Human Tear Osmotic Pressure

Terry, Jack E.

doi:10.1001/archopht.1978.03910050076019

Cited by 93 publications

(29 citation statements)

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“…Research has shown that knowledge of tear film osmolarity can be clinically valuable for assessing dry eye disease. Human tears are isotonic with a 0.9% sodium chloride solution15,16 and the recommendation for adjusting the osmotic concentration of eye drops to this presumed tonicity has found general acceptance 10. Tear hyperosmolarity is regarded as a central mechanism causing dry eye symptoms and ocular surface inflammation by activating a cascade of inflammatory events and the release of inflammatory mediators into the tears.…”

Section: Introductionmentioning

confidence: 99%

Effects of preservative-free tafluprost on tear film osmolarity, tolerability, and intraocular pressure in previously treated patients with open-angle glaucoma

Janulevičienė

Derkač²,

Grybauskiene³

et al. 2012

OPTH

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PurposeTo compare the effects on tolerability, tear osmolarity, and intraocular pressure (IOP)-lowering effect of switching from benzalkonium chloride (BAK) containing prostaglandin analog (PGA) latanoprost to preservative-free tafluprost.Patients and methodsThirty patients with open-angle glaucoma (N = 60 eyes), 26 women (87%) and four men (13%) aged 64.1 (SD 14.1) years, showing abnormal values of tear osmolarity, corneal fluorescein staining, tear film break-up time (TBUT), or subjective discomfort with current latanoprost treatment were included. After tear osmolarity (TearLab™ Osmolarity System), TBUT, corneal fluorescein staining, and baseline IOP (Goldmann tonometer) measurements and the completion of Ocular Surface Disease Index and Ocular Surface Symptoms in Glaucoma Scale questionnaires, patients were assigned to preservative-free tafluprost treatment. Measurements were repeated 2, 6 and 12 weeks after change of medication.ResultsNo statistically significant differences in IOP were observed 2, 6, and 12 weeks after switching to preservative-free tafluprost. Mean IOP at baseline was 16.4 mmHg (SD 2.9), after 2 weeks 16.2 mmHg (2.8), after 6 weeks 16.2 (2.6), and after 12 weeks 16.3 mmHg (2.3). Mean tear osmolarity decreased significantly from 315.7 mOsm/L (SD 15.1) at baseline to 308.0 ± 14.4 mOsm/L (P = 0.002), 301.7 ± 14.5 mOsm/L (P < 0.001), and 302.0 ± 9.9 mOsm/L (P < 0.001) 2, 6, and 12 weeks after changing medication to preservative-free tafluprost, respectively. Tear osmolarity was lower in 37 eyes (61.7%) after 2 weeks, in 46 eyes (76.7%) after 6 weeks, and in 49 eyes (81.7%) after 12 weeks (P < 0.005; t-test). At baseline corneal fluorescein staining was observed in 43 eyes (71.7%), after 2 weeks in 34 eyes (56.7%), after 6 weeks in 12 eyes (20.0%), and after 12 weeks in 7 eyes (11.7%) (P < 0.005; McNemar test). Mean TBUT increased from 3.7 seconds (SD 1.1) at baseline to 4.1 seconds (SD 1.0) at week 2, 5.2 seconds (SD 1.5) at week 6, and 6.5 seconds (SD 1.5) at week 12 (P < 0.001; t-test). The number of patients expressing discomfort with latanoprost diminished from 30 (100%) at baseline, to 19 (63.3%) after week 2, and to 11 (36.6%) (P < 0.05; McNemar test) after 12 weeks.ConclusionPreservative-free tafluprost is better tolerated than BAK-containing latanoprost, showing lower tear osmolarity levels while maintaining effective IOP control.

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Section: Introductionmentioning

confidence: 99%

Effects of preservative-free tafluprost on tear film osmolarity, tolerability, and intraocular pressure in previously treated patients with open-angle glaucoma

Janulevičienė

Derkač²,

Grybauskiene³

et al. 2012

OPTH

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“…1–5 Because of these implications in the pathogenesis of DED, there has been a multitude of studies estimating the values of tear osmolarities in normal and dry eye (DE) patients with a variety of techniques. For example, earlier methods using freezing point depression 6–8 and vapor pressure techniques 9 yielded generally a narrow distribution ranging from approximately 284 to 316 mOsm/L in normal individuals compared to a much wider distribution curve ranging from approximately 286 to 364 mOsm/L in DE patients. 10 More recent studies by means of user-friendly, low volume sampling methods (TearLab Corporation, San Diego, CA, USA) also have demonstrated similar ranges of values that have been claimed to show a high correlation with DED severity.…”

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confidence: 99%

Estimating the Osmolarities of Tears During Evaporation Through the “Eyes” of the Corneal Nerves

Hirata

Mizerska

Dallacasagrande

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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PurposeA population of corneal neurons in rats preferentially sense and monitor the hyperosmolar conditions of tears when the tears begin to evaporate during corneal dryness. The present study exploited this ability in an effort to estimate tear osmolarities by comparing the responses to corneal dryness to their responses to hyperosmolar stimuli.MethodsExtracellular recordings were performed from single neurons in the trigeminal ganglia innervating the corneas of rats. To determine the extent to which the corneal neurons' responses to drying of the cornea were induced via the activation by hyperosmolar stimuli, we assessed the responses to ocular instillation of 500 and 600 mOsm/L, and a graded series of hyperosmolar stimuli ranging from 350 to 1000 mOsm/L.ResultsThe magnitudes of the responses to drying of the cornea were matched almost exactly to those induced by the ocular instillation of the 600 mOsm/L stimuli but not the 500 mOsm/L solutions. The response magnitudes to a graded series of hyperosmolar solutions were nearly linear from the 350 to the 600 mOsm/L stimuli, but reached a plateau or declined slightly thereafter.ConclusionsOur results demonstrate that the tear osmolarity in rats could reach 600 to 1000 mOsm/L during ocular dryness. Furthermore, a spontaneous eye blink could be generated at a tear osmolarity of approximately 400 mOsm/L if the blink is solely determined by hyperosmolar tears, but ocular surface cooling also can become a major factor if hyperosmolar tears occurring during ocular dryness lower the threshold of activation of the neurons.

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“…Later, samples as small as 5 ml from a single eye were measured with a dew point-depression method (Mastman et al 1961;Terry & Hill 1978). Gilbard et al (1978) used a freezing point depression method requiring sample volumes of only a few tenths of a cubic millimeter (0.1 to 0.3 ml).…”

Section: Discussionmentioning

confidence: 99%

“…Holly & Lamberts (1981) found an accuracy ∫2 mOsm/kg in a range of 200 to 400 mOsm/kg using 5-ml sample volumes. Terry & Hill (1978) took 78 readings using 5-ml volumes of a standard 290 mOsm/kg reference solution and found a mean of 289.9 mOsm/kg with a standard deviation less than 1%. We found, here, means insignificantly different than 290 mmol/kg and standard deviations increasing from 0.68% (1.98 mmol/kg) to 1.07% (3.09 mmol/kg), respectively, as sample volume ranged from 2.0 ml to as little as 0.8 ml.…”

Section: Discussionmentioning

confidence: 99%

“…Though the instrumentation for vapor pressure osmometry is relatively compact and easier to master, its use in tear fluid research has been limited by the larger sample volume (5 ml) previously required (Terry & Hill 1978;Holly & Lamberts 1981). The total tear fluid volume averages 7 to 8 ml in the normal human eye (Mishima et al 1966) and 4.8 ml in keratoconjunctivitis sicca patients (Scherz et al 1974).…”

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confidence: 99%

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Vapor pressure osmometry, Minimum sample microvolumes

Pensyl

Benjamin

1999

Acta Ophthalmologica Scandinavica

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ABSTRACT.Purpose: Vapor pressure osmometers are currently designed to handle sample volumes as small as 2.0 microliters (ml) but smaller sample volumes are desirable in tear fluid studies. We determined the minimum sample size required for adequate validity and repeatability of osmolality measurements. Methods: A standard saline solution (290 mmol/kg) was sampled by a variable, calibrated pipette. Forty samples were processed with a Wescor 5520 vapor pressure osmometer at each of the following volumes: 2.0, 1.6, 1.2, 1.0, 0.8, 0.7, 0.6 and 0.5 ml. Prior to each test series, the instrument was calibrated with the identical volume of 290 mmol/kg saline. Relevant descriptive statistics were computed and an analysis of variance (ANOVA) was performed on the resulting data. Results: The mean osmolalities of the eight 40-sample groups ranged from 288.42 to 290.68 mmol/kg and were not significantly different from 290 mmol/ kg or each other (p±0.05). The standard deviations were inversely correlated with the sample volumes, gradually increased to approximately 1% as sample volume was reduced to 0.8 ml, then more rapidly increased as the sample volume was lowered still further. Conclusion: Sample microvolumes as small as 0.8 ml can be collected for accurate and repeatable results with the Wescor 5520 vapor pressure osmometer when a standard deviation of approximately 1% is acceptable. Microvolumes from 0.7 to 0.5 ml may also be used if the expanded spread of data can be offset by multiple repeated readings. Using a 2.0 ml sample volume, the ultimate accuracy and repeatability of the Wescor vapor pressure osmometer was ∫2% at 290 mmol/kg: 99% of all readings (∫3 standard deviations) should fall within ∫6 mmol/kg of the true value.

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Human Tear Osmotic Pressure

Cited by 93 publications

References 8 publications

Effects of preservative-free tafluprost on tear film osmolarity, tolerability, and intraocular pressure in previously treated patients with open-angle glaucoma

Effects of preservative-free tafluprost on tear film osmolarity, tolerability, and intraocular pressure in previously treated patients with open-angle glaucoma

Estimating the Osmolarities of Tears During Evaporation Through the “Eyes” of the Corneal Nerves

Vapor pressure osmometry, Minimum sample microvolumes

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