Assessment of factor effectiveness on the bilateral corneal graft rejection in the keratoconus with cure frailty model

Although corneal graft may be rejected by the immune system of the recipient it remains as the most successful operation as compared to transplantation of other tissues. Since most patient do not reject the grafts, those who do are in the minority. This study was carried out to assess the usefulness of the cure frailty model for determining the significance of risk factors associated with the rejection of bilateral corneal transplants in patients with keratoconus.

Patients with keratoconus receiving bilateral corneal transplants were included in the study. For analysis of the time of bilateral graft rejection in the keratoconus disease we used the cure frailty model and the promotion time cure frailty and used the Cox frailty model for comparison. For estimating the parameters we used the Bayesian approach. For comparison of proposed models we used the Deviance Information Criteria (DIC).

238 individuals received corneal transplants during the study period and 22.7 percent experienced graft rejection. Mean and median of graft rejection time was 13.5±22.8 and 6.9 months respectively. Vascularization and old age were important risk factors for graft rejection. In the cure frailty model the cure rate in the patients with vascularization were 34 percent versus 75 percent without vascularization. In the time promotion cure frailty model the cure rates in cases with vascularization were 32 percent and without vascularization were 70%. The cure models that include the parameter for cure rate in the comparison to the Cox frailty model that do not have parameters for cure rate are better for data analysis.

For analysis of survival data in which selection of patients is highly selected using the cure model gives more accurate results.