H
“H” selections in the Glossary of Terms for
Anatomy, Physiology & Pathology of the Human Eye
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A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z
- hemorrhage, retinal
- leakage of blood from blood vessels into or underneath the retina
- hemorrhage, subconjunctival
- leakage of blood from blood vessels underneath the conjunctiva, often due to a sudden jolt from blunt trauma, coughing, or sneezing; normal reabsorption of blood usually takes 1-2 weeks
- heterochromia iridis
- a difference in color between the irises of the two eyes or between parts of one iris (heterochromia iridium); usually a congenital (autosomal dominant) trait, but can result from pathologies such as pigment dispersion syndrome, Horner’s syndrome (with the affected side being blue), Waardenburg syndrome, Fuch’s heterochromic cyclitis, and piebald syndrome, as well as injury to an eye, bleeding or inflammation within an eye, or eye tumors
- heterotropia
- see strabismus
- high blood pressure
- see hypertension
- hippus
- a normal fluctuation in pupillary size under steady illumination
- histoplasmosis
- a respiratory disease caused by a fungus of the genus Histoplasma (H. capsulatum) with symptoms like those of influenza; endemic in the Mississippi and Ohio river valleys of the U.S.; and is marked by benign involvement of lymph nodes of the trachea and bronchi, usually without symptoms or by severe progressive generalized involvement of the lymph nodes and the reticuloendothelial system with fever, anemia, leukopenia and often with local lesions (as of the skin, mouth, throat, or retina)
- hordeolum
- sty or stye; an inflamed swelling of a sebaceous gland at the margin of an eyelid; treated with warm compresses or antibiotics
- Horner’s syndrome
- an interruption of the oculosympathetic nerve pathway somewhere between its origin in the hypothalamus and the eye; typically causes ptosis, pupillary miosis and facial anhidrosis, as well as possibly apparent enophthalmos, increased amplitude of accommodation, heterochromia of the irides (if it occurs before age two), paradoxical contralateral eyelid retraction, transient decrease in intraocular pressure, and changes in tear viscosity
- humor, aqueous
- see aqueous humor
- humor, vitreous
- see vitreous humor
- hyaloid artery
- a branch of the primitive dorsal ophthalmic artery; extends, in the fetus, from the optic cup of the optic nerve into the vitreous cavity and forward to the lens to aid its development; regresses during the last trimester of fetal formation, leaving behind the “Cloquet’s canal” through the vitreous
- hyaloid artery, persistent
- see persistent hyaloid artery
- hyalosis, asteroid
- see asteroid hyalosis
- hyaluronic acid
- a viscous glycosaminoglycan that occurs especially in the vitreous humor, the umbilical cord, and synovia and as a cementing substance in the subcutaneous tissue
- hydrophilic
- of, relating to, or having a strong affinity for water; easily wettable
- hydrophobic
- of, relating to, or having a lack of affinity for water; resistant to wetting
- hydrops
- edema
- hyperemia, rebound
- see rebound hyperemia
- hypermetropia
- see hyperopia
- hyperopia
- farsightedness, hypermetropia; a condition in which visual images come to a focus behind the retina of the eye and vision is better for distant than for near objects; may be due to the surface(s) of the cornea and/or crystalline lens having reduced (too flat) curvature, an eyeball which is too short, and/or an index of refraction of one of the ocular media that is too low
- hypertension
- abnormally high arterial blood pressure; can occur without apparent or determinable prior organic changes in the tissues, possibly because of hereditary tendency, emotional tensions, faulty nutrition, or hormonal influence; also can be associated with demonstrable organic changes (as in nephritis, diabetes, and hyperthyroidism); uncontrolled, can cause mild to severe changes in the retina: cotton wool spots, flame-shaped hemorrhages, arteriosclerosis, retinal or macular edema, macular star, and papilledema (optic disc edema)
- hyperthyroidism
- thyrotoxicosis; excessive production of thyroxine by the thyroid gland, as well as the resulting condition marked by increased metabolic rate, enlargement of the thyroid gland (goiter), rapid heart rate, high blood pressure, and exophthalmos (protruding eyes)
- hypertonic
- having a higher osmotic pressure than a surrounding fluid or medium
- hypertropia
- a strabismus where the deviating eye turns upward, as compared to the other eye which remains pointing straight ahead
- hyphema
- a hemorrhage in the anterior chamber of the eye
- hypopyon
- an accumulation of white blood cells (pus) in the anterior chamber of the eye
- hypothyroidism
- deficient production of thyroxine by the thyroid gland, as well as the resultant bodily condition characterized by a lowered metabolic rate, weight gain, and general loss of vigor
- hypotonic
- having a lower osmotic pressure than a surrounding fluid or medium
- hypotropia
- a strabismus where the deviating eye turns downward, as compared to the other eye which remains pointing straight ahead
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