C

Glossary

age-related macular degeneration (AMD)—A degenerative eye disease that causes damage to the macula. “Dry” AMD is caused by the breakdown of light-sensitive cells in the macula, where as neovascular or “wet” AMD is caused by fluid leaking from abnormal vessels under the retina, leading to blurred vision, dark areas or distortion in central field of vision, and loss of central vision (NEI, 2015a).

amblyopia—A neurological disorder in children, also referred to as “lazy eye,” in which reduced vision in one or both eye occurs due to abnormal interaction or lack of a clear image (Barrett et al., 2013; Pascual et al., 2014).

anti-VEGF injection—“Anti-VEGF drugs are injected into the vitreous to block a protein called vascular endothelial growth factor (VEGF), which can stimulate abnormal blood vessels to grow and leak fluid. Blocking VEGF can reverse abnormal blood vessel growth and decrease fluid in the retina” (NEI, 2015d).

aphakia—The absence of the lens due to surgical removal, a wound or ulcer, or congenital anomaly (Anjum et al., 2010).

aqueous humor—“An optically clear, slightly alkaline liquid that occupies the anterior and posterior chambers of the eye. The aqueous humor . . . provides nutrients [and] oxygen to eye tissues that lack a direct blood supply . . . and removes their waste products. In addition, it provides an internal

pressure, known as intraocular pressure, that keeps the eyeball properly formed” (Albert and Gamm, 2007).

aqueous shunt—A device that is used to reduce the intraocular pressure by draining the fluid from inside the eye to a small bleb behind the eyelid (Minckler et al., 2006).

astigmatism—A common refractive error that causes blurred or stretched vision. “An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others.” As a result, the light is not refracted properly onto the retina and near and far vision become blurry (NEI, 2010c).

atropine—A topical medication used to induce dilation of the pupils to block the response to light and paralyze the accommodative reflex (Walsh and Hoyt, 2005, p. 770).

blind spot—“A zone of functional blindness all normally sighted people have in each eye, due to an absence of photoreceptors where the optic nerve passes through the surface of the retina” (Miller et al., 2015).

blindness—Total loss of sight (i.e., no light perception) (see Chapter 1).

cataract—Clouding or discoloration of the lens caused by the clumping of proteins (NEI, 2010f). Over time the cataracts may grow denser and cloud more of the lens, making it more difficult to see. Infants may be born with cataracts.

choroid—A primarily vascular structure lying between the sclera with the outer retina. Impairment of the flow of oxygen from choroid to retina may cause age-related macular degeneration (Nickla and Wallman, 2010).

chronic vision impairment—A vision impairment that is present and must be managed over the lifespan to maintain the activities of daily living (see Chapter 1).

color blindness—A defect in the perception of colors caused by genes that affect the sensitivity or loss of photo pigments found in cones. There are “three main kinds of color blindness, based on photo pigment defects in the three different kinds of cones that respond to blue, green, and red light. Red-green color blindness is the most common, followed by blue-yellow color blindness. A complete absence of color vision—total color blindness—is rare. Sometimes color blindness can be caused by physical or chemical

damage to the eye, the optic nerve, or parts of the brain that process color information. Color vision can also decline with age, most often because of cataract” (NEI, 2015c).

community health needs assessment (CHNA)—Legislation imposed on all not-for-profit hospitals requiring such hospitals explicitly and publicly demonstrate community benefit by conducting a CHNA and adopting an implementation strategy to meet identified health needs, in order to maintain their tax-exempt status. This must be conducted every 3 years, with tax penalties imposed on hospitals that fail to comply (NICHSR, 2016).

comprehensive eye examination—A dilated eye examination that may include a series of assessments and procedures to evaluate the eyes and visual system, assess eye and vision health and related systemic health conditions, characterize the impact of disease or abnormal conditions on the function and status of the visual system, and provide treatment and follow-up options (see Chapter 1).

conjunctiva—“The mucous membrane that covers the front of the eye and the inside of the eyelids” (NEI, 2016b).

conjunctivitis—Also known as pink eye, the inflammation or infections of the conjunctiva, which lines the eyelid and covers the white part of the eyeball (NEI, 2015f).

contrast sensitivity—A measure of visual function related to how one sees objects that may not be outlined clearly or that do not stand out from their background. Contrast sensitivity is affected by situations “of low light, fog or glare, when the contrast between objects and their background often is reduced. Driving at night is an example of an activity that requires good contrast sensitivity for safety” (Heiting, 2016).

cornea—The transparent layer forming the front of the eye. It lies in front of the pupil, iris, and anterior chamber and its main function is to refract, or bend, light. The cornea shields the eye from germs, dust, and other harmful matter (UMN Eye Center, n.d.). The cornea is made up of cells and proteins and “unlike most tissues in the body . . . contains no blood vessels to nourish or protect it against infection. Instead, the cornea receives its nourishment from the tears and aqueous humor that fills the chamber behind it” (UMN Eye Center, n.d.).

corrective lens—A lens worn in front of the eye, usually to correct a refractive error. Examples of corrective lenses include glasses (which include lenses and frames) and contact lenses (see Chapter 1).

depth perception—Also known as binocular stereopsis, “the ability to perceive depth by combining images from the two eyes” (NEI, n.d.c).

diabetic retinopathy and diabetic macular edema—Two complications of diabetes that affect the eyes. Diabetic retinopathy is caused by damage to the blood vessels of the retina that leak fluid and/or hemorrhage and is progressive with diabetic macular edema leading to a build-up of fluid in the macula (NEI, 2015d). New blood vessels may also form either within the retina. Symptoms include seeing “floating” spots, blurred vision, and permanent vision loss (NEI, 2015d).

double vision—“A condition that causes people to see two images of an object. A variety of conditions cause diplopia, including strabismus, cranial nerve palsies, multiple sclerosis, myasthenia gravis, orbital injury, stroke, and intracranial tumor” (NEI, 2010h).

drusen—“Yellow deposits under the retina. Often found in people over age 60, drusen can be seen by an eye care professional during an eye exam in which the pupils are dilated. Drusen by themselves do not usually cause vision loss, but an increase in their size and/or number increases a person’s risk of developing advanced AMD, which can cause serious vision loss” (NEI, 2001).

dry eye—“Dry eye occurs when the eye does not produce tears properly, or when the tears are not of the correct consistency and evaporate too quickly. In addition, inflammation of the surface of the eye may occur along with dry eye. If left untreated, this condition can lead to pain, ulcers, or scars on the cornea, and some loss of vision. However, permanent loss of vision from dry eye is uncommon. Dry eye can make it more difficult to perform some activities, such as using a computer or reading for an extended period of time, and it can decrease tolerance for dry environments, such as the air inside an airplane” (NEI, 2013b).

endophthalmitis—“[A] severe inflammation inside the eye caused by a bacterial or fungal infection. It is a rare complication of eye surgery, trauma, eye injections or bloodstream infections” (NEI, 2010f). Endophthalmitis can be caused by a preexisting infection in the bloodstream, or by a new infection originating from outside the body (CDC, 2015a).

eye and vision health—Creating the conditions where people can have the fullest capacity to see and that enable them to achieve their full potential (see Chapter 1).

eyestrain—Also known as asthenopia, eyestrain is a “condition arising from the efforts made by individuals to keep their eyes adjusted for seeing, . . . with emphasis on fixation, convergence, and control of the size of the pupil. . . . Discomfort [is] found to increase as the day progresses, being accompanied by the appearance of headache and fatigue, without refractive errors or changes in amplitude of accommodation, pupil size, phorias and fusional capacity” (NIOSH, 2015).

federally qualified health center (FQHC)—FQHCs are outpatient centers that are “receiving grants under Section 330 of the Public Health Service Act (PHS). FQHCs qualify for enhanced reimbursement from Medicare and Medicaid, as well as other benefits. FQHCs must serve an underserved area or population, offer a sliding fee scale, provide comprehensive services, have an ongoing quality assurance program, and have a governing board of directors” (HRSA, n.d.b).

fovea—Located at the center of the macula, the fovea is a small depression that contains the highest concentration of cones. These cones provide the sharpest daytime vision (NEI, 2009a).

functional vision loss—“A decrease in visual acuity or loss of visual field with no underlying physiologic or organic basis” (Chen and Chen, 2013).

glaucoma (open angle)—Loss of nerve tissue and axons in the optic nerve associated with elevated intraocular pressure above the level that the eye can tolerate, although normotensive glaucoma occurs in patients without elevated intraocular pressure (NEI, n.d.a).

halos—Circles appearing around lights (CDC, 2016). Halos are a common symptom of cataract (NEI, 2015b).

health impact assessment (HIA)—A “structured process that uses scientific data, professional expertise, and stakeholder input to identify and evaluate public-health consequences of proposals and suggests actions that could be taken to minimize adverse health impacts and optimize beneficial ones” (NRC, 2011, p. 3).

health literacy—The degree to which individuals have the capacity to obtain, process, and understand basic health information and services needed to make appropriate health decisions (see Chapter 4).

health professional shortage area—An area designated “by the HRSA as having shortages of primary medical care, dental or mental health providers. The area may be geographic (a county or service area), demographic (low income population) or institutional (comprehensive health center, federally qualified health center or other public facility)” (HRSA, n.d.a).

health risk assessment (HRA)—“A collection of health-related data a medical provider can use to evaluate the health status and the health risk of an individual. An HRA will identify health behaviors and risk factors known only to the patient (e.g., smoking, physical activity and nutritional habits) for which the medical provider can provide tailored feedback in an approach to reduce the risk factors as well as the potential inevitability of the disease to which they are related” (Staley et al., 2011, p. 2).

hyperopia—“Also known as farsightedness, [hyperopia] is a common type of refractive error where distant objects may be seen more clearly than objects that are near . . . it develops in eyes that focus images behind the retina instead of on the retina, which can result in blurred vision. This occurs when the eyeball is too short” (NEI, n.d.b).

intraocular lens (IOL)—A clear, plastic, artificial lens that often replaces the cloudy natural lens after cataract surgery. The IOL focuses light clearly, creating good vision (NEI, 2010a).

iris—“The colored part of the eye. It is located between the cornea and lens. The round, central opening of the iris is called the pupil. Very small muscles in the iris cause the pupil to get smaller and bigger to control how much light comes into the eye” (NLM, 2015a).

keratitis—“Inflammation of the cornea. . . . Infection is the most common cause of keratitis” (NEI, 2016b). Keratitis can be caused by infectious agents (bacteria, viruses, fungi, or parasites) or by noninfectious means (minor injury, wearing contact lenses too long) (NEI, 2016b).

keratoconjunctivitis—Inflammation of the cornea and conjunctiva (NEI, 2010g).

laser photocoagulation—A surgical technique that uses a laser to coagulate tissue. Laser photocoagulation is used primarily to treat retinopathy (NLM, 2016; Santos, 2015).

laser trabeculoplasty—The application of a laser surgery to burn areas of the trabecular meshwork, located near the base of the iris, to drain fluid (NEI, n.d.a). Laser trabeculoplasty is often used in the treatment of open-angle glaucoma.

legal blindness—A definition used by governments to determine eligibility for vocational training, rehabilitation, schooling, disability benefits, low vision devices, and tax exemption programs. Visual acuity of 20/200 or less in the better eye with the best possible correction and/or a visual field of 20 degrees or less (Social Security Act § 216(i)(1)(B)).

lens of eye—A structure that “focuses light rays onto the retina. The lens is transparent, and can be replaced if necessary. [The] lens deteriorates [with] age” (University of Michigan, 2015).

macula—A structure “made up of millions of light-sensing cells that provide sharp, central vision. It is the most sensitive part of the retina, which is located at the back of the eye” (NEI, 2015a).

macular edema—Swelling and thickening of the retina due to leaking of fluid from blood vessels within the macula. It can occur from damaged blood vessels in the nearby retina from diabetic retinopathy, after eye surgery, in association with age-related macular degeneration, or as a consequence of any inflammatory disease that affects the eye (NEI, 2015e).

myopia—“Also known as near sightedness, is a common type of refractive error where close objects appear clearly, but distant objects appear blurry. . . . In a myopic eye, the eyeball is usually too long from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. This makes distant objects blurry” (NEI, 2016a).

night vision—“The ability to see in the dark” (Merriam-Webster, n.d.). Problems with night vision may be associated with cataracts, nearsightedness, drug use, birth defects, and retinis pigmentosa (NLM, 2014b).

onchocerciasis—Also known as African river blindness, a tropical skin disease caused by a parasitic worm, transmitted by the bite of black-flies that breed in fast-flowing rivers. The infection can cause blindness.

Onchocerciasis is the second most common cause of infectious blindness in the world (CDC, 2015b).

optic disk—A disk at the back of the eye where the optic nerve fibers connect the eye and the brain (NEI, n.d.d).

optic nerve—“The bundle of nerve fibers that connects the eye to the brain” (NEI, 2015d).

orthoptics or vision therapy—A program of eye exercises designed to help people with amblyopia, strabismus, eye teaming and fusion problems (Nash, 2013, pp. 385–389).

patching—Eye patching is used to cover the better-seeing eye in young patients with amblyopia to improve vision in the weaker eye (NEI, 2013a).

peripheral vision—Side vision; what is seen on the side by the eye when looking straight ahead (NEI, n.d.a).

presbyopia—A condition resulting in the inability to focus up close. “The eye is not able to focus light directly onto the retina due to the hardening of the natural lens” (NEI, 2010d).

pseudophakia—An eye in which the natural lens has been removed and an artificial intraocular lens has been implanted, usually after cataract surgery (NEI, 2010b).

refractive error—Irregular shape of cornea, lens, or eyeball prevents light from focusing properly on the retina, causing blurred vision (NEI, 2010i). “The most common types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism” (NEI, 2010e).

retina—A structure that “detects light and converts it to signals sent through the optic nerve to the brain” (NEI, 2015d).

retinal detachment—An injury of the eye in which the retina “is lifted or pulled from its normal position” (NEI, 2009b). The three types of retinal detachment are rhegmatogenous, tractional, and exudative. Retinal detachment can result in permanent vision loss if not treated promptly (NEI, 2009b).

sclera—“The white outer coating of the eye. It is tough, fibrous tissue that extends from the cornea (the clear front section of the eye) to the optic

nerve at the back of the eye. The sclera gives the eyeball its white color” (NLM, 2015b).

strabismus—A condition in which there is a misalignment of the eyes, such that one eye constantly or intermittently turns in (esotropia), out (exotropia), up, or down as the other eye looks straight ahead (Hatt and Gnanaraj, 2013).

trabeculectomy—A surgical procedure used to treat the intraocular pressure associated with glaucoma. During a trabeculectomy “a small piece of tissue is removed to create a new channel for the fluid to drain from the eye. This fluid will drain between the eye tissues layers and create a blister-like filtration bleb” (NEI, n.d.a).

trachoma—“An eye infection that is more common in the rural areas of developing countries. The bacteria Chlamydia trachomatis causes trachoma. People can spread the bacteria by touching infected clothing or skin. Repeated trachoma infections can cause scars inside the eyelids. The scar tissue inside the eyelids causes the eyelashes turn in—a condition known as trichiasis. This causes the lashes to constantly rub and irritate the cornea. This can eventually lead to severe vision loss and blindness. If antibiotics are used early to clear up the infection, it can prevent long-term damage” (NLM, 2011).

traumatic brain injury (TBI)—“A form of acquired brain injury [that] occurs when a sudden trauma causes damage to the brain” (NINDS, 2016).

uveitis—“A group of inflammatory diseases that produces swelling and destroys eye tissue. These diseases can slightly reduce vision or lead to severe vision loss. . . . Uveitis is not limited to the uvea. These diseases also affect the lens, retina, optic nerve, and vitreous, producing reduced vision or blindness” (NEI, 2011).

vision impairment—A measure of the type and severity of clinical or functional limitation of one or both eyes or visual information processing structures in the brain (see Chapter 1).

vision loss—The process by which physiological changes or structural, neurological, or acquired damage to the structure or function of one or both eyes or visual information processing structures in the brain occurs, resulting in vision impairment (see Chapter 1).

vision rehabilitation—A medical rehabilitation aimed at restoring functional ability, independence and quality of life in an individual who has lost visual function through illness or injury (see Chapter 7).

vision screening—A tool that allows for the possible identification, but not diagnosis, of eye disease (see Chapter 1).

visual acuity—A number that indicates the sharpness or clarity of vision, measured by the ability to discern objects at a given distance according to a fixed standard (see Chapter 1).

visual field—The total area an individual can see off to the side without moving the eye (see Chapter 1).

visual fixation—Maintaining a visual gaze on an object (Martinez-Conde et al., 2004).

vitrectomy—“The surgical removal of the vitreous gel in the center of the eye. . . . A clear salt solution is gently pumped into the eye . . . to maintain eye pressure during surgery and to replace the removed vitreous” (NEI, 2015d).

vitreous body—The clear colorless transparent jelly that fills the eyeball behind the lens and in front of the retina at the back of the eye. The vitreous body consists mostly of water and remains stagnant (NEI, 2009c).

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