Big-bubble DALK: A technique in evolution

Deep anterior lamellar keratoplasty (DALK) is considered a valuablealternative to penetrating keratoplasty (PK) for treatingcorneal disordersthat do not involve theendothelium. DALK preserves the host endothelium, eliminating the risk of endothelial rejection and reducing the risk of late graft failure due to endothelial decay. Despite its not recent introduction, DALK has been considered a difficult, lengthy, and poorly reproducible procedure, limiting its adoption worldwide. With the introduction of the big-bubble technique (BBT) the reproducibility and the time required to complete the procedure were significantly improved, encouraging many surgeons to approach DALK. With BBT air is injected into the stroma to induce separation between the layers of the cornea, facilitating the separation of the diseased or scarred stroma from the healthy endothelium; this allows the creation of a graft-host interface of pristine optical quality, granting clinical results equal to those obtained with PK.Understanding the anatomy and physics behind the big bubble (BB) formation is crucial for thesurgical success of this technique. The discovery of the pre-Descemet's layer (Dua's layer)played a significant role in understanding the principles behindBBformation, considerablyimpacting the safety and reproducibility of the technique. BB formation is influenced by preoperative pathology, trephination size, and instruments used for air injection.Continue advancements have helped to refine BBT's efficacy and reproducibility, broadening its applicability in corneal transplantation whenever the endothelium is healthy.This review provides a detailed account of the procedural steps involved in DALK using the BBT, addressing the most common challenges, highlightingtechnical innovations, and handlingthe most frequent complications.

Microbubble technique in failed deep anterior lamellar keratoplasty: 2-year outcomes

Purpose:

To compare the long-term results of big-bubble technique and microbubble techniques to complete stroma dissection after failure of achieving a big-bubble.

Methods:

A total of 35 eyes with keratoconus underwent lamellar keratoplasty with the big-bubble technique (15 eyes) or the microbubble technique (15 eyes). Conversion to penetrating keratoplasty was performed in 3 eyes of the big-bubble group and in 2 eyes of the microbubble group. Best-corrected visual acuity, corneal thickness, corneal astigmatism, and endothelial cell count were assessed preoperatively and at 12 and 24 months after surgery.

Results:

Mean preoperative visual acuity was 0.29 ± 0.18 in the big-bubble group and 0.25 ± 0.15 in the microbubble group. Postoperatively, all patients showed a regular interface between donor and recipient tissue. At 24 months, mean best-corrected visual acuity was 0.84 ± 0.16 in the big-bubble group and 0.68 ± 0.17 in the microbubble group (p = 0.013), and mean central corneal thickness was 530 ± 39 µm in the big-bubble group and 545 ± 30 µm in the microbubble group. Astigmatism was 2.41 ± 1.29 D and 3.59 ± 1.48 D (p = 0.036), respectively, while endothelial cell density was 1,671 ± 371 in the big-bubble group and 1,567 ± 275 in the microbubble group.

Conclusions:

The microbubble technique appears to be a valid alternative as it was safe and provided good functional results.

Big-bubble deep anterior lamellar keratoplasty using central vs peripheral air injection: a clinical trial

PURPOSE

To compare 2 sites of air injection to achieve Descemet membrane (DM) detachment in big-bubble deep anterior lamellar keratoplasty (DALK).

METHODS

In this prospective, randomized study, 48 eyes of 48 keratoconus-affected patients who underwent DALK by cornea fellows were enrolled. Each patient was randomly assigned into one of 2 groups. After trephination to approximately 80% of the corneal thickness, a 27-G needle was inserted into the stroma from the trephination site. The needle was moved radially inside the trephination site and advanced to the central or paracentral cornea in group 1. In group 2, the needle was inserted into the deep stroma from the trephination site and advanced into the peripheral cornea to approximately 1.5 mm anterior to the limbus. Air was gently injected into the deep stroma until a big bubble was formed. The rates of DM separation and complications were compared between the 2 groups.

RESULTS

Big-bubble formation was successful in 79.2% of the eyes in the study group. A bare DM was achieved by central injection in 68.0% of group 1 and by peripheral injection in 69.6% of group 2 (p = 0.68). This rate was increased to 80.0% and 78.3% in groups 1 and 2, respectively, after the injection site was shifted when injections failed. The study groups were comparable in terms of complications including DM perforation and bubble bursting.

CONCLUSIONS

Both injection sites were equivalent in their rates of big-bubble formation and complications. Less experienced surgeons are advised to initially inject air outside the trephination.

Common complications of deep lamellar keratoplasty in the early phase of the learning curve

PURPOSE

To evaluate and record the common complications that face surgeons when they perform their first few series of deep lamellar keratoplasty and measures to avoid these.

SETTING

Dar El Oyoun Hospital, Cairo, Egypt.

METHODS

Retrospective study of the first 40 eyes of 40 patients carried out by two corneal surgeons working in the same center. All patients were planned to undergo a deep anterior lamellar keratoplasty using the big bubble technique. Twelve patients suffered from keratoconus while 28 patients had anterior corneal pathologies. Recorded complications were classified as either intraoperative or postoperative.

RESULTS

Perforation of Descemet's membrane was the most common intraoperative complication. It occurred in nine eyes (22.5%): five eyes (12.5%) had microperforations while four eyes (10%) had macroperforations, three eyes (7.5%) had central perforations, and six eyes (15%) had peripheral perforations. Other complications included incomplete separation of Descemet's membrane and remnants of peripheral stromal tissue. Postoperative complications included double anterior chamber which occurred in four eyes (10%) and Descemet's membrane corrugations. Postoperative astigmatism ranged from 1.25 to 4.5 diopters with a mean of 2.86 diopters in the whole series, but in the six cases with identified residual stroma in the periphery of the host bed, the astigmatism ranged from 2.75 to 4.5 diopters with a mean of 3.62 diopters.

CONCLUSION

Deep lamellar keratoplasty is sensitive to procedural details. Learning the common complications and how to avoid them helps novice surgeons to learn the procedure faster.