Eyes hold a special importance among the body’s organs. “Eyes are bold as lions — roving, running, leaping, here and there, far and near,” wrote US philosopher Ralph Waldo Emerson, in his 1860 collection of essays, The Conduct of Life. “What inundation of life and thought is discharged from one soul into another, through them!” The concept of eyes being windows onto the mind rings true in medicine: changes in eyes or vision can provide clues about neurological or psychiatric disorders.

The identification of a light-sensitive receptor in the retina that serves as the master switch for the body’s internal clock, which led to the realization that artificial lighting is disrupting people’s sleep and waking cycles, has prompted researchers to develop lighting systems that complement basic physiology. Meanwhile, evidence is mounting that during the reign of the dinosaurs, from about 252 million to 66 million years ago, early mammals followed nocturnal lifestyles to avoid predation — a situation that predisposed humans to certain eye conditions.

Because sight is so crucial a sense, people often deeply fear its loss. Sometimes, this fear can lead to the provision of well intentioned but incorrect medical advice. But scientists suspect that emerging technologies such as optogenetics and bionics will eventually enable many people with currently untreatable eye conditions to see again.

To improve access to eye care, volunteers are combing remote areas of Kenya to identify people who need glasses. And researchers are creating artificial-intelligence systems that can quickly screen large populations for eye diseases. Using machines in conjunction with physicians to make such diagnoses could provide huge benefits, as long as society is also willing to accept the risks.