Studies on the Mechanism of Salt and Water Secretion From the Lacrimal Gland

Yoshimura, Hisato; Hosokawa, Keimei

doi:10.2170/jjphysiol.13.303

Cited by 19 publications

(10 citation statements)

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“…Some authors demonstrated a constant osmolality and secretion of sodium, bicarbonate and chloride ions independent of the tear flow rate. 63,71 Botelho and Martinez 72 demonstrated a constant flow of sodium and chloride between 2 and 30 ml/min, but an increase in concentration if the flow rate was less than 0.5 ml/min. The dependence of potassium secretion on the flow rate remains equivocal.…”

Section: Osmolality Of the Tear Filmmentioning

confidence: 99%

“…Controversy has evolved around the impact of the tear flow rate on electrolyte secretion and osmolality. Some authors demonstrated a constant osmolality and secretion of sodium, bicarbonate and chloride ions independent of the tear flow rate 63,71 . Botelho and Martinez 72 demonstrated a constant flow of sodium and chloride between 2 and 30 µl/min, but an increase in concentration if the flow rate was less than 0.5 µl/min.…”

Section: Tear Film Osmolalitymentioning

confidence: 99%

“…Botelho and Martinez 72 demonstrated a constant flow of sodium and chloride between 2 and 30 µl/min, but an increase in concentration if the flow rate was less than 0.5 µl/min. The dependence of potassium secretion on the flow rate remains equivocal 63,71,72 . Although calcium is only a minor contributor to osmolality, an increase in concentration occurs if the flow rate falls below 2.0 µl/min, but otherwise it is independent of the flow rate 73 .…”

Section: Tear Film Osmolalitymentioning

confidence: 99%

“…54,61 Due to their low concentration and high molecular weight, the colloidal osmolality of tear proteins and sugars approximates 2.0 mmHg and therefore is less than one per cent of the total tear film osmolality. 62 Of the electrolytes present in the tear film, the cations sodium and potassium, and the anions chloride and bicarbonate are the major contributors to tear osmolality 63 ( Table 1).…”

Section: Osmolality Of the Tear Filmmentioning

confidence: 99%

“…The dependence of potassium secretion on the flow rate remains equivocal. 63,71,72 Although calcium is only a minor contributor to osmolality, an increase in concentration occurs if the flow rate falls below 2.0 ml/min, but otherwise it is independent of the flow rate. 73 Gilbard and Dartt 74 investigated the osmolality of lacrimal gland fluid over a range of flow rates in rabbits and demonstrated an elevation of tear osmolality with decreasing flow rates.…”

Section: Osmolality Of the Tear Filmmentioning

confidence: 99%

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Osmolality and tear film dynamics

Stahl

Willcox

Stapleton

2012

Clinical and Experimental Optometry

132

102

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The tear film is a nourishing, lubricating and protecting layer that bathes the ocular surface. It is continuously replenished through cycles of production and elimination via evaporation, absorption and drainage. These processes are often referred to as tear film dynamics. Osmolality is an objective clinical measurement that provides insight into the balance of these complex tear film dynamics. Balanced tear production and elimination is vital for tear film integrity, stability and normal osmolality. Imbalances cause alterations of the tear film structure and composition, ultimately leading to tear film instability and measurable tear film hyperosmolality. Elevated tear film osmolality is considered a core mechanism in dry eye, forming the basis of dry eye symptoms and leading to ocular surface damage. Despite its immense potential in the diagnosis of dry eye, tear film osmolality is not commonly assessed. This review will focus on the current knowledge of tear film dynamics and tear film osmolality. The pre-ocular tear film is the outermost layer of the eye and is of critical importance to the health of the ocular surface. A continuous cycle of production, evaporation, absorption and drainage leads to a dynamic equilibrium in the pre-ocular tear film. Tear film osmolality or tear saltiness can be considered a consequence of these various factors in tear film dynamics.1 Homeostatic balance leads to tear film stability, enabling the tear film to fulfil its vital functions such as lubrication, nourishment and protection of the ocular surface.2,3 Homeostatic imbalance causes alteration of the tear film structure and composition, ultimately leading to tear film instability and tear film hyperosmolality.2 Measurement of tear film osmolality has been suggested as a gold standard in the diagnosis of dry eyes as elevated tear film osmolality is considered a core mechanism in symptoms and ocular surface damage in dry eye. 2,4,5 Despite its immense potential in the diagnosis of dry eye, measurement of tear film osmolality has not been amenable to in-office use and is largely confined to use in research. Newly available technology might increase its uptake by clinicians. This review focuses on the current knowledge of tear film dynamics and the relevance and clinical implications of tear film osmolality. TEAR FILM STRUCTURE AND FUNCTIONThe classical description of the tear film is a three-layered structure, with a predominant aqueous phase, a superficial thin oily layer, which interfaces with the environment, and a deep mucous layer at the base. 6,7 The thickness of the tear film was originally estimated to be 4 to 8 mm, with the aqueous layer being the thickest

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Section: Osmolality Of the Tear Filmmentioning

confidence: 99%

Section: Tear Film Osmolalitymentioning

confidence: 99%