Creating a Healthy, Moist Environment
Find out how viscoelastic material in eye drops benefits contact lens wearers.
By Louise A. Sclafani, OD, FAAO

Contact lens wearers often turn to lubricant eye drops to ease discomfort from dry eye symptoms. In fact, a 1998 survey showed that 65% of contact lens patients used eye drops to relieve discomfort.

Many eye drops are commercially available to relieve dry eye, but only a few are designed specifically for contact lens wearers. We now have a new drop -- Blink Contacts with sodium hyaluronate (HA) -- that's answering a need among many patients. In this article, I'll describe how this product can help contact lens wearers stay more comfortable longer.

OCULAR APPLICATIONS OF HA

Sodium hyaluronate is a natural viscoelastic material found throughout the body, including the vitreous and aqueous humor, joints and organs. It functions as a lubricant thanks to its viscosity, and a shock absorber owing to its elasticity. It helps maintain hydration and the integrity of the intercellular matrix.

A water-retaining polymer, HA has been used in ocular surgery since 1979. It helps maintain the shape of the anterior chamber and protects the corneal endothelium during phacoemulsification and intraocular lens implantation. When used in eye drops, HA supports tear film stability, maintains corneal lubrication, decreases tear film evaporation and shortens healing time for the corneal epithelium.

STUDIES CONFIRM HA BENEFITS

Rewetting or lubricant eye drops are a popular option for treating the symptoms of dryness, foreign body sensation and stinging. HA has been shown to help relieve discomfort and dryness in patients with Sjögren's syndrome. What's more, it reduced the itching, burning and foreign body sensation in 26 of 28 dry eye patients treated with hyaluronate 0.1% solution four times daily for 2 months. Fifteen patients in this study had longer tear breakup times (TBUTs) and eight had reduced mucus strands.

In another study, 40 patients with Sjögren's syndrome used the 0.4% concentration six times daily for 90 days. Their symptoms improved significantly by day 15; and TBUT and epithelium protection improved over the course of the study.

UNDERSTANDING THE HA MOLECULE

Some high-viscosity agents help bind water to the eye. However, they may leave a crusty residue, may not spread evenly over the ocular surface, and can decrease lubrication by increasing friction and drag.

Hyaluronate is a long molecule that retains large amounts of water and is highly viscous under low shear force -- when the eye is open, for example -- because the molecules are random and tangled. This helps slow TBUT and resist moisture evaporation. When the eye blinks, HA is under high shear force. The molecules become untangled and aligned, so fluid flows freely around them and spreads over the ocular surface. After the blink, the molecules return to their random and tangled state, water binds to the surface, and the eye stays moist.

HA BENEFITS CONTACT LENS WEARERS

Blink Contacts contains 0.15% HA and a gentle peroxide-free, non-sensitizing oxychloro complex preservative that breaks down into sodium chloride and water when exposed to light.

Most contact lens wearers use a rewetting product to add moisture to their eyes. The new generation of lubricant eye drops, such as Blink Contacts, is now available to bring the benefits of a dry eye product to contact lens users.

References
1. Ky W, Scherick K, Stenson S. Clinical survey of lens care in contact lens patients. CLAO J. 1998;24:216-219.
2. DeLuise VP, Peterson WS. The use of topical Healon tears in the management of refractory dry-eye syndrome. Ann Ophthalmol. 1984;16:823-824.
3. Aragona P, Di Stefano G, Ferreri F, Spinella R, Stilo A. Sodium hyaluronate eye drops of different osmolarity for the treatment of dry eye in Sj�gren's syndrome patients. Br J Ophthalmol. 2002;86:879-884.
4. Goa KL, Benfield P. Hyaluronic acid: a review of its pharmacology and use as a surgical aid in ophthalmology, and its therapeutic potential in joint disease and wound healing. Drugs. 1994;47:536-566.
5. Bernatchez SF, Camber O, Tabatabay C, Gurny R. Use of hyaluronic acid in ocular therapy. In: Edman P, ed. Biopharmaceutics of Ocular Drug Delivery. Boca Raton, Fla: CRC Press; 1993:106-120.

Dr. Sclafani is is an associate professor of ophthalmology and director of optometric services at the University of Chicago. Her main interests include contact lenses, corneal disease and refractive surgery.