Doctors in Britain have long suspected that patients who wear tinted eyeglasses are abnormally prone to depression and hypochondria  Psychological tests given there to hospital patients admitted for physical complaints like heart pain and digestive distress confirmed such a relationship  Perhaps people whose relationship to the world is psychologically painful choose such glasses to reduce visual stimulation, which is perceived as irritating
At any rate, it can be concluded that when such glasses are worn, it is because the wearer has a tendency to be depressed or hypochondriacal
For hypochondriacs wearing tinted glasses, the glasses serve as a visual signal to others that the wearer's health is delicate.