Keratorefractive effect of microwave keratoplasty on human corneas

To determine the change in dioptric power on excised human corneoscleral buttons after microwave keratoplasty application and to determine the qualitative effect on the cornea using histology and scanning electron microscopy.

Department of Academic Ophthalmology, Rayne Institute, St. Thomas' Hospital, London, United Kingdom.

Excised human corneoscleral buttons were treated with a prototype microwave keratoplasty ring applicator. A 28.12 W, 1-second application was performed on the corneas using a 6.0 mm diameter inner conductor and an 8.4 mm diameter outer conductor. Videokeratography was performed with a topographic modeling system (TMS-1) before and after microwave keratoplasty. The induced change in corneal curvature was calculated using the mean dioptric power of rings situated 2.0 to 6.0 mm from the geometrical apex of the corneas. Scanning electron microscopy and toluidine-blue light microscopy were performed to determine the effect on the corneal stroma.

Six excised corneoscleral buttons from 6 donors were used. The mean reduction in curvature after microwave keratoplasty application was 3.07 diopters +/- 2.62 (SD). Scanning and light microscopy showed microwave-induced shrinkage of corneal stromal collagen with little disturbance to the overlying epithelium.

Microwave keratoplasty reduced corneal curvature and has therapeutic potential as a noninvasive alternative to excimer laser surgical correction of myopia and as a treatment for corneal ectasia.