Basal values, intra-day and inter-day variations in tear film osmolarity and tear fluorescein clearance

Abstract

Tear osmolarity was unaffected by intra-day variations; however, the T-FCT showed an inter-day variation, which indicated that the time of day when the test is performed must be considered when it is used to evaluate the diagnosis of dry eye disease, disease progression or therapeutic effectiveness.

TFOS DEWS II Tear Film Report

“…In accordance with previous studies, prolonged eye closure has been found to lead to tear hypo-osmolarity but data about diurnal variations are equivocal [130,134,139,142,149]. Some authors [130,142] show a shift towards lower values mid-day, followed by an increase, whilst others [134,139,149] show no significant effect of time. There is a positive relationship between plasma osmolarity and tear osmolarity and both are raised in patients with dry eye disease or with systemic dehydration [150–152].…”

“…An increase in tear osmolarity has been observed after sleep deprivation, exposure to high altitude and religious fasting [135,147,148]. In accordance with previous studies, prolonged eye closure has been found to lead to tear hypo-osmolarity but data about diurnal variations are equivocal [130,134,139,142,149]. Some authors [130,142] show a shift towards lower values mid-day, followed by an increase, whilst others [134,139,149] show no significant effect of time.…”

Diagnosis of dry eye disease and emerging technologies

“…In addition, further studies need to be performed in larger patient populations to assess the sensitivity and specificity of OCT in diagnosis of dry eye. With OCT, the tear lake can be captured in a single moment in time, but whether that single measurement represents the true volume of the tear film throughout the day is questionable because there can be intraday variations 64. Serial OCT measurements may need to be done to establish a mean tear lake volume and tear film thickness.…”

Biomarker sources for Parkinson's disease: Time to shed tears?

“…For example, a biomarker can indicate a change in expression or state of a protein that correlates with the risk or progression of a Basal Ganglia 5 (2015) [63][64][65][66][67][68][69] Parkinson's disease (PD) is the most frequent neurodegenerative movement disorder. In nearby future its importance will increase, especially due to changes in age structure.…”

“…Among the detected proteins are growth factors [50], cytokines [51], matrix metalloproteinases [52], immunoglobulins [53], complement factors [54], sex hormones [55], proteases and protease inhibitors [56], calcium-binding proteins [57] and glycoproteins like mucins [58]. The tear protein profile can change depending on local or systemic diseases [59], sex [60], age [61], diurnal variation (daytime changes) [62] and can even show an inter-day variation [63]. At least 97 proteins are considered to be unique for the tear fluid [64].…”