Prospective corneal topographic analysis in surgery for postkeratoplasty astigmatism
G. T. Frangieh, S. Kwitko and P. J. McDonnell
Doheny Eye Institute, University of Southern California School of Medicine, Los Angeles 90033.
Computer-assisted photokeratoscopy was used to evaluate the topographic
characteristics of corneas preoperatively and postoperatively in seven
patients who underwent surgery for correction of postkeratoplasty
astigmatism. The steep hemimeridians were typically separated by an angle
other than 180 degrees (mean, 162.5 degrees) and the flat hemimeridians
were often not orthogonal to the steep hemimeridians. Asymmetry of power
(1.5 or more diopters) between these two major hemimeridians was also
observed in three patients. Relaxing incisions were placed in the two steep
hemimeridians and compression sutures were placed in the flat
hemimeridians. The mean percent of reduction of astigmatism
(vector-corrected) was 81.1%. The amount of keratometric astigmatism, and
the degree of asymmetry of the hemimeridians were not correlated with the
percent of reduction of astigmatism after placement of the relaxing and
compression sutures. Computer-assisted topographic analysis may prove
useful in planning transverse keratotomies centered on the steep
hemimeridians and in placement of compression sutures in flat
hemimeridians.
