Relationships among Tear Film Stability, Osmolarity, and Dryness Symptoms

Abstract

Purpose To examine the relationships among tear osmolarity, tear film stability, and several measures of dry eye (DE) symptoms in a multivariable analysis. Methods A cross-sectional study was conducted with 137 subjects (68 non–contact lens [CL] wearers and 69 soft CL wearers) recruited from a university campus. Tear breakup time (TBUT) was measured noninvasively (NITBUT) and with fluorescein (FTBUT). Tear osmolarity was measured by an osmometer. Dry eye symptoms were assessed using the Dry Eye Flow Chart and several different questionnaires. Results Subjects ranged in age from 18 to 67 years, with a mean of 28 years. Subjects had a mean (SD) osmolarity of 293 (10) mOsm/L, NITBUT of 14.1 (10.9) seconds, and FTBUT of 14.8 (12.6) seconds. Shorter NITBUT and FTBUT were significantly associated with female sex (p = 0.001 and p = 0.027, respectively) and Asian ethnicity (p = 0.030 and p = 0.004, respectively). There were no clinically significant relationships between tear osmolarity and FTBUT, NITBUT, or DE symptoms. Higher Dry Eye Flow Chart score (i.e., worse symptoms) was associated with older age (p < 0.001), female sex (p = 0.014), CL wear (p < 0.001), shorter NITBUT (p < 0.001), and shorter FTBUT (p = 0.028). The sensitivities and specificities for using clinical measurements to diagnose moderate to severe DE were as follows: osmolarity, 0.67 and 0.46, respectively; NITBUT, 0.72 and 0.52, respectively; and FTBUT, 0.68 and 0.57, respectively. Conclusions In a population of asymptomatic, mild and moderate DE patients, increased tear osmolarity was not significantly associated with reported symptom severity and frequency. Tear osmolarity, NITBUT, and FTBUT exhibited similar sensitivities and specificities when used to diagnose moderate to severe DE.

Diagnostic Ability of Conventional Dry Eye Tests and their Correlation with Ocular Surface Temperature

“…Studies on correlation among conventional clinical tests for dry eye have been undertaken for many years [4,5,22,[44][45][46][47][49][50][51][52] with inconsistent results. Such findings confirmed the complexity of DED and how the disease is multifactorial, depending on the dry eye subtypes, symptom questionnaire used and population studied [53].…”

Accounting for Ethnicity-Related Differences in Ocular Surface Integrity as a Step Toward Understanding Contact Lens Discomfort

“…62,63 Studies have shown that Asians have less stable tear films compared with non-Asians. 64,65 Despite similar lipid film thicknesses, healthy Asian subjects have a 11% to 24% shorter tear film breakup time than non-Asians. 64,66,67 Although no single component can be attributed to contact lens discomfort, a rapid tear breakup time was found to be the most consistent finding.…”

“…64,65 Despite similar lipid film thicknesses, healthy Asian subjects have a 11% to 24% shorter tear film breakup time than non-Asians. 64,66,67 Although no single component can be attributed to contact lens discomfort, a rapid tear breakup time was found to be the most consistent finding. 7 This suggests that even healthy Asian subjects may experience more discomfort with contact lens wear than non-Asians.…”

“…Their results showed that Asians demonstrated shorter NITBUT and fluorescein tear breakup times, which were correlated clinically with more severe dry eye symptoms and signs. 64 Since Asians experience more severe dryness even without contact lens wear, it is not surprising that they also experience more dryness with lens wear. 5,6 Dryness is also a common complication after laser in situ keratomileusis (LASIK), a commonly performed surgical procedure to correct refractive error.…”

“…64 However, current clinical techniques for measuring tear osmolarity have limitations. A major drawback of osmolarity measurement exists because of the location of tear sample collection from the inferior tear lake.…”