Newly Identified Dua's Layer in Cornea May Improve Surgeries

Lara C. Pullen, PhD

June 20, 2013

Investigators have identified a novel, acellular, strong layer in the pre-Descemet's cornea. Harminder S. Dua, MD, PhD, from the University of Nottingham in the United Kingdom, and colleagues discovered the layer by examining the separation that often occurs along the last row of keratocytes during the big bubble (BB) technique. Investigators named the novel layer the Dua's layer and published their discovery online May 28 in Ophthalmology.

Surgeons have long used the BB technique and others like it to effectively peel off the Descemet's membrane (DM) for use in the deep anterior lamellar keratoplasty (DALK) procedure. In 2002, investigators found that there was a layer attached to the deep stroma that was also removed by mechanical dissection.

The current study expands on this previous work and identifies and characterizes a distinct layer that is 10.15 ± 3.6 microns thick at the posterior surface of the corneal stromal. The authors emphasize that this layer is not "residual stroma."

The analysis was performed on 31 human donor sclerocorneal discs (including 6 controls). The study was performed in adult eyes with a mean age of 77.7 years.

"Having performed all types of corneal transplants myself, I had certain doubts about the plane at which the air injected into the cornea separated the 'DM.' There were clues that told me that it was not the DM that I was separating when doing DALK. So I decided to investigate this by simulating the operation in human eyes (not suitable for transplant for various reasons) obtained from the UK eye banks," Dr. Dua wrote in an email to Medscape Medical News.

Dr. Dua and colleagues identified two types of BB: type 1 was well-circumscribed with an elevation of up to 8.5 mm (n = 14), and type 2 was thin-walled with a maximum diameter of 10.5 mm (n = 5). The researchers also found eyes with a mixed type of BB (n = 3).

"I was able to induce separation of the layer by injecting air and prove by electron microscopy and other means that there was a new layer and that the cleavage was not between DM and stroma, as everyone thought. The simple and clinical evidence is in the videos linked to the paper, but [they] can be accessed only online at the Ophthalmology journal's Web site," elaborated Dr. Dua.

"If it is, indeed, an actual layer of the cornea, it should be present in children as well, and that work still needs to be done," Shameema Sikder, MD, from the Wilmer Eye Institute of Johns Hopkins University in Baltimore, Maryland, said to Medscape Medical News.

The authors suggest that recognition of this novel layer will affect posterior corneal surgery. Specifically, it may be possible to use the plane between the Dua's layer and stroma to generate tissue for endothelial transplant. The authors also propose that the discovery will aid in the understanding of corneal biomechanics and pathology. Patients with acute hydrops, Descematocoele, and pre-Descemet's dystrophies are most likely to benefit from the discovery.

"I am pleased by my discovery, as it explains a few things that were happening during lamellar corneal surgery that we did not previously understand. It will make the operation safer and may also improve our understanding of some corneal diseases," noted Dr. Dua.

The authors and Dr. Sikder have disclosed no relevant financial relationships.

Ophthalmology. Published online May 28, 2013. Abstract


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