By David F. Chang MD
Many patients over the age of 50 complain that their eyes frequently water. Although these symptoms are not serious, they are annoying and irritating. The most common cause of this sudden watering is an “unstable tear film”.
Unlike the rest of the body, there is no skin covering the external surface of the eyeball. Although the upper and lower lids cover part of the eyeball, the rest of the surface is exposed to the environment all day long. Potential irritants include dust, pollen, smog, smoke, wind, and sunlight.
Protecting our eye surface from these elements is a thin layer of viscous tears, called the “tear film”. This lubricates and protects the eye surface, much like saliva does for our mouth. The purpose of blinking is to constantly spread a new tear film over the eye surface.
With age, the quality of the “tear film” diminishes, and it tends to evaporate more easily. Small dry spots form, and these exposed areas of the eye surface become slightly irritated. This causes a reflex watering to occur. The watery, runny tears rinse the eye, but do not lubricate it. As an analogy, water rinses our mouth, but does not coat and lubricate the inside of our mouth in the way that saliva does.
This explains why the sudden tearing occurs during certain activities. Evaporation is more likely in outdoor, windy environments, and with air currents caused by fans and vents. Activities that cause us to stare, such as reading and driving, will cause momentary evaporation of the tear film, and reflex watering. None of these activities or situations are harmful. They only serve to irritate eyes with a poor tear film. Other symptoms of a poor tear film include redness, burning, itching, and a sandy or scratchy feeling.
Although treatment is not of medical importance, artificial tears can provide some relief. These are over the counter drops that lubricate the eye and augment our natural tear film. They contain no medicine and, unlike water, they lubricate rather than rinse the eye surface. They can be used up to four times a day, and are best instilled immediately before or after activities that provoke the watering (e.g. outdoor exercise, prolonged reading, etc.) These drops are available over the counter without a prescription. There is no one superior brand among the dozen or so that are available. Like choosing a soap or shampoo, patients can follow their own preferences.
All bottles of eye drops contain a small amount of chemical, called a “preservative”. This prevents germs from growing inside the bottle during the weeks after the original seal is opened. If one averages more than four drops of artificial tears daily, it is preferable to use unpreserved tears, to avoid potential irritation from excessive amounts of this chemical preservative. Unpreserved artificial tears are more expensive since they require disposable packaging. These tiny vials contain a small number of drops that will be used up within a day or two, and therefore do not require a preservative inside.
Floaters: When should they be examined?
“Floaters” within our vision are a common and curious symptom which most of us will experience at some point. They usually appear as dark spots or strands which drift across the vision of one eye as it is moving. Floaters are actually tiny particles suspended inside the eye, and are best visualized against a plain white background, such as an empty wall. While most floaters are normal, the sudden onset of new floaters in one eye may indicate a serious problem, and should not be ignored. We proudly serve our patients throughout the greater Los Altos area with the correct treatment to get you back to normal.
How the Eye Works?
The eye functions very much like a camera. Light first enters through the cornea, the clear “front window” of the eye. It reaches the back of the eye by passing through the pupil, which is the hole in the iris. Just behind the pupil is the natural lens of the eye which focuses the image onto the retina, the thin layer of tissue lining the back of the eye. Like the film in the back of a camera, the retina receives the image or picture, which is then relayed to the brain along the optic nerve.
The inside cavity of the eyeball is filled with a sac of transparent jelly-like material called the “vitreous”. Early in life the vitreous has the solid consistency of Jello. With age, it gradually becomes more watery. Harmless strands of thickened gel and clumps of cells develop within the watery vitreous, where they can drift back and forth. If they happen to cross our line of vision, we notice something “float” by. These occasional floaters are harmless, but are usually permanent. Fortunately, they become less distracting over time as we adapt to them.
When should floaters become cause for concern?
The vitreous sac normally rests in contact with the retina which in turn lines the back of the eyeball interior. As a part of normal aging, the sac of vitreous gel gradually shrinks and contracts. Eventually, and inevitably, the sac of gel will suddenly start to peel away from the retina. This spontaneous separation is normal and is called a vitreous detachment. It can only happen once per eye, and will eventually occur in most of us after the age of 50.
The sudden appearance of a large new floater – as though a hair or cobweb is drifting in front of one eye – may signal the new onset of a vitreous detachment. Other symptoms might include a shower of many tiny dots, or the sudden onset of bright instantaneous flashes of light. Because a vitreous detachment can produce a tear or detachment of the retina, a dilated eye exam should always be performed.
What Causes Retinal Detachments?
Approximately 10 to 15 % of the time, the detaching vitreous, instead of separating cleanly, will pull hard enough to tear the delicate retina. Fluid from inside the eye can eventually pass through the tear and pass beneath the retina. The retina, like a large sheet of wallpaper, can then be lifted away from the back wall of the eye by this fluid. This is called a retinal detachment..
Although tears alone do not affect one’s eyesight, vision is lost from any portion of the retina which detaches. Initially, if a side portion of the retina detaches, a dark shadow will appear across the vision, corresponding to that area. Untreated, the entire retina might eventually detach and all vision would be lost.
Since it is a spontaneous, natural event, a vitreous detachment can neither be prevented, nor its timing predicted. It is a one-time event whose likelihood increases with age. If the retina is not torn, a vitreous separation is harmless, and requires no treatment. It will not affect the vision, health, appearance, or sensation of the eye.
If a retinal tear occurs, however, it should be treated promptly to prevent the development of a retinal detachment. Depending on its location, a tear can be sealed without surgery, by using either a laser or a special freezing “cryoprobe”. Although retinal detachments can be repaired surgically, the vision may not completely recover. Thus, prevention of retinal detachments by prompt diagnosis and treatment of retinal tears is far better.
In conclusion, if a vitreous detachment is suspected because of a sudden onset of floaters or flashes, an ophthalmologist should be consulted promptly. The pupil should be dilated since tears usually develop in the peripheral, side regions of the retina. Since retinal detachments or tears do not cause any sensation, pain, or change in appearance of the eye, they can only be discovered through a thorough eye exam.