[Effect of strabismus operation of corneal topography]

In order to determine the short- and long-term influence of strabismus surgery on corneal curvature, a prospective study was carried out measuring corneal topography before and after operation.

Corneal topography was performed using a computer assisted videokeratoscope. 77 eyes of 74 patients were examined 1 day before and 1 day as well as 3 months after surgery. Data of the semimeridians at 0 degree, 90 degrees, 180 degrees and 270 degrees in the 3-, 5- and 7-mm zone and of the corneal center were analyzed. Objective refraction, induced astigmatism and simulated keratometer reading were evaluated. 39 horizontal recess-resect procedures. 12 inferior rectus recessions, 10 horizontal resections. 10 inferior oblique recessions and 6 other procedures were performed.

The spheric equivalent of objective refraction decreased by 0.23 D. The absolute astigmatism increased by 0.16 D, the maximum change was 1 D. Changes of objective refraction were statistically not significant. The simulated keratometer reading increased by 0.2 D postoperatively and returned to the initial value after 3 months. With few exceptions, corneal topographic changes were small, statistically not significant and nearly disappeared after 3 months. Corneal flattening tended to occur in the semimeridian of resection while corneal steepening was observed at the site of recession.

The influence of strabismus surgery on corneal astigmatism is usually small and mostly transitory. In a few cases, however, the induced astigmatism persists. Patients should be informed about this possibility preoperatively.