Surgically Induced Astigmatism after Manual Small Incision Cataract Surgery

Background: Cataract surgery is of extraordinary importance because it is the commonest cause of avoidable blindness worldwide. Over the years patient's expectations from cataract surgery have increased significantly. Appropriate calculation of intraocular lens power, innovations in intraocular lens (IOL) designs and material has allowed complete spherical correction. Advances in incision construction have improved the refractive results of cataract surgery by minimizing surgically induced astigmatism (SIA). Astigmatism prevention and control is one of the biggest challenges for a surgeon after cataract surgery. The major determinants of astigmatism are the site and size of incision, the type of suture used and suturing technique. Aim and Objective: To know the type and extent of induced astigmatism after manual small incision cataract surgery. Material and Methods: This prospective study was conducted at a tertiary eye care centre in rural Maharashtra.Patients fulfilling selection criteria were included in the study after thorough clinical examination. Preoperative keratometric values were recorded in addition to visual acuity in 108 selected patients. Manual small incision cataract surgery was performed in all patients with incisions at superior, supero-temporal and temporal sites. The size of incision varied according to the size of nucleus. The surgically induced astigmatism was calculated after 40 days of surgery in all patients. Results: Out of the 108 patients, majority of patients were in age group of 60-69 and 70-79 years. Only 3 patients were above 90 years of age. Male: Female ratio in this study was 1: 0.64. Against-therule astigmatism was present in 77% of patients; 21% of the patients had with-the-rule astigmatism, and 4% were astigmatically neutral and no patients had oblique astigmatism. The magnitude of postoperative astigmatism at end of 40 days with superior-temporal incision was 0.56 D, 0.63D, 0.75D with 5.5mm, 6mm and 6.5mm size of incisions respectively. With temporal incision it was 0.9D, 1.08D and 1.34 D with 5.5mm, 6mm and 6.5mm size of incisions respectively. With superior incision SIA was 1.36 D, 1.38D and 1.95D with 5.5mm, 6mm and 6.5mm size of incisions respectively. Conclusion: The SIA was least with supero-temporal incision. The superior incision showed more astigmatism than the supero-temporal and temporal incision.