G
“G” 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
- ganglion cells
- nerve cells having their bodies outside of the central nervous system, such as those located in layer 8 of the retina
- giant papillary conjunctivitis (GPC)
- inflammation of the conjunctiva, most commonly associated with soft contact lens wear and marked by the presence of giant bumps or papillae (greater than 1 millimeter in diameter) on the posterior surface of the upper eyelids, as well as redness, itching, burning, mucous discharge, and blurred vision; may be related to irritation due to excess protein build-up on the lenses and/or to chemicals (such as preservatives) in the cleaning and sterilization solutions used to care for the lenses; treatment consists of decreasing (or even ceasing) contact lens wear, more frequent enzymatic cleaning of lenses (to remove protein deposits), discontinuance of preserved solutions, storage in unpreserved saline solutions, sterilization by hydrogen peroxide, and possibly obtaining new contact lenses
- gland, lacrimal
- tear gland; a gland, about the size and shape of an almond, that is the major producer of a watery secretion which forms the middle (lacrimal), thickest layer of the tear film; situated laterally and superiorly to the eyeball in a shallow depression on the inner surface of the frontal bone
- glands, tear
- glands located near the eye and in the eyelids which produce the lipid, lacrimal, and mucoid layers of the tear film coating the anterior surface of the cornea; consist of the lacrimal gland, Meibomian glands, Zeis glands, Krause glands, Wolfring glands
- glands, Meibomian
- elongated sebaceous glands in the eyelids that discharge a fatty, oily secretion which forms the most exterior (lipid) layer of the tear film, preventing tear evaporation
- glands, Krause
- small glands in the eyelids that discharge a watery secretion which forms the middle (lacrimal), thickest layer of the tear film
- glands, Wolfring
- small glands in the eyelids that discharge a watery secretion which forms the middle (lacrimal), thickest layer of the tear film
- glands, Zeis
- sebaceous glands in the eyelids that discharge a fatty, oily secretion which forms the most exterior (lipid) layer of the tear film, preventing tear evaporation
- glasses
- see eyeglasses
- glaucoma
- a progressive optic neuropathy (a disease of the optic nerve) characterized by a specific pattern of retinal ganglion cell, axon, and optic nerve damage, resulting in a reduction in the visual field (beginning in the periphery and gradually moving inward) and even blindness; most significant risk factor is elevated intraocular pressure (IOP), which results from less fluid leaving the eye than is entering the eye; other possible risk factors, most of which have been as yet little explored, may include low blood pressure, abnormally low intracranial pressure, autoimmune phenomena, sleep apnea, sleeping with the pillow or one’s knuckles pressed against the eye, an abnormally hard or soft lamina cribrosa (the stack of platelike “perforated wafers” through which the optic nerve fibers pass through the eye), inherited or acquired abnormalities of the connective tissue of the lamina cribrosa, primary ganglion cell degeneration, and other as yet unconsidered possibilities.
- glaucoma, open angle
- most common glaucoma commonly caused by a blockage or malfunction of the trabecular meshwork (the “drainage” channel in the irido-corneal angle through which aqueous fluid leaves the eye), leading to elevated intraocular pressure; also may be due to a weakened lamina cribrosa, making it susceptible to even normal pressures (“low tension” glaucoma), thereby causing it to compress or pinch the optic nerve fibers passing through it, resulting in optic nerve damage or destruction; also may be due to a “pupillary block” where there is an adherence between the iris and the crystalline lens, preventing the normal flow of aqueous fluid through the pupil and causing an increase in pressure on (and subsequent damage of) the ganglion cells and axons in the retina
- glaucoma, closed angle
- narrow angle glaucoma; less common type of glaucoma in which the trabecular meshwork (the “drainage” channel in the irido-corneal angle through which aqueous fluid leaves the eye) is compromised due to the iris’ being moved forward and narrowing or blocking the irido-corneal and/or compressing the trabecular meshwork, preventing fluid from leaving the eye at a normal rate, increasing intraocular pressure, and damaging or destroying ganglion cells and axons in the retina and optic nerve; can cause intraocular pressures of 60 mm Hg or more, as well as severe eye pain, nausea, vomiting, redness, blurred vision with halos or rainbows around lights, and sudden loss of vision
- glycosaminoglycan
- mucopolysaccharide; any of various polysaccharides derived from an amino hexose that are constituents of mucoproteins, glycoproteins, and blood-group substances
- goblet cells
- mucous-secreting epithelial cells (as of columnar epithelium) located on the bulbar conjunctiva of the eye
- Graves’ disease
- a common form of hyperthyroidism characterized by a goiter (enlargement of the thyroid gland), an increased basal metabolism due to excessive thyroid secretion, and often a slight to moderate exophthalmos (protrusion of the eyeballs)
- guttata
- thickened areas in the posterior caused by abnormal production of Descemet’s collagen by the endothelial cells; has an “orange peel” or “beaten metal” appearance; associated with Fuch’s dystrophy
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