Comparison of intersecting trapezoidal keratotomy and arcuate transverse keratotomy in the correction of high astigmatism.

BACKGROUND

High astigmatism can be corrected using trapezoidal or arcuate transverse keratotomies. Videokeratography enables qualitative evaluation of the corneal topography.

METHODS

Fifty-five eyes of 41 patients 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 trapezoidal or arcuate transverse keratotomies. Corneal topographic maps were analyzed and classified into keratographic patterns. Mean follow up was 3 years (range, 1 to 6 years).

RESULTS

The mean net decrease in refractive astigmatism was 3.60 D (52.7% reduction). The flattening/steepening ratio was on average higher for intersecting trapezoidal keratotomy (7.26 for astigmatism after penetrating keratoplasty and 8.31 for naturally occurring astigmatism) than for arcuate transverse keratotomy (.98 in astigmatism after penetrating keratoplasty and 1.76 in naturally occurring astigmatism). Accordingly, intersecting trapezoidal keratotomy tended to produce a hyperopic shift in the spherical equivalent refraction (mean hyperopic shift, 2.65 and .56 D, respectively). The mean vector-corrected change of refractive astigmatism after intersecting trapezoidal keratotomy was 88.8% in naturally occurring (n = 21 eyes) and 70.3% in penetrating keratoplasty astigmatism (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 pattern as the most frequent pattern for both procedures. Intersecting trapezoidal keratotomy was characterized by relatively higher incidences of polygonal and irregular patterns. Arcuate transverse incisions caused less wound healing defects and glare than intersecting trapezoidal keratotomy.

CONCLUSIONS

Both intersecting trapezoidal keratotomy and arcuate transverse incisions effectively reduced high naturally occurring astigmatism and astigmatism after penetrating keratoplasty. However, greater corneal surface irregularity and more complications were seen following intersecting trapezoidal keratotomy. Trapezoidal keratotomy should not be used unless a large decrease of myopia is needed, and then a nonintersecting technique is preferable.