A team of eye specialists at the University of Nottingham has discovered a new way to improve the success of corneal transplants for patients whose sight has been affected by the disease. The study was led by Harminder Dua, Professor of Ophthalmology and colleagues in the University’s Division of Clinical Neuroscience.

Professor Dua said: “This work has explained why the Descemet’s membrane rolls in one direction when peeled off the donor’s eye.” This understanding will pave the way to develop strategies to unroll it during transplantation, with minimal damage to the cells it supports.”

The Problem with Descemet’s Membrane

In Descemet membrane endothelial keratoplasty (DMEK), the patient’s damaged membrane is replaced with a donated Descemet membrane. The surgeon separates the membrane from other layers of the cornea to prepare it for transplant. It then curls into a cigar-shaped roll which facilitates insertion into the cornea via a small incision. But once in place, it’s extremely tricky to unfurl. The manipulation of the rolled tissue may damage, sensitive endothelial cells and reduce the success of the transplant.

It has been found that while there is still a roll, it is not as pronounced because the pre-Descemet’s or Dua’s layer stabilizes the Descemet layer, acting as a kind of splint.

Ophthalmologists have puzzled why the membrane only rolls in one direction, placing endothelial cells on the outside of the curl,
The Nottingham research has revealed for the first time that the direction of the roll is governed by the content and distribution of elastin – elastic-like fibers within the membrane.

Using 31 corneal discs earmarked for research purposes through the National Health Service’s Manchester Eye Bank, the team measured the elastin content in the Descemet membrane, the pre-Descemet membrane, the stroma, and other sites of the cornea.

Unrolling with an Enzyme

They also looked at whether treating the Descemet membrane with an enzyme that digests elastin would affect the rolling up of the tissue and whether removing endothelial cells impacted this behavior.
The found that the pre-Descemet layer had the highest elastin content of all the tissues studied but that the elastin was evenly distributed across the tissue.
However, when they came to study the Descemet membrane, they found that the elastin was concentrated in a band across its front which was causing the membrane to roll up.

Endothelial Cells were not the Culprit

The study also found that the removal of the endothelial cells from the membrane made no difference to the direction of rolling proving that it was the elastin and not the cells that were responsible for the characteristic unidirectional rolling.

Treating the Descemet membrane with the enzyme reversed the rolling effect and was associated with the degradation of elastin in the membrane.

The results show that enzymes could potentially be used to weaken the rolling of the tissue, making it much easier for surgeons to successfully implant it into the cornea. This would reduce potential damage to the endothelial cells, which are critical to hydrating the cornea.

The research, published in October’s American Journal of Ophthalmology, has shed light on a characteristic of Descemet’s membrane which can pose difficulties for ophthalmic surgeons performing the intricate Descemet’s Membrane transplant procedure.