PRTN3 and Schnyder corneal dystrophy: Six genes were selected based on the training data: CX3CR1, KLRD1, MMP8, PRTN3, RETN and SCD. The risk score for disease severity = (-1.209) + (-0.132 × normal expression value of CX3CR1) + (-0.683 × normal expression value of KLRD1) + (0.304 × normal expression value of MMP8) + (0.258 × normal expression value of PRTN3) + (0.145 × normal expression value of RETN) + (0.023 × normal expression value of SCD).