A new concept for the correction of astigmatism: Full-arc, depth-dependentastigmatic keratotomy

Objective: The purpose of this study is to introduce and evaluate a new con cept in astigmatic keratotomy (AK) named full-arc, depth-dependent AK (FDAK ). Design: Noncomparative interventional case series. Participants: FDAK was performed on a total of 37 eyes with regular astigma tism; of these, 16 eyes received FDAK alone, and 21 eyes received FDAK comb ined with cataract surgery. Methods: Corneal topography was used to divide the cornea into two discreet regions of "steep" and "flat." Then, paired arcuate incisions, 90 degrees in length, were placed along the full are of the steep area. The level of a stigmatic correction was controlled by varying the incision depth from 40% to 80% on the basis of a provisional nomogram developed by the authors. Main Outcome Measures: Keratometries, corneal topographies, and visual acui ties were measured. Results: The FDAK alone group showed a significant improvement from a preop erative corneal astigmatism of 2.90 +/- 0.78 diopters (D) to a postoperativ e value of 0.89 +/- 0.52 D. The "combined" group also showed significant im provement from a preoperative corneal astigmatism of 2.97 +/- 1.01 D, to a postoperative value of 1.02 +/- 0.45 D. The deviation of achieved. Correcti on from attempted correction using vector analysis was between 1.37 D of un dercorrection and 0.98 D of overcorrection, with 91.9% of cases within the range of +/-1.0 D. Slight oblique change caused by axis deviation was obser ved in seven cases. Both uncorrected and corrected visual acuity showed sta tistically significant improvement. No serious complications were encounter ed. Conclusions: Controlling the level of correction by varying the incision de pth allowed the surgeon to use long incisions (90 degrees in length in regu lar astigmatism) covering the entire steep area, minimizing the undesirable changes induced by conventional deep and narrow incision AK and resulting in an ideal corneal sphericity after surgery. FDAK enabled the surgeon to a ccurately control the level of astigmatic correction with minimal risk of c orneal perforation. Ophthalmology 2000;107:95-104 (C) 2000 by the American Academy of Ophthalmology.