contact lens business
The Dry Eye Connection
Imperfect contact lens fit could be a direct cause of lacrimal gland disfunction -- and dry eye.
By William D. Mathers, M.D.

Unfortunately, dry eye and contact lenses often go together. Yet the connection between dry eye and contact lenses has remained unclear.

My colleagues and I at the Casey Eye Institute of Oregon Health Sciences University in Portland, Ore., have developed a new theory to explain dry eye, with implications for contact lens wear. We were puzzled by the fact that seborrheic blepharitis -- which causes increased oil production and a resulting increase in moisture retention on the ocular surface -- is associated with dry eye. Eventually we realized that the common element shared by many situations associated with dry eye, from LASIK to contact lens wear to seborrheic blepharitis, was concurrent corneal irritation and lacrimal gland malfunction.

The Hidden Link

When dry eye symptoms are present, the lacrimal gland is still functioning; it simply isn't producing sufficient tears. To explain this, we postulated a neural feedback loop between the corneal surface and the lacrimal gland. In this model, when the cornea is irritated or inflamed, the lacrimal gland reacts by suppressing the rate of tear production. This, of course, tends to increase corneal irritation, causing a slow but steady downward spiral.

Our research has shown that damage to the cornea does cause significant changes in the lacrimal gland, including alterations in the rate of cell replacement in the gland, a general stress response indicated by modified regulation of heat-shock proteins, and different behavior from the genes that regulate immune function. (We recently repeated the experiment with a larger gene array. We'll be reporting the results at ARVO later this year.)

Basically, repeated trauma to the corneal surface, possibly including low-level trauma caused by contact lens wear, appears to suppress lacrimal gland function.

The Contact Lens Connection

The implications for contact lens wear are not hard to see:

• Contact lenses need to be as atraumatic as possible, in order to preserve the tear process. The move to higher DK and more biocompatible lenses should help to prevent the dry eye feedback loop from being triggered. Eliminating the gradual onset of dry eye should also mean extending the number of years patients can wear contact lenses.
• Although we're not sure yet, the changes we're observing in the lacrimal gland could occur slowly over time, with low-level chronic inflammation triggering long-term lacrimal gland disfunction. If this is the case, just making the patient comfortable may not be sufficient; precise fitting, and materials that prevent any inflammation at all from occurring, may be crucial.
• The cornea/lacrimal gland feedback loop could have implications for contact lens design. As we learn more about the specific corneal triggers that cause suppression of the lacrimal gland, it may be possible to design lenses that avoid problematic factors not currently known.

Resolving the irritation/inflammation and interrupting the feedback loop will probably cause the lacrimal gland to return to normal function. Treating dry eye can improve tear function, so eliminating low-level inflammation and irritation from contact lens wear could have the same effect.

Creating the Upward Spiral

In an ideal world, contact lenses should be good for the eye. After all, they do decrease eyelid trauma, which is one reason we use them as bandage lenses. For now, however, we have to focus on improving materials and more careful fitting. In the process, we may be preventing dry eye as well.

Dr. Mathers is professor of ophthalmology at the Oregon Health Sciences University, Casey Eye Institute in Portland, Ore., where he maintains an active practice specializing in cornea and external disease. Dr. Mathers is widely known for his clinical research, and is a past president of the Contact Lens Association of Ophthalmologists and a recipient of the American Academy of Ophthalmology Honor Award.