What Is the Value of Incorporating Tear Osmolarity Measurement in Assessing Patient Response to Therapy in Dry Eye Disease?
abstract
This abstract is available on the publisher's site.
Access this abstract nowPurpose: To evaluate the correlation between changes in tear osmolarity, symptoms, and corneal fluorescein staining in patients with dry eye disease (DED).
Design: Retrospective, clinic-based cohort study.
Methods: In this single-institution study, we reviewed the charts of 186 patients with DED from whom we had data on tear osmolarity, symptoms, and corneal fluorescein staining from 2 separate visits. Main outcomes included the correlation of the changes between the 2 visits for tear osmolarity (TearLab system), symptoms (Ocular Surface Disease Index), and corneal fluorescein staining (modified Oxford scheme). For tear osmolarity and corneal fluorescein staining the scores from the eye with highest readings were analyzed. The correlations were repeated on subgroups based on proposed cutoffs for DED severity and on patients' treatment.
Results: We found a modest, though statistically significant, correlation between changes in corneal fluorescein staining and symptoms of DED (R = 0.31; P < .001). However, there was no correlation between the recorded change in tear osmolarity and symptoms (R = −0.091; P = .38) or between changes in tear osmolarity and corneal fluorescein staining (R = −0.02; P = .80). This lack of correlation was consistent in all the subgroups studied. A multivariate analysis revealed that changes in corneal fluorescein staining had predictive value on symptom changes, whereas tear osmolarity changes did not.
Conclusions: Changes in tear osmolarity do not correlate significantly with changes in patient symptoms or corneal fluorescein staining in dry eye disease.
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Additional Info
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Experts agree that dry eye disease (DED) is a multifactorial entity that can perplex clinicians due to the wide variety of objective and subjective signs and symptoms and the lack of definitive indices to determine severity, progression, and response to treatment. The same seems to hold true of rheumatoid arthritis (RA), a multifactorial disease process that ebbs and flows, often without apparent rhyme or reason. Authorities further agree that early detection and management of both entities hold the greatest promise in limiting the severity of disease progression, and that a balance between key biomarkers and symptom surveys with high specificity and sensitivity is essential.
Are the similarities between these two clinical conditions happenstance? Two recent articles, seemingly contradictory on the surface, suggest that at least some forms of DED and early RA may, in fact, be intimately related. The article by Türkyılmaz and colleagues investigating tear osmolarity (TO) in early RA and its relation to disease activity shows that 60% of patients with early RA also had DED, and that TO was a more sensitive indicator than response to topical dyes such as fluorescein staining. This should not be entirely surprising, as RA is a joint disease and the eye in its orbit, as a ball-in-socket, can be conceived as a specialized joint space adapted for sight. Given that the eye is the only joint directly exposed to air, lubrication is at a premium. Hence, the early detection of DED may be a signpost in the early detection of RA.
It would, therefore, be appealing if TO measurement proved to be a sensitive indicator in assessing patient response to therapy in DED. At first blush, the article by Amparo and colleagues does not appear to support this. Upon closer inspection, however, the paper merely suggests that TO cannot be used as an independent index of response to therapy for DED. The message of these two articles is that TO may be useful as a biomarker both in early DED detection and in early RA detection. Its utility as both diseases progress may be less beneficial; but, by then, there are more overt signs and symptoms by which we judge responsiveness to intervention.
Its availability as a reliable clinical instrument, positions TO as a potentially crucial early biomarker for DED and early RA, particularly when the two conditions coexist. If time proves that the high comorbidity between the two diseases points to common inflammatory pathways early in the process, measurement of TO may become commonplace as part of the differential diagnosis.