Clinical application of full-arc, depth-dependent, astigmatic keratotomy

Purpose. To report a case series of the first clinical application of a new method of astigmatic keratotomy termed full-are, depth-dependent astigmatic keratotomy (FDAK). Methods. The type of astigmatism was analzed by corneal topography. If the astigmatism was regular, paired arcuate incisions of 90 degrees length were used. Incision depth varied between 40% and 75% of local corneal thickness for controlling the level of astigmatic correction. Results. All 13 cases had regular astigmatism, and paired arcuate incisions of 90 degrees length were used. Four cases with incisions at 40% depth, five cases at 50% depth, three cases at 60% depth, and one case at 75% depth induced vector astigmatic change of 0.93 +/- 0.33 D, 1.92 +/- 0.24 D, 3.17 +/- 0.26 D, and 4.44 D, respectively, 3 months after surgery. From 3 months to I year or 3 years, the postoperative astigmatism was stable, and no cases showed astigmatic regression of 0.50 D or more. Every topographic difference map indicated effective flattening and steepening occurring with a 1:1 coupling ratio. All postoperative color maps showed a marked improvement in corneal sphericity. Conclusions. In FDAK using paired 90 degrees incisions at 40-75% depth, an almost linear relationship between the incision depth and degree of astigmatic change was observed. FDAK may be an effective and safe method of astigmatic keratotomy that accurately controls the level of astigmatic correction. More clinical applications are necessary for drawing final conclusions and making a nomogram.