Dry Eyes or Dry Eye Syndrome is a very common eye
condition that affects millions of Americans. It is estimated that dry eyes
affect up to 11% of people aged 30 to 60 years of age and 15% of those 65 years
of age or older according to the International Task Force assembled by the Johns
Hopkins University-Wilmer Eye Institute. They also concluded that as many as 12
million Americans have moderate to severe dry eyes and that this number is
likely to increase with the aging populations resulting in a significant
decrease in the quality of life.
Simply, dry eyes are caused by either a deficiency in
the quantity or the quality of the tears or tear film. Fortunately, today eye
care patients can benefit from better diagnostic procedures for dry eyes as well
as more advanced dry eye treatments from eye physicians.
About Tears & the Tear
Film
Understanding the structure of tears is important in
order to understand how the tears and tear film provide the eye with a number
specialized functions. Tears are composed of three layers. The innermost layer
is called the mucus layer. The mucous layer acts to coat the cornea with a
smooth layer of lubricating material called mucin. The mucous layer serves to
provide a surface that allows the tear film to stick to the eye. The middle
layer of the tear film is called the aqueous layer, and as the name implies is
composed primarily of water. In fact, it is composed of about 98% water and
serves to provide moisture, oxygen and nutrients to the cornea. The outermost
layer of the tear film is called the lipid layer. The lipid layer is actually an
oily film that acts to prevent evaporation of the tear film from the eye. A
deficiency in any one or more of the tear film layers can lead to dry eyes. Eye
physicians can use specialized diagnostic tests to determine which layers of the
tear film are contributing to the dry eye symptoms.
Tears are produced by a number of different gland
structures around the eye. The innermost layer, the mucous layer, and the
outermost layer, the oily layer are produced by tiny tubular shaped glands that
are in the eyelids. The middle layer, the aqueous layer, is produced by the
lacrimal gland which is a structure located just under the upper eyelid. Each
time you blink, the eyelids act like squeegee to smooth and spread the tear film
so that it is uniform across the surface of the cornea. This smoothing of a
normal tear film creates a high quality optical surface. In some cases of dry
eye, the tear film is deficient enough that the eyelids cannot provide a smooth
optical surface and patients then experience blurry vision that clears with
repeated blinking.
Normally, excess tears flow out of the eye along the
lower eyelid toward the nose and into two tiny ducts called lacrimal puncta. The
lacrimal puncta open into small tube like canals that drain into the nasal
passage. As a result of this connection between the drainage of tears from the
eye and the nasal passage, often times when we cry we may actually experience a
runny nose. Usually tears are produced on a continual basis in order to
lubricate the eye. And maintain the crisp optical surface of the cornea. Reflex
tears are also produced in response to pain, trauma or even an emotional event.
Reflex tears tend to be overly watery and do not to alleviate a dry eye or even
the symptoms of a dry eye. There are may causes of dry eye syndrome. As a result
of the normal aging process it is common to experience dry eyes. In general, as
we age our body produces less oil to lubricate the skin and skin like tissues.
In fact, on average we produce 60% less oil at age 65 than we do when we are 18.
Women tend to have drier skin in general so this is considerably more noticeable
to them. As discussed previously, production of the oily layer of the tear film
serves and important role in preventing the evaporation of tears. Without a
healthy and sufficient oily layer it is likely that there will be excess
evaporation resulting in dry spots on the cornea, blurry vision and a sensation
of dryness.
There are many other factors that can contribute to dry
eyes. These include being exposed to hot, dry, windy climates for example as
well as poor air quality from pollution or cigarette smoke. Dry eye symptoms are
often associated with prolonged computer use or intense reading due to the
decrease in the frequency of blinking with these activities.
It is extremely common for contact lens wearers to
experience dry eye syndrome due to the fact that contact lens materials tend to
absorb tears and protein from the tears creating dry spots on the lens
surface.
Finally, dry eyes are a frequent side effect of many
systemic medications, medical conditions such as Thyroid disease, Parkinson's
Disease and Sjorgren's Syndrome and Vitamin A Deficiency. Most women report
experience dry eyes as they enter menopause due to the hormonal changes they
encounter, particularly changes in estrogen.
Symptoms of Dry Eye Syndrome
The most common symptoms of dry eyes
include dryness, itching, burning, irritation or grittiness, redness, blurry
vision that gets clearer as you blink, light sensitivity and contrary to common
sense..excessive tearing. These symptoms typically increase during vision
related activities such as reading, computer use, night driving, or watching
television. They may also increase in response to environmental conditions such
as wind, low humidity, airplane travel, or smoking or being in a smokey
environment. Many of these symptoms of dry eyes may also be found in other eye
conditions, making careful diagnosis especially
important.
What are the causes of dry eye
syndrome?
- Environment: Sunny, dry, or windy weather,
heaters, air conditioners, and arid high altitudes increase the evaporation of
tears from the surface of your eyes. In fact there are a number of cities that
have been recognized by the National Women's Health Resource Center as being "Dry Eye Hotspots". You may experience
dry eye symptoms while viewing television, computer screens, while reading or
doing anything that reduces your rate of blinking.
- Aging:During the normal aging process, our
bodies and our eyes produce gradually less and less oil. This reduction in oil
in the tear film results in quicker evaporation leading to the formation of dry
spots on our eyes.
- Contact Lenses:Contact Lenses are subject
to dehydration or loss of their water content. As they dehydrate, they can
absorb the tear film causing dry eye symptoms. In some cases, the continued
drying of the contact lens surface causes it to become deposited with protein
making the lenses even more uncomfortable than the dryness alone.
- Medical Conditions: Women experiencing
hormonal changes, those patients suffering from thyroid disease, rheumatoid
arthritis, psoriasis, eczema, acne rosacea and a number of other systemic
conditions may experience dry eye syndrome.
- Medications: Diuretics taken for high
blood pressure, allergy medication. antihistamines, acne medications and may
others may all produce dry eye symptoms.
How do I know if I have dry eye syndrome?
Common symptoms of dry eyes may include dryness, burning and
stinging. A foreign body sensation, like sand being in the eye, is often
encountered. Your vision can be blurred. Reflex tearing may actually be
stimulated resulting in excessively watery eyes. Some patients may experience
redness of their eyes. It is not uncommon for your eyes to lose their normal
luster and clearness when looking in the mirror.
To help you determine whether you suffer from one or more
symptoms of dry eyes you can take a brief
self assessment quiz for dry
eyes.
Diagnosis of Dry Eyes
There are several clinical examination methods that are
useful for helping to diagnose and determine the severity of dry eyes. Your eye
doctor may use all or some of the following tests to help make the
diagnosis:
- Tear Break Up Time is a measurement made by observing
the rate at which the tear film begins to evaporate and indicates the overall
stability of the tear film.
- Tear Staining is a method of using special dyes to help
highlight problems with the surface of the eye and the tear film quality. By
placing these eyedrops in the tear film the severity of the dryness can more
easily be recognized.
- Tear Film Height is a measurement made with the slit
lamp biomicroscope to evaluate tear volume
- A Schirmer Test may be performed by placing a small
piece of special paper inside your lower eyelid to measure tear production.
From these tests an assessment can be made as to whether
the dry eye condition is mild, moderate or severe and thus what type of
treatment options may be best.
Treatment of Dry Eyes
For those patients with mild to moderate dry eyes the
first course of treatment may be to use unpreserved artificial tears as
prescribed by the doctor. Depending on the nature of your tear film deficiency,
the doctor may have you use a specific type of artificial tear that has
different characteristics in terms of salt content and viscosity. Follow these
instructions carefully. In addition, your doctor may counsel you on
environmental factors that need to be modified. Sometimes, if the oily layer of
the tear film is deficient, they may suggest that you increase your consumption
of oily fish or even take flax seed oil as a dietary supplement. Most likely you
will be asked to drink plenty of water.
For patients with moderate to severe dry eyes, who may
already be using artificial tears and already have punctual plugs without
relief, the prescription of Restasis eye drops in addition to the other
treatments can often help alleviate your symptoms. Restasis works by suppressing
a type of inflammatory cell from entering the Lacrimal Gland and thus allows the
lacrimal gland to function more effectively so that you can actually make more
of your own natural tears.
If these approaches do not work, the eye doctor will
likely suggest the insertion of tiny punctual plugs that will slow down or even
stop the drainage of tears from the eye. These plugs are easily and comfortably
placed in the lacrimal puncta in the eyelids. Initially you may have a temporary
dissolving plug put in place to see if your signs and symptoms are actually
responsive to this treatment. If the results are good, it may be necessary to
place a more permanent type of plug in the lacrimal puncta to affect a long-term
solution.
Occasionally there are some cases that may not respond
to the above sequence of treatment options because of some underlying low-grade
inflammatory or infectious process. In these cases it may be necessary to also
prescribe an oral antibiotic such as a tetracycline or an anti-inflammatory eye
drop such as a corticosteroid eye drop.
As you can see, the
diagnosis and treatment of dry eyes is complex and requires patience and
persistence on the part of the physician and the patient. With careful diagnosis
and a systematic therapeutic approach, sufferers of dry eye syndrome can most
often experience considerable improvement.
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