Analyses of surgically induced astigmatism and axis deviation in microcoaxial phacoemulsification

To evaluate surgically induced astigmatism (SIA) and axis deviation after coaxial microincision superotemporal clear corneal phacoemulsification incision in eyes with differently located steep axis. This prospective, comparative study included four groups of 45 eyes with age-related cataracts; each group underwent 2.2-mm superotemporal clear corneal incision (CCI) cataract surgery. The four groups of patients were divided by location of the steep axis. Groups were matched according to symmetry of the steep axis for both right and left eyes as follows--0°-45° of steep axis for right eyes, and 136°-180° for left eyes (group 1); 46°-90° for right eyes and 91°-135° for left eyes (group 2); 91°-135° for right eyes and 46°-90° for left eyes (group 3); and 136°-180° for right eyes and 0°-45° for left eyes (group 4). Outcome measures included changes in mean total astigmatism, SIA, and axis deviation. Astigmatism was measured by manual keratometry readings before surgery and week 1, week 4, week 8, and week 12 postoperatively. SIA was calculated by the vector analysis (Holladay-Cravy-Koch method). The magnitude of mean total astigmatism was lowest in group 3 and highest in group 1 at week 12. SIA was 0.39 diopters (D), 0.22 D, 0.17 D, and 0.28 D in group 1, group 2, group 3, and group 4, respectively. The change in astigmatic axis deviation was highest in group 3 (23.6 ± 16.6) (P < 0.05). Axis deviation and SIA were stable after week 4. Planning of CCI on or near the steep axis can help decrease corneal astigmatism.