Date Published: 11 June 2013

Discovery of Dua's Layer of the cornea of the human eye

A previously undetected layer in the cornea of the human eye, that is the clear window at the front of the human eye, has recently been discovered by scientists at Nottingham University (Nottinghamshire, England). This discovery could help eye surgeons to improve the outcomes for patients undergoing corneal grafts and transplants.

The new layer of the cornea has been called the Dua's Layer after the academic Professor Harminder Dua who discovered it.

Professor Dua, Professor of Ophthalmology and Visual Sciences at Nottingham University, 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."

The human cornea is the clear protective surface on the front of the eye through which light (see What is light ?) enters the eye. Scientists used to think of the cornea as comprised of five layers, from front to back:

1. Corneal epithelium,
2. Bowman's layer,
3. Corneal stroma,
4. Descemet's membrane, and
5. Corneal endothelium.

The new layer that has recently 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 researchers then subjected the separated layers to electron microscopy, to enable them to study the layers at many thousand times their actual size.

Understanding the properties and location of the new Dua's layer could assist surgeons to understand more about where in the cornea the bubbles are occurring and therefore to 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, hence potentially a better outcome for the patient.

This discovery is expected to lead to improvements in the advancing understanding of a number of diseases of the cornea, including acute hydrops, Descematocele and pre-Descemet's dystrophies. The scientists at Nottingham University 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 causing waterlogging.

Ref. to Paper:
Harminder S. Dua, Lana A. Faraj, Dalia G. Said, Trevor Gray James Lowe, Human Corneal Anatomy Redefined : A Novel Pre-Descemet's Layer (Dua's Layer) Ophthalmology, 2013. For further details see http://bit.ly/12ML0KN

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