correction of moderate to severe degree of pre-existing corneal astigmatism by toric intraocular lens implantation in patients undergoing phacoemulsification surgery- a one year hospital based prospective interventional study at kles dr. Prabhakar kore charitable hospital and mrc, belagavi

Abstract

Background and objectives As physiological astigmatism is practically invariable, up to 95% of eyes have some clinically detectable astigmatism. More than 1 D of pre-operative corneal astigmatism is seen in approximately 40 % of the patients who undergo cataract surgery. There has been tremendous advancement in the technique of cataract surgery, from the ancient technique of couching to modern manual SICS and phacoemulsification. Earlier, ECCE induced more postoperative astigmatism due to longer incision and sutures. With the advent of phacoemulsification through a small clear corneal incision and foldable intraocular lens, the aim has transformed from reduction of surgically induced astigmatism to correction of pre-existing astigmatism. Various techniques have been described for the correction of astigmatism during cataract surgery like incision on steep meridian, limbal relaxing incisions, toric intraocular lens and laser vision correction. The purpose of this study is: 1. To correct moderate to severe degree of pre-existing corneal astigmatism in patients undergoing phacoemulsification surgery. 2. To assess the safety, efficacy, post-operative refractive outcome and spectacle independence for distance viewing following implantation of toric IOLs in patients undergoing phacoemulsification surgery. Methodology The present observational study was conducted at the Department of Ophthalmology, KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi on patients having >1 D (diopter) of pre-existing corneal astigmatism over a period of one year, who underwent phacoemulsification cataract surgery with implantation of toric intraocular lens. Results In the present study, the mean age was 61.15 ± 12.08 years. Majority of patients were in the range of 61-70 years. Also, 47.06 % (16) patients were male and 52.94 % (18) patients were female with male : female ratio of 0.89:1. In this study, 41.18 % (14) of patients had pre-operative visual acuity in the range of 6/36 to 6/18, 14.71 % (5) had pre-operative visual acuity of 6/60 to CF 3M and 44.12 % (15) had pre-operative visual acuity of CF 2M to HMCF. In this study, range of pre-existing astigmatism between 1 - 1.5 D was seen in 44.12 % (15) patients, 1.5 - 2 D in 32.35 % (10) patients, 2 - 2.5 D in 17.65 % (6) patients and more than 2.5 D in 5.88 % (3) patients. In the present study, mean pre-operative astigmatism was 1.64 ± 0.80 and residual astigmatism achieved at 6 weeks follow up was -0.13± 0. 39 (p <0.0001) which was highly statistically significant. In this study, 47.06 % (16) of patients had WTR astigmatism and 52.94 % (18) had ATR astigmatism. A significant reduction in the magnitude, but no variation in the type of astigmatism was seen in cases post operatively. In the present study, 1 week post-operatively 5.88 % (2) of patients had uncorrected visual acuity ranging from 6/60 – 6/36, 11.76 % (4) had uncorrected visual acuity ranging from 6/24 – 6/18, 82.35 % (28) had visual acuity ranging from 6/12-6/6. Also, uncorrected visual acuity 6 weeks post-operatively was 6/18-6/12 in 5.88 % 2 and 6/9-6/6 in 94.12 % (32) of patients. In this study, best corrected visual acuity 6 weeks post operatively was 6/9 in 32.35 % (11) and 6/6 in 67.65 % (23) of patients. Spectacle freedom for distance viewing was achieved in 59 % of patients 6 weeks postoperatively and all patients were given near vision correction of + 2.5 to compensate for loss of accommodation seen in pseudophakic eyes. In the present study, the anticipated residual astigmatism as calculated by the toric nomogram was -0.04 ± 0.14 and the mean residual astigmatism achieved at 1 week and 6 weeks postoperatively was -0.25 ± 0.87 (p value <0.1292) and -0.13 ± 0.39 (p value <0.2179) respectively, both of which are not statistically significant. Establishing that expected amount of residual astigmatism can be achieved using this toric nomogram. Conclusion and interpretation Toric intraocular implantation is a effective and satisfactory method for ensuring optimal correction of moderate to severe degree of pre-existing astigmatism and good visual outcome in patients undergoing phacoemulsification surgery