Posts tagged cornea
Articles and news from the latest research reports.
Scientists discover new layer of the human cornea
Scientists at The University of Nottingham have discovered a previously undetected layer in the cornea, the clear window at the front of the human eye.
The breakthrough, announced in a study published in the academic journal Ophthalmology, could help surgeons to dramatically improve outcomes for patients undergoing corneal grafts and transplants.
The new layer has been dubbed the Dua’s Layer after the academic Professor Harminder Dua who discovered it.
Professor Dua, Professor of Ophthalmology and Visual Sciences, said: “This is a major discovery that will mean that ophthalmology textbooks will literally need to be re-written. Having identified this new and distinct layer deep in the tissue of the cornea, we can now exploit its presence to make operations much safer and simpler for patients.
“From a clinical perspective, there are many diseases that affect the back of the cornea which clinicians across the world are already beginning to relate to the presence, absence or tear in this layer.”
Tough and strong
The human cornea is the clear protective lens on the front of the eye through which light enters the eye. Scientists previously believed the cornea to be comprised of five layers, from front to back, the corneal epithelium, Bowman’s layer, the corneal stroma, Descemet’s membrane and the corneal endothelium.
The new layer that has been discovered is located at the back of the cornea between the corneal stroma and Descemet’s membrane. Although it is just 15 microns thick — the entire cornea is around 550 microns thick or 0.5mm — it is incredibly tough and is strong enough to be able to withstand one and a half to two bars of pressure.
The scientists proved the existence of the layer by simulating human corneal transplants and grafts on eyes donated for research purposes to eye banks located in Bristol and Manchester.
During this surgery, tiny bubbles of air were injected into the cornea to gently separate the different layers. The scientists then subjected the separated layers to electron microscopy, allowing them to study them at many thousand times their actual size.
Better outcomes
Understanding the properties and location of the new Dua’s layer could help surgeons to better identify where in the cornea these bubbles are occurring and take appropriate measures during the operation. If they are able to inject a bubble next to the Dua’s layer, its strength means that it is less prone to tearing, meaning a better outcome for the patient.
The discovery will have an impact on advancing understanding of a number of diseases of the cornea, including acute hydrops, Descematocele and pre-Descemet’s dystrophies.
The scientists now believe that corneal hydrops, a bulging of the cornea caused by fluid build up that occurs in patients with keratoconus (conical deformity of the cornea), is caused by a tear in the Dua layer, through which water from inside the eye rushes in and causes waterlogging.
Ontario man’s sight restored with help of stem cells
When Taylor Binns slowly began going blind because of complications with his contact lenses, he started to prepare for living the rest of his life without vision. But an innovative treatment using stem cells has changed all that, and returned to him the gift of sight.
Four years ago, while on a humanitarian work mission to Haiti, Binns developed intense eye pain and increasingly blurry vision. Doctors at home couldn’t figure out what was wrong and, over the next two years, Binns slowly went legally blind, no longer able to drive or read from his textbooks at Queens University, where he was studying commerce.
“Everything you could do before was being taken away, day by day, and it got worse and worse,” he recalls.
Doctors finally diagnosed him with a rare eye disease called corneal limbal stem cell deficiency, which was causing the normal cells on Binns’ corneas to be replaced with scar tissue, leading to painful eye ulcers that clouded over his corneas.
A variety of things can cause the condition, including chemical and thermal burns to the corneas, which are the glass “domes” over the coloured part of our eyes. But it’s also thought that microbial infections and wearing daily wear contact lenses for too long without properly disinfecting them can lead to the disease, too.
Since a corneal transplant was not an option for Binns, his doctors at Toronto Western Hospital proposed something new: a limbal stem cell transplant.
The limbus is the border area between the cornea and the whites of the eye where the eye normally creates new epithelial cells. Since Binns’ limbus was damaged, doctors hoped that giving him healthy limbal cells from a donor would cause healthy new cells to grow over the surface.
While the treatment is available in certain centres around the U.S., Binns became the first patient to try the treatment at a new program at Toronto Western Hospital.
“Within a month he could see 20/40,” says ophthalmologist Dr. Allan Slomovic. “His last visit he was 20/20 and 20/40.” Slomovic says “it’s extremely exciting” that the procedure was a success, “especially when you realize there is really nothing else that would have worked for him.”
Binns is now living pain-free, returning to doing everything he used to before his three-year sight loss. “Being able to see my computer, being able to go for a walk or a drive — I am so happy for that,” he says.
The Toronto team hopes to do many more of these procedures in the future, says Dr. Sherif El Defrawy from the Canadian Ophthalmological Society and University of Toronto’s ophthalmology department.
“We are already seeing this in a number of centres across the country and you will see it more and more as we understand how to improve the success rate,” he says.
For Binns, the experience has been life-changing in one more important way: He has now decided to switch his studies from commerce to medicine, and hopes to go to school to become an ophthalmologist.
New technique to deliver stem cell therapy may help damaged eyes regain their sight
Engineers at the University of Sheffield have developed a new technique for delivering stem cell therapy to the eye which they hope will help the natural repair of eyes damaged by accident or disease. This could help millions of people across the world retain – or even regain - their sight.
In research published in the journal Acta Biomaterialia, the team describe a new method for producing membranes to help in the grafting of stem cells onto the eye, mimicking structural features of the eye itself. The technology has been designed to treat damage to the cornea, the transparent layer on the front of the eye, which is one of the major causes of blindness in the world.
Using a combination of techniques known as microstereolithography and electrospinning, the researchers are able to make a disc of biodegradable material which can be fixed over the cornea. The disc is loaded with stem cells which then multiply, allowing the body to heal the eye naturally.
“The disc has an outer ring containing pockets into which stem cells taken from the patient’s healthy eye can be placed,” explains EPSRC Fellow, Dr Ílida Ortega Asencio, from Sheffield’s Faculty of Engineering. “The material across the centre of the disc is thinner than the ring, so it will biodegrade more quickly allowing the stem cells to proliferate across the surface of the eye to repair the cornea.”
A key feature of the disc is that it contains niches or pockets to house and protect the stem cells, mirroring niches found around the rim of a healthy cornea. Standard treatments for corneal blindness are corneal transplants or grafting stem cells onto the eye using donor human amniotic membrane as a temporary carrier to deliver these cells to the eye. For some patients, the treatment can fail after a few years as the repaired eyes do not retain these stem cells, which are required to carry out on-going repair of the cornea. Without this constant repair, thick white scar tissue forms across the cornea causing partial or complete sight loss. The researchers have designed the small pockets they have built into the membrane to help cells to group together and act as a useful reservoir of daughter cells so that a healthy population of stem cells can be retained in the eye.