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Learning curve quickly decreases for DALK with big bubble technique
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Deep anterior lamellar keratoplasty by air dissection using the big bubble technique involves a steep early learning curve that rapidly decreases as surgeons gain experience, a study found.
“The learning curve showed that complications related to this technique decrease significantly after the first 10 cases,” the study authors said.
The retrospective study included 44 eyes of 42 patients with moderate to advanced keratoconus who underwent DALK with the big bubble technique. Mean patient age was 33 years; mean follow-up was 9.9 months.
DALK was successful in 32 cases, and 12 cases were converted to penetrating keratoplasty. Twenty-seven DALK cases were available for analysis.
Intraoperative events were analyzed to gauge rates of complications and conversion to PK and to establish a learning curve that leads to successful execution of DALK with the big bubble technique. Outcomes were analyzed only for DALK cases that were not converted to PK.
Study results showed that at 12 months, mean logMAR best corrected visual acuity was 0.88; BCVA was 20/30 or better in 93.3% of patients and 20/40 or better in 100%. LogMAR visual acuity improved a mean 6.12 lines at 6 months (P < .0001) and 6.94 lines at 12 months (P < .005).
The intraoperative complication rate was 31.8%, and the postoperative complication rate was 4.5%.
Data showed that 60% of the first 10 grafts, 20% of the subsequent 20 grafts and 14% of the final 14 grafts were converted to PK. Overall, DALK with the big bubble technique was successful in 72% of cases, the authors said.
Perspective
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Thomas John, MD
The authors present a single surgeon’s experience in performing DALK-air dissection (AD) for keratoconus in 27 eyes that were analyzed with a primary focus on the effect of learning curve on DALK-AD results. At 12 months, best corrected visual acuity was 20/40 in all cases. The PK conversion rate decreased from 60% in the first 10 eyes, 20% in the subsequent 20 eyes, and 14% in the last 14 eyes. These DALK results are encouraging but the major limitation of DALK using air dissection (big bubble) is the inconsistency in achieving successful, uniform, complete Descemet‘s membrane separation from the stroma that often requires supplemental dissection techniques to complete the procedure. Hence, a DALK surgeon should be armed with multiple dissection techniques and use these techniques as needed to complete the procedure. The upside to DALK is the retention of the endothelium, thus eliminating endothelial graft rejection. Uniplanar dissection and meticulous attention to the interface is equally essential for optimal post-DALK visual results.
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