Changes in corneal shape after suture cutting using the argon laser for postoperative astigmatism following cataract extraction

Abstract

We studied the changes in corneal shape after suture cutting with an argon laser to reduce corneal astigmatism following cataract extraction. Sixty-two patients who exhibited high with-the-rule astigmatism (>3 diopters [D]) following extracapsular lens extraction had argon laser suture cutting. The patients were classified into three groups: Group A comprised 30 patients whose sutures were cut two to three months after planned extracapsular cataract extraction (p-ECCE); Group B consisted of eight patients who had the same treatment five to nine months after p-ECCE; Group C comprised 24 patients who had the treatment one to two months after phaccemulsification (PE). The dioptric reduction of corneal astigmatism (the percent reduction of astigmatism) was 1.83 ± 0.98 D (37.4 ± 18.3%) in Group A, 3.20 ± 2.35 D (55.6 ± 34.4%) in Group B, and 2.08 ± 1.20 D (41.4 ± 20.4%) in Group C. There was no statistical significance in the dioptric reduction and the percent reduction among Groups A, B, and C. This suggests that the wound size and time of cutting are not directly correlated to the effect of argon laser suture cutting. To examine the relationship between the effect and changes in corneal shape from suture cutting, we divided the patients into two subgroups; one was Subgroup (+) in which the percent reduction of astigmatism was above 25%; the other was Subgroup (-) in which the percent reduction was below 25%. Keratometric measurement demonstrated an elongation of corneal curvature in the steeper meridian, a shortening in the flatter meridian, and a shift of axis in Subgroup (+) that were statistically significant compared with Subgroup (-). Corneal topographical analysis demonstrated a flattening of the upper cornea that corresponded to the site of the cut suture and a concomitant steepening of the other part of the cornea in Subgroup (+). In contrast, corneal configuration remained virtually unchanged in Subgroup Our results indicated that a change in the overall corneal shape by argon laser suture cutting was necessary to reduce postoperative astigmatism.