The Dry Eye Zone

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Abstract: Tear film osmolarity best measure of disease severity in all categories

An objective approach to dry eye disease severity.
Invest Ophthalmol Vis Sci. 2010 Jul 14. [Epub ahead of print]
Sullivan BD, Whitmer D, Nichols KK, Tomlinson A, Foulks GN, Geerling G, Pepose JS, Kosheleff V, Porreco A, Lemp MA.
TearLab, Corp., San Diego, United States.

Purpose: A prospective, multi-site clinical study (10 sites in the E.U. and U.S.) evaluated the clinical utility of commonly used tests and tear osmolarity for assessing dry eye disease severity.

Methods: 314 consecutive subjects between the ages of 18-82 years were recruited from the general patient population, 299 of which qualified with complete datasets. TearLab osmolarity, Schirmers without anesthesia, tear film breakup time (TBUT), corneal staining, meibomian dysfunction assessment, and conjunctival staining were performed bilaterally. A symptom questionnaire (OSDI), was also recorded for each patient. Distributions of clinical signs and symptoms against a continuous, composite severity index were evaluated.

Results: Osmolarity was found to have the highest correlation coefficient to disease severity (r2=0.55), followed by conjunctival staining (r2=0.47), corneal staining (r2=0.43), OSDI (r2=0.41), meibomian grading (r2=0.37), TBUT (r2=0.30), and Schirmers (r2=0.17). Comparison of standard threshold-based classification with the composite severity index revealed significant overlap between the disease severities of prospectively defined "Normal" and "Dry Eye" groups. Fully 63% of the subjects were found to be poorly classified by combinations of clinical thresholds.

Conclusions: Tear film osmolarity was found to be the single best marker of disease severity across normal, mild/moderate and severe categories. Other tests were found to be informative in more severe forms of disease, thus clinical judgment remains an important element in clinical assessment of severity. The study also indicates that the initiation and progression of dry eye is multifactorial, and supports the rationale for redefining severity of dry eye based on a continuum of clinical signs.