Dry Eye Disease is a chronic eye problem that causes tired, irritated eyes and potentially serious vision consequences
Definition of Dry Eye Disease
Dry eye disease is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbances and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.
That is the definition as reported by the Definition and Classification Subcommittee of the International Dry Eye Workshop in 2007.
Dry Eyes are often referred to as ocular surface disease, keratoconjunctivitis sicca or dry eye syndrome. It is often associated with blepharitis and meibomian gland disease (meibomitis).
Dry Eye Syndrome is the decline of the quantity and/or quality of the tears produced by our eyes or the increased evaporation of the tears. It is one of the most common ocular conditions and affects approximately 20% of the population.
What is osmolarity? Osmolarity is the particle concentration in a solution that generates an osmotic force across a semi-permeable membrane. It is a measure of the concentration of active particles in a solution.
Prevalence of Dry Eye Disease
The Schepens Eye Research Institute at Harvard University estimates that in the United States there are almost 40 million Americans with dry eye disease.
- 6 million women with moderate to severe dry eye
- 3 million men with moderate to severe dry eye
- Up to 30 million with mild dry eye disease
Function and Importance of the Tear Film
The tear film is a very important component of the complex visual system. The tears are the first refractive surface and the layer of tears functions as a lens in the refractive optical system of the eye.
The tear film layer also provides protection to the eye from infection from various viruses and bacteria, etc. It washes out debris and contaminants and provides comfort to the ocular surface by acting as a lubricant to the tissues of the ocular surface.
There are two different types of tears - lubricating tears and reflex tears. Lubricating tears are produced continuously to provide the functions listed above. Reflex tears are produced in response to some type of irritation to the eyes, such as smoke, foreign particles or onions. Reflex tears are also secreted as a result of injury to the eye or emotion. In fact, even dry eye disease can cause reflex tears, which are produced to help overcome the severe dryness. However, reflex tears do not have the needed lubricants that lubricant tears possess. Therefore, the discomfort or irritation will continue. Ironically, watery eyes can actually be a symptom of dry eye disease!
Tears consist of three layers:
- 1. The outermost oil (lipid) layer
- 2. The middle water (aqueous) layer
- 3. The innermost (closest to the eye) layer is the mucin layer
The oil/lipid layer protects the water layer from evaporation. It is produced by the meibomian glands in the eyelid. When the oil layer is too thin the tears evaporate too quickly and then become too salty (increased osmolarity). Dry eye patients with a compromised lipid layer can have four times the aqueous evaporation rates found in healthy eyes. Lipids help the tear film maintain its structure. They also enter the middle aqueous layer and interact with other tear film components such as mucin proteins.
The water layer is produced by the lacrimal gland and functions in providing nutrients to the cells of the cornea since there are no blood vessels supplying nutrients to the cornea.
The mucin layer provides natural lubrication directly against the eye's surface. This layer is decreased as a result of higher salt concentrations (hyperosmolarity) and further causes dry eye symptoms.
Chronic dry eyes that are left untreated will increase in discomfort, probably result in reduced corneal sensitivity, become susceptible to serious ocular infections and loss of corneal cells and possibly develop a pinguecula or pterygium.
Symptoms of Dry Eyes
There are many symptoms related to dry eyes. The high salt concentration (hyperosmolarity) and the resulting inflammation and changes to the ocular surface cause the symptoms. When the dry eye condition is very mild or prior to significant ocular changes, the diagnosis of dry eyes by an eye doctor is often based on the assessment of patient symptoms and not on clinical findings.
The primary symptoms of dry eye are:
- Red eyes
- Burning/stinging Eyes
- Itching on and around the eyes
- Foreign body sensation
- Sandy or gritty feeling
- Light sensitivity (photophobia)
- Watery eyes
- Occasional tearing
- Constant tearing
- Pain or soreness in or around eyes
- Contact lens discomfort
- Decreased tolerance to wearing contact lenses comfortably
- Seasonal allergies
- Blurry vision
- Ocular fatigue / tired eyes
Causes of Dry Eyes
There are many causes of dry eyes. Dry eye disease is categorized as either "tear (aqueous) deficient" (decreased tear production) or "evaporative" (increased tear evaporation).
The most common causes of tear deficient dry eyes include:
- Aging - tear flow usually decreases with increasing age. Approximately 75% of people over age 65 have Dry Eye Disease.
- Hormonal changes in women - hormonal changes associated with menopause, pregnancy and oral contraceptives can contribute to dry eyes.
- Sjogren's disease - this is a disorder of the immune system characterized by inflammation and dryness of the mouth, eyes and other mucous membranes. Sjogren's can damage the lacrimal glands and reduce tear production.
- Rheumatoid disease (e.g. rheumatoid arthritis)
- Lacrimal gland duct obstruction
- LASIK - this type of refractive surgery damages corneal nerves which provide information to the lacrimal glands regarding the need for tears in the eyes. Therefore the lacrimal gland does not produce the normal amount of tear flow. These corneal nerves do regenerate after 6-12 months. However, during this period of regeneration of the nerves the eyes can be very dry.
- Refractive Intraocular lens patients that also receive limbal relaxing incisions at the time of their surgery will have parts of their corneas that are neurotrophic (severed corneal nerves that destroy the feedback mechanism from the cornea to the lacrimal gland). This leads to dry eyes.
- Side Effects of some Medication - antihistamines (e.g. Claritin, Zyrtec, etc.) and Accutane are some of the primary medicines that reduce the production of tears. Others include some antidepressants, acid blockers, diuretics, birth control pills and hormone replacement therapy for menopausal women.
- Deficiency in Omega 3 fatty acids
- Long term contact lens wear that may cause mild corneal anesthesia and reduce the feedback mechanism to the lacrimal gland.
The most common causes of evaporative dry eyes include:
- Excessive near vision tasks - the normal blink rate decreases when one is viewing objects up close (computer use or reading) thereby reducing the amount of tear flow in the eyes.
- Meibomitis (meibomian gland disease)
- Environmental factors - high altitudes, smoke, air pollution, wind, sun, cold or dry air conditions all contribute to possible dry eye syndrome.
- Use of air conditioning which lowers the humidity in the rooms we live and work
- Contact lens wear - wearing contacts can increase tear evaporation causing dry eyes. Dry eye syndrome is the leading cause of contact lens intolerance and dropouts from contact lens use.
- Having large eyes or thyroid eye disease causing larger areas of eye surface for more evaporation.
- Vitamin A deficiency
- Topical ocular drug preservatives
Hyperosmolarity of the tears is related to dry eyes but not classified as a cause. However, hyperosmolarity of the tears is the central mechanism that causes ocular surface inflammation, damage and symptoms in dry eyes. Dry eye disease is dependent upon and proportional to the increase in tear film osmolarity.
Conjunctival Goblet Cells
One important change that occurs in dry eye syndrome is a reduction in the number of conjunctival goblet cells. The conjunctiva is the thin, clear tissue that covers the sclera (white part of the eye). There are thousands of these cells on the surface of the eye. They contain mucus to help lubricate the eye by supplying the innermost layer of the tear film. Mucus is the most slippery substance in the human body and helps maintain tremendous lubrication between the cornea and the eyelids. Loss of these conjunctival goblet cell is one more reason why dry eyes are so uncomfortable.
Treatment of Dry Eyes
Dry eye disease is a chronic, progressive disease that requires proper, prompt attention to solve the problem and reduce or eliminate its complications.
Studies have shown that treating all levels (mild to severe) of dry eye disease benefit from therapeutic medical treatment vs. only artificial tears or no treatment.
Medications and treatments must be targeted at the following:
- Reducing the inflammation caused by tear hyperosmolarity
- Reducing the tear osmolarity
- Treating any eyelid margin diseases such as blepharitis or meibomian gland disease (meibomitis)
According to a recent Gallup Poll, most patients do not feel that their dry eye disease is being properly treated by their eye doctor. Most eye doctors are simply providing minor symptomatic relief that is only partially helpful and certainly does not solve this chronic problem.
Treating dry eye disease is challenging. There is not one treatment that is effective on everyone and knowing the specific protocols with exact dosages is critical just like a perfect recipe. Knowing when to treat, how much to use and what treatment is critical to success. It is even important to differentiate between symptoms that begin early in the day or upon awakening vs. those that get worse throughout the day. People who wake up with dry, burning, gritty eyes often have inflammatory eyelid margin disease. Those whose eyes get dry and tired as the day goes on usually have tear deficiency. At Master Eye Associates we are experts at treating dry eye disease. Our treatments include some or all of the following:
- Lotemax (by Bausch & Lomb) Loteprednol ophthalmic suspension 0.05%
- Cyclosporine ophthalmic emulsion 0.05% (brand name - Restasis by Allergan)
- Azithromycin ophthalmic solution 1% (brand name - Azasite by Inspire Pharmaceuticals)
- Theratears brand artificial tears by Advanced Vision Research Inc.
- Soothe XP brand eye drops with Restoryl by Bausch & Lomb
- Systane Balance eye drop lubricant drops by Alcon
- Doxycycline monohydrate capsules
- Eyelid scrubs
- Warm compresses
- Lacrimal Punctal occlusion (occlusion of the tear drainage ducts)
- Omega 3 Essential Fatty Acids
Restasis Two Trays
60 Vials (one month supply)