MATERIALS AND METHODS : 

A. Study design - Hospital based, prospective, interventional study. 

B. Study period – 6 months, June 2025 - November 2025 

C. Study site - Nethradhama Super Speciality Hospital, Jayanagar, Bengaluru

 Sample size – 50 eyes The sample size was calculated with G*Power software based on the formula an effective size was 0.66 derived from the literature. Based on this, a minimum of 45 subjects/eyes were required to achieve a statistical power of over 80% with significance level (a) of 5%. To account for potential dropouts or data loss (~10%), a total of 50 eyes were considered for this study. 

Inclusion criteria : Patients, both male and female, aged above 50 years and with nuclear sclerosis of grade 1-4 (LOCS III), cortical or posterior subcapsular cataract with pre existing regular against the rule corneal astigmatism(steep axis 180°+/- 20°) between 0.5D to ID on partial coherence interferometry (PCI) automated keratometry (IOLMaster 700, Carl Zeiss Meditec) and Pentacam(Oculus) 

Exclusion criteria : Irregular astigmatism on tomography. Clinical or topographical keratoconus Cormeal scars, dystrophies or peripheral degenerations Previous ocular surgeries Other ocular pathologies that could have an effect on the post operative visual functions Any intraoperative or postoperative complication will be excluded from the study Pre operative: All patients satisfying the inclusion and exclusion criteria will undergo a complete ophthalmic evaluation including uncorrected distance visual acuity (UDVA) and best corrected visual acuity (BCVA), slit lamp examination, applanation tonometry and fundoscopy. Keratometry, biometry with IOL Master 700(Carl Zeiss Meditec) and Schiempflug topography using Pentacam(Oculus) will be done. 

Procedure : All patients will undergo topical phacoemulsification with posterior chamber intraocular lens implantation by one of two operating surgeons. The main port clear corneal incision will be made on steep meridian which will be projected on the surgeon’s oculars using the Callisto Eye System(Carl Zeiss Meditec) through data obtained from IOL Master 700(Carl Zeiss Meditec) and from Pentacam(Oculus). Routine phacoemulsification and posterior chamber intraocular lens implantation of a non toric IOL will be done. Following this a 2.8-mm, self-sealing clear corneal incision will be made with a keratome 180° opposite to the main incision on the steep meridian.

 Post operative: Patients will be evaluated postoperatively on day 1, day 15 and 3 months for the following tests. UDVA (day 1, day 15 and 3months) BCVA (day 1, day 15 and 3months) Refraction (day 1, day 15 and 3months) Keratometry and WTW using IOL Master 700(Carl Zeiss Meditec) and Pentacam(Oculus) (day 15 and 3 months) 

General statistical methods and types of analyses: All the statistical analysis will be performed using Python (version 3.13), and Jamovi (version 2.6.44). Variables will be presented as means ± SD, median with interquartile ranges(IQR), or percentages, depending on the data distribution. Normality of data will be assessed using the Kolmogorov-Smirnov (KS) test and Shapiro-Wilk test. For group comparisons, a paired sample t-test/Wilcoxon Signed-Rank test will be used. Repeated measured ANOVA will be used to compare differences across follow up periods. A two-tailed p-value of less than 0.05 will be considered statistically significant.