Contact Lenses and Dry Eyes
What causes dry eyes from contact lenses?
According to the Schepens Eye Research Institute in Boston, approximately 10 million people in the United States suffer from Dry Eyes. One risk factor for dry eyes that might be surprising is that wearing contact lenses can actually cause Dry Eyes. Why is it that contact lenses can cause Dry Eyes? Simply stated, Dry Eyes can occur if you either don't have a sufficient quantity of tears or if the composition of the tears you do have is not correct.
Dry Eyes and Soft Contact Lenses
Contact lenses are manufactured from one of two types of polymeric materials. Soft contact lenses are made from hydrophilic plastics that contain water. In fact they may contain anywhere from 30-75% water depending on what type of wearing schedule they are designed for. In general, the more water a soft contact lens contains, the more prone it is to dehydration and losing its water. This is not a desirable attribute because as water evaporates from the front surface of the lens while being worn, it reacts by absorbing water from your natural tear film, causing you to have symptoms of Dry Eyes. While in most situations dehydration is usually not a problem, common environmental conditions and activities can cause the dehydration to occur with resulting Dry Eyes. Conditions that may cause dryness, such as the heat being on in a room, using a hair drier, someone smoking or being exposed to smoke from any source, exposure to wind while running or even bike riding can cause soft contact lenses to produce Dry Eyes. Fortunately, dry eye symptoms from contact lenses is usually temporary and can often be minimized or eliminated by changing lens materials and or water content of the soft contact lenses. However, for patients who have been wearing their lenses for many years, there may be another cause. The continual rubbing of the lens across the surface of the cornea, may result in sloughing off of the microscopic hairlike structures that exist on the outermost layer of the cornea to assist in keeping the tear film stable. Years and years of gently chaffing these fine structures can result in poor tear film stability resulting in Dry Eyes. This can occur even if you are totally comfortable with you contact lenses and wear them successfully for most waking hours.
Rigid Gas Permeable Lenses and Dry Eyes
Rigid Gas Permeable Lenses are manufactured from polymeric materials that do not contain any water all. One would think that this is preferred to having the possibility of water evaporating from the lens and causing dry eye symptoms. However, the very nature of the Rigid Gas Permeable Contact Lens polymer is that is "hydrophobic" and tends to repel water and thus the tear film. Rigid Gas Permeable Contact Lenses must be specially formulated to enhance their wetting characteristics so that they are compatible with the tear film. Even with these formulations, their surfaces are more prone to drying and creating dry eye symptoms. The problem of mechanically chaffing the fine structures that attract the tear film and make it stable is even greater with Rigid Gas Permeable Lenses because of the stiffness of the lens...it is rigid.
Contact lenses can provide a great improvement over eyeglasses for people who are bothered by the cosmetic appearance of eyeglasses or the limitation to activities that they pose. To have a comfortable and successful contact lens wearing experience you should always be under the care of an eye care practitioner to be sure that the lens fit and lens materials you currently have are the best possible choice for you.
[Page updated 12/2010]
