Purpose: To evaluate the corneal horizontal diameter [white-to-white (WTW) distance] as a factor influencing surgically induced astigmatism (SIA) and postoperative astigmatism.
Methods: A total of 330 eyes with corneal astigmatism ≤1.5 D underwent cataract surgery with phacoemulsification. A 3-step, superotemporal for the right eye and superonasal for the left eye, clear corneal incision of 3.0 mm was made. Four groups were created according to WTW distance: group A ≤11.6 mm, group B 11.7 to 11.9 mm, group C 12.0 to 12.2 mm, and group D ≥12.3 mm. SIA was calculated by vector analysis using the Alpins method. We noted all cases, in which a change greater than 0.5 diopters (D) in astigmatism took place and a change greater than 20 degrees in axis torque, despite axis direction, on the first and sixth postoperative months.
Results: SIA was found in group A 0.98 D ± 0.6 (SD), B 0.79 D ± 0.43 (SD), C 0.68 D ± 0.45 (SD), and D 0.53 D ± 0.32 (SD) at the first postoperative month. At the sixth postoperative month, SIA was 0.77 D ± 0.43 (SD), 0.69 D ± 0.34 (SD), 0.62 ± 0.36 (SD), and 0.49 D ± 0.27 (SD), respectively. A change greater than 0.5 D in corneal astigmatic power at the first and sixth months postoperatively was significantly lower in eyes with WTW distance 12.0 to 12.2 mm and ≥12.3 mm in comparison with eyes with WTW distance ≤11.6 mm and 11.7 to 11.9 mm (P < 0.05). Changes greater than 20 degrees in astigmatic axis at the first and sixth postoperative months were not significantly different according to the horizontal corneal diameter.
Conclusions: WTW distance should always be measured preoperatively when planning cataract surgery and should be accounted for in cases of large and small corneas.