With so many parameters (PRK, transepithelial-PRK, TG-PRK, and transepithelial TG-PRK in combination with different CXL protocols) and a relatively stable disease, the optimum parameters for PRK and simultaneous CXL are difficult to determine without large-scale, comparative, randomized trials with an extended duration of follow-up to establish the long-term stability of this procedure in keratoconus treatment. This evidence concerns the gene PLK3 and keratoconus.