Cutting Edge: How Incision Size Influences Corneal Hysteresis In Cataract

Corneal hysteresis (CH) is a crucial biomechanical parameter reflecting corneal viscoelasticity, with significant implications for cataract surgery outcomes. This study investigates the effects of phacoemulsification incision size (2.4 mm vs. 2.7 mm) on CH, intraocular pressure (IOP), refractive outcomes, corneal thickness, and nerve integrity using Pentacam, Corvis ST, and confocal microscopy.

This prospective, comparative study was conducted at University Hospital of Messina, Ophthalmology Department from July 2023 to July 2024, with a cohort of patients undergoing routine phacoemulsification for age-related cataracts, with a mean period of follow-up of 10 months post cataract surgery. 

A total of 140 eyes undergoing phacoemulsification were enrolled, with 70 eyes receiving a 2.4 mm incision and 70 undergoing a 2.7 mm incision. Preoperative assessments included CH (Corvis ST), corneal thickness (Pentacam), IOP measurements, and confocal microscopy to evaluate corneal nerve morphology. Postoperative follow-ups at one week, one month, and three months assessed changes in CH, IOP, corneal thickness, refractive outcomes, and nerve integrity. Confocal microscopy was used to assess nerve fiber density and damage induced by different incision sizes.

Postoperatively, Pentacam analysis showed minimal corneal thickness variations, with mean values of 549 μm in the 2.4 mm group and 547 μm in the 2.7 mm group. CH increased significantly in the 2.4 mm group from 9.5 to 10.2 mmHg, while the 2.7 mm group exhibited a modest increase from 9.3 to 9.6 mmHg. IOP reduction was more pronounced in the 2.4 mm group compared to the 2.7 mm group. Refractive analysis indicated a slightly higher incidence of myopic shift in the 2.4 mm group. Confocal microscopy revealed less nerve damage and better nerve recovery in the 2.4 mm incision group, with higher nerve fiber density and reduced inflammatory cell infiltration postoperatively compared to the 2.7 mm group.

Smaller phacoemulsification incisions (2.4 mm) confer biomechanical and physiological advantages, leading to greater CH preservation, improved IOP regulation, and better nerve integrity compared to larger incisions (2.7 mm). These findings emphasize the role of incision size in optimizing surgical outcomes, reducing nerve damage, and enhancing corneal stability postoperatively. Further studies with long-term follow-up may elucidate the extended benefits of incision size selection in cataract surgery.