A prospective randomized clinical study was performed to see the effect of donor-recipient corneal size on the ultimate refractive error induced in keratoconus at our facility. The patients were randomly divided into two groups, A and B. In Group A, the difference in size between the donor and the recipient cornea was 0.25 mm (18 patients). In Group B, the difference in size between the donor and the recipient cornea was 0.50 mm (20 patients). Both groups underwent the surgical procedure with the same surgeon (M.A.J.) and the same technique. Two months after suture removal, keratometry readings and refractive errors induced were compared. The mean keratometry reading in Group A was 43.3 diopters; in Group B, the reading was 44.8 diopters. There was a mean difference of 1.5 diopters between the two groups (p = 0.01). The mean refractive error in terms of spherical equivalent in Group A was -1.55 diopters and in Group B was -3.33 diopters. There was a difference of -1.8 diopters between the two groups (p < 0.05).