Inflammation: Role in Dry Eye Disease

Inflammation: Role in Dry Eye Disease

Inflammation I: Role in Dry Eye Disease

Gary N. Foulks, MD, FACS

Dry eye disease results from the interaction of multiple factors, including environmental insults, hyperosmolarity, tear film instability, and inflammation. While the individual contributions of these components are still being evaluated, inflammation is clearly a central aspect of the mechanism that produces symptoms in dry eye disease, and it may also be an inciting event in the development of the condition.

The Disease Mechanism

While we do not yet know whether inflammation plays a role in all cases of dry eye disease, our growing understanding of this condition suggests that inflammation is often a significant factor in the disease, particularly in cases of aqueous deficient dry eye. Measurement of inflammatory mediators in the lacrimal gland and on the ocular surface shows that inflammation occurs in patients with non-Sjogren aqueous deficient dry eye, and the level of inflammatory mediators is even higher in patients with dry eye disease related to Sjogren syndrome.

The form of dry eye called “evaporative” also appears to have an inflammatory component, but more research is needed to assess the role of inflammation in these cases.

Another question that remains to be answered is whether inflammation is a primary inciting event in dry eye disease or whether it is secondary to other aspects of the disease mechanism. While some researchers believe that inflammation is an initiating event, elevated tear film osmolarity and other conditions can also induce inflammatory changes, in which case inflammation could be a secondary response.

Impact on Diagnosis and Symptoms

While inflammation occurs frequently in dry eye disease, it is also associated with a number of other conditions, including systemic autoimmune disease, infections, immune-mediated inflammation such as uveitis, and allergic conditions such as seasonal allergic conjunctivitis and hay fever conjuncti­vitis. Because inflammation can occur in such a range of conditions—and since a standard clinical examination cannot distinguish dry eye-related inflammation from inflammation related to other causes—the presence of inflammation may be indicative of dry eye disease, but it is not definitively diagnostic.

However, the presence of inflammation can help to determine the severity of dry eye disease, once other signs have been used to establish the diagnosis. Inflammation is typically more severe in advanced stages of dry eye disease: so, signs of inflammation, such as redness or the presence of inflammatory cells in the tear film, are useful indicators of disease severity. I also look to exclude signs of intraocular inflammation, since they would indicate a condition other than dry eye disease.

Gary N. Foulks, MD, FACS, is the Arthur and Virginia Keeney professor of ophthalmology, University of Louisville, Louisville, KY, and is editor-in-chief of The Ocular Surface.