Fourier analysis of irregular astigmatism after trabeculectomy

Abstract

Objective: To examine irregular astigmatism following trabeculectomy using Fourier analysis of videokeratography data.

Patients and methods: Forty eyes of 40 glaucoma patients, undergoing primary trabeculectomy, underwent videokeratographic examinations preoperatively, and at 2 weeks and 1, 3, 6, and 12 months postoperatively. The dioptric data of the central cornea were decomposed into spherical, regular astigmatic, and irregular astigmatic (decentration and higher-order irregularity) components using Fourier analysis.

Results: The mean spherical equivalent did not change throughout the observation period. The regular astigmatic component from 2 weeks to 6 months post-operatively was greater than the preoperative diopter, but the increase was not significant. In contrast, the decentration component increased significantly after surgery, but returned to the preoperative level by 12 months. The higher-order irregularity component also presented a transient increase postoperatively.

Conclusions: Irregular astigmatism, particularly decentration component, increases significantly after trabeculectomy, but returns to the preoperative level 12 months after surgery.