Corneal Diameter as a Factor Influencing Corneal Astigmatism After Cataract Surgery.

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.