Eye Conditions
Dry Eye Syndrome
Introduction
Symptoms associated with dye eye are among the most common of
all problems reported to eye doctors. Tears bathe the eye, washing
out dust and debris and keeping the eye moist. They also contain enzymes
that neutralize the microorganisms that colonize the eye.
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How it works
Scientifically called the "pre-corneal tear film multi-layer
structure", the tears have a number of specific functions:
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Provide water to maintain the hydration of the cornea
and
carry oxygen and nutritional support
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Carry anti-bacterial and anti-viral cells to protect the
exposed structures of the eyeball from infection
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Carry off debris so it does not damage the sensitive tissue
of the eye
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Provide lubrication between the inside of the lids and the
cornea
The tear film is composed of three separate layers, distributed
according to weight, heaviest to lightest:
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Mucus - lies against the eyeball
·
Water - the middle layer
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Oil - covers the other two |
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The lacrimal gland, located in the eyelids above the eyeball, is the main producer
of these components. In a properly functioning system, the three layers are produced
in perfect balance, mixed and distributed across the eyeball with every blink.
You are normally unaware of the tear film's existence.
Occasionally though, something happens to disrupt the natural balance of components
and our bodies try to compensate in the simplest manner: produce more tears.
The problem is that these tears produced, quickly upon demand, are reflex tears
(see below) and they simply run off the now destabilized tear film. The resulting
dry spots on the cornea cause the eyes to get red and irritated, resulting in
more discomfort, which causes more reflex tearing, further destabilizing the
tear film: resulting in an endless loop of discomfort called dry
eye.
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Types of tears
The name "dry eye" can be a little confusing since one
of the most common symptoms is excessive watering. In the picture
to the right, notice the purplish Rose-Bengal staining. The white of
the eye normally should not take up any stain. Even though there is
no deficiency of tear production, the |
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eye is dry because the tear film is very unstable and breaks easily. There may be increased evaporation of tears as well. The symptoms are of constant eye irritation. To understand better how this works, learn about the two different
types of tears:
·
Lubricating tears are produced slowly and steadily throughout
the day. Lubricating tears contain a precise balance of mucous, water,
oil, nutrient proteins, and antibodies that nourish and protect the
front surface of the eye.
·
Reflex
tears, also called lacrimal
tears, consist mostly
of just water and salt and do not have much lubricating value.
Reflex tears serve as a kind of emergency response to flood the
eye when it is suddenly irritated or injured. Reflex tears might
occur when you get something in your eye, when you're cutting onions,
when you're around smoke, or when you accidentally scratch your
eye. The reflex tears gush out in such large quantities that the
tear drainage system can't handle them all and they spill out onto
your cheek. Still another cause of reflex tearing is irritation
of the eye from lack
of lubricating tears. Even if you have tons of reflex tears,
if your eye is not producing enough lubricating tears, you
have dry eye .
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Symptoms
These symptoms alone may be enough for your doctor to diagnose dry
eye syndrome:
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Watery eyes
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Feeling that there's sand
in your eyes
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Eyes that itch and burn
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Blurred vision following periods of reading TV, watching or using a computer
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Red, irritated eyes that
produce a mucus discharge
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Causes
Common causes of dry eye include:
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Age: glands in the eyelid produce oil that keeps tears from evaporating
off the eye. We produce less of this oil as we age.
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Gender: dry eye syndrome is more common in women, possibly due to hormone
fluctuations, especially after menopause, or due to birth control
pills
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Diseases: including diabetes, Parkinson's, lupus, rheumatoid arthritis,
thyroid dysfunction, rosacea or Sjogren's syndrome (a triad of dry
eyes, dry mouth, and rheumatoid arthritis or lupus)
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Related conditions: incomplete closure of the eyelids, eyelid disease and a deficiency
of the tear-producing glands
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Dehydrating irritants: such as smoking, alcohol, caffeine
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Prescription medications: including some high blood pressure medications,
antihistamines, diuretics, antidepressants, anti-anxiety pills, sleeping
pills and pain medications. Over-the-counter medications including
some cold and allergy products, motion sickness remedies, and sleeps
aids
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Environmental: hot, dry or windy conditions, high altitude, air-conditioning,
chemical vapors, heating, and smoke
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Intensive and prolonged near vision tasks: reading, using a computer,
watching TV - due to the fact that the blink rate decreases
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Contact lenses: a very common side effect. Recent research indicates
that contact lens wear and dry eyes can be a vicious cycle. Dry eye
syndrome makes contact lenses feel uncomfortable, and the rubbing
of the lenses against the conjunctiva seems to be a cause of dry
eyes, according to a report in the January 2001 Contact Lens Academy
of Optometry Journal .
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Eye surgery: some types of eye surgery can aggravate dry eye.
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Inflammation: recent research suggests that dry eye may also be
caused by inflammation due to an imbalance of "good" fats
and "bad" fats and that eating a lot of omega-3 fatty acids
(found in cold-water fish) may decrease your risk.
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Diagnosing
You should have an examination to determine whether you actually have dry eyes and if so which type. Around 80% of patients have dry eyes due to lack of tear volume (aqueous or water layer deficiency) and 20% have dry eyes by evaporation where plug treatment is inappropriate. For evaporative dry eyes a different treatment |
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Dry eye viewed with a microscope under blue light
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is prescribed. Many patients have both aqueous and evaporative components to their dry eye, so tests are needed.
There are several methods used to test for dry eye:
- Examining the eyes with magnifying instruments
- Measuring the rate of tear production using thin strip of filter
paper placed at the edge of the eye, called a Schirmer
test
- Checking the amount of time it takes for tears to evaporate
between blinks. Tear evaporation rate is counted as the number
of seconds after a blink before the tear film destabilizes and tear volume
assessed by analyzing the "pool" of tears clinging along the edge
of the lower eyelids. The dynamic flow of tears over the surface of your eye
following a blink and the size of your tear ducts are also noted.
- Checking for pinpoint scratches on the front surface of the eye caused by dryness using special, colored eye drops call
fluorescein or Rose Bengal. A fluorescent yellow dye is painlessly introduced into the tears of each eye. Viewed with a microscope under blue light, any area on the surface of the eye damaged by dehydration glows brightly.
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Treatments
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Artificial tears
The treatment of a dry eye involves re-establishing the normal relationship
between the three tear layer components. The most common treatment
is use of artificial teardrops , of which there are a number of brands
and formulations - liquids, gels and ointments (most often recommended
for nighttime use). The primary differences are: preservatives or
non- preserved, and the level of viscosity (thickness), and lubricating
(slipperiness) agents.
Many different brands of artificial tears are available over-the-counter.
Lanolin-free ointments are preferable for those with allergy
to wool. Unpreserved tears may be recommended for people whose
eyes are sensitive to preservatives. The down side of preservative
free products is their limited shelf life and the possibility of contamination
from misuse (the tip of the dropper must not contact the eye
or fingers). Single use containers solve most of these problems. Users must not allow the packaging to be exposed to extremes
in temperature.
How to:
If your doctor recommends frequent use, this means every one or
two hours. Proper application requires the placement of one drop
into the sack created when you gently pull the lower lid out and
away from the eyeball.
You then close your eyes slowly, open and
blink once (to mix the drop with the natural tears) and then close
the eyes for 30 seconds. This allows the |
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artificial tears to form
temporary attachments to the ocular surface, prolonging the beneficial
effects.
This therapy is continued for three to five days (up to two weeks
if severe symptoms), then the frequency is diminished - first using
the drops every fours hours, then every six hours over the next week
or so. You will find that there is a certain frequency of administering
the drops that maintains comfort. Sometimes it is possible to slowly
taper off the artificial tears completely. It appears that, if the
underlying cause is mitigated, the use of tear replacements may stabilize
the tear layer situation, allowing the body to resume normal tear
film production.
It is not appropriate to prescribe tear replacement drops for use
as needed or desired. By the time the person experiences dry eye
symptoms, the tear film has already destabilized, the cornea surface
has been impacted and the syndrome has been established. Proper treatment is designed to prevent this situation from occurring by
intervening early on in the process and encouraging the body to create
a more normal environment.
Restasis eye drops (cyclosporine in a castor-oil base) go one step
further: they help your eyes to increase tear production. Restasis
treatment is the first of its kind, and can be very useful in certain
cases of dry eye syndrome. Restasis is a newer artificial
teardrop that has been very effective in a number of patients.
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Environmental
When infection, inflammation of the eyelids or clogged oil glands
contribute to dry eye, special lid cleaning techniques or antibiotics
may be recommended. It may also help to avoid hot, dry or windy environments
or to humidify the air in your home or office.
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Punctal occlusion
Punctal occlusion is a medical treatment for dry eye that may enable
your eyes to make better use of the few lubricating tears you do
produce. Plugging the lacrimal (tear) ducts keep tears in your eye
from draining away as quickly.
How this works:
There are four opening in the eyelid called puncta that drain tears
from the eye into the nasal-lacrimal duct and ultimately into the
throat. Plugs can be painlessly inserted |
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into the puncta, and are
normally not felt once inserted. These plugs can be temporary, made
from a dissolvable collagen - excellent as a diagnostic aid. They
can be semi-permanent, made of silicone. Or, the puncta can
be permanently closed by cautery, a procedure useful as a more permanent
treatment for a condition that cannot otherwise be mitigated (read
more).
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Nutrition
Sometimes special nutritional supplements are beneficial for dry
eyes. Studies have found that supplements containing certain
essential fatty acids - linoleic, gamma-linoleic, and omega-3 found
in cold-water fish - can decrease dry eye symptoms.
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Removing cause
If medications are the cause of dry eyes, sometimes switching to
a different type of medication alleviates the dry eye symptoms while
keeping the needed treatment. In some cases, the benefits of the
drug must be weighed against the side effect of dry eyes.
Treating any underlying eyelid disease helps as well. This may call
for antibiotic or steroid drops plus frequent eyelid scrubs with
an antibacterial shampoo.
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Future developments
Quite a few products are in clinical testing for possible dry eye
treatment. For example, both trehalose (a carbohydrate) and castor
oil solutions improved dry eye symptoms in small studies, and further
testing is underway. As advancements are made, we will continue
to update this section.
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Dry
eye
