Effect Of Surgically Induced Astigmatism On Final Visual Outcomes Of Cataract Patients Requiring Toric Intraocular Lens : A Real World Single-Centre Study

Toric intraocular lens (IOL) are routinely implanted in patients undergoing cataract surgery with a significant regular corneal astigmatism in the National Health System. Surgically induced astigmatism (SIA) is felt to be clinically relevant when the clear corneal incision (CCI) length is more than 2.0mm. Inclusion of SIA in the toric calculation is considered an important step but it is currently not mandatory on most online calculators. Literature on the impact of SIA on final refractive and visual outcomes are scarce. This study aims to assess the effect of SIA on final refractive outcomes and visual perceptions in patients undergoing uncomplicated toric IOL insertion for routine cataract surgery in a real-world setting.

Ophthalmology department in a tertiary referral hospital.

In this retrospective cohort study, 23 patients who underwent routine phacoemulsification with toric IOL insertion (enVista One-Piece Hydrophobic Acrylic Toric IOL) from June 2024–January 2025 were included. Patients with ocular co-morbidities including corneal abnormalities, glaucoma, retinal pathologies were excluded. Data was collected from electronic patient records, with patient reported outcome measures (PROMs) questions asked to ascertain subjective visual outcome. Association between SIA, axis of CCI, post-operative residual corneal astigmatism, uncorrected visual acuity (UCVA) and subjective visual outcomes were studied. Statistical analysis done using Mann-Whitney U test and Spearman’s rank correlation coefficient, Python 3.9. 

Twenty-two patients included in the final analysis (95.6%). SIA was included in the calculation for 17 patients (77.2%), with mean of 0.21D ±0.10 (range 0.2-0.5). Mean reduction of 60.32% in their corneal astigmatism noted. Mean post-operative residual corneal astigmatism was 1.17D ±0.60, with 22.0%

>0.5D but <1D and 66.7% >1D. No statistical difference in UCVA in the group of eyes with SIA recorded versus those without SIA (p=1.00). SIA value inputted was found to have a negative correlation to the residual corneal astigmatism, Spearman correlation (-0.47,p=0.17). 21/22 patients reported a subjective improvement in vision despite residual astigmatism, with no record of visual disturbances such as glare, coma or starburst.

This study demonstrates that although SIA value is an important component for toric IOL calculation and post-operative refraction, it does not seem to have a significant real-world impact on UCVA and subjective visual outcome in patients treated within the publicly funded NHS setting. SIA values had an inverse relationship with residual corneal astigmatism and therefore potentially indicating an underestimation of SIA values in our cohort.