Comparative Study of Surgically Induced Astigmatism and Post-Operative visual Acuity in Small Incision Cataract Surgery and Phacoemulsification – A one year Randomized Trial at KLES Dr. Prabhakar Kore Hospital and Medical Research Centre, Belagavi

Abstract

BACKGROUND AND OBJECTIVES Cataract is the leading cause of avoidable blindness in India and is responsible for upto 50-80 percent cases of bilateral blindness. The history of cataract surgery starts from around 20 centuries ago, when Indian surgeon Susruta performed couching treat cataracts by dislodging the cataractous lens away from pupillary area. The surgeries have developed since then and the two most common techniques used nowadays for cataract extraction are small incision cataract surgery (SICS) and phacoemulsification. Phacoemulsification, is the surgery of choice in developed countries whereas Small Incision Cataract Surgery is the most commonly performed cataract surgery in developing nations. The reason for this is high costs involved in setting up and doing a Phacoemulsification surgery which requires a Phacoemulsifier machine compared to Small Incision Cataract Surgery which is manual and is therefore much economical. Patients who undergo cataract surgeries want less dependence on spectacles. Thus surprises in refractive errors after cataract surgery have become unacceptable in recent few years. As a result, cataract surgery has become refractive surgery offering improvements both in “best corrected” and “uncorrected” visual acuity. Presence of astigmatism after cataract surgery can cause blurred images and glare. This astigmatism can be residual or surgically induced. Surgically induced astigmatism (SIA) calculates the magnitude and axis of postoperative induced astigmatism. Postoperative astigmatism is affected by various factors such as preoperative astigmatism, location, type, size, closure, and healing of the surgical incision, amount of scleral cauterization performed, type of suturing material used and its placement, position of IOL, and postoperative use of steroids, and all these have effects on corneal curvature. Control of surgically induced astigmatism has become a clinical efficacy benchmark when evaluating cataract surgical outcomes. Therefore it is important to find the effective method of cataract surgery (phacoemulsification or manual small incision cataract surgery) which induces the least or no astigmatism post surgically and gives better visual outcome. This study will compare the surgically induced astigmatism and post-operative visual acuity of two groups of patients who have undergone phacoemulsification and small incision cataract surgery. Thus the objectives of this study are: 1. To compare the surgically induced astigmatism in Small Incision Cataract Surgery (SICS) and Phacoemulsification. 2. To compare the Post-Operative Uncorrected and Best Corrected Visual acuity in SICS and Phacoemulsification. MATERIALS AND METHODS. This study, A one year randomized trial, was conducted at KLES Dr. Prabhakar Kore Hospital and Medical Research Centre on patient with age related cataracts who attended the ophthalmology OPD in the hospital from 1 January 2017 to 31 December 2017. Patients with age related cataracts without any other ocular pathology were selected and divided randomly into two groups, one who underwent Phacoemulsification and one who underwent SICS. Phacoemulsification was done using divide and conquer technique through a 3.2 mm superior limbal incision and SICS was done using a 6 mm superior scleral incision. All the patients were evaluated at 1 day, 1 week and 6 weeks post-operatively. RESULTS The mean age of patients who underwent phacoemulsification was 63.20 years and those who underwent SICS was 63.26 years. 55% of all patients were females as compared to 45% males. 32 patients underwent cataract surgery in the right eye and 28 in the left eye. The mean pre-operative uncorrected visual acuity in phaco group was 1.32 logMAR while that in SICS group was 1.23 logMAR. The mean pre-operative best corrected visual acuity in PHACO group was 0.86 logMAR and in SICS group was 0.81 logMAR. All the patients had Nuclear Opalescence grade 2 or grade 3. The patients who underwent phacoemulsification had mean uncorrected visual acuity as 0.35, 0.30 and 0.27 logMAR at 1 day, 1 week, and 6 weeks post-operative respectively while those who underwent SICS had a mean visual acuity of 0.38, 0.38 and 0.33 logMAR at 1 day, 1 week, and 6 weeks post-operative respectively. Using unpaired t-test, it was found that the difference of mean UCVA at 1 week was significant (p<0.05), while at follow-ups done at 1 day post-op and 6 weeks post-op, it was not significant. Best corrected visual acuity in patients who underwent Phacoemulsification was 0.14, 0.11 and 0.04 logMAR at 1 day, 1 week and 6 weeks post-operative respectively. Those who underwent SICS had a mean best corrected visual acuity of 0.19, 0.13 and 0.10 logMAR respectively. The difference of best corrected visual acuity at 6 weeks post-operative follow-up was statistically significant (p<0.05). The astigmatism induced in both the groups was against the rule (ATR). The mean surgically induced astigmatism in Phaco group was 0.84 D, while that in SICS group was 1.87 D. The difference of the astigmatism induced among the two groups was statistically significant (p<0.000). The SIA in patients with pre-operative with the rule (WTR) astigmatism in PHACO group at follow-ups done on 1 day, 1 week and 6 weeks post-operatively was 0.56 D, 0.81 D and 1.02 D respectively and in those with pre-operative against the rule (ATR) astigmatism at follow-ups done on 1 day, 1 week and 6 weeks post-operatively was 0.48 D, 0.52 D and 0.63 respectively. In SICS group with pre-operative WTR astigmatism, the SIA at follow-ups done on 1 day, 1 week and 6 weeks post-operatively was 1.40 D, 1.79 D and 1.96 D respectively and in those with pre-operative ATR astigmatism at follow-ups done on 1 day, 1 week and 6 weeks post-operatively was 1.30 D, 1.40 D and 1.65 D respectively. The difference of SIA in PHACO group between patients with pre-operative WTR and ATR astigmatism was statistically significant at 1 week (p=0.015) and 6 weeks (p=0.000) post-operatively, while that in SICS group was not statistically significant. Thus the SIA in patients with pre-operative WTR astigmatism was higher than in those with pre-operative ATR astigmatism in both the study groups. CONCLUSION AND INTERPRETATION Phacoemulsification induces lesser astigmatism than SICS when incisions are made in the same meridian. The best corrected visual acuity at 6 weeks in phacoemulsification was significantly higher than that of SICS (p<0.05). Thus we concluded that Phacoemulsification gives better visual outcome than SICS with minimal astigmatism. Small incision cataract surgery was safe and was nearly as effective as phacoemulsification in terms of visual outcome to the patient. Even though it induced higher astigmatism than Phacoemulsification it provided patients with good vision after cataract surgery.