Corneal astigmatism. The effect of transverse corneal incisions

Linear–long incisions with a small optical zone for the correction of astigmatism in older patients

PURPOSE

To evaluate the efficacy of astigmatic keratotomy (AK) by paired linear (transverse)-long incisions within a small optical zone in older patients with 3.00 diopters (D) or more of astigmatism who are intolerant of contact lenses, spectacles, or both.

DESIGN

Prospective, noncomparative case series.

PARTICIPANTS

Twenty-one eyes (20 patients; age range, 58-87 years) treated at clinics of the Taipei Veterans General Hospital were included in this study.

METHODS

Paired linear incisions (90 degrees in length) with a central optical zone (OZ) of 4.5 mm were made to correct high astigmatism in older patients. The incisions were 80% of the corneal thickness and parallel to the axis of the steepest cylinder.

MAIN OUTCOME MEASURES

Refraction, keratometry, corneal topography, and visual acuity with and without correction were measured as the outcome indicators.

RESULTS

The mean course of the stabilization of corneal curvature was 1.8 months. Significant improvement from a preoperative corneal astigmatism of 4.52+/-1.39 D to a postoperative value of 1.82+/-0.88 D (P<0.0001) was shown. Marked axis deviations of more than 30 degrees were observed in 5 cases and corneal perforation was observed in 1 case. When the corneal curvature stabilized, uncorrected visual acuity was improved by 2 lines or more in 15 eyes (71.4%). Spherical equivalents and best-corrected visual acuity did not change significantly. Postoperative glare was absent in all patients.

CONCLUSIONS

We conclude that AK by linear-long incisions extending from a small OZ is effective and safe for correcting astigmatism.

Paracentral photoablations to correct higher grades of naturally occurring astigmatism

PURPOSE

To evaluate the efficacy of paracentral ablations in treating higher degrees of naturally occurring myopic and hyperopic astigmatism.

SETTING

Augenklinik, Kreiskrankenhaus Bad Hersfeld, Germany.

METHODS

Twenty-five eyes (7 with hyperopia, 18 with myopia) with naturally occurring corneal astigmatism greater than 1.75 diopters (D) were treated by excimer laser. The mean refractive cylinder was -4.05 D +/- 1.46 (SD) (range -1.75 to -7.00 D). The intention was to reduce the astigmatism without consideration of the spherical refractive error. Two paracentral ablations were performed by photorefractive keratectomy with treatment zones of 3.5 mm in the flatter meridian of the cornea. Objective refraction, best corrected visual acuity (BCVA), changes in corneal radius, development of haze, and regression were recorded.

RESULTS

The paracentral ablations induced a steepening of the corneal radius in the flatter meridian from 8.12 mm (mean preoperative value) to 7. 84 mm (mean postoperative value) and thus reduced the mean refractive cylinder to -1.12 +/- 0.82 D (range 0.00 to - 3.00 D), corresponding to a mean reduction of 78%. No eye experienced a loss of Snellen lines. The preoperative BCVA (mean 20/25; range 20/50 to 20/20) was unchanged postoperatively

CONCLUSIONS

Paracentral ablations resulted in a stable corneal curvature immediately after epithelial healing, with a moderate regression over time. Paracentral ablations with the excimer laser appear to be a safe and effective method to correct higher grades of corneal astigmatism.