The dioptric power of the cornea (spherical equivalent) was studied in 60 eyes operated on for penetrating keratoplasty. In order to determine the possible influence of (1) the underlying pathology, (2) the presence of neovascularisation, or (3) the size of the graft the sample was divided into four groups, with the following results: group A (keratoconus, same-sized graft) = 42.25 D; group B (keratoconus, oversized graft) = 45.16 D; group C (keratopathy with minimal or no vascularisation) = 45.34 D; group D (keratopathy with significant vascularisation) = 45.36 D. The results showed that donor-receptor disparity is the main factor determining the outcome of the postoperative corneal spherical power. There was no demonstrable influence from underlying pathology or the presence of vessels in the receptor cornea.