'Dysfunctional Tear Syndrome' may be more appropriate term for dry eye

May 15, 2005

When are dry eyes not dry? Fairly often, in my clinical practice.

When are dry eyes not dry? Fairly often, in my clinical practice.

"Dry eye" is a big problem,affecting large numbers of patients and with a significant impact on quality of life.

Although epidemiologic studies suggest this is a fairly common disorder, with a prevalence on the order of 10% in adult European populations, our understanding of this problem remains quite limited.

Yet, the condition often has a major negative impact on the lives of patients, with quality-of-life studies ranking it as equivalent to unstable angina in terms of impact. Patients and physicians are often frustrated.

Cornea specialists, like me, have seen a lot of these miserable patients in consultation and know that some patients suffer tremendously.

But it is remarkable how some patients have obvious corneal staining or very low tear production, yet deny having any symptoms.

On the other hand, some very symptomatic patients have normal Schirmer tests and minimal staining, and the clinician has to look hard for any objective evidence of disease. Lack of concordance between signs and symptoms should make us pause.

Twenty years ago, while a resident, the disease of "dry eye" seemed fairly simple to me. With age, some people experienced a diminution of tear volume as a consequence of lacrimal gland dysfunction or atrophy, resulting in drying of the ocular surface. The treatment was similarly apparently straightforward-build up tear volume with artificial lubricants and punctal occlusion.

Today, we know the condition is much more complex. Many patients with "dry eye" have normal tear volumes, but suffer as the result of reduction or abnormality of lipids from the lid glands, a loss of goblet cells, an abnormal composition of tears harboring inflammatory cytokines, or a disruption of a complicated, probably neural-mediated feedback mechanism between the corneal surface and the glands that generate nurturing tear-film components.

The fairly recent appreciation for the complexity of this condition has resulted in new therapies that are approved or being tested in FDA-supervised trials, including "soft steroids," cyclosporine, mucin-augmenting agents, tetracycline derivatives, etc. We now understand why punctal occlusion may, seemingly paradoxically, make patients worse-abnormal tears containing inflammatory molecules are retained on the eye's surface, and the eye becomes further inflamed.

Occasionally patients with normal Schirmer tests, and perhaps intermittent epiphora from the ocular surface irritation, will have many of the other signs and symptoms typical for "dry eye," including corneal staining. Informing such patients that they have "dry eye" often results in confusion and a quizzical or challenging response from the patient, who doubts what seems a very counterintuitive diagnosis. "No, doctor-my eyes are wet, not dry." This typically requires a lengthy education about basal versus reflex tear production, the qualitative disorders of tear composition, etc.

To me, this is a situation where the name we use for a condition may not be helpful, either to the patients who are trying to understand why they are suffering, or to the physicians who seek to help them. Clearly everyone with "dry eye" does not have eyes that are actually dry, reduced tear volume often is not demonstrable, and the condition may occur as the sequela of different disease states that have an impact on the ocular surface and associated structures, and that may or may not reduce tear volume.

My view is that use of the term "dry eye" may be far too simplistic, misleading, difficult for many patients to understand, and perpetuating faulty concepts about pathogenesis and treatment.

For this reason, I agree with the recommendation of a recent panel of experts that we consider using the term "Dysfunctional Tear Syndrome" as an alternative. The term captures the essence of what we believe is happening, with the precorneal tear film having one or a combination of problems (low volume, insufficient lipid or mucin, inflammatory molecules, etc.), and that this tear dysfunction fails to support the health and nutrition of the ocular surface cells.