#new layer

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British ophthalmologists have discovered a new layer in the cornea, the clear, dome-shaped surface that covers the front of the eye The layer has been named the Dua’s Layer after the academic Prof Harminder Dua who discovered it. “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 Dr Harminder Dua, Professor of Ophthalmology and Visual Sciences at the University of Nottingham and lead author of a paper published in the journal Ophthalmology. “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 lens on the front of the eye through which light enters the eye. Scientists previously believed the cornea to be comprised of five layers, from front to back, the corneal epithelium, Bowman’s layer, the corneal stroma, Descemet’s membrane and the corneal endothelium. The Dua’s Layer is located at the back of the cornea between the corneal stroma and Descemet’s membrane. Although the layer 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 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’s layer, through which water from inside the eye rushes in and causes waterlogging. 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. --------- Bibliographic information: Harminder S. Dua et al. 2013. Human Corneal Anatomy Redefined: A Novel Pre-Descemet’s Layer (Dua’s Layer). Ophthalmology, in press; doi: 10.1016/j.ophtha.2013.01.018 Source: http://www.sci-news.com/othersciences/anthropology/article01151-human-eye-duas-layer.html

Ophthalmology. 2013 May 25. pii: S0161-6420(13)00020-1. doi: 10.1016/j.ophtha.2013.01.018. [Epub ahead of print] Dua HS, Faraj LA, Said DG, Gray T, Lowe J. Source Larry A Donoso Laboratory for Eye Research, Division of Ophthalmology and Visual Sciences, School of Clinical Sciences, Division of Histopathology, University of Nottingham, United Kingdom. Electronic address: [email protected]. Abstract PURPOSE: To define and characterize a novel pre-Descemet's layer in the human cornea. DESIGN: Clinical and experimental study. PARTICIPANTS: We included 31 human donor sclerocorneal discs, including 6 controls (mean age, 77.7 years). METHODS: Air was injected into the stroma of donor whole globes (n = 4) and sclerocorneal discs (n = 21) as in the clinical deep anterior lamellar keratoplasty procedure with the big bubble (BB) technique. The following experiments were performed: (1) creation of BB followed by peeling of the Descemet's membrane (DM); (2) peeling off of the DM followed by creation of the BB, and (3) creation of the BB and continued inflation until the bubble popped to measure the popping pressure. Tissue obtained from these experiments was subjected to histologic examination. MAIN OUTCOME MEASURES: Demonstration of a novel pre-Descemet's layer (Dua's layer) in the human cornea. RESULTS: Three types of BB were obtained. Type-1, is a well-circumscribed, central dome-shaped elevation up to 8.5 mm in diameter (n = 14). Type-2, is a thin-walled, large BB of maximum 10.5 mm diameter, which always started at the periphery, enlarging centrally to form a large BB (n = 5), and a mixed type (n = 3). With type-1 BB, unlike type-2 BB, it was possible to peel off DM completely without deflating the BB, indicating the presence of an additional layer of tissue. A type-1 BB could be created after first peeling off the DM (n = 5), confirming that DM was not essential to create a type-1 BB. The popping pressure was 1.45 bar and 0.6 bar for type-1 BB and type-2 BB, respectively. Histology confirmed that the cleavage occurred beyond the last row of keratocytes. This layer was acellular, measured 10.15±3.6 microns composed of 5 to 8 lamellae of predominantly type-1 collagen bundles arranged in transverse, longitudinal, and oblique directions. CONCLUSIONS: There exists a novel, well-defined, acellular, strong layer in the pre-Descemet's cornea. This separates along the last row of keratocytes in most cases performed with the BB technique. Its recognition will have considerable impact on posterior corneal surgery and the understanding of corneal biomechanics and posterior corneal pathology such as acute hydrops, Descematocele and pre-Descemet's dystrophies. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article. Source: http://www.ncbi.nlm.nih.gov/pubmed/?term=dua's+layer

46 layers on the last one. how does that even happen