Level of tear cytokines in population-level participants and correlation with clinical features

Tear cytokine levels indicate severity of ocular surface inflammation. Previous reports of cytokine concentrations were based on hospital-based studies or non-Chinese populations. We determine the range of tear concentration of cytokines in a representative adult Chinese population.

Thirty-nine participants were recruited from a population-based study of Chinese adults in Singapore, and standardized clinical ocular surface/eyelid features evaluated. Tear was extracted from Schirmer strips and analysed using a multiplex bead-based assay.

Tear concentrations of 14 cytokines were investigated and quantifiable in each participant. Eight cytokines increased with increasing age, and 4 cytokines (IL-4, IL-12, IL-10 and IFN-γ) were increased in people with increased frequency of ocular discomfort. Three cytokines (MCP-1, IP-10 and IL-13) had increased levels in people with lower Schirmer tests, while 9 other cytokines were increased in patients with eyelid crusting (TNF-α, IL-1β, IL-17α, IL-2, IL-4, IL-6, IL-12, IL-10 and IFN-γ). Twelve percent of participants had eyelid crusting.

Using a convenient collection technique that is a routine clinical test, 14 tear cytokines could be quantifiable even in Singapore Chinese adults without a dry eye diagnosis. Elevation of different tear cytokines may be linked to subclinical aqueous tear deficiency or eyelid inflammation even in asymptomatic people.