Visual Outcomes after Successful versus Failed Big-bubble Deep Anterior Lamellar Keratoplasty in Keratoconus

To compare visual outcomes after deep anterior lamellar keratoplasty (DALK) between eyes with and without successful big-bubble formation. In this retrospective comparative study, a total of 290 consecutive eyes from 257 keratoconus-affected patients underwent DALK with the big-bubble technique were enrolled. In cases where the big bubble could not be accomplished, manual stromal dissection down to DM was progressively performed using a crescent knife. The rate of successful big-bubble formation was determined. Visual acuity and refractive outcomes were compared between the bare Descemet membrane (DM) group (group 1) and manual dissection group (group 2). The surgery was completed as DALK in 289 of 290 eyes and a bare DM was successfully achieved in 229 (79.2%) eyes. The study groups were comparable in terms of age (27.8±7.9 years in group 1 versus 27.5±8.5 years in group 2, P=0.79), preoperative best-spectacle corrected visual acuity (BSCVA) (1.28±0.49 versus 1.31±0.51 logMAR, respectively, P = 0.15), and postoperative follow-up (38.4±20.4 versus 37.4±19.9 months, respectively, P=0.73). Postoperative BSCVA was significantly better in group 1 than in group 2 throughout the follow-up period (P<0.05). At final follow-up examination, a BCVA ≤0.30 logMAR was achieved in 82.1% of group 1 and 54.5% of group 2 (P<0.001). Groups 1 and 2 were comparable in terms of postoperative spherical equivalent refractive error (-4.24±3.35 versus -4.49±3.25 D, respectively, P=0.61) and keratometric astigmatism (3.62±1.92 versus 3.38±1.71 D, respectively, P=0.39). Retention of posterior corneal stroma resulted in a lower visual acuity as compared to the bare DM group.