If you live in Southern California and are of working age, you've probably experienced dry eyes. Symptoms can include: a sense of pressure in or around the eyes; red, tired, aching, itchy eyes; sharp pain in the eyes; blurred vision, and even tearing. In my eye care practice, I often hear, "But, Dr. Richardson, I can't have dry eyes. My eyes are constantly tearing!" Yet, excessive tearing is a very common, albeit unintuitive, symptom of dry eye. How? To understand that, we must first review what tears are made of and how they function.
The cornea is the clear front surface of a human eye. It must be kept moist at all times. Our tear film performs this function. Many people think of their tear film as similar to salt water as we've all at some point tasted our tears after a good cry. This salty liquid is the watery (or "aqueous") portion of our tear film. It is produced by the lacrimal glands. Small "accessory" lacrimal glands are constantly at work creating just enough watery liquid to cover the surface of the eye. When we cry or get something in the eye, a larger "main" lacrimal gland releases a gush of fluid over the surface of the eye.
The watery tear must be smoothly distributed across the surface of the cornea in order to maintain clear vision. Think about your car's windshield in the rain. Can you see clearly through it during the rain? No, not unless your windshield wipers are evenly distributing the water across the glass surface. The same is true of your cornea. Tiny cells on the surface of your eyes produce a substance called "mucin" that works to spread the watery tear across the surface of the eye.
Finally, the tear film must stay on the surface of the eye to function. Our eyelids produce an oily substance that mixes with the watery tear preventing it from evaporating. Every time we blink, our tear film is mixed and evenly spread across the surface of our eyes ensuring clear vision. If our lids are not functioning correctly or any of the tear film components are deficient, then dry eye results.
If the tear film does not fully cover the surface of the eye, the unprotected cornea will become sensitive. The brain interprets this sensitivity as resulting from something that is irritating the surface of the eye. It responds by flooding the eye with watery tears in an attempt to flush out the foreign material, thus, the common experience of excessive tearing despite having dry eyes.
So how can dry eye be treated? Just as there are three main components to the tear film, there are three main treatments for dry eye:
- Over-the-counter artificial tears can be used multiple times each day to replace the watery portion of the tear film. These are inexpensive and can be safely used up to six times per day.
- Eating a diet rich in oily seafood or taking an omega-3 fatty acid supplement (such as fish oil) works to maintain a good quality lipid (oil) layer in the tear film.
- Prescription cyclosporine (Restasis®) works by improving the mucin layer of the eye.
The hot, dry weather we experience most of the year here in Southern California virtually guarantees we will experience the symptoms of dry eye. Knowing why this occurs, as well as how to treat it, will allow most of us to enjoy this paradise with minimal annoyance. For those who do not respond to simple over-the-counter treatment, it would be prudent to schedule a consultation with an ophthalmologist for more advanced treatment.
About Dr. David Richardson
Dr. Richardson is a board certified ophthalmologist. He earned a Bachelor of Science in Biology with a minor in Chemistry from the University of Southern California. After receiving his medical degree from Harvard Medical School, Dr. Richardson completed his residency training in the LA County/ USC Ophthalmology Program. Since joining the medical staff of San Gabriel Valley Medical Center, Dr. Richardson has held many leadership roles including Chair of the Surgery Department.
Dr. Richardson's practice is located at 2020 Huntington Drive in San Marino. To contact Dr. Richardson's office, please call (626) 289-7856.