Dry Eyes
Testing for Dry Eye
The traditional test for dry eye is a Schirmer's test which determines whether the
eye produces enough tears to keep it moist.
This test is used when a person experiences very dry eyes or excessive watering of the eyes.
It poses no risk to the subject. A negative (more than 10 mm of moisture on
the filter paper in 5 minutes) test result is normal. Both eyes normally secrete the same amount of
moisture.
Schirmer's test uses paper strips inserted into the eye for several minutes to measure the production
of tears. The exact procedure may vary somewhat. Both eyes are tested at the same time. Most often,
this test consists of placing a small strip of filter paper inside the lower eyelid (conjunctival sac).
The eyes are closed for 5 minutes. The paper is then removed and the amount of moisture is measured.
Sometimes a topical anesthetic is placed
into the eye before the filter paper to prevent tearing due to the irritation from the paper. The use
of the anesthetic ensures that only basal tear secretion is being measured. This technique measures
basic tear function.
A young person normally moistens 15 mm of each paper strip. Because hypolacrimation occurs with aging,
33% of normal elderly persons may wet only 10 mm in 5 minutes. Persons with Stevens Johnson Syndrome
moisten less than 5 mm in 5 minutes. The results after 5 minutes will show as follows:
- Normal: 15+ (greater than or equal to) mm wetting of the paper
- Mild: 14-9 mm wetting of the paper
- Moderate: 8-4 mm wetting of the paper
- Severe: 4- (less than or equal to) mm wetting of the paper
Even though this test has been available for over a century, several clinical studies have shown that
it does not properly identify a large group of patients with dry eyes. Newer and better tests of tear
production and function are now emerging.
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One test measures an iron-binding molecule
called lactoferrin.
The amount of this molecule appears to be closely related to tear production. Patients with low
tear production and dry eyes have low levels of this molecule. This test may be especially valuable
for patients with dry eyes since it can point to specific treatment strategies for dry eye.
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The tears may also be examined for their content of lysozyme,
an enzyme normally found in tears.
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Another test involves fluorescein
eye drops, which contain a dye that is placed in the eye.
The dye should drain with the tears through the lacrimal duct into the nose within 2 minutes.
If patients do not have enough tears to flush the dye into the nose, this time will be longer.
A new test is also available to more accurately measure the flow of dye out of the eye.
Classifications
Dry eye is classified as mild, moderate or severe.
In mild cases, people simply become more "aware" of their eyes and feel an occasional burning-especially
when in low humidity (e.g., in centrally-heated conditions, at high altitudes and during airplane
flights), and in highly polluted areas.
Those with moderate dry eye may feel that their eyes are constantly burning and irritated: they require replacement or "artificial" tears four to six times daily.
With severe dry eye, in addition to the above complaints, people experience severe photophobia
(light-aversion), debilitating eye-pain and diminished vision. These patients are at high risk for
bacterial infections leading ulcers and corneal “melts”. Severe dry eye reduces visual clarity due
to scar tissue or opacity formed by corneal abrasions, ulcers, vascularization and loss of stem cells.
Severe dry eye patients may use lubricating drops and ointments as frequently as every 15 minutes.
Symptoms
Itching: Dry eye patients have very irritated eyes causing the eyes to itch. Itching can also occur with
allergies, which is usually treated with anti-histamines. A well-known side effect of anti-histamines is
dry eyes so a vicious circle for SJS patients
Burning: Burning occurs because one of the functions of the tear film is to lubricate
the eye. When the tear film breaks down, the surface of the cornea dries out. The cornea, which is
filled with nerves, fires an impulse to the brain to be interpreted as a burning sensation. The eye
and eyelids physically become hot and the cycle of inflammation begins.
Foreign Body Sensation: One of the hallmark symptoms of dry eye syndrome is the feeling
of a piece of sand, grit or other foreign body stuck in the eye. A foreign body sensation is produced
when the eye is not properly lubricated. When this occurs, the brain sends a message back to the eye
telling it to water excessively to flush out the foreign body. However, with SJS, the Lacrimal Glands
which produce the aqueous tears, are incapable of producing fluid tears and the pain / inflammation
intensifies.
Redness: Redness is a sign of inflammation. When the eye is not lubricated properly,
it becomes inflamed. Underlying inflammation is sometimes the root cause of a dry eye. Our tears are
also responsible for maintaining ocular health by supplying nutrients to the tissues. When the
nutrient pathway is interrupted, our eyes become red and angry often producing a mucus discharge.
Photophobia: Light sensitivity is caused by dry eye, because as a result of the uneven
tear film, the light entering the eye, hits the retina at irregular angles. Adding to that is the
complication of an irregular cornea, or distortion caused by ocular surface disease as experienced
by many SJS patients.
Blurred Vision improved by blinking: The tears supply a smooth optical surface for
light rays to properly refract to the back of the eye. As the eye dries, the surface of the eye
becomes irregular, causing blurred vision. Blinking renews the tear film, producing a smooth optical
surface for a quality picture to be imaged on the retina. SJS patients have distorted corneas and
scarred eyelids, so blinking is not effective, because any moisture in the eye (eyedrops or ointments)
cannot be spread evenly to give a clear picture.
Increased discomfort after watching television, reading or using computers:
The rate at which our eyes blink tends to decrease when we are concentrating on a task.
Because blinking renews the tear film, a dry eye patient may actually blink at a much higher rate to
ensure proper lubrication of the eye. The increased blink rate is subconscious and for SJS this will
only serve to have the scar tissue on the inner lids physically slice away microscopic layers of the cornea.
The Tear Film
In healthy eyes, tears spread over the eye by a blink. The tear film makes the eye surface smooth and
optically clear, facilitating vision. Tears bathe the eye and allow the lids to slide smoothly over
them; they carry oxygen and nutrients to nourish the cells of the cornea; they dilute and remove
noxious toxins. Tears contain electrolytes,
enzymes,
proteins,
immunoglobulin,
peroxidases and
protective antibacterials that prevent infection and keep the eye's surface safely sterile.
Our tears are produced by three different glands to produce the perfect combination of mucous, water and
oil (lipids). They work together to allow the fluids to stay on our eye.
| Tear Layer |
Description |
| Mucous Layer |
The mucous layer provides the base for the other tear components. The mucous layer is
produced by goblet cells located in the white of the eye and in the inner surfaces of the
eyelids.
|
Lacrimal
(watery / aqueous) Layer |
The aqueous layer sits on top of the mucous layer. The watery layer is produced by the Lacrimal
gland between the eye and the eyebrow. Lacrimal gland tear production slows down during sleep,
which is why dry eyes can feel worse when you first wake up.
|
| Meibomian (oily) Layer |
The meibomian or oily layer is the top layer and which serves to prevent evaporation of the
watery layer. The meibomian gland secretes oil from the 23 oil glands that line the inner edge
of the eyelid.
|
Each of the three types of tear glands can produce insufficient tears. In addition, the meibomian
glands can experience chronic inflammation, which blocks the oily tears from entering the eye.
In both cases (insufficient tears or chronic inflammation), dry spots can form on the cornea. These
dry spots, which are not visible to the naked eye and do not necessarily make the eyes appear red,
causing incapacitating pain. In SJS there is chronic dysfunction of all three layers of the tear film.
Often the glands have been "burnt" and scarred shut.
Treatments for Dry Eye
Eye drops, ointments, to lubricate or increase tear production:
Typically, the standard initial treatments for dry eye include eye drops and ointments. Ointment
and gels should also be preservative free where possible or at least preservative free in the eye.
Hylauronic acid is used by surgeons to keep the cornea moist during surgery, and where possible,
artificial drops which contain Hylauronic acid are best. Generally speaking the preservative
free drops come in individual vials which are expensive, bulky and extremely inconvenient to
carry around. However we have found new products which are utilizing a newer technology to
eliminate the need for preservatives while allowing the use of a large volume container.
Cyclosporine is a prescription eye drop that may help to increase the eyes’ natural ability to
produce tears, which may be reduced by inflammation due to Chronic Dry Eye. In trials, Cyclosporin
did not increase tear production in patients using topical steroid drops or tear duct plugs and has
not been effective in SJS patients who have tried this therapy.
Autologous Serum Drops
Eye drops made from a person's own blood serum are superior to artificial tears for relieving signs
and symptoms of severe dry eyes. The autologous serum contains essential components for maintaining
eye surface health. None of the commercially available artificial tear preparations contain growth
factors, vitamin A and other natural components, which have been shown to play an important role in
maintaining eye health.
Punctal occlusion (prevents tears from draining)
When using artificial tears and other lubricating products is insufficient to provide relief from
dry eye pain, an eye doctor might recommend punctal occlusion. This is a relatively simple procedure
performed with local anesthesia in the doctor's office. A small silicone plug is inserted into the
duct opening at the inner corner of each eye that normally allows excess tears to drain from the eye.
The plug blocks the outflow of tears so that a person who has insufficient tears can retain what
tears do exist. In SJS patients punctal occlusion is not an option because the "puncta" or duct has
already been "burnt" closed.
Boston Ocular Surface Prosthetic Lens
The highly oxygen-porous Boston Scleral Lens Prosthetic Device (BOSP)
is designed to rest on the tough relatively insensitive white tissue of the eye called the sclera.
The key to its effectiveness is the artificial tear-filled reservoir that it maintains over the
diseased cornea, the principal focusing lens of the eye and the most sensitive tissue of the human
body. By functioning as a soothing and healing liquid eye bandage, this device relieves the pain
and light sensitivity of severe dry eyes and chronic corneal inflammation while nurturing the healing
of erosions and ulcers even in eyes that have failed to respond to all other available treatments.
The B.O.S.P. has proven to be invaluable to SJS patients, for whom constant application of
lubricant eye drops is ineffective in providing relief. In addition to providing lubrication
as described, the device successfully protects the eye (cornea) from ingrown lashes, eyelids
turning in, scar tissue on the insides of the eyelids and the resultant loss of vision that
these issues can cause. This is the prosthetic lens that Ian wears and he is totally dependant
on it for his quality of life.
Saliva Gland Transplant (not widely available)
The saliva glands are the fluid-producing glands in the mouth and throat. The glands secrete saliva
into the mouth through tiny ducts. There are also many minor salivary glands in the inner cheeks,
mouth and throat.
The saliva gland transplant is not an exact substitute for tears. Fluid production occurs at a
constant rate. Since patients can’t control the flow of fluid, there are no real "tears." Saliva
is a little thicker and stickier than tears. However, that turns out to be an advantage because
the fluid doesn’t evaporate as readily and stays in the eye longer. So far, doctors haven’t seen
any adverse effects from the mild digestive enzymes that are naturally present in saliva.
Saliva gland transplant could be useful for many patients with severe dry eye problems. However,
it is not an option for patients with Sjogren’s Syndrome because that disease also causes damage
to the salivary glands. SJS patients are not ideal candidates because of the ongoing systemic
inflammation of all mucus membranes.
Resources
For an excellent tutorial on dry eye please visit www.systane.ca/ca_en/professional/default.asp.
Be sure to read every item in the side menu and click on the "show me" animations.