Mohamed Hosny, Mohamed Abdel Moneim Hassaballa, Ahmed ShalabyOphthalmology Department, Faculty of Medicine, Cairo University, Cairo, EgyptPurpose: To evaluate corneal biomechanics with the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Depew, NY) after penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK).Subjects and methods: Sixty-three eyes of 63 patients were included in this prospective comparative study. Patients were divided into 3 groups: the first included 21 eyes of normal subjects (control group); the second included 21 eyes with PK; the third included 21 eyes with DALK. ORA was performed 2 months postoperatively for all patients.Results: Both mean corneal hysteresis (CH) and mean corneal resistance factor (CRF) were significantly lower in the PK group than both the DALK group and matched controls. No statistically significant difference was found between mean CH and mean CRF between the DALK group and matched controlsConclusion: Corneas after PK have weaker biomechanical properties than normal corneas. DALK preserves the biomechanical strength of the corneas to almost normal values.Keywords: hysteresis, keratoplasty, keratoconus