COMPARISON OF INTERSECTING TRAPEZOIDAL KERATOTOMY AND ARCUATE TRANSVERSE KERATOTOMY IN THE CORRECTION OF HIGH ASTIGMATISM

BACKGROUND: High astigmatism can be corrected using trapezoidal or arc uate transverse heratotomies. Videokeratography enables qualitative ev aluation of the corneal topography. METHODS: Fifty-five eyes of 41 pat ients presenting with high astigmatism after penetrating keratoplasty or naturally occurring astigmatism (mean, 6.29 diopters [D]; range, 3. 00 to 16.00 D) underwent correction using either intersecting trapezoi dal or arcuate transverse keratotomies. Corneal topographic maps were analyzed and classified into keratographic patterns. Mean follow up wa s 3 years (range, 1 to 6 years). RESULTS: The mean net decrease in ref ractive astigmatism was 3.60 D (52.7% reduction). The flattening/steep ening ratio was on average higher for intersecting trapezoidal keratot omy (7.26 for astigmatism after penetrating keratoplasty and 8.31 for naturally occurring astigmatism) than for arcuate transverse keratotom y (.98 in astigmatism after penetrating keratoplasty and 1.76 in natur ally occurring astigmatism). Accordingly, intersecting trapezoidal ker atotomy tended to produce a hyperopic shift in the spherical equivalen t refraction, whereas arcuate transverse keratotomy generally preserve d the spherical equivalent refraction (mean hyperopic shift, 2.65 and .56 D, respectively). The mean vector-corrected change of refractive a stigmatism after intersecting trapezoidal keratotomy was 88.8% in natu rally occurring (n=21 eyes) and 70.3% in penetrating keratoplasty asti gmatism (n=13). Arcuate transverse incisions corrected on average 79.9 % of naturally occurring (n=13) and 60.8% of penetrating keratoplasty astigmatism (n=8). Videokeratography showed the asymmetric bowtie patt ern as the most frequent pattern for both procedures. Intersecting tra pezoidal keratotomy was characterized by relatively higher incidences of polygonal and irregular patterns. Arcuate transverse incisions caus ed less wound healing defects and glare than intersecting trapezoidal keratotomy. CONCLUSIONS: Both intersecting trapezoidal keratotomy and arcuate transverse incisions effectively reduced high naturally occurr ing astigmatism and astigmatism after penetrating keratoplasty. Howeve r, greater corneal surface irregularity and more complications were se en following intersecting trapezoidal keratotomy. Trapezoidal keratoto my should not be used unless a large decrease of myopia is needed, and them a nonintersecting technique is preferable.