AUG 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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30 EW CORNEA August 2013 New corneal layer discovered by Michelle Dalton EyeWorld Contributing Writer Researchers in the U.K. discover a layer between stroma and Descemet's membrane S cientists at the University of Nottingham have discovered a previously undetected layer in the cornea,1 dubbed Dua's layer after Harminder S. Dua, MD, PhD, TORIC/LRI MARKERS S9-2033 Pre-Operative Alignment Marker For marking patient on gurney or at slit lamp prior to procedure • Three fine marking points at 3, 6 and 9 for accurate reference • Properly angled handle allows an unimposing approach to patient Light microscopic image of Dua's layer separated from the back of the cornea. The Descemet's membrane has been removed. Source: Harminder S. Dua, MD, PhD S9-2060 Mendez Style Degree Gauge Intra-operative ring for aligning to steep axis and defining LRI points • Large 11.7mm internal diameter provides for maximum visualization • Beveled surface reduces reflections form microscope lighting • Crisp laser etched markings every 5˚ for greater marking accuracy S9-2065 Axis Marker Works inside the Degree Gauge to mark prime meridian (steep axis) for LRIs and Toric alignment. • Fits inside Degree Gauge perfectly • Crisp edges create a fine demarcation • Length of marks accommodates both limbal and corneal marking S9-2050 LRI Marker Provides crisp marks at commonly used LRI Positions • Fits inside Degree Gauge perfectly • Creates symmetrical, opposing marks for 30˚, 45˚ and 60˚ incisions • Fine arc connects degree endpoints for easy, acurate incisions 2500 Sandersville Rd., Lexington, KY 40511 USA Phone: 800-354-7848, 859-259-4924 Fax: 859-259-4926 E-Mail: stephensinst@aol.com www.stephensinst.com professor of ophthalmology and visual sciences, University of Nottingham, U.K., who discovered it. "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 'big bubble' 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, Descemetocele and pre-Descemet's dystrophies," the authors wrote. According to Prof. Dua, the layer is a mere 15 microns thick, but strong enough to withstand approximately 700-950 mm of mercury pressure (although this was in a small sample size). Prof. Dua said the layer's existence was proven by "simulating human corneal transplants and grafts on eyes donated for research purposes to eye banks." During the surgery, "air was injected into the cornea to separate the different layers just as is done during the operation in a patient undergoing deep anterior lamellar keratoplasty. The group then subjected the separated layers to electron microscopy." The group suggested that acute corneal hydrops in keratoconus could be related to a tear not just in Descemet's membrane but in Dua's layer as well. Prof. Dua and his colleagues "are convinced this is a distinct layer that considerably informs our approach to lamellar corneal surgery. In deep anterior lamellar keratoplasty (DALK), surgeons were observing 'things' that made no sense," he told EyeWorld. "The best explanation offered for close to a decade for one of the 'things' was a 'split' in the Descemet's membrane between banded and non-banded zones." In reality, that split does not occur during surgery; the appearance is due to a mixed bubble, a combination of a type-1 bubble formed between Dua's layer and posterior stroma and a type-2 bubble formed between Dua's layer and Descemets membrane, Prof. Dua Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.)

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