Scientists believe the discovery of a sixth corneal layer will help surgeons dramatically improve outcomes for patients undergoing corneal grafts and transplants.
The breakthrough was announced in the journal Ophthalmology.
“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,” says Harminder Dua, Professor of Ophthalmology and Visual Sciences at the University of Nottingham, after whom the new layer has been named.
“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.”
Further studies need to be undertaken with more eyes and from a broader range of age groups to confirm the findings and clinical implications…
Scientists previously believed the human cornea – the clear protective lens on the front of the eye through which light enters – 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.
Stephanie Watson, Clinical Professor at Save Sight Institute, University of Sydney said the findings are of interest.
“A similar layer in the cornea has been described before as far back as 1991 by Dr. Perry Binders’ group and reported in Investigative Ophthalmology and Visual Science, however this report highlights the clinical implications of this tissue and probably gives us a new way to think about corneal transplantation using newer techniques,” said Prof. Watson.
“Surgeons undertaking endothelial transplantation have been trying to use Descemet’s membrane alone, but it’s possible that including this extra layer – the Dua layer – in the transplant may make it more robust,” she said, adding that the finding may increase understanding of why wound strength is greater when a deep anterior lamellar keratoplasty (DALK) is performed, as opposed to a full thickness penetrating keratoplasty (PK).
“The finding may also have an impact on the way in which surgeons perform the big bubble technique – because it suggests that surgeons should try to achieve a smaller bubble,” said Professor Watson. This is because Dua’s layer finishes before Descemet’s membrane, in the peripheral cornea.
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 water-logging.
Professor Watson cautioned that the study conducted at the University of Nottingham was small – with just 31 eyes from people ages in their 70s.
“Further studies need to be undertaken with more eyes and from a broader range of age groups to confirm the findings and clinical implications,” she said.