As this week’s issue contains a major CET article in our dry eye assessment series and a first glimpse at the soon to be published TFOS DEWS2 report, I thought I would complete the subject coverage with a brief discussion of crying.

As eye care practitioners, we tend to concentrate quite reasonably on those aspects of ocular function that influence vision or indicate disease or compromised function. There is less focus on those aspects of ocular response which have a behavioural impact and may elicit a response in other humans when exhibited.

A good example here is the sympathetic nervous response causing pupil dilation that indicates in others enhanced attraction and sexual desire. Those women in the middle ages squirting deadly nightshade-derived atropine were not always mad. Another good example is the shedding of tears to express emotional response. Crying in newborns, as many parents reading this will testify, is present from birth and established well before laughing as a signal cue. Suppression of crying as an emotional cue rather than indicating physical pain, as many public school survivors or readers of Eddie Izzard’s new autobiography will testify, is possible around puberty.

The effectiveness of crying in changing other’s behaviours is fraught with variation, and the older a child becomes, the less potent a messenger the behaviour becomes. Factors affecting potency of response include the background and, arguably, the ethnicity of the viewer. One study has shown that adults in the US are most likely to cry while adult males from Bulgaria and Iceland least likely to do so.

Other studies have suggested that the changed chemical nature of emotional tears (increased levels of the hormones prolactin, adrenocorticotropic hormone, and leu-enkephalin and the elements potassium and manganese) may have a pheromone effect though, despite the efforts of the advertisers at Lynx body sprays, no human pheromones have yet to be isolated.