Ophthalmic Viscosurgical Devices
Ophthalmic viscosurgical devices (OVDs) protect ocular tissues, such as the corneal endothelium and epithelium, from surgical trauma; help maintain the intraocular space; and facilitate tissue manipulation. Thus, they are indispensable tools in cataract and glaucoma surgery, penetrating keratoplasty, anterior segment reconstruction, and retinal surgery. Chemical and physical properties of OVDs include the capacity to resist flow and deformation. OVDs for ophthalmic use must also be inert, isosmotic, sterile, nonpyrogenic, nonantigenic, and optically clear. In addition, they must be sufficiently hydrophilic to allow easy dilution and irrigation from the eye. Naturally occurring and synthetic compounds available in various concentrations include sodium hyaluronate, chondroitin sulfate, hydroxypropyl methylcellulose, and polyacrylamide. Combined chondroitin sulfate/sodium hyaluronate materials are also available.
The 2 basic categories of OVDs are cohesive and dispersive. A cohesive OVD has a higher molecular weight and surface tension and tends to cohere to itself. A dispersive OVD has a lower molecular weight and surface tension and tends to coat intraocular structures. Available OVDs form a continuum on the basis of their cohesive and dispersive properties. The Healon, Healon GV, and Healon-5 products are mostly cohesive, and Ocucoat and Viscoat are mostly dispersive. There are also single agents with both cohesive and dispersive properties. (See also BCSC Section 11, Lens and Cataract.)
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.