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Allergenic and Irritating Environmental Exposures Affect Tear Levels in Individuals with Dry Eye, Study Finds

Dry eye – a condition in which a person does not have enough quality tears to nourish and lubricate the eye – affects more than 16 million Americans and up to 30 percent of people worldwide who are over 50 years of age.

Individuals with the condition present symptoms that include ocular irritation, dryness, discomfort, or unusual body sensations. Causes of dry eye have been linked to internal and external factors, such as thyroid disease, diabetes, medications, surgery, and environmental exposures.

“Dry eye is a complex disease not only because of its varying signs and symptoms but also because it can be caused by many factors, including lack of tear production, excessive loss of tear due to evaporation and changing tear composition resulting in frequent tear break,” said Naresh Kumar, Ph.D., associate professor in the Miller School of Medicine’s Department of Public Health Sciences, who co-authored the study.

While allergic conjunctivitis, an eye inflammation that is caused by an allergic reaction to substances like pollen or mold, is considered different from dry eye, they both share similar symptoms and signs. These shared symptoms and signs include discomfort, itching, bulbar hyperemia, and ocular surface inflammation.

Given these similarities, researchers have questioned if allergies could be linked to dry eye, as past research has shown that individuals with dry eye had severe symptoms in the spring – when pollen levels are most high. Other dry eye triggers are environmental exposures, such as humidity, dust mites, and tobacco smoke, which are also known as triggers for allergic conjunctivitis.

“There is some overlap between dry eye and allergic conjunctivitis signs and symptoms. For example, excessive dryness can cause inflammation, which is also found in patients with allergenic conjunctivitis. Nonetheless, causes of these two diseases are different, and dry eye can exacerbate the risk of allergic conjunctivitis and vice-versa,” said Dr. Kumar, who is also director of the Master of Science in Climate and Health program at the Department of Public Health Sciences.

Additionally, the total and allergen-specific tear immunoglobin levels – a set of protein classes that are present in the serum and cells of the immune system, and function as antibodies – have been studied in relation to allergic conjunctivitis, but not in relation to dry eye.

For more accurate prevention measures, a biomarker is needed to identify when dry eye has an allergic component. There are five classes of immunoglobins – A, D, E, G, and M. Immunoglobin E has played a key role in type 1 hypersensitivity reactions, which are allergic reactions that are provoked by re-exposure to a specific type of antigen referred to as an allergen, and has been used as a biomarker to assist in the diagnoses of allergic disease.

Researchers from the University of Miami’s Miller School of Medicine’s Department of Public Health Sciences and Bascom Palmer Eye Institute, as well as from the Illinois Eye and Ear Infirmary at the University of Illinois’s Department of Ophthalmology, investigated the frequency of detectable tear immunoglobin levels in individuals with dry eye symptoms and/or signs, but without a diagnosis of allergic conjunctivitis. The objective of the study, published in the Journal of Clinical Medicine, was to evaluate which factors were associated with high total tear immunoglobin levels, focusing on environmental conditions and exposures associated with allergy.

To conduct the study, male and female subjects were recruited from the Miami Veterans Medical Center’s Eye Clinic between October 2010 through December 2011. Researchers performed a cross-sectional study in 75 individuals with dry eye symptoms and/or signs. Their immunoglobin levels in tear samples were quantified and home environmental exposures were assessed through a standardized survey. Tears were collected utilizing the Schirmer strip, a test that determines whether a person’s eye produces enough tears to keep their eye moist and healthy. In the sample, 62 individuals had dry eye symptoms and 75 had one or more signs of the disease.

Results showed that detectable total tear immunoglobin levels were observed in 76 percent of subjects, where 17.3 percent of those individuals had high levels. Individuals with exposure to pets and smoke at home were more likely to have high immunoglobin levels compared to those not exposed.

Individuals whose tears were collected during the spring or summer were 3.9 times more likely to have a high immunoglobin compared to those sampled at other times of the year. In terms of those born within and outside of the United States, results showed that they were 3.45 times more likely to have high immunoglobin levels if born within the U.S.

This study found that a majority of individuals with dry eye symptoms and/or signs had detectable immunoglobin levels in their tear and high tear immunoglobin levels were correlated with allergy season and exposures in the home. These findings are important as determining which factors contribute to dry eye in an individual patient is crucial for the delivery of precision medicine.

“I was not surprised by these results given many homes in Miami have allergenic conductions that can result in an allergenic response, including in tears, as shown in our research. Therefore, it is important to reduce indoor allergenic conditions to avoid the risk of developing dry eye and allergic conjunctivitis. We provide simple home indoor air quality improvement measures on our website [www.dryeye.miami.edu],” Dr. Kumar said.

“Future studies will focus on the allergen-specific assessment of IgE, direct measurement of home allergens and comprehensive lipid and protein profiling of tears,” Dr. Kumar added. “This, in turn, will help us identify which specific sources are causes of dry eye and allergic conjunctivitis.”

Written by Amanda Torres
Published on December 11, 2019