Residual Refractive Errors Following Cataract Surgery in Northern Tanzania: Prevalence, Patterns, and Associated Factors: A Prospective Cohort Study

Background: Cataract is a leading cause of blindness worldwide, particularly in developing countries. The most common type of cataract is age-related. Surgery is the principal treatment for cataracts in eye departments. Although surgical extraction remains the best intervention for blinding cataracts, residual refractive errors are common complications after surgery. Refractive error correction after cataract surgery is often necessary, as high magnitudes of residual refractive errors are a major obstacle to successful surgical outcomes especially in developing countries in sub-Saharan Africa, including Tanzania. Objectives: This study aimed to determine the patterns of residual refractive errors and associated factors among patients following cataract surgery at KCMC Hospital from September 2022 to May 2023. Methods: A prospective cohort study was conducted, and clinical profile data were gathered using a data collection form from patients who underwent cataract surgery. One day after surgery, patients were thoroughly examined in the ward and postoperative findings including UCVA and any complications were recorded. At six weeks after cataract surgery, UCVA, refraction, keratometry readings and BCVA were recorded. Results: A total of 223 patients were analysed. The proportion with residual refractive error was 66.8%.The most common refractive error was astigmatism in 78 patients (35.0%), including against-the-rule astigmatism in 63 (28.3%). Myopia was found in 58 (26.1%), followed by hyperopia in 13 (5.8%), which was the least common. There were 74 emmetropic patients (33.2%).At six weeks postoperatively, 92.8% had good BCVA.Surgeon rank, type of surgery, surgical wound suturing and intraoperative complications were examined as factors associated with residual refractive errors following cataract surgery. Conclusion: This study highlights the need for interventions to address the high prevalence of refractive errors, particularly astigmatism, which was frequently observed after ECCE and SICS. However, the magnitudes of spherical and astigmatic refractive errors were within the moderate range, and best-corrected visual acuity was within the recommended range. Type of surgery, surgeon rank and complications appeared to be associated with residual refractive error following cataract surgery.