achromatopsia color blindness. Also called acritochromacy. acyanoblepsia a form of color blindness characterized by the inability to see blue. aniseikonia a defect of the eyesight in which the images on the retinas are different in size. —aniseikonic, adj. anisometropia a defect of the eyesight in which each eye has a different power to refract light. Cf. isometropia. —anisometropic, adj. astigmatism a defect in a lens, eye, or mirror that causes rays from one direction not to focus at one point. —astigmatic, adj. blepharism twitching of the eyelids. blepharitis soreness or inflammation of the eyelids. blepharoptosis Pathology. a drooping of the upper eyelid. collyrium an eyewash or other liquid preparation for the eyes. See also remedies. conjunctivitis inflammation of the conjunctiva. Daltonism red-green color blindness. deuteranopia a defect of the eyesight in which the retina does not respond to green. —deuteranope, n. —deuteranopic, adj. dichromation a form of color blindness in which the sufferer can perceive only two of the three primary colors. dioptometer an instrument for measuring the refractive index of the lens of the eye. dyschromatopsia color blindness. emmetropia the normal refractive function of the eye in which light is focused exactly on the retina with the eye relaxed. —emmetropic, adj. esotropia a condition of the eyes in which while one eye focuses on the object viewed the other eye turns inward; cross-eye. glaucoma a disease of the eyes, in which the pressure inside the eyeball increases, often resulting in blindness. —glaucomatous, adj. hemeralopia a condition of the eyes in which the sufferer can see clearly at night but has impaired vision during the day; day blindness. hypermetropia the condition of farsightedness. Also called hyperopia. —hypermetropic, adj. hyperopia hypermetropia. —hyperopic, adj. iridotomy Surgery. the making of an artificial pupil in the eye by transverse division of iris fibers. isometropia the state or quality of the eyes being equal in refraction. Cf. anisometropia. keratitis an inflamed condition of the cornea. keratoplasty the surgical process of corneal grafting. keratotomy the process of surgical incision of the cornea. lacrymatory, lachrimatory a lacrymal vase or small vessel for storing shed tears. Iagophthalmia, lagophthalmus a persistent, abnormal retraction of the eyelid so that the eyeball is not covered during sleep. —lagophthalmic, adj. leucoscope an instrument for testing the eyes to determine the ability to distinguish variations in color or intensity of light. leucosis the development of leucoma, a whitish clouding of the cornea caused by ulceration. lippitude soreness of the eyes; a bleary-eyed condition. macrography study or examination of an object with the naked eye as contrasted with examination under the microscope. megalopsia a defect of the eyesight in which what is viewed is greatly magnified. melanosity darkness or blackness of eyes, hair, or complexion. miosis, myosis abnormal constriction of the pupil of the eye, caused by drugs or illness. Cf. mydriasis. —miotic, myotic, adj. monoblepsia, monoblepsis a defect of the eyesight in which vision is best when only one eye is open. monochromation a defect in which the retina cannot perceive color. mydriasis abnormal dilatation of the pupil, the result of disease or the use of certain drugs. Cf. miosis. —mydriatic, adj. myopia the condition of nearsightedness. —myopic, adj. myosis miosis. —myotic, adj. nauscopy the ability, sometimes pretended, to sight ships or land at great distances. nictitation, nictation the process of winking or blinking rapidly, as in certain birds or animals or as the result of a tic in humans. nyctalopia a condition of the eyes in which the sufferer can see clearly during the day or in bright light but has impaired vision at night or in poor light; night blindness. nystagmus uncontrollable and rapid movement of the eyeball in any direction. —nystagmic, adj. oculist a physician who specializes in ophthalmology. ommatophobia an abnormal fear of eyes. ophthalmology the branch of medical science that studies the eyes, their diseases and defects. —ophthalmologist, n. —ophthalmologic, ophthalmological, adj. optician a person who makes and sells glasses according to prescriptions prepared by an oculist or optometrist. optogram an image on the retina caused by bleaching of the pupils. optography the act or practice of reproducing optograms. optology Archaic. the testing of the eyes for lenses. optometry the practice or profession of testing eyes for defects in vision and the prescribing of corrective glasses. —optometrist, n. —optometrical, adj. optotype type used in the testing of eyesight. orthoptics the art of treating visual defects by exercise and retraining in Visual habits. —orthoptist, n. —orthoptic, adj. oxyopia, oxyopy an extremely heightened acuteness of the eyesight, resulting from increased sensibility of the retina. phantasmascope, phantascope an optical device that enables the viewer to converge the optical axes of the eyes and experience some of the phenomena of binocular vision. photalgia pain in the eyes caused by light. photangiophobia an abnormal fear of photalgia. photopia vision, or the ability to see in bright light. Cf. scotopia. —photopic, adj. polyopia multiple vision; the seeing of one object as more than one. presbytism a form of farsightedness that occurs in old age. Also called presbyopia, presbytia. Cf. hypermetropia. —presbytic, adj. protanopia a defect of the eyesight in which the retina does not respond to red. —protanope, n. —protanopic, adj. retinoscopy a method of determining the refractive error of an eye using an ophthalmoscope to illuminate the retina through the lens of the eye. Also called skiascopy. —retinoscopist, n. scotopia vision in dim light or darkness. Cf. photopia. —scotopic, adj. strabism the inability of both eyes to focus on one object thereby producing the effect of squinting or cross-eyes. Also called strabismus. —strabismal, strabismic, adj. synechia a diseased condition characterized by adhesion, especially the adhesion of the iris to the cornea. trachoma a contagious form of conjunctivitis, with the formation of inflammatory granules on the inner surface of the eyelid. —trachomatous, adj. trichiasis a condition in which the hair, especially of the eyelashes, grows inward. tritanopia a defect of the eyesight in which the retina does not respond to blue and yellow. —tritanope, n. —tritanopic, adj. uveitis an inflamed condition of the uvea. —uveitic, adj. xanthocyanopsy, xanthocyanopy a form of color blindness in which only yellows and blue can be perceived. xerophthalmia a form of conjunctivitis, the result of a deficiency of vitamin A, marked by a dry and dull condition of the eyeball. Also called xeroma. xerosis abnormal dryness, as of the eyes or skin. Also called xeransis. —xerotic, adj.