Relaxing incisions. Corneal topography.

The topography of circumferential corneal relaxing incisions in eye bank eyes was studied using the corneascope. Significant flattening in the meridian perpendicular to the corneal relaxing incision was found with steepening 90 degrees away in a ratio of two diopters of flattening to one diopter of steepening. This study demonstrates the range of change in corneal astigmatism from 0.58 D for a single one clock hour incision to 5.93 D for a unilateral three clock hour incision. This is compared to symmetrical relaxing incisions placed 180 degrees apart which produce 0.78 D of astigmatic change for one clock hour incisions, and 13.97 D of change for symmetrical three clock hour incisions. The larger shifts in corneal power were also associated with a small degree of central corneal flattening or decreased corneal power.