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‘Double bubble’ technique enhances safety, efficiency of DALK
The new technique promotes Descemet’s membrane exposure and reduces the risk of perforation or rupture.
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A variant of the big bubble technique for deep anterior lamellar keratoplasty aids visualization and enables safe separation of Descemet’s membrane from the corneal stroma, a clinician said.
The “double bubble” technique minimized complications and yielded positive visual outcomes, Jun Shimazaki, MD, PhD, reported in a study slated for publication in the Journal of Cataract and Refractive Surgery.
“We believe that a small, but important, improvement that this technique offers will assist surgeons in performing DALK more safely and efficiently,” Dr. Shimazaki wrote in the study abstract.
Deep anterior lamellar keratoplasty (DALK), indicated for corneal scarring, dystrophy, keratoconus and post-herpetic keratitis, is preferable to penetrating keratoplasty because of a reduced risk of complications such as expulsive hemorrhage, endophthalmitis, endothelial cell loss and traumatic wound dehiscence, Dr. Shimazaki said.
 Jun Shimazaki |
However, DALK is difficult and challenging, with up to 39.2% risk of Descemet’s membrane perforation, Dr. Shimazaki said.
“The safe and efficient exposure of Descemet’s membrane is the key to success in DALK,” he said. “Although widely used, the big bubble technique suffers from the drawback of difficulty in maintaining appropriate needle insertion depth in the corneal stroma, resulting in injected air sometimes escaping to the peripheral cornea without separation of [Descemet’s membrane].”
The study included 11 eyes that underwent DALK with the double bubble technique performed by a single surgeon. The ratio of male to female patients was 9-to-2. Mean patient age was 50.7 years (range: 27 to 72 years). Mean follow-up was 16.6 weeks. Eight eyes had keratoconus, two eyes had corneal scarring and one eye had lattice dystrophy.
Study results showed Descemet’s membrane exposure in nine eyes; successful DALK was performed in 10 eyes. Descemet’s membrane microperforation occurred in two eyes, macroperforation in one eye and a double chamber in one eye. The eye with macroperforation was converted to PK. Postoperative logMAR best corrected visual acuity ranged from 0.1 to 1.
Separating Descemet’s membrane
The double bubble technique is a modification of the big bubble technique devised by Mohammad Anwar, MD, combined with the mirror image technique developed by Gerrit Melles, MD, Dr. Shimazaki said.
“By observing the reflection created on the surface of the air, a needle can be inserted deep into the stroma without puncturing Descemet’s membrane,” Dr. Shimazaki said. “This allows safe and efficient separation of Descemet’s membrane. Moreover, air in the anterior chamber can be used as an indicator of successful Descemet’s membrane separation, as air is shifted to the periphery with creation of the big bubble. Once Descemet’s membrane has been separated from the corneal stroma, excision of stromal tissue is relatively easy.
“There is, however, a distinct difference between the Melles technique and ours,” he continued. “While the knife has to proceed immediately above [Descemet’s membrane] in the Melles technique, the needle does not have to be located so deep in our technique. The injected air smoothly infiltrates the supra-[Descemet’s membrane] space if the needle is deep enough. Therefore, the approach to [Descemet’s membrane] in our technique is not as technically demanding as that of the Melles technique.”
In the big bubble technique, air is also injected into the corneal stroma to facilitate separation of Descemet’s membrane from the deep stromal layer. Although widely used, the big bubble technique poses a risk of corneal whitening, or opacity, that hampers visualization and surgical manipulation. Dr. Shimazaki quoted a study showing that 36% of big bubble procedures fail to separate Descemet’s membrane.
The double bubble technique involves the creation of two air bubbles, one in the anterior chamber and the other in the corneal stroma. Injected air in the anterior chamber helps guide and confirm safe Descemet’s membrane separation. – by Matt Hasson
- Jun Shimazaki, MD, PhD, can be reached at Tokyo Dental College Ichikawa General Hospital Department of Ophthalmology, 5-11-13 Sugano, Ichikawa-shi, Chiba 272-8513, Japan; +81-47-322-0151; fax: +81-47-325-4456; e-mail: jun@eyebank.or.jp.