Effects of pterygium surgery on front and back corneal astigmatism.

Objective: To evaluate changes in front and back corneal astigmatism after pterygium surgery using the Scheimpflug imaging of Pentacam.

Design: Prospective interventional case series.

Participants: We studied 96 eyes with primary pterygium that underwent surgery.

Methods: Preoperatively and at 1, 3, and 6 months after surgery, Pentacam (Oculus, Wetzlar, Germany) was used to measure astigmatism at the front and back corneal surfaces. Surgically induced astigmatism (SIA) on the front corneal surface was also calculated, using vector analysis.

Results: Of the eyes, 73 completed 6-month postoperative follow-up without developing pterygium recurrence. Front corneal astigmatism decreased from 3.97 ± 4.49 D preoperatively to 1.23 ± 1.88 D at 1 month (p < 0.001). Back corneal astigmatism decreased, but nonsignificantly, from 0.35 ± 0.39 D preoperatively to 0.32 ± 0.2 D at 1 month (p = 0.49). However, although back astigmatism was with-the-rule in 43.8% of patients and against-the-rule in 24.6% of patients preoperatively, these changed to 87.7% and 4.1%, respectively, at 1 month (p = 0.02). Refractive cylinder (52 eyes) reduced from 2.62 ± 2.22 D preoperatively to 1.06 ± 1.57 D at 1 month (p = 0.05). There was no significant change in any parameter after 1 month throughout the 6 months after surgery. SIA was 3.51 ± 2.66 D at 1 month postoperatively, which showed significant correlation with age, preoperative astigmatism, and pterygium length and area, but there was no correlation with gender, pterygium width, preoperative spherical power, or surgical technique. Moreover, higher grades of pterygium morphology had higher SIA postoperatively (p = 0.05).

Conclusions: Pterygium surgery was associated with significant changes in front and back corneal surfaces. Eyes with more advanced pterygia achieved higher SIA.