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Progress in Retinal and Eye Research May 2018The osmolarities of various bodily fluids, including tears, saliva and urine, have been used as indices of plasma osmolality, a measure of body hydration, while tear... (Review)
Review
The osmolarities of various bodily fluids, including tears, saliva and urine, have been used as indices of plasma osmolality, a measure of body hydration, while tear osmolarity is used routinely in dry eye diagnosis, the degree of tear hyperosmolarity providing an index of disease severity. Systemic dehydration, due to inadequate water intake or excessive water loss is common in the elderly population, has a high morbidity and may cause loss of life. Its diagnosis is often overlooked and there is a need to develop a simple, bedside test to detect dehydration in this population. We hypothesize that, in the absence of tear evaporation and with continued secretion, mixing and drainage of tears, tear osmolarity falls to a basal level that is closer to that of the plasma than that of a tear sample taken in open eye conditions. We term this value the Basal Tear Osmolarity (BTO) and propose that it may be measured in tear samples immediately after a period of evaporative suppression. This value will be particular to an individual and since plasma osmolarity is controlled within narrow limits, it is predicted that it will be stable and have a small variance. It is proposed that the BTO, measured immediately after a defined period of eye closure, can provide a new metric in the diagnosis of systemic dehydration and a yardstick against which to gauge the severity of dry eye disease.
Topics: Dehydration; Dry Eye Syndromes; Humans; Organism Hydration Status; Osmolar Concentration; Tears
PubMed: 29476817
DOI: 10.1016/j.preteyeres.2018.02.001 -
Optometry and Vision Science : Official... Dec 2014To determine whether tear collection by flushing the ocular surface with saline (flush tears) or collection by stimulation (reflex tears) can be used as an alternative... (Comparative Study)
Comparative Study
PURPOSE
To determine whether tear collection by flushing the ocular surface with saline (flush tears) or collection by stimulation (reflex tears) can be used as an alternative to basal tear collection for the identification and quantification of lipids in the tear film.
METHODS
Tear samples were collected from 10 participants with no history of ocular surface disease or contact lens wear. Up to 10 μl of basal, reflex, and flush tear samples were collected from each eye using a microcapillary tube on three occasions with the order of methods randomized and allowing at least 24 hours between each collection method. Lipids were quantified from each tear sample using nano-electrospray ionization tandem mass spectrometry.
RESULTS
Total lipids significantly differed in their concentration (pmol/μl) and mole % with each collection technique. Cholesterol esters [mean % (SE)] formed the major component of the total lipidome in basal [54.8% (3.1)], reflex [35.7% (6.4)], and flush [33.0% (3.1)] tear samples. However, the mole % of each lipid class substantially varied with each tear collection method. Nonpolar lipids, including cholesterol, wax esters, and triacylglycerols, dominated the tear lipidome in basal [92.8% (1.9)], reflex [71.8% (7.9)], and flush [83.6% (3.8)] tear samples. However, the mole % of phospholipids in reflex [27.5% (8.1)] and flush [15.8% (3.8)] tear samples was higher (p = 0.005) than that in basal tears [5.4% (2.0)].
CONCLUSIONS
Flush or reflex tears did not have similar lipid profiles in either concentration or in mole % to basal tears. It is recommended that basal tears are used for tear lipid analysis as the reflex or flush tears contain very low levels of most lipid components.
Topics: Adult; Healthy Volunteers; Humans; Lipids; Specimen Handling; Spectrometry, Mass, Electrospray Ionization; Tears
PubMed: 25325761
DOI: 10.1097/OPX.0000000000000411 -
Cornea Feb 2019To evaluate lower tear meniscus and corneal sub-basal nerve plexus in primary Sjögren's syndrome (pSS) and Sicca syndrome patients.
PURPOSE
To evaluate lower tear meniscus and corneal sub-basal nerve plexus in primary Sjögren's syndrome (pSS) and Sicca syndrome patients.
METHODS
Cross-sectional study of 116 patients with Sicca syndrome associated with pSS and not associated with Sjögren's syndrome (non-SS Sicca) and 20 normal control subjects. Tear meniscus height and area were measured using anterior segment optical coherence tomography; corneal sub-basal nerve plexus density, length, and tortuosity were evaluated using in vivo confocal microscopy. Data analysis was performed using IBM-SPSS Statistics 24.0.
RESULTS
Corneal sub-basal nerve plexus density and length were significantly lower, and tortuosity was significantly higher in pSS and non-SS Sicca groups than in normal control subjects (P < 0.001; P = 0.018, respectively). Corneal sub-basal nerve plexus presented a strong association with Schirmer test I and tear breakup time. Cutoff values of sub-basal nerve plexus density (36.5 nerve/mm) and length (12.5 mm/mm) presented 80.2% to 81.9% sensitivity and 85% specificity for detecting Sicca syndrome patients. No significant differences were found between the 3 groups regarding tear meniscus height and area.
CONCLUSIONS
Corneal sub-basal nerve plexus in vivo confocal microscopy may be a useful tool in the assessment of dry eye disease in Sicca syndrome, complementing the information provided by the conventional modalities used in dry eye disease evaluation.
Topics: Adult; Aged; Case-Control Studies; Cornea; Cross-Sectional Studies; Dry Eye Syndromes; Female; Humans; Male; Microscopy, Confocal; Middle Aged; Sjogren's Syndrome; Tears; Tomography, Optical Coherence
PubMed: 30379721
DOI: 10.1097/ICO.0000000000001800 -
Current Opinion in Allergy and Clinical... Oct 2022To review the neuroanatomy and physiology of the basal and reflex tearing and present the available and developing therapies using the concept of neurostimulation in dry... (Review)
Review
PURPOSE OF REVIEW
To review the neuroanatomy and physiology of the basal and reflex tearing and present the available and developing therapies using the concept of neurostimulation in dry eye disease (DED).
RECENT FINDINGS
The most prevalent current DED treatments seek to supplement low tear volume and tear components or reduce inflammation. Neurostimulation is a unique approach gaining momentum in recent years, geared toward increasing the production of all basal tear components by stimulating the nerves responsible for producing the various tear components. The neuroanatomy of the lacrimal unit provides several possible access points to stimulate tear production through two arms of the sensory trigeminal nerves. Modes of stimulation include chemical or energy in electrical or magnetic form. Research thus far has shown that neurostimulation can achieve lacrimal, goblet cell, and meibomian gland stimulation. Subjectively it improves symptoms of DED. Clinically, neurostimulation has improved the signs and symptoms of DED by increasing basal tear production and tear volume.
SUMMARY
Neurostimulation using electrical, mechanical, or chemical means is a novel concept to increase tear production and was demonstrated to be an effective, safe, and well-tolerated method for managing DED.
Topics: Dry Eye Syndromes; Humans; Lacrimal Apparatus; Tears
PubMed: 35779066
DOI: 10.1097/ACI.0000000000000841 -
Contact Lens & Anterior Eye : the... Feb 2018Tear osmolarity (tOsm) is used as a measure of severity in dry eye disease (DED) and has been proposed as an index of body hydration. In DED the level of tear...
PURPOSE
Tear osmolarity (tOsm) is used as a measure of severity in dry eye disease (DED) and has been proposed as an index of body hydration. In DED the level of tear hyperosmolarity is compared with that of a control population. It is proposed here that a better index of body hydration and a more valid reference point in DED can be acquired by measuring the tOsm after a period of evaporative suppression.
METHOD
8 normal and DED subjects were recruited, their tOsm measured in uncontrolled environmental 'clinic conditions'. Then in experiment 1 they entered a controlled environment chamber and had tOsm measured after 45 minutes of eye closure and then, with the eyes open, at 15 minute intervals for a further 45 minutes, at a relative humidity (RH) of 45%. Alternatively, in experiment 2, they had tOsm measured every 15 minutes for 45 minutes during exposure to 70% RH, as a separate measure to suppress evaporation.
RESULTS
A significant decrease in tOsm occurred in both normal and DED subjects after lid closure in experiment 1 (normal RE p=0.015; normal LE p=0.006; DED RE p=0.0002; DED LE p=0.01). The tOsm also fell slightly after exposure to 70% RH in experiment 2 significant in the LE of normal group only (normal LE p=0.045).
CONCLUSIONS
Suppression of tear evaporation resulted in a fall in tOsm, close to that of plasma osmolarity (285-295mOsm/L). It is proposed that this new measure, termed Basal Tear Osmolarity (BTO), could provide a valuable index of plasma osmolarity and hence of body hydration and in DED, a personal baseline against which to gauge the severity of tear hyperosmolarity.
Topics: Adult; Aged; Dry Eye Syndromes; Female; Humans; Male; Middle Aged; Osmolar Concentration; Tears; Young Adult
PubMed: 28958415
DOI: 10.1016/j.clae.2017.09.005 -
Diagnostics (Basel, Switzerland) Feb 2021Systemic dehydration due to inadequate water intake or excessive water loss, is common in the elderly and results in a high morbidity and significant mortality.... (Review)
Review
Systemic dehydration due to inadequate water intake or excessive water loss, is common in the elderly and results in a high morbidity and significant mortality. Diagnosis is often overlooked and there is a need for a simple, bedside diagnostic test in at-risk populations. Body hydration is highly regulated with plasma osmolality (pOsm) being tightly controlled over a wide range of physiological conditions. By contrast, normal tear osmolarity (tOsm) is more variable since the tear film is exposed to evaporation from the open eye. While plasma hyperosmolality is a diagnostic feature of systemic dehydration, tear hyperosmolality, with other clinical features, is diagnostic of dry eye. Studies in young adults subjected to exercise and water-deprivation, have shown that tOsm may provide an index of pOsm, with the inference that it may provide a simple measure to diagnose systemic dehydration. However, since the prevalence of both dry eye and systemic dehydration increases with age, the finding of a raised tOsm in the elderly could imply the presence of either condition. This diagnostic difficulty can be overcome by measuring tear osmolality after a period of evaporative suppression (e.g., a 45 min period of lid closure) which drives tOsm osmolality down to a basal level, close to that of the pOsm. The arguments supporting the use of this basal tear osmolarity (BTO) in the diagnosis of systemic dehydration are reviewed here. Further studies are needed to confirm that the BTO can act as a surrogate for pOsm in both normally hydrated subjects and in patients with systemic dehydration and to determine the minimum period of lid closure required for a simple, "point-of-care" test.
PubMed: 33668748
DOI: 10.3390/diagnostics11030387 -
Therapeutic Advances in Ophthalmology 2018The aim of this study is to evaluate the difference between reflex and basal tear osmolarity among healthy normal subjects.
PURPOSE
The aim of this study is to evaluate the difference between reflex and basal tear osmolarity among healthy normal subjects.
METHOD
The right eyes of 20 healthy normal male subjects aged 20 to 40 years were recruited for this study. The inclusion criteria for the subjects were the Ocular Surface Disease Index questionnaire score of less than 12 and wetting length of the phenol red thread of more than 10 mm. Tear film osmolarity was assessed using TearLab osmometer. Basic tear osmolarity was measured normally without inducing any irritation to the eye. In order to stimulate reflex tear, subjects were asked to open their eye as long as they can till they feel ocular surface irritation (minimum 20 s).
RESULTS
The mean score on the Ocular Surface Disease Index questionnaire was 5.5 ± 3. The mean value obtained from the phenol red thread was 21 ± 4.5 mm. There were no statistically significant differences between the osmolarity readings of basal and reflex tear osmolarity ( > 0.05). The mean value was 308 ± 12 and 306 ± 9 mOsm/l for basic and reflex tear osmolarity, respectively.
CONCLUSION
This study found that the osmolarity of the basal and reflex tears fell within the same range. The values found in this study are in agreement with published results for normal subjects.
PubMed: 30151502
DOI: 10.1177/2515841418794886