Keratometry and ultrastructural changes after microwave thermokeratoplasty in rabbit eyes

To conduct keratometry and investigate the ultrastructural changes after microwave thermokeratoplasty (MTK) in rabbit eyes.

Eighteen New Zealand rabbits (18 eyes) were recruited for this study. Ten eyes were chosen for slit-lamp photography and corneal topography at 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively. Two rabbits were sacrificed on 1 day, 1 week, 1 month, and 3 months postoperatively. All remaining rabbits were sacrificed at 6 months postoperatively. The cornea was observed using hematoxylin and eosin staining and transmission electron microscopy. Data are expressed as mean ± standard deviation. p value was determined using repeated-measures analysis of variance.

Corneal edema, disorganized corneal collagen fibers in the heated area, and necrotic fibroblasts were observed at 1 day and 1 week postoperatively. At 1 month postoperatively, corneal edema was not observed, and corneal cell morphology was normal. Moreover, corneal collagen fibers in the heated area shrunk and tended to be organized. The K1 and K2 values significantly decreased from 49.0 ± 1.2 D and 50.5 ± 0.9 D preoperatively to 40.3 ± 1.2 D and 43.2 ± 0.8 D 6 months postoperatively, respectively. The corneal thickness was 353.1 ± 9.3 µm preoperatively and 317.8 ± 27.7 µm at 6 months postoperatively; the difference was not statistically significant.

Corneal keratometry showed flattening after MTK. Moreover, corneal collagen fibers in the heated area shrunk and tended to be organized at 6 months postoperatively. Further studies are required to determine the safety and stability of MTK.