title: Visual Outcomes of Successful versus Failed Big-Bubble Deep Anterior Lamellar Keratoplasty for Keratoconus.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Javadi
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Mohammad-Rabei
authors.affiliation: Ocular Tissue Engineering Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sepehr
authors.initials: S
authors.lastname: Feizi
authors.affiliation: Department of Ophthalmology, Baqiyatallah University of Medical Sciences, Tehran, Iran.
authors.forename: Seyed-Hashem
authors.initials: SH
authors.lastname: Daryabari
keywords: Big-Bubble Technique; Deep Anterior Lamellar Keratoplasty; Keratoconus; Success Rate; Visual Acuity