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Ophthalmic viscosurgical devices (OVDs) are a class of clear gel-like material used in eye surgery to maintain the volume and shape of the anterior chamber of the eye, and protect the intraocular tissues during the procedure. They were originally called viscoelastic substances, or just viscoelastics.
Unlike purely elastic substances, a viscoelastic substance has an elastic component and a viscous component. The viscosity of a viscoelastic substance gives the substance a strain rate dependence on time. Purely elastic materials do not dissipate energy (heat) when a load is applied, then removed.
It forms a viscoelastic solution in water. Mechanical protection for tissues (iris, retina) and cell layers (corneal, endothelium, and epithelium) are provided by the high viscosity of the solution. Elasticity of the solution assists in absorbing mechanical stress and providing a protective buffer for tissues. In facilitating wound healing, it ...
An OVD is a viscoelastic solution, a gel-like substance used to maintain the shape of the eye at reduced pressure, as well as protect the inside structure and tissues of the eye without interfering with the operation. [1] In 1980, D.M. Colvard made the cataract incision in the sclera, which limited induced astigmatism. [9]
Hypromellose , short for hydroxypropyl methylcellulose (HPMC), is a semisynthetic, inert, viscoelastic polymer used in eye drops, as well as an excipient and controlled-delivery component in oral medicaments, found in a variety of commercial products. [1] [2] The full form of HPMC is Hydroxypropyl Methyl Cellulose.
The political beltway over the weekend was upended by a bombshell report that Texas Rep. Kay Granger had been absent from the public eye for nearly six months, only to be discovered at an ...
Factory-sealed units have been known to sell for thousands at auctions, with one “exceedingly rare” 4GB model selling for an eye-gouging $190,373 in 2023. Even used ones in good condition can ...
The zonule of Zinn (/ ˈ t s ɪ n /) (Zinn's membrane, ciliary zonule) (after Johann Gottfried Zinn) is a ring of fibrous strands forming a zonule (little band) that connects the ciliary body with the crystalline lens of the eye. [1] The Zonular fibers a viscoelastic cables, although their component microfibrils are stiff structures.