Viscoelastic materials in veterinary ophthalmology.

Viscoelastic materials have applications in both human and veterinary ophthalmology and orthopedics and for humans in otorhinolaryngology, urinary incontinence, cosmetic surgery and cosmetics. In ophthalmology, viscoelasties are most commonly used in facilitating cataract and other anterior segment surgeries, but also have applications in posterior segment surgery and in the topical management of keratoconjunctivitis sicca. Viscoelastics are routinely used during anterior segment surgery in filling and maintaining the anterior chamber, repositioning the iris, and to coat and protect the corneal endothelium, and expand the capsular bag prior to intraocular lens implantation. Viscoelastics can also be essential in the management of intraoperative complications such as miosis, hemorrhage, posterior capsular tears, and vitreous presentation. The most common products available for ophthalmic use include various concentrations of sodium hyaluronate, chondroitin sulfate, and hydroxypropylmethylcellulose. The physical properties of each viscoelastic material are dependent on chain length, and intra-and interchain interactions. The rheologic properties of viscosity, pseudoplasticity, viscoelasticity, and surface tension dictate the usefulness of each material for a specific purpose.