Normal Tear Film Osmolarity As A Rule-Out Test For Dry Eye Disease In Patients Presenting With Classic Dry Eye Signs And Symptoms

Hyperosmolarity is defined as the core pathogenic mechanism of Dry Eye Disease (DED). However, classic signs and symptoms of DED are poorly correlated. The primary objective of this study is to assess the ability of tear osmolarity to rule-out DED in patients who are missing the core mechanism but present with other signs and symptoms commonly associated with DED. A secondary objective is to assess whether an alternative, non-DED ocular surface disease may be responsible for the observed signs and symptoms in the general patient population.

This was a multicenter study with sites across a broad spectrum of ophthalmology and optometry clinics in urban and rural areas in the United States and Canada.

This was a single visit study on subjects presenting with three (3) or more symptoms typically associated with dry eye disease (DED): fluctuating vision, blurry vision, foreign body sensation, tired eyes, light sensitivity, itching, dry eyes, watery eyes, burning, redness, feeling of sand or grit in the eye, stringy mucus in or around eyes, or contact lens discomfort, a normal tear osmolarity < 308 mOsm/L OU and an inter-eye difference < 8 mOsm/L. Patients were assessed by slit lamp examination to identify DED signs including tear film breakup time (TBUT), and corneal fluorescein staining. A final diagnosis and treatment decision, based on clinical opinion, was determined for each subject.

60 subjects (M=25, F=35, age=48.6±19.9 years) with normal osmolarity (298.5±5.4 mOsm/L, ∆eye=3.7±2.2 mOsm/L) averaged 4.6±2.0 symptoms (range 3–10). 42% of subjects had an abnormal TBUT <10 seconds (average 9.3±3.4 s) and 35% an abnormal staining grade > 0 on a 0-3 scale (average 0.5±0.9). Signs were uncorrelated (all r2 < 0.1). Alternative non-DED ocular surface disease diagnoses for 78.3% (47/60) of subjects were established, with allergic conjunctivitis (15), computer vision syndrome (10), anterior blepharitis (6), contact lens intolerance (6), floppy eyelid syndrome (5), treated DED (4), conjunctivochalasis (3), demodicosis (3), pterygium (2), EBMD (1), keratoneuralgia (1), and lagophthalmos (1) identified.

In patients presenting with symptoms and signs commonly associated with DED, but without the core pathogenic mechanism of hyperosmolarity, a majority of subjects were diagnosed with an alternative, non-DED ocular surface disease (OSD). Standard slit lamp examinations of TBUT and staining may confound an accurate diagnosis when osmolarity is normal as the signs and symptoms of DED overlap significantly with other OSDs. As a rule-out test, normal tear osmolarity should increase suspicion for alternate etiologies, since treatment for 11 of the 12 OSDs in this study would likely require some variation from standard dry eye therapy. Allergic conjunctivitis, computer vision syndrome and anterior blepharitis were the most common non-DED diagnoses.