Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease
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 re...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2021-02-01
|
| Series: | Diagnostics |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2075-4418/11/3/387 |
| _version_ | 1797395385662046208 |
|---|---|
| author | Anthony J. Bron Catherine Willshire |
| author_facet | Anthony J. Bron Catherine Willshire |
| author_sort | Anthony J. Bron |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-03-09T00:33:42Z |
| format | Article |
| id | doaj.art-aab83000344b45c6baa43588e9164865 |
| institution | Directory Open Access Journal |
| issn | 2075-4418 |
| language | English |
| last_indexed | 2024-03-09T00:33:42Z |
| publishDate | 2021-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Diagnostics |
| spelling | doaj.art-aab83000344b45c6baa43588e91648652023-12-11T18:20:21ZengMDPI AGDiagnostics2075-44182021-02-0111338710.3390/diagnostics11030387Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye DiseaseAnthony J. Bron0Catherine Willshire1Nuffield Department of Clinical Neurosciences and Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford OX2 6HZ, UKOphthalmology Research, Hinchingbrooke Hospital, North West Anglia Trust, Huntingdon PE29 6NT, UKSystemic 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.https://www.mdpi.com/2075-4418/11/3/387basal tear osmolaritydehydrationdry eyeplasma osmolalitytonicityhyperosmolar |
| spellingShingle | Anthony J. Bron Catherine Willshire Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease Diagnostics basal tear osmolarity dehydration dry eye plasma osmolality tonicity hyperosmolar |
| title | Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease |
| title_full | Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease |
| title_fullStr | Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease |
| title_full_unstemmed | Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease |
| title_short | Tear Osmolarity in the Diagnosis of Systemic Dehydration and Dry Eye Disease |
| title_sort | tear osmolarity in the diagnosis of systemic dehydration and dry eye disease |
| topic | basal tear osmolarity dehydration dry eye plasma osmolality tonicity hyperosmolar |
| url | https://www.mdpi.com/2075-4418/11/3/387 |
| work_keys_str_mv | AT anthonyjbron tearosmolarityinthediagnosisofsystemicdehydrationanddryeyedisease AT catherinewillshire tearosmolarityinthediagnosisofsystemicdehydrationanddryeyedisease |