Effect of thermokeratoplasty on corneal curvature.

A cadaver eye model was used to evaluate and quantify the use of thermokeratoplasty for steepening the central cornea to correct hyperopia. Four groups of eye-bank eyes were treated with four separate surgical plans. Each plan involved the placement of controlled thermal burns (in the depths of the corneal stroma, using a cautery probe) applied in a radial pattern up to a premarked optical zone. The plans differed in the sequence of surgical steps. All plans progressively added radials and applications (to decrease optical zone) in various sequences. Corneal curvature was measured at baseline and at each surgical step. As more surgery was done within each plan, the corneas became progressively steeper. Total mean changes in corneal curvature ranged from 16.26 diopters to 19.76 diopters, depending on the plan. At each optical zone, as the number of radials increased, the effect increased. With progressively smaller optical zone size, the effect also increased.