Corneal first-surface aberration analysis of the biomechanical effects of astigmatic keratotomy and a microkeratome cut after penetrating keratoplasty

Astigmatic keratotomy (AK) was performed in a patient after penetrating keratoplasty (PKP) for keratoconus to reduce high post-PKP astigmatism. The procedure led to a significant decrease in astigmatism, but corneal higher-order aberrations (HOAs) increased. After PKP, the patient was scheduled for 2-step laser in situ keratomileusis (LASIK) to correct myopia and astigmatism. One day after the microkeratome cut, a decrease of −2.75 diopters in the spherical equivalent (SE) was noted. Although subjective manifest cylinder and corneal spherical aberrations were marginally affected, a marked decrease in coma and other HOAs could be observed. One month after the cut, the SE was unchanged. Excimer laser ablation was not performed as the patient was satisfied with the result and refused further treatment. This case shows that AK cuts can induce HOAs and a single microkeratome cut performed in corneal grafts can have strong biomechanical effects on lower-order aberrations and HOAs. If LASIK is planned after PKP, a 2-step approach is recommended to anticipate biomechanical effects and avoid overcorrection or undercorrection.