Frequency of Surgically Induced Astigmatism after Phacoemulsification

Background: Cataract is the leading cause of avoidable blindness worldwide, and phacoemulsification is now the preferred surgical technique due to its superior visual and refractive outcomes compared to older methods. Despite these advantages, surgically induced astigmatism (SIA) remains a frequent concern, potentially limiting uncorrected visual acuity and patient satisfaction. Objective: To determine the frequency of surgically induced astigmatism following phacoemulsification at a tertiary eye hospital in Karachi. Methods: This descriptive study was conducted at the Cataract Clinic of Al-Ibrahim Eye Hospital, Karachi, from August 2024 to January 2025. A total of 373 patients aged 50–70 years undergoing phacoemulsification with foldable intraocular lens implantation were enrolled through non-probability consecutive sampling. Patients with pre-existing astigmatism ≥0.5 D, ocular comorbidities other than cataract, or loss to follow-up were excluded. Preoperative evaluation included visual acuity, slit lamp examination, keratometry, and fundus assessment. Postoperative assessments were performed at Day 1, Week 2, and Week 6. Surgically induced astigmatism was defined as ≥1.00 D at the final follow-up. Data were analyzed using SPSS v23, applying Chi-square or Fisher’s exact test where appropriate, with p ≤ 0.05 considered significant. Results: Of the 373 patients, the mean age was 61.4 ± 5.8 years, with 53.1% males and 46.9% females. At six weeks, uncorrected visual acuity of 6/12 or better was achieved in 84.2% of patients, while best corrected visual acuity of 6/9 or better was achieved in 90.3%. Surgically induced astigmatism ≥1.00 D was observed in 115 patients (30.8%), whereas 258 patients (69.2%) remained below this threshold. No significant association was found between SIA and age (p = 0.67) or gender (p = 0.42). However, higher preoperative keratometry values were significantly associated with the development of SIA (p < 0.05). Conclusion: Phacoemulsification is highly effective in restoring vision; however, nearly one-third of patients develop clinically significant surgically induced astigmatism. Preoperative corneal curvature emerged as a key determinant, while demographic factors such as age and gender were not associated with SIA. Optimizing incision technique and considering toric intraocular lenses may help reduce postoperative astigmatism and improve refractive outcomes.