A Comprehensive Look at Dry Eyes and Soft Contact Lenses
Dry eyes are the most common reason that people stop wearing soft contact lenses. In fact, 25% of contact-lens wearers develop dry-eye symptoms. In the past, patients either decreased their overall contact lens wear time or decided to wear spectacles full-time. In recent years, contact-lens options and treatments for dry eyes have increased markedly, and a large part of the “dropout” population again is considering soft contact lenses for improved sight.
When a patient complains of dry eyes, his or her medical history, environmental and circumstances are pieces of the puzzle that help in diagnosing and treating the root cause(s). Outside of a patient’s health and age, successful contact-lens wear depends on a trio of conditions: environment of the eye, contact-lens material and cleaning solution.
Dry eyes can result from disruption of the quality or quantity of the ocular tear film. When evaluating the environment of the eye, we inspect the integrity of the eye’s hydration. The tear film consists of a lipid layer (oil), aqueous layer (water) and the mucin layer (glue). Each layer plays a vital role in the tear film’s overall quality, so they must be in equilibrium. The interruption of one or more the complex mechanisms responsible for tear film production can result in dry eyes.
For instance, the aqueous layer is produced by the lacrimal glands, and compromises 90 percent of the tear film. Its production commonly decreases as we age. The lipid layer delays evaporation of tear film. If lipids are inadequate, tear film evaporates rapidly. The mucin layer is produced by the goblet cells and facilitates even spread of the tear film. When patients have increased allergies, their goblet cells may have abnormal mucin production, disrupting the equilibrium and causing dry eyes.
Contact-lens materials continue to evolve. Manufacturers strive for superior optics, health and comfort. In 1999, the first silicone hydrogel contact lens was sold. This material increased all-day comfort and had outstanding material characteristics:
- Deposit resistance – the ability to protect against accumulation of foreign bodies
- Modulus – tendency to be elastic yet maintain form
- Water content
- Wettability – ability to maintain contact with liquid
New-generation contact lenses are made from materials that are inherently wettable with improved hydrophilicity (having a strong affinity for water). The latest plastic materials have changed and no longer require an internal wetting agent or surface treatment. As a result, patients who gave up on contact lenses 10 or 15 years ago now can wear soft contact lenses again.
Many different contact-lens cleaners are sold. Sometimes a patient might wear one of the best contact lenses for dry eyes, but use a generic multipurpose cleaning solution that triggers the condition. Patients can use one cleaner for 20 years but suddenly become hypersensitive to it. Some dry-eye patients benefit from preservative-free cleaning solutions; others benefit from wearing disposable daily contact lenses to negate any adverse effect contact-lens cleaners.
Patients who have dry eyes report a number of symptoms:
- blurry, fluctuating vision
- foreign-body sensation
- “gritty or sandy” eyes
- light sensitivity
Patients might experience one or more symptoms, and in varying severity. Symptoms can be exacerbated with long hours of reading and computer use. A hallmark for contact lens-induced dryness is an increase of the described symptoms toward day’s end. Contact-lens wearers can complain of these symptoms during wear, though sometimes symptoms worsen when contact lenses are out. Symptoms can spur people to decrease their wear time or even stop wearing contact lenses altogether.
Even the best contact lenses can be uncomfortable when the wearer is in an arid or smoky environment or undertakes activities that require concentration, or lacks sleep or eats poor nutrition. Medical health, visual demands of occupation and hobbies can all put patients at a higher risk for developing dry eyes.
By closely evaluating day-to-day routines for each patient, we better understand their potential triggers. Patients who must be in airplanes for their job or who spend all day at their computer, for instance, risk environmental eye dryness. Computer work can cause a blink-rate decrease from fifteen to seven blinks per a minute. The result is eyes that are open longer cause tear film to evaporate quicker.
Beyond aging, environmental and hygiene considerations, many systemic health conditions are associated with tear-film abnormalities. Inflammatory disorders such as Sjogren’s syndrome, rheumatoid arthritis and collagen vascular disease can disrupt the mucosal membranes and the tear-film quality. Patients with acne rosacea and Vitamin A deficiency have higher risk of dry eyes. Grave’s disease can cause incomplete blinks resulting in constant exposure of the surface, hence making the eyes dry. Studies indicate that hormone changes, such as those experienced by post-menopausal women, can also cause dry eyes.
Aside from thorough history and careful slit-lamp exam, these are some other tests that can be utilized in evaluating dry eyes:
Schirmer’s Test assesses tear production. A standardized strip of paper is inserted across the lower eyelid margin and the patient closes his eyes for five minutes. The amount of moisture on the strip is measured. A topical anesthetic solution might be used, and both eyes are tested at once.
Tear Break Up Time (TBUT) helps measure the quality of the tear film. Fluorescein dye is dripped onto the eyes’ surface and the optometrist measures how long it takes to form dark areas. A TBUT of less than 10 seconds is considered significant for dry eyes.
Tear Meniscus Height assesses tear volume. The meniscus, in the lower eyelid, is the main reservoir of tear film. With a slit lamp, the optometrist can examine the amount of tear fluid sitting at the lid margin. The meniscus’ dimensions also can be photographed with a special device that projects black and white stripes and calculates meniscus changes by capturing images at a steady rate.
Rose bengal and lissamine green dyes help in indentifying devitalized eye cells. The dyes, on paper strips, are wet with sterile water and applied to parts of the eye, such as the cornea and conjunctiva. The optometrist observes the pattern and intensity of the resulting stains, which can signify gradations of dry eye.
Complications can range from contact lens intolerance or, in extreme cases, can lead to scarring and decreased best-corrected-visual acuity.
We recommend that patients be proactive in their eye care. Annual eye exams, healthy diet and good contact-lens hygiene are keys to healthy vision.