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A team of vision specialists from the University of Nottingham has made another breakthrough that could help improve the success of corneal transplants in patients whose eyesight has been affected by disease.
The research, published in the October edition of American Journal of Ophthalmology, has highlighted a feature of the thin membrane called Descemets membrane that can cause difficulties for surgeons performing the complex procedure of Descemets membrane transplantation.
The study was conducted by Harminder Dua, professor of ophthalmology and colleagues from the University's Division of Clinical Neuroscience, the same team that was the first to discover a new layer of the pre-layer – descendant of the cornea, also called layer of Dua.
Professor Dua said: "This work demonstrated the clear structural uniqueness of the pre-Descemets layer (Dua layer) and also answered a curious surgical question about why the Descemets membrane rolls in one direction This understanding will pave the way for the development of strategies to unfold it during transplantation, with minimal damage to the cells that it supports. "
Descemet's membrane, named after the French doctor who discovered it at the end of the 18th century, lies between the pre-Descemets layer (Dua layer) and the endothelial layer at the end of the 18th century. 39, back of the cornea, responsible for pumping excess fluid and keep the cornea sufficiently dehydrated to maintain a clear vision.
In certain diseases such as Fuchs dystrophy or after cataract surgery, the endothelial cells and Descemet's membrane are damaged, leading to corneal saturation and vision impairment. Over time, vision deteriorates and, if left untreated, may result in loss of vision.
To remedy this problem, patients can be offered one of several types of corneal grafting, in which all parts of the damaged or different cornea are removed and replaced with healthy tissue from a donor.
In Descemet's membrane endothelial keratoplasty (DMEK), the damaged Descemet's membrane is scraped off and replaced with a Descemet's membrane. When the membrane is separated from the other layers of the cornea to prepare it for transplantation, it turns into a cigar-shaped roll that facilitates insertion into the cornea through a small incision, but once in place, it is extremely difficult to deploy. When handling laminated tissue, sensitive endothelial cells that cover the outside of the membrane can be damaged, reducing the success of the transplant.
In the pre-Descemet endothelial keratoplasty (PDEK), Descemet's membrane is transplanted while it is attached to another layer, the pre-Descemet layer, also called Dua layer after its discovery by Professor Harminder Dua in 2013 layer by the American Association of Oncologists and Ocular Pathologists. It has been found that, even though there is still a rolling, it is not so pronounced, as the pre-Descemets or Dua layer stabilizes the Descemet layer acting as a kind of "wear and tear". splint.
Ophthalmologists have long observed that Descemet's membrane would only roll in one direction, leaving the endothelial cells on the outside of the loop, but wondered why.
Nottingham's research revealed for the first time that the direction of the roll is governed by the content and distribution of elastic-type elastin fibers in the membrane.
Using 31 corneal disks for research through the National Health Service's Manchester Eye Bank, they measured the elastin content of the Descemet membrane, the pre-Descemet membrane, the stroma, and 39, other sites of the cornea.
They also examined whether the treatment of Descemet's membrane with an enzyme that digests elastin had any effect on tissue rolling and whether the elimination of endothelial cells had an impact on this behavior .
They found that the pre-Descemet layer had the highest elastin content of all the tissues studied, but that elastin was evenly distributed in the tissues.
However, when they studied Descemet's membrane, they discovered that elastin was concentrated in a band on the front, which caused the membrane to coil up.
The study also showed that the removal of endothelial cells from the membrane made no difference in the direction of rolling, proving that it was elastin and not the cells that were responsible for the unidirectional rolling characteristic.
The treatment of Descemet's membrane with the enzyme reversed the rolling effect and was associated with the degradation or disappearance of elastin in the membrane.
The results are significant because they show that enzymes could potentially be used to weaken tissue turnover, which will make it easier for surgeons to successfully implant in the cornea while reducing potential damage to endothelial cells, which are so important for survival. regulate the fluid content of the cornea.
Explore more:
Scientists discover a new layer of human cornea
More information:
Imran Mohammed et al., Elastin Content and distribution in the endothelial keratoplasty tissue determines the direction of scrolling, American Journal of Ophthalmology (2018). DOI: 10.1016 / j.ajo.2018.07.001
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