The Surgically Induced Total Corneal Astigmatism In Cataract Surgery. Is The Smaller The Better?: A Randomized Controlled Trial

To compare the surgically induced astigmatism (SIA) measured using total keratometry (TK) and surgical outcomes between small incision (2.4 mm) and conventional incision (3 mm) for cataract surgery

A randomized controlled trial conducted in the Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand

One hundred eyes from 100 cataract patients were randomized into 2 groups (2.4 mm and 3.0 mm incision). An ocular biometry was performed using a swept-source optical biometer. Dry eye was evaluated by corneal fluorescein staining (Oxford scheme) and the SPEED II questionnaire before and after surgery. Standard phacoemulsification with IOL implantation was performed in all cases. The outcomes include SIA measured using TK, the best corrected visual acuity (BCVA), mean refractive error (ME), mean absolute refractive error (MAE), postoperative dry eye, and surgical complications. All outcomes were assessed at 1 day, 1 week, 1 month, and 3 months, postoperatively. The results at 3 months were analyzed and compared between the 2 groups.

Each group comprised 50 eyes. There were no demographic differences between both groups. The mean SIA and centroid SIA were 0.38±0.18 D and 0.04±0.42 D @102 degree in the 2.4-mm group vs. 0.34±0.21 D and 0.10±0.39 D @98 degree in the 3.0-mm group, all p>.05. Although the surgical time was slightly longer in the 2.4-mm group compared to the 3.0-mm group, no surgical complications occurred in any eyes and the BCVA of the 2 groups was comparable (p=0.14). At 3 months post-operation, the ME and MAE were 0.19±0.47 and 0.36±0.36 in the 2.4-mm group vs. 0.20±0.49 and 0.39±0.36 in the 3.0-mm group, all p>.05. Postoperative dry eye of the 2 groups was similar in both corneal staining (p=0.11) and symptoms (p=0.59).

The incision size of cataract surgery is considered a contributing factor to surgically induced corneal astigmatism and affects the postoperative outcomes. The smaller wound is deemed to induce less SIA and better results compared to the larger one. In this study, we reduced the incision size from the conventional 3.0 mm to 2.4 mm, but the results did not show significant improvement in either SIA or overall surgical outcomes. A consistent surgical technique yields predictable results. However, the much smaller incision (less than 2.4 mm) may turn out different outcomes needed to be verified.