Contact Lens Wear, Dry Eye & Fatty Acids
Contact Lens Wear Can Lead to Dry Eye
Most people are aware that dry eye is a pervasive problem. Estimated to affect up to 1 in 5 adults, it is the most common condition seen in ophthalmology practices. Lesser known, however, is that dry eye is also the most common complaint among those who wear contact lenses.
In some cases, people who already have existing, marginal dry eye can experience worsening of the condition when they begin to wear contact lenses. For others, the lenses themselves may lead to dry eye symptoms over time.
Disturbing the Tear Film
The tear film that hydrates and lubricates the optical surface of the eye is composed of several layers. There is an oily outer layer which helps prevent the tear fluid from evaporating, and an inner layer of fluid that also contains a mucous-like gel which allows the fluid to spread evenly over the surface. A normal and stable tear film is necessary in order to be a successful contact lens wearer who does not suffer from symptoms of dryness or sensation of grittiness.
When a contact lens is placed in the eye, the lens can alter the normal structure of the tear film and affect its rate of evaporation. Greater evaporation leads to increased osmolarity (saltiness or lower volume of tear fluid) - a good predictor of dry eye. Tear osmolarity is often elevated in contact lens wearers, and even more so in those who can't tolerate them.
Microvilli Losses
For those who have been wearing their lenses for many years, there may be another contributing factor. The continual rubbing of the lens across the surface of the cornea may result in some loss of the microscopic hair-like structures called microvilli that exist on the outermost layer of the cornea. The microvilli bind to the mucous-like gel in the tear fluid so that the tear film adheres well to the cornea and maintains a stable, uniform layer on the cornea.
It's believed that the constant movement of the contact lens across the surface of the cornea over years of wear may reduce the microvilli. In turn, this can destabilize the tear film and result in contact lens-induced dry eye. It is also thought that discontinuing lens use temporarily will help restore microvilli.
Strategies for More Successful Lens Wear
Contact lenses are often a good alternative for people who are bothered by the cosmetic appearance of eyeglasses or the limitation to activities that they pose. To have a comfortable experience with contact lenses, it's important to be under the care of an eye care practitioner to ensure that the lens fit and lens materials you currently have are the best possible choice for you.
The type of lens chosen may make a difference in reducing the chance for dry eye. While some research has not shown a difference in tear osmolarity between soft, water-containing lens and the rigid, gas-permeable type of lens, in some cases soft, high-water content lenses may not be the best choice. In general, the more water a soft contact lens contains, the more prone it is to become dehydrated. As water evaporates from the front of the water-containing lens during wear, the lens draws moisture from the tear film. In addition to choosing appropriate lens materials, your eye doctor may also recommend lubricating drops or other aids, and suggest ways to modify environmental factors that can exacerbate dry eye such as overheated rooms, use of hairdryers or uninterrupted time at the computer.
Important Fatty Acids Can Be Helpful
An additional strategy is to try supplemental GLA and EPA, fatty acids that can bolster one's own natural, inflammation-fighting ability. Whatever the cause of dry eye - insufficient tear production, evaporation, chronic allergy or other - the result is an inflammatory reaction, and the contact lens wearer with symptoms of dryness is no exception. Research suggests that fatty acid supplementation can help calm inflammation and improve dry eye symptoms. Balanced amounts of GLA and EPA work together to reduce production of pro-inflammatory compounds while increasing the manufacture of compounds that are anti-inflammatory.
- Tomlinson A, et al. Tear film osmolarity: determination of a referent for dry eye diagnosis. Invest Ophthalmol Vis Sci 47:4309-15, 2006.
- Iskelei G, et al. Comparison of tear-film osmolarity in different types of contact lenses. CLAO J 28:184-6, 2002.
- Kallinikos P, et al. Assessment of stromal keratocytes and tear film inflammatory mediators during extended wear of contact lenses. Cornea 25:1-10, 2006.
- Barabino S, et al. Systemic linoleic and gamma-linolenic acid therapy in dry eye syndrome with an inflammatory component. Cornea 22:97-102, 2003.