Dr. Richard Davis is an associate professor of ophthalmology at UNC Chapel Hill and a researcher at the N.C. Translational and Clinical Sciences Institute. Here he explains what causes – and what is contained within – the tears that frequently surface during the holidays. Questions and answers have been edited.
On a more general level, crying makes people feel better and, therefore, may represent a release or letting go of more extreme or stressful emotional states. Crying may also occur as a result of shared experiences of good things or bad, such as a birthday, graduation or loss of a loved one. Interestingly, the chemical makeup of emotional tears is different from tears caused when the surface of the eye is simply irritated. Some scientists believe that these chemicals, which have built up during times of stress and are released in emotional tears, explain why people can feel better after crying.
Tears are formed by tiny glands that surround the eye. These glands produce tears in three layers. First, there is an innermost mucous layer that coats the surface of the cornea, a windowlike covering to the eye. The middle layer is made up of primarily water and electrolytes. The outer, oily layer helps hold the tears together and prevent evaporation. All layers work together to provide a lubricating function for the surface of the eye.