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Higher tear osmolarity tied to lower symptom severity in Sjögren’s syndrome
Tear osmolarity testing also linked with significantly less patient discomfort compared to Schirmer's testing in severe cases.
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Signs and symptoms of Sjögren’s syndrome were not strongly correlated, but higher tear osmolarity was associated with lower symptom severity using the Ocular Surface Disease Index, according to a study.
“We were surprised to find that higher osmolarity correlated with lower symptom scores,” principal investigator Vatinee Y. Bunya, MD, an assistant professor of cornea and external disease and co-director of the Penn Dry Eye and Ocular Surface Center at the Scheie Eye Institute, Philadelphia, told Ocular Surgery News. “Before we did this study, we were expecting that higher osmolarity would be associated with increased dry eye symptoms.”
It is possible that some patients with severe dry eye due to Sjögren’s syndrome have decreased corneal sensation, which would decrease perception of their dry eye, Bunya said.
Patients
The study, which appeared in Cornea, enrolled 49 patients with Sjögren’s syndrome. Patients’ mean age was 53.7 years. Eighty-six percent of the patients were receiving systemic therapy, predominately hydroxychloroquine, for severe Sjögren’s syndrome.
The investigators assessed the relationship between tear osmolarity, Schirmer testing 1, and dry eye signs and symptoms.
Vatinee Y. Bunya
“Currently, when evaluating dry eye patients for possible Sjögren’s syndrome, we perform ocular surface staining and unanesthetized Schirmer’s testing. However, both of these tests have flaws,” Bunya said.
For example, various grading scales for staining are subjective and interpretation can vary widely. Likewise, a test strip can be irritating and may cause excessive reflex tearing, thus compromising accuracy or making results difficult to interpret. Furthermore, the Schirmer test 1 does not account for the evaporative features of dry eye.
“We were interested in exploring other possible objective tests for dry eye that would be both accurate and better tolerated by patients,” Bunya said.
The authors found an average tear osmolarity of 314 mOsm/L, “which falls within the mild-moderate dry eye range, depending on which cut-off you use,” Bunya said. “However, it is important to note that the majority of our subjects were on treatment at the time of enrollment, which could explain why we did not find higher tear osmolarity values.”
Schirmer’s test
The authors found that higher tear osmolarity was moderately associated with lower Schirmer’s scores. Additionally, tear osmolarity testing was less painful than Schirmer’s testing by a median of 2.75 on a pain scale of 0 to 5.
“The unanesthetized Schirmer’s test is very uncomfortable for patients, especially if they have severe dry eye,” Bunya said. “However, presently, if a patient is being evaluated for possible Sjögren’s syndrome, we must perform ocular surface staining and unanesthetized Schirmer’s testing, as these are part of the current ocular criteria for the diagnosis of Sjögren’s syndrome. But there is a need for accurate and better tolerated objective tests that may be able to replace one or both of these tests in the future.”
When performing ocular surface staining, Bunya said clinicians should consider having standardized reference images from grading scales to refer to each time they examine a patient at the slit lamp. She also emphasized the importance of consistency and being systematic in how each patient is graded at each visit.
For the Schirmer’s test, Bunya recommended using a timer and inserting the Schirmer’s strips slowly at the lateral canthus for minimal eye irritation.
“I think that it is important to recognize that Sjögren’s syndrome continues to be an underdiagnosed disease and to always keep it in the back of your mind as a possible diagnosis in dry eye patients,” Bunya said. “I personally have a low threshold for referring dry eye patients for a Sjögren’s syndrome work-up.”
Although the majority of patients in the study were receiving some form of dry eye therapy, a good proportion still had Schirmer’s values of less than 5 mm and persistent dry eye symptoms, according to Bunya.
“This highlights the complex nature of dry eye syndrome and shows that there is still a need for better therapies,” she said.
Bunya said there has been a trend in recent years to use objective, point-of-care tests for dry eye, such as the assessment of tear osmolarity, but their clinical utility requires further study before drawing any conclusions about possible roles in the care of Sjögren’s syndrome patients.
Bunya and colleagues are now conducting a study to analyze the inflammatory cytokine levels in the tear film of Sjögren’s syndrome patients to determine how they correlate with tear osmolarity and other dry eye tests. – by Bob Kronemyer