New corneal layer important for intraocular pressure maintenance

By Sara Freeman, medwireNews Reporter

UK researchers have found that a newly discovered layer of the human eye is an important part of the structural tissue that helps to maintain intraocular pressure and thus may play a role in the development of glaucoma.

The pre-Descemet’s layer (PDL), which is also known as Dua’s layer after the academic professor of ophthalmology who discovered it, is an important extension of the trabecular meshwork (TM), according to the team based at the University of Nottingham.

“The human TM is a wedge-shaped band of tissue that extends circumferentially across the angle of the anterior chamber of the eye,” Harminder Dua and colleagues explain in the British Journal of Ophthalmology.

“It is made of beams of collagen wrapped around a basement membrane that offers attachment to trabecular cells/endothelial cells,” they add. These collagen beams branch out and join to each other adjacently to form a meshwork of fibres.

The TM plays an important role in maintaining intraocular pressure within the eye, Dua and colleagues note, as it provides a place for aqueous humour to drain through. Defective drainage through the TM is an important cause of glaucoma.

Dua and team examined 20 human eyeballs from 17 donors. Sixteen of the donors had died and one living donor had their eyeball removed due to orbital malignancy. The age of donors ranged from 51 years up to 93 years, with the median age around 87 years.

The researchers examined the peripheral part of the PDL and Descemet’s membrane in the donor eyes using light and scanning electron microscopy. Samples from five eyes were also examined using immunohistochemistry.

“We were able to demonstrate that at its extreme periphery the collagen fibres of PDL arborise and extend as the collagen core of the beams that constitute the TM,” Dua et al write. “At the corneal periphery, PDL is populated by trabecular cells resting on basement membrane.”

Taken together, these findings suggest that the Dua layer is a continuation of the TM. “These are important observations that have implications for the understanding of aqueous drainage and should impact on future glaucoma research,” the team concludes.

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