Prediction of the extent of thermal damage in the cornea during conductive keratoplasty

Conductive keratoplasty (CK) is a sub-ablative thermal therapy used to treat hyperopia and presbyopia. In this study, a 3-D finite element model of the cornea was developed to predict the transient temperature distributions and the resultant thermal damage fields in the cornea during simulated CK procedures. The model incorporated collagen denaturation and vaporization of water as well as ablation-induced thermal/electrical contact loss. The effects of the radiofrequency power applied on the electrode and the duration of the treatment on the extent of thermal damage in the tissue were examined and compared with the previously published experimental results on human cornea. It was shown that with clinical settings (60% power and 0.6 s treatment duration), the temperature maximum near the tip of the radiofrequency probe exceeded the temperature for vaporization. The results also indicated that the increase in the treatment duration had a much more significant effect on the size of the thermally modified region than increased radiofrequency power (as verified by the experimental results). The model predictions matched the experimental results well and showed the feasibility of using simulations to optimize thermal treatment of the cornea.