Dry eyes, also known as dry eye disease, dry eye syndrome, and keratoconjunctivitis sicca (KCS) is one of the most common reasons for a visit to an eye doctor. The tears have three layers. The innermost layer is the mucin layer. The middle layer is the thickest and is the aqueous layer. The outermost layer is the lipid layer.
Causes of dry eye disease include:
Medications such as antihistamines, major tranquilizers, diuretics, Parkinson medications and antidepressants.
Skin diseases on or around the eyelids.
Meibomian gland dysfunction is a common co-morbidity with thickening of the eyelids, thickened secretions of the oil glands and erythema of the lids.
Laser vision correction such as LASIK and PRK. This dryness typically lasts for three to four months postop but may last much longer and may even be permanent in some individuals.
Chemical or thermal burns that scar the conjunctiva.
Allergies, as well as allergy medication.
Computer Vision Syndrome manifested by decreased blinking when working at computer or video screen.
Excess or insufficient dosages of vitamins. The classic vitamin deficiency associated with dry eyes is a lack of Vitamin A which leads to Bitot spots.
Decreased sensation in the cornea from long-term contact lens wear, herpes infections, or other causes of a neurotrophic cornea.
Sjogren syndrome, rheumatoid arthritis, lupus, and other autoimmune disorders lead to inflammation causing dryness of the mouth, eyes, and other mucous membranes.
Environmental factors such as exposure to irritants like chemical fumes, cigarette smoke, drafts from air conditioners or heaters can lead to chronic inflammation of the conjunctiva and dryness eyes; exposure of the eye such as seen in thyroid disease, when the eyelids fail to close after cosmetic surgery, or other causes of exposure keratitis.
Dry eye disease is more common in women than men and has an increased incidence with aging in both sexes. It has become much more common as more people spend time staring at computer screens. Computer vision syndrome is typically associated with a decreased blink rate and therefore dry eyes. Laser vision correction is a common cause of dry eye, typically for three to four months post-op. Those that have inherent dry eyes also are more prone to have laser vision correction because their contact lenses are uncomfortable.
There are two main types of dry eye syndrome. The first is a deficiency to the water component of the tears because the lacrimal glands fail to produce enough of the watery component to maintain a healthy tear surface. This is found in those with Sjogren syndrome and autoimmune disorders such as rheumatoid arthritis. The lack of water also can be seen in situations where there is poor closure of the lids or where the lids to not adequately touch the cornea. The second type of dry eye syndrome is caused by a problem with the lipid layer which is produced by the meibomian glands. The top oily surface of the tears slows down the rate of evaporation of the tears. In situations such as meibomian gland dysfunction, the oil is abnormal and does a poor job of stabilizing the tear film, allowing the tears to evaporate more quickly. Dry eyes also can occur when there is an inadequate production of surfactant (mucin) to keep the tears sticking to the front of the cornea.
History and Physical
Dry eye syndrome may have any of the following signs and symptoms:
Stinging, burning, or a feeling of pressure in the eyes. This feeling of pressure may be dull or sharp, and the patient may localize the pain to many different areas around the eyes.
A sandy, gritty, or foreign body sensation is common, with patients commonly rubbing the eyes because of the feeling of a foreign body.
Epiphora or tearing may seem counterintuitive. Watering of the eyes is a sign of irritation, and when the tear film is abnormal and the surfactant is decreased, the eyes water more and can become dryer.
Stringy mucus discharge can be seen in those who stick their fingers in their eyes and pull the mucous out. The more that the patient does this action, the more the stringy mucous occurs.
Pain is a broad term, and sharp and dull pain can be described, which may be localized to some part of the eye, behind the eye, or even around the orbit.
Redness is a common complaint and is often made worse with the rebound effect of vasoconstrictors such as Visine Red Out, Clear Eyes, or Naphcon. All of these decrease redness for the short term by constricting the vessels of the episclera but have a dramatic rebound effect and increased redness after the drops wear off in a relatively short period of time. It is better to treat the irritation rather than the redness.
Blurry vision is a common complaint and may also be described as glare or haloes around lights at night.
A sensation of heavy eyelids or difficulty opening the eyes. As patients rub their eyes because of discomfort, the cornea is damaged leading to mild photophobia and difficulty in keeping the eyes open.
Dryness is a common problem for contact lenses wearers, and irritation may make contact lenses uncomfortable or even impossible to wear.
Tired eyes and a desire to go to sleep is a sign of irritation. Closing the eyes gives substantial relief to most with dry eyes.
A confirmation of the diagnosis of dry eye disease may best be made by history and with the use of the slit lamp. The magnification allows the practitioner to visualize the tear lake which gives a concept of the amount of tears. A small or non-existent tear lake would suggest aqueous deficiency. The appearance of debris in the tear film is associated with lid disease such as blepharitis. Fluorescein break-up time (FBUT) is determined by measuring the interval between instillation of fluorescein dye and the appearance of dry spots on the cornea. An FBUT of less than 10 seconds is considered abnormal. A decreased FBUT indicates tear instability and is a good sign of overall poor tear function. Classically, Schirmer tests were used to measure the amount of tear production, but fewer practitioners use it now than in the past.
Treatment / Management
Treatment of dry eye syndrome is usually taken on a step-wise approach and includes the following:
Preserved artificial tears;
Preservative-free artificial tears;
Preservative-free artificial tears with sodium hyaluronate;
Anti-inflammatory agents, including prescription strength 0.05% topical cyclosporine (Restasis), lifitegras (Xiidra), and topical steroids (controversial);
Systemic omega-3 fatty acids;
Treatment of concomitant lid disease with systemic doxycycline or topical antibiotics (erythromycin, bacitracin/polymyxin, azithromycin);
1% cyclosporine and lifitegras increase tear production but can take several weeks to start working. The longer that the patient uses these products, the better the effect. Even stopping for a few days may add months before the patient achieves the same result from the treatment;
Autologous serum drops;
Dry eyes are more commonly seen in women than men and are most common in postmenopausal women. During dry winter months, complaints of dryness is common even among young people, particularly those who wear contacts and spend long hours in front of a computer screen. Some younger patients seem to have significant problems for a few years and then get better.
Commonly, the issue is the wearing of contact lenses, and the individual, with age, gives up contacts as appearance means less. Others have LASIK removing the added stress of the contacts and becoming more comfortable. Many patients get used to the discomfort and manage their dry eye disease with little thought to its treatment.