Following publication in the journal Ophthalmology last May of a groundbreaking paper that established the existence of a sixth layer in the cornea — medical science till then recognised only five corneal layers — Professor Harminder Singh Dua and his team at Nottingham University have published another paper in the British Journal of Ophthalmology last month on yet another breakthrough that will have significant implications for the understanding of glaucoma.
Glaucoma is the second leading cause of blindness in the world particularly affecting women and persons of Asian origin.
The newly detected sixth corneal layer was named the Dua layer, in recognition of Dr. Dua’s work. Two other layers, the Bowman’s layer and the Descemets membrane, already carry the names of the doctors who discovered them. The Dua layer lies in front of the Descemet’s membrane.
Corneal surgeons have hailed the isolation of the Dua Layer as a major advance that considerably improves our understanding of lamellar corneal surgery, which in turn will lead to improved safety and outcomes for patients undergoing corneal grafts.
It was the most downloaded paper from the journal in the first three months of its publication. According to Science Direct, it was also the 11 most downloaded paper in all of medicine and dentistry.
“By retaining the innermost lining of the patient’s cornea we can almost completely avoid corneal transplant rejection. We always knew that corneal grafts performed by injecting air in the cornea were stronger than full thickness grafts. We have demonstrated that the sixth layer is very strong and this explains the strength of the eye after this type of corneal transplant,” Dr. Dua explained.
Dr. Dua is currently Chair and Professor of the Department of Ophthalmology at University of Nottingham, and President of the Royal College of Ophthalmologists, U/K. After the paper was published, he presented its findings at several international conferences where it received an enthusiastic response from specialists in the field of corneal transplant.
The son of an Indian Air Force officer, Dr. Dua studied in India, and later worked in the U.K. and the United States.
In their second paper Dr. Dua and his team built on their earlier finding. The aqueous fluid of the eye drains out of the eye through a sieve-like structure located at the periphery of the cornea called the trabecular meshwork. The paper in simple terms shows that the Dua Layer opens up at the periphery and extends outwards as the beams of the sieve (meshwork) through which the eye fluid drains. Damage to or hardening of the beams of the sieve reduces the flow of fluid, causing pressure to build up resulting in glaucoma.
“Now that we know that the Dua layer contributes a major proportion to the structure of the sieve, appropriate research can be directed to understand the relationship of the deep layer of the cornea to glaucoma,” Dr. Dua told The Hindu .
“Scientifically, I think that the second paper is more important than the first,” the soft-spoken India-born Sikh doctor said. “Compare this: in Britain we do about 3000 corneal transplants a year. However, two per cent of people over the age of 40 contract glaucoma, so the figures of those affected run into millions of people.”
The surgical interventions that derive from the new understanding is the subject matter of a third paper that has been published in the British Journal of Ophthalmology (online), which Dr. Dua has co-authored with Dr. Amar Agarwal from Dr. Agarwal’s Eye Hospital and Research Centre in Chennai.
The surgical technique, which Dr. Agarwal has performed successfully in Chennai is called pre-Descemet’s endothelial keratoplasty (PDEK), and involves the transplant of the Dua layer together with the Descemet’s membrane.
The technique has not been performed on humans in the U.K. yet, as it is still in the process of getting the approvals mandated by a rigorous regulatory mechanism that exist in the U.K. “Ethical regulations protect patients but are often seen as impediments to research,” says Dr. Dua, adding, “In this conflict, the patient’s interest should be placed foremost.”
