Visual Outcomes of Successful versus Failed Big-Bubble Deep Anterior Lamellar Keratoplasty for Keratoconus

Purpose: To compare the visual outcomes of deep anterior lamellar keratoplasty (DALK) for keratoconus with and without successful big‑bubble formation. Methods: In this retrospective comparative study, a total of 289 consecutive eyes from 257 patients underwent DALK using the big‑bubble technique. In cases where the big bubble could not be accomplished, manual stromal dissection down to Descemeton membrane (DM) was performed using a crescent knife. Visual acuity and refractive outcomes were compared between the bare DM group (Group 1) and manual dissection group (Group 2). Results: A bare DM was successfully achieved in 229 (79.2%) eyes and manual dissection was performed in 60 (20.8%) eyes. The study groups were comparable in terms of age (P = 0.79), preoperative best‑spectacle corrected visual acuity (BSCVA) (P = 0.15), and follow‑up duration (P = 0.73). Postoperative BSCVA was significantly better in Group 1 than in Group 2 throughout follow‑up (P < 0.05). In Group 2, BSCVA was significantly lower in eyes with advanced keratoconus as compared to those with moderate keratoconus (P = 0.007). At final follow‑up, BSCVA ≤ 0.30 logarithm of minimum angle of resolution (logMAR) was achieved in 82.1% of eyes in Group 1 versus 54.5% of eyes in Group 2 (P < 0.001). Groups 1 and 2 were comparable in terms of postoperative spherical equivalent refractive error (P = 0.61) and keratometric astigmatism (P = 0.39). Conclusion: Retention of the posterior corneal stroma which occurs with manual dissection during failed big bubble formation in DALK is associated with lower visual acuity as compared to achieving a bare DM.