diseases of the eyeball, its accessories (the eyelid, conjunctiva, and lacrimal organs), and the orbit; also classified as eye diseases are anomalies of refraction of the eye (myopia, hyperopia, and astigmatism).
Eye diseases may be classified as congenital and acquired, infectious and noninfectious, acute and chronic, and unilateral and bilateral. Eye diseases may arise as a result of generalized disease of the body, including infectious diseases (tuberculosis, syphilis, rheumatism, influenza, diphtheria, typhus, typhoid, and others), parasitic diseases (various helminths, for example, echinococci), endocrinologic (diabetes mellitus) or vascular (hypertension) diseases, blood diseases (leukemia), tumors (cancer, sarcoma), and disorders of the central nervous system (meningitis, brain tumors); eye diseases may be a result of the extension of a process from neighboring areas (from accessory areas of the nose, sinusitis, for example). More rarely, primary eye diseases (intraocular malignant tumors with a tendency to metastasis) may be the source of disease of the whole body. A fundamental role in the development of eye diseases during generalized affection of the body belongs to endogenic (internal) factors. Among the exogenic (external) causes capable of producing eye diseases, those of greatest significance are the causative agents of infections entering the eye, mechanical traumas, chemicals, (acids, alkalis), and physical factors (heat, light, radioactivity). A number of eye diseases—glaucoma, serious traumas and burns of the eyes, retinal detachment, atrophy of the optic nerve, and trachoma, for example—may lead to blindness. The distribution and character of eye diseases depends on the influence of social, geographic, and climatic factors, the conditions of everyday life, and the organizational system of therapeutic and prophylactic care of the populace. The study of eye diseases is ophthalmology.
M. L. KRASNOV