Influence of corneal biomechanical properties on surgically induced astigmatism in cataract surgery

To perform an overall follow-up of the morphologic, optical, and biomechanical properties of the cornea to determine new parameters influencing the refractive outcomes of cataract surgery.

Clinical study.

Patients scheduled for cataract surgery were assessed for surgically induced corneal astigmatism (SIA) and higher-order aberrations, (HOAs) using a Scheimpflug rotating camera (Pentacam) together with corneal imaging by optical coherence tomography (Spectralis) and biomechanical analysis by the Ocular Response Analyzer preoperatively and 1, 7, and 30 days postoperatively. The central and peripheral corneal thicknesses; incision width, length, and architecture; corneal hysteresis (CH); and corneal resistance factor (CRF) were computed to identify new parameters influencing corneal optical changes that determine the final refractive result.

The study enrolled 40 patients (40 eyes). The SIA and HOAs were significantly lower after microincision surgery (≤ 2.2 mm) than after small-incision surgery (2.75 mm) (both P<.01). The CRF was significantly reduced with a direct corneal incision compared with a constructed incision (P<.01). Multivariate analysis showed that SIA was correlated not only with incision width (P<.05) but also with preoperative CH (P<.01). Corneal 3rd-order trefoil depended on incision width (P<.01).

In addition to the well-known influence of incision size on SIA, CH also modulates optical changes. The biomechanical features of the cornea should be taken into account preoperatively to better predict the refractive outcomes of cataract surgery.