Discovery of Dua’s Layer: Human Corneal Anatomy Redefined
After hours of studies for professional examinations, I switched to the internet for some relaxation. While surfing and browsing purposelessly, I checked my mail to find an update on the new issue of Ophthalmology. The article “Human Corneal Anatomy Redefined” about the discovery of sixth layer of cornea, the Dua’s layer left my eyes glued to the screen.
For the last six years I had been studying that there are five layers of cornea; from front to back, the corneal epithelium, Bowman’s layer, the corneal stroma, Descemet’s membrane and the corneal endothelium. These layers give cornea a thickness of 0.5 mm or 550 micron. Many of the famous authors including Ramanjit Sihota & Radhika Tandon and Jack J. Kanski had written this in “Parsons’ Diseases of the Eye” and “Clinical Ophthalmology: A Systematic Approach” respectively. But Professor Dua has changed that apparently.
“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” said Professor Dua, head of Ophthalmology and Visual Sciences Department at University of Nottingham, UK.
This newly discovered layer of only 15 micron thickness is located at the back of the cornea between the corneal stroma and Descemet’s membrane and is incredibly tough and strong, enough to withstand 1.5-2 bars of pressure. It is not merely a theory but a proven fact by the scientists who proved the existence of Dua’s layer by simulating human corneal transplants and grafts on eyes donated for research purposes to eye banks located in Bristol and Manchester, UK. Tiny bubbles of air were injected into the cornea to gently separate the different layers. Separated layers were then visualized by electron microscope, allowing the scientists to study these layers at many thousand times their actual size.
It has been postulated that this discovery will have an impact on understanding of a number of corneal diseases, 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, is caused by a tear in the Dua layer, through which water from inside the eye rushes in and causes waterlogging.
What will be the impact of this discovery on diagnosis, medical and surgical treatment of diseases of cornea? Will surgical procedures or corneal transplants have to be modified? All these and many others questions will be answered after further research studies. We could just wait and watch or step forward and explore it!
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