Using Artificial Tears Before Lens Application and Removal
BY SUSAN J. GROMACKI, OD, MS, FAAO
Keeping mild to moderate dry eye patients successfully wearing their contact lenses is a well-documented challenge. For several years, I have recommended the instillation of an artificial tear drop before both lens application and removal. This small step alone can prolong wearing time. When combined with other measures (see "Contact Lens Solutions for Dry Eye," Contact Lens Care column, April 2003), it has contributed to preventing contact lens dropout for several of my patients. What is the scientific basis for this mechanism how does this work?
To answer this question, I spoke with Joe Vehige, OD, senior director of Clinical Research & Development at Allergan. According to Dr. Vehige, there are several benefits to instilling an artificial tear drop prior to contact lens application.
The first benefit for patients instilling an eye drop is physical lubrication. An eye drop residing between the eye and contact lens helps to bathe the cornea, providing a miniature lacrimal lake. This improves comfort for the patient.
In addition, the enhancement of the post-lens tear film provides an improved barrier to ocular surface desiccation. This protects the cornea.
The artificial tear functions also to increase viscosity and lower tension of the tear film as well as to bind water.
Dr. Vehige also discussed the added benefits of carboxymethylcellulose (CMC), the primary wetting agent in several artificial tear formulations (Refresh Tears, Refresh Contacts, Refresh Liquigel, Celluvisc [Allergan]; Thera Tears, Thera Tears [preservative free], Thera Tears Liquid Gel, Thera Tears Contact Lens Comfort Drops [Advanced Vision Research], and Tears Again Liquid Gel Drops [OcuSoft]).
Although CMC doesn't reduce surface tension as much as other agents do, it has unique properties because of its negative charge. Because of this, CMC will form an ion complex with multipurpose solutions bound to contact lenses.
The two most popular solution preservatives, polyquaternium-1 (Polyquad) and polyaminopropyl biguanide (PHMB), are both highly positively charged. As a result, CMC under a lens can tie up left-over disinfectant. This can decrease irritation and even some of the corneal staining associated with some of the older PHMB products.
Because CMC can reduce disinfection activity, it should not go into a lens case intentionally or by accident.
Additional research also has shown that CMC binds readily to corneal cells. As a result of this, CMC is predicted to have significantly enhanced retention on the eye or under a contact lens. This could also assist in wound healing.
Dr. Vehige states that sodium hyaluronate (hyaluronic acid) is similar in structure and function to CMC and likely has similar benefits.
Facilitates Lens Removal
It is universally accepted that contact lenses lose moisture over the course of the day. Lenses feel drier and fit tighter. The addition of a rewetting, saline or multipurpose solution drop prior to contact lens removal wets the lens, facilitating removal and preventing lens damage while also preventing the extraction of corneal epithelium along with the dry, tight lens.
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #127.
Dr. Gromacki has a specialty contact lens and post-surgical co-management practice as part of a multi-subspecialty ophthalmology group in Ann Arbor, MI.