Combined microwave heating and surface cooling of the cornea

The authors investigated a nonsurgical means of reshaping the cornea to correct hyperopia, keratoconus, or myopia. The object was to heat the central stroma of the cornea to the shrinkage temperature of collagen, 55-58 degrees C. The heating device was an open-ended, coaxial, near-field applicator driven at 2450 MHz; it incorporates cooling of the cornea surface by slow of saline. The system was investigated theoretically by computing the 2-D, axisymmetric temperature distribution with the finite-element method. The system was investigated experimentally by heating excised steer corneas. Histology showed that the system could shrink the stroma to a depth of 0.6 mm while sparing the epithelium in 75% of the cases; the diameter of shrinkage was 1.3 mm. Theory predicted a significantly deeper and narrower region of shrinkage than was observed.