the ability of the eye to change focus from distance to near. This ability is gradually lost after age 40.
loss of, or less than the age appropropriate amount of accommodation
the accessory structures of the eye, including the eyelids, lacrimal gland, lacrimal ducts etc.
automated lamellar keratoplasty (removal of a part of the central corneal stroma) to effect a change on the refractive error
partial or total blindness
refractive condition in which parallel rays do not focus on the retina; manifestation of refractive error
often called "lazy eye" it is a condition in which the best corrected vision in one eye is poorer than 20/20 (6/6) in the absence of any obvious structural anomalies or ocular disease
a hand held chart featuring equally spaced horizontal and vertical lines, usually white on black background, used to detect central visual field defects.
a condition of unequal refracive state for the two eyes
the part of the eye anterior to the crystalline lens, including the cornea, anterior chamber, iris and ciliary body
micronutrients which destroy or neutralize free radicals, molecules which have been implicated as one causative factor in the stimulation of abnormal cellular reproduction (cancer) and cellular destruction (aging).
the absence of the eye's natural crystalline lens, usually after cataract removal.
thick, plus-powered eyeglasses that were once the standard optical correction following extraction of cataract. The glasses were cumbersome and greatly distorted peripheral vision. Today, an intraocular lens (IOL) is implanted in the eye after the cataract is removed to replace the focusing power of the natural lens eliminating the need for aphakic spectacles.
ARMD: age related macular degeneration:
degeneration of the photoreceptors in the macular (central) region of the retina resulting in decreased central vision
subjective symptoms or distress arisnig from the use of the eyes; as in eyestrain.
a refractive error caused by unequal refraction of light in different meridians, resulting in a distorted and blurred image.
Astigmatic Keratotomy (AK):
an incisional refractive surgical technique in which transverse incisions are made in the cornea to reduce or eliminate astigmatism
the simultaneous use of the two eyes. Normal binocular vision yields a stereoscopic image and depth perception
an opacity or loss of transparency of the crystalline lens which results in loss of light transmission, image degradation and reduced vision
the ability to perceive differences in color, including hue, saturation and brightness
inflammation of the conjunctiva.. May be caused by bacteria, virus, allergens or chemicals
the thin transparent membrane overlying the sclera (white part of the eye) and inside surface of the eyelid
the turning of the eyes simultaneously inwards/outwards so that they are both "aimed" towards the object being viewed
the clear front surface of the eye. The transparent "window" and primary refractive surface of the eye.
The natural lens of the eye, located behind the pupil, which helps bring rays of light to focus on the retina. The original state of the lens is transparent, but the lens becomes cloudy with age.(see cataract)
the ability of the vision system to perceive the relative positions of objects in the visual field.
a unit measurement of the degree to which light converges or diverges; Diopters are used to define of lens's refractive power. Equal to the reciprocal of the focal length of a lens (in meters), e.g., a 2-diopter lens brings parallel rays of light to a focus at half a meter.
a condition in which a single object is perceived as two; also called double vision.
refractive condition in which no refractive error is present and distant images are focused sharply on the retina with no need for corrective lenses.
the position of the eyes in an over-converged position compensated by the external eye muscles so that the eyes do not appear turned inward
the position of the eyes in an over-converged position so that non-fixating eye is turned inward
the position of the eyes in an over-diverged position compensated by the external eye muscles so that the eyes do not appear turned outward.
the position of the eyes in an over diverged position so that non-fixating eye is turned outward
Extra-ocular/external ocular muscles:
the six muscles that turn the eyes to position them appropriately for viewing objects in various fields of view
Extracapsular Cataract Extraction (ECCE): a surgical procedure which removes the cataractous lens but leaves the rear lens capsule in place.
Functional Visual Disability:
the degree to which a visual error interferes with a person's ability to perform normal daily activities, such as reading, driving at night, or performing hobbies.
characteristic optic nerve damage often associated with abnormally increased intraocular pressure and loss of visual field
loss of one half of the visual field in one or both eyes
farsightedness, long-sighted (UK): a refractive condition in which light entering the eye is focused virtually behind the retina, resulting in a blurred image..
a deficiency of oxygen supply to a tissue
Intraocular lens (IOL):
a plastic lens that is surgically implanted to replace the focusing power of the natural lens of the eye following cataract extraction. There are numerous styles of IOLs, including foldable IOLs and multifocal IOLs.
the internal fluid pressure within the eye created by the continual production and drainage of aqueous fluid in the anterior chamber.
pigmented tissue that lies behind the cornea that gives color to the eye (e.g., blue eyes) and controls the amount of light entering the eye by varying the size of the black pupillary opening.
inflammation of the cornea
Laser assisted in situ keratomileusis (LASIK): laser assisted in situ keratomileusis, or LASIK, combines excimer laser PRK with elements of ALK used to reduce refractive error
a collection of fluid in and under the macular portion of the retina
Nearsightedness, short-sighted (UK): a refractive condition in which light entering the eye is focused short of the retina, resulting in a blurred image
the formation of new blood vessels, often fragile and inappropriate for the location
a rapid, repetative, involuntary movement or rotaion of the eyes
a physician specializing in medical, and surgical treatment of eye diseases and disorders
a condition of inflamation of the optic nerve
a physician who treats refractive errors and eye diseases.
examination of the internal structures of the eye using an illumination and magnification system.(ophthalmoscope)
a non-surgical procedure using contact lenses to alter the shape of the cornea to effect a change in the refractive error
non-inflammatory swelling/elevation of the optic nerve due to increased intracranial pressure
Phacoemulsificatiion (fay-koh-ee-mul-sih-fih-KAY-shun): a form of extracapsular cataract extraction in which an ultrasonic instrument is used to shatter and break up a cataract, making it easier to remove.
sensitivity to light
a technique employing an excimer laser to reshape the surface of the cornea and thereby reducing nearsightedness.
a (usually) irritation caused by degeneration of the conjunctiva resulting in a thickening and yellowing of the normally thin transparent tissue
Posterior Capsular Opacification (PCO):
opacification of the posterior lens capsule following cataract extraction. Sometimes called "after cataract," and may cause blurred vision.
the part of the eye posterior (behind) to the crystalline lens, including the vitreous, choroid, retina and optic nerve
Posterior Vitreous Detachment (PVD):
the separation of the vitreous body from it1s attachment from the retinal surface due to shrinkage from age, degenerative or inflammatory conditions or trauma.
loss of accommodative ability as the eye fails to allow for the focusing of near objects, resulting from age-related changes in the crystalline lens or cilliary muscle
an optical element which deviates the path of light
drooping of the upper or lower eyelid from it's normal postion
the center hole in the iris through which light must pass to reach the back of the eye.
the constriction and dilation of the pupil due to stimulation by light or accommodation
Radial keratotomy (RK):
a surgical procedure using diamond scalpel blades to create linear incisions into the cornea which result in the flattening of the tissue and thereby altering the refractive error
a determination of the optical error of the eye
the degree to which images received by the eyes are not focused on the retina, e.g.: myopia, hyperopia, astigmatism
the thin neurological tissue which lines the back wall of the eye which receives light and converts it to electrical signals for transmission via the optic nerve to the brain
a separation of the retina from the back wall of the eye. Results in loss of vision in the detached area. Repairable with fair to good prognosis for vision in the early stages.
an area of partial or complete loss of vision surrounded by an area of normal vision
the condition in which binocular fixation is not present; commoly referred to as "cross eyed"
the ability to perceive three dimensional depth
the inability to perceive all of part of objects in the field of vision of one eye
a procedure for the measurement of intraocular pressure
radiant energy with a wavelength just below that of the visible light. UV-c is the shortest wavelength at 200-280nm and is absorbed by the atmosphere before reaching the surface. Extremely damaging to living tissue. UV-b, a t 280-315nm is "burning rays" of the sun and is damaging to most living tissue. UV-a, at 315-400nm are "tanning rays" of the sun and is somewhat damaging to certain tissues. UV radiation has been described as a contributing factor to the processes which result in ARMD and cataracts.
(orthopedics, vision training, eye exercises) a treatment process for the improvement of visual perception and/or coordination of the two eyes for efficient and comfortable binocular vision
a measure of spatial resolution. the measure of the abiltiy to visually discriminate
the area or extent of space visible to an eye in a given position of gaze
the gel-like transparent fluid substance filling the posterior four fifths of the globe between the crystalline lens and retina
the YAG laser is an instrument that emits a short pulsed, high energy light beam that can be precisely focused to cut, vaporize, or fragment tissue.
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