dry eye dx and tx

Do Your Research to Draw Conclusions From Research

BY WILLIAM TOWNSEND, OD

I've heard well-recognized authorities on ocular surface disease state at the podium that caffeine is a risk factor for and causative agent of dry eye syndrome. I've said the same on numerous occasions. But often when we look at the literature, what we presume to be a scientific fact is in fact highly questionable.

Some large, well-recognized studies addressing the epidemiology of dry eye would have benefited from consistent objective or subjective means of identifying subjects who truly have dry eyes. Despite these flaws, the extensive histories obtained from large numbers of subjects suggest that we can glean valuable information from them. It's also interesting how some study data and conclusions conflict with others.

Three Dry Eye Studies

In an extension of the original Blue Mountains Eye Study (Australia), researchers evaluated the relationship among risk factors and dry eye syndrome. They identified 1,174 subjects who qualified for the study based on a questionnaire. These subjects then underwent a comprehensive medical history including present illnesses, medications, alcohol consumption, smoking and caffeine intake. Females composed 57.5 percent of patients and were more likely than males to report dry eye symptoms. Systemic factors significantly associated with dry eye included arthritis, asthma, diabetes, gout and smoking. Other positive risk factors included the use of corticosteroids, antidepressants and hormone replacement therapy (HRT). They found that caffeine intake was not a risk factor for dry eye.

The Beaver Dam Eye Study, a long-term NEI study conducted in Beaver Dam, Wis., found that 57 percent of dry eyed individuals were female. This study revealed that antidepressants, aspirin and multivitamins were positive risk factors for dry eye. Some of the medications found not to be risk factors for dry eye included ACE inhibitors, α or β adrenergic agents, antihistamines, anti-anxiety agents and HRT. They found that a history of heavy drinking and smoking was also related to dry eye. Caffeine consumption was demonstrated to reduce the risk for dry eye. The authors suggest that caffeine, a xanthine, may stimulate tear production. It's interesting to note that the findings of this study regarding HRT were in direct opposition to those of the Blue Mountains Study.

In a study evaluating nutrient intake of women who have primary and secondary Sj&omul;gren's Syndrome (SS), researchers found that subjects who have primary SS have elevated caffeine intake, while those who have SS secondary to rheumatoid arthritis had reduced dietary caffeine levels. Concerning the specific discrepancies between subgroups regarding their caffeine intake, the authors suggest that primary SS subjects may increase caffeine intake to reduce pain (caffeine has anti-nociceptive properties), reduce fatigue (a common symptom in SS) and to increase cholinergic transmission, theoretically increasing salivation.

In the same study, the researchers found decreased intake of omega-3 fatty acids in primary and secondary SS patients. This is counterintuitive to the emerging theory that increasing intake of these compounds may actually benefit these individuals by reducing levels of inflammatory mediators.

Drawing Conclusions

These three well-respected studies demonstrate that we must remain current with the literature to make the best treatment decisions for our patients rather than assuming a finding is fact based on the results of one study. CLS

For references, please visit www.clspectrum.com/references.asp and click on document #144.

Dr. Townsend practices in Canyon, Texas and is an adjunct faculty member at UHCO. E-mail him at drbilltownsend@gmail.com.