New layer discovered in human cornea
21 June 2013
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.
It was previously believed that the cornea was comprised of
five layers, from front to back, the corneal epithelium, Bowman’s
layer, the corneal stroma, Descemet’s membrane and the corneal
The new layer has been dubbed the Dua’s Layer after the professor
who discovered it. Harminder 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 new layer 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.
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.
1. Dua HS et al. Human Corneal Anatomy Redefined: A
Novel Pre-Descemet’s Layer (Dua’s Layer). Ophthalmology.