Purpose: To evaluate and compare visual and optical performance outcomes by means of analysis of the contrast sensitivity function (CSF) and ocular higher order aberrations (HOA) in patients with keratoconus who had deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PK)., Methods: In this prospective, randomised case series, 174 eyes of 140 consecutive patients with moderate to advanced keratoconus were included. The big-bubble technique was attempted to perform DALK. Intraoperative and postoperative complications, uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), refraction, topographic astigmatism, CSF and ocular HOA were evaluated., Results: The DALK and PK groups consisted of 99 and 75 eyes, respectively. Postoperative BSCVA was 20/40 or better in 64 eyes (85%) in the PK group and and 82 eyes (83%) in the DALK group (p>0.05). The mean spherical equivalent and maximum keratometry were -1.50 (-6.25 to +4.75) and 46.85 (40.60 to 56.00) in the PK group and -2.25 (-8.75 to +4.00) and 46.90 (40.60 to 53.60) in the DALK group, respectively. The differences were not statistically significant (p=0.08 and p=0.66, respectively). No significant differences in photopic contrast sensitivity were found for each of the spatial frequencies (p>0.05 for all). However, mesopic contrast sensitivity for three cycles/degree was significantly higher in the DALK group (p=0.01). No significant differences between groups were detected for any of the aberrometric parameters (p>0.05)., Conclusions: DALK is an alternative treatment option in eyes with moderate to advanced keratoconus, providing comparable results to PK in terms of visual acuity, refraction, CSF and HOA.