better alternative in such conditions. In the older cataract population about 66.9% of the eyes have astigmatism equal to or >1.00D, and 6.12% had astigmatism >3.00D. An incision on the steeper meridian of the cornea helps to reduce astigmatism by inducing flattening along that axis and steepening along the axis perpendicular to it. Hence pre and post-operative astigmatism can be reduced by placement of site of the incision along the steeper meridian. The purpose of this study is to see the beneficiary effect of an incision placed on the steepest meridian in controlling the astigmatic outcome in eyes with pre-existing astigmatism and to lower the amount of surgically induced astigmatism induced. OBJECTIVES OF THE STUDY Primary Objective To evaluate the effect of postoperative Surgically Induced Astigmatism (SIA) caused due to sclerocorneal tunnel incision in SICS which is placed along the steepest meridian either superior or temporal which is determined pre-operatively by keratometry. Secondary Objective To compare the amount of Surgically Induced Astigmatism (SIA) caused by Superior and Temporal incisions in Manual SICS. MATERIALS AND METHODS This study was carried out on 60 eyes of 60 patients undergoing Cataract surgery by Manual SICS method at KLES Dr. Prabhakar Kore Charitable Hospital, Belagavi. The study was carried out over one year during the time period of 1st January 2016 to 31st December 2016. The patients underwent Manual SICS with the incision placed along the steeper meridian which was determined pre-operatively. The patients were followed up on post-operative days 1, 7, 21 and 6 weeks for reduction in the pre-operative astigmatism and the amount of surgically induced astigmatism post-operatively. RESULTS The average age of the patients was 63.7+9.73 years with range being from 35 years to 81 years. The maximum numbers of patients were in the age group of 61-70 years which was 23 (38%). In the study, about 47% of the patients were male while about 53% of the patients were female. Maximum number of patients (21 patients) had pre-operative astigmatism between 0.6D – 1.0D (35%). The range of pre-operative astigmatism was from 0.25D to 2.5D. 52% of patients had post-operative astigmatism of 0.5D – 1.0D. 38% of patients post-operative astigmatism of about 0 - 0.5D. 10% had post-operative astigmatism of 1.1D – 2.0D. The average SIA was 1.12D + 0.6D with p value < 0.001 (Statistically significant). The average SIA with Superior incision was 1.33D + 0.45D. The average SIA with the Temporal incision was 0.84D + 0.67D. The difference between the SIA caused by both the Superior and Temporal incisions was Very Significant with a p value of 0.0011. With Temporal Incision, the keratometric reading in the steeper meridian was reduced from 44.63D + 1.52D pre-operatively to 44.05D + 1.40D post-operatively with p value of 0.003. With Superior Incision, the keratometric reading in the steeper meridian was reduced from 44.57D + 1.57D pre-operatively to 43.87D + 1.44D post-operatively with p value of 0.0016. On the post-operative follow-up of 6 weeks, about 67% of the patients were seen to have visual acuity from 6/6 – 6/12 and 31% had visual acuity of 6/18 – 6/24. INTERPRETATION AND CONCLUSION The study clearly indicates that taking the incision on the steeper meridian during cataract surgery in eyes of patients with pre-existing astigmatism helps to reduce the astigmatism significantly. The surgically induced astigmatism with temporal incision was much less than the surgically induced astigmatism with superior incision and the difference between the two was statistically significant.