Viscoelastic materials in veterinary ophthalmology

Abstract

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.

Intraocular pressure development after cataract surgery: a prospective study in 50 dogs (1998–2000)

“…In a study comparing the removal of visco‐elastic materials after experimental cataract surgery, Assia showed that sodium hyaluronate is the most easily, rapidly and completely removed 14 . However, its high cohesiveness also increases the tendency to plug the trabecular meshwork, resulting in an acute increase in postoperative IOP 16 . The various properties of visco‐elastic agents used in cataract surgery may explain the different results concerning the incidence of acute POH.…”

“…Sodium hyaluronate appears to be most easily, rapidly and completely removed in comparison with chondroitin sulfate‐sodium hyaluronate, hydroxypropylmethylcellulose and polyacrylamide 14 . However, as with other visco‐elastic materials, the risk of postoperative ocular hypertension (POH) remains if it is not well aspirated at the end of surgery 16 …”

Modified extracapsular extraction versus endocapsular phacoemulsification: intraoperative and immediate postoperative events

“…The use of a combination of 3% sodium hyluronate-4% chondroitin sulfate (dispersive) and 1% sodium hyaluronate (cohesive) has been recommended (Arshinoff, 1999;Wilkie and Willis, 1999). Pigatto (2004) studied corneal endothelial repercussions in dogs submitted to phacoemulsification and EE using the same combination of viscoelastic agents in a soft-shell technique.…”

Update on veterinary cataract surgery

“…It was also determined that preoperative IOP did not significantly correlate with POH [17,18 ]. The prevalence of POH may be reduced by complete removal of the viscoelastic material [49,50]. Other methods to control POH include intracameral injection of carbachol or tPA or preoperative use of carbonic anhydrase inhibitors.…”