“T” selections in the Glossary of Terms for
Anatomy, Physiology & Pathology of the Human Eye

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tear film
the thin layer of tear fluid coating the front surface of the cornea; composed of three layers: lipid layer (most anterior), lacrimal layer (middle), and mucoid layer (most posterior)

tear glands
see glands, tear

tear, retinal
see retinal tear

the flooding of “reflex” tear fluid (usually lacrimal fluid from the lacrimal gland) into the eye, due to some type of irritation or from crying

tears, artificial
manufactured eyedrops or ointments, approximating the pH, osmolarity, osmolality, and tonicity of normal tears; often used to treat dry eye conditions, although prolonged use can disrupt the eye’s natural production of tears and can wash away the infection fighting agents contained in the eye’s natural tear film

Tenon’s capsule
the bulbar sheath surrounding the posterior half of the eye

the formation or presence of a blood clot within a blood vessel

a clot of blood formed within a blood vessel and remaining attached to its place of origin

an instrument, such as a Goldmann tonometer or an “air puff” tonometer, used to measure intraocular pressure in millimeters of mercury (mm Hg)

the measuring of intraocular pressure using a tonometer

the quality, relative degree, or specific degree of being toxic or poisonous

infection with or the disease caused by nematode worms of the genus Toxocara

infection with or the disease caused by a sporozoan of the genus Toxoplasma (T. gondii) that invades the tissues and may seriously damage the central nervous system, especially of infants

trabecular meshwork
a network of fibers, located near the junction of the cornea and the sclera, responsible for the continual drainage of the aqueous humor from the eye and into the canal of Schlemm

tract, optic
see optic tract

tract, uveal
see tunica vasculosa

transplantation, corneal
see corneal transplantation

trichromatism, anomalous
see anomalous trichromatism

a type of anomalous dichromatism color deficiency marked by confusion of blue and yellow, due to a lack of (or lack of function of) “S-cone” photoreceptors sensitive to short (bluish) wavelengths of light

a ring-like tendon, functioning as a pulley, through which the superior oblique muscle passes before it attaches to the eye

see strabismus

tuberculosis (TB)
a usully chronic, highly variable disease that is caused by the tubercle bacillus and rarely in the U.S. by a related mycobacterium (Mycobacterium bovis); usually is communicated by inhalation of the airborne causative agent; affects especially the lungs but may spread to other areas (as the kidneys or spinal column) from local lesions or by way of the lymph or blood vessels; characterized by fever, cough, difficulty in breathing, inflammatory infiltrations, formation of tubercles, caseation (necrosis with conversion of damaged tissue into a soft cheesy substance), pleural effusion, and fibrosis

tunica fibrosa
the outermost, tough, protective layer of the eye, including the opaque sclera (posterior 5/6) and the clear cornea (anterior 1/6)

tunica intima
the inner, mostly photosensitive layer of the eye, including the neural retina, pigmented epithelium, and posterior portion of the iris and ciliary body

tunica vasculosa
uveal tract; the middle, heavily pigmented layer of the eye, including the anterior iris, the anterior ciliary body, and the choroid

tunic, fibrous
see tunica fibrosa

tunic, internal
see tunica intima

tunic, vascular
see tunica fibrosa

tunnel vision
constriction of the visual field, resulting in loss of peripheral vision

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