The Relationship between Preoperative Astigmatism and Postoperative Astigmatism Induced by Cataract Surgery and Monofocal IOL Implantation

Background: Cataract is one of the most common ophthalmic disorders among older adults. Even though phacoemulsification is the standard method of treatment, with the improvement of surgical techniques and intraocular lens (IOL) models, the expectations of both patients and physicians have increased. This study aimed to determine the correlation between the pre-existing astigmatism and postoperative astigmatism after cataract surgery and monofocal IOL implantation. Methods and Results: This retrospective, observational study included the data of 101 patients who underwent cataract surgery with phacoemulsification and monofocal IOL implantation over a 12-month period. The data of patients were collected in two different periods: preoperatively and 2 months postoperatively. All patients underwent a detailed ophthalmic examination with the slit lamp, and the astigmatism was evaluated using the autokeratoferactometer, and the central corneal thickness (CCT) was measured using optical coherence tomography. We divided our patients based on the type of cataract (presenile and senile cataract) and based on the CCT into two groups: Group 1 (n=29): CCT < 550 µm and Group 2 (n=72): CCT ≥ 550 µm. In patients of Group 1, there was a pre-existing astigmatism of 0.66±1.16 dcy; in Group 2, there was a lower pre-existing astigmatism of -0.15±1.09 dcyl; however, there was no statistically significant difference between the groups (P=0.092). The 2-month postoperative astigmatism was -0.59±1.11 dcyl in Group 1 and -0.32± 1.14 dcyl in Group 2, and there was no statistically significant difference between the groups (P=0.315). Through regression analysis, we obtained a statistically significant correlation (R=0.7972, P<0.0001) between the pre-existing astigmatism and the 2-month postoperative astigmatism. According to our results, the 2-month postoperative astigmatism was affected by the pre-existing astigmatism by 63.5%. Conclusion: there is a statistically significant correlation between a pre-existing astigmatism and a postoperative astigmatism in patients who undergo cataract surgery and are implanted with monofocal IOLs. Awareness of this correlation by physicians may help to minimize patients’ postoperative refractive error and produce better postoperative outcomes after cataract surgery.