The perception of light, in its most basic form, is arguably the most important sense that allows human beings to interact with the outside world. After cancer, most people fear losing their sight above all other potential ailments, with deterioration in vision with age often having secondary effects on accidental injury and the ability to remain independent.

Every stage of the reception and processing of light has highly developed tissues for the role (see Ocular Biology). A wide range of conditions, with both genetic and environmental can cause damage to these tissues, resulting in a detriment to vision. In the elderly, sight loss due to glaucoma, cataract and macular degeneration are amongst the commonest of morbidities. The eye also performs another form of light detection, quite separate from image-detection, which regulates circadian rhythm and sleep systems. Disruption of these physiological systems results in a broad range of interconnected pathologies ranging from poor vigilance and memory, reduced mental and physical reaction times, reduced motivation, depression, insomnia, metabolic abnormalities, obesity, immune impairment, and even a greater risk of cancer.

Hence by understanding light detection in its most general sense and by treating disorders of vision, the science of ophthalmology has significant implications for human health, both socially and economically for the foreseeable future.