To compare the visual and refractive outcomes and anterior segment optical coherence tomography (AS-OCT) findings of 2 different deep anterior lamellar keratoplasty (DALK) techniques in the treatment of advanced keratoconus with and without successful big bubble formation.
In this retrospective comparative case series, data from 79 consecutive eyes of 69 patients who underwent either big bubble (group 1, n: 62) or manual DALK (group 2, n: 17) were analyzed. The visual and refractive results, keratometric values and residual stromal thickness were assessed. Patients were seen at 1, 3, 6 and 12 months after the procedure and 1 month after complete suture removal.
A big bubble was successfully obtained in 62 eyes (78.5%; group 1) and manual dissection was performed in the 17 remaining eyes (21.5%; group 2). The final best spectacle-corrected visual acuity (BSCVA) was 0.38 logMAR and 0.55 logMAR in Group 1 and 2, respectively (P<0.05). At the final visit, BSCVA≤0.30 logMAR was achieved in 80% and 60.8% of eyes in Groups 1 and 2, respectively (P<0.001). Groups 1 and 2 were comparable in terms of mean keratometry: 47.80D±2.81D (range, 41.30D to 54.2D) versus 45.90D±3.62D (range, 41.10D to 53.8 D), respectively; (P=0.56) and keratometric astigmatism: 3.81D± 2.1D (range, 1.0D to 6.20D) versus 3.56D±1.92D (range 1.2D to 6.85D), respectively; (P=0.40) at the final follow-up. The mean residual stromal thickness was 36.90±17.80μm in group 2.
The presence of residual posterior corneal stroma when big bubble formation is not successfully achieved in DALK is correlated with lower postoperative visual acuity.

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