COLOR BLINDNESS
The inability to clearly tell one color from another. Color information is conveyed by the cone cells in the retina. Color blindness is a condition in which the cone cells are not being stimulated properly. Some people with color blindness cannot see color at all, seeing everything as gray. Others seecolor but cannot differentiate between certain hues. Very few people are color blind to the color blue.
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CONES, CONE CELLS
One type of specialized light-sensitive
cells (photoreceptors) in the retina that
provide sharp central vision and color
vision.
Also see RODS.
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CONJUNCTIVA (KAHN-junk-TY-vuh)
The thin, moist tissue (membrane) that
lines the inner surfaces of the eyelids
and the outer surface of the sclera.
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CONJUNCTIVITIS (KAHN-junk-ti-VY-tis)
An inflammation of the Conjunctiva.
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CONTRAST
SENSITIVITY
The ability to perceive differences
between an object and its background.
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CORNEA (KOR-nee-uh)
See the cornea!
The outer, transparent, dome-like
structure that covers the iris,
pupil,
and anterior chamber; part of eye's
focusing system.
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DILATION
A process by which the pupil is
temporarily enlarged with special eye
drops (mydriatic); allows the eye care
specialist to better view the inside of
the eye.
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DRUSEN
Tiny yellow or white deposits in the
retina or optic nerve head.
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ESOPHORIA
A condition in which one eye involuntarily turns inward toward the other when the eyes are not focused on an object.
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ESOTROPIA
An internal strabismus in which one eye deviates inward in relation to the other.
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EXOPHORIA
A condition in which one eye involuntarily turns outward when at rest.
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EXOTROPIA
An external strabismus in which one eye deviates outward in relation to the other.
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FLOATERS
One or more spots that appear to drift in front of the eye. Floaters are made by the shadow cast on the retina of material within the eyeball.
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FOVEA (FOH-vee-uh)
The central part of the macula that
provides the sharpest vision.
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FUNDUS
The interior lining of the eyeball,
including the retina, optic disc, and
macula; portion of the inner eye that
can be seen during an eye
examination by looking through the
pupil.
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GLAUCOMA
Disease of the eye, marked by a mechanical increase in
intraocular pressure causing organic changes in the
optic nerve and defects in the
visual field.
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HYPEROPIA (hy-pur-OH-pee-uh)
Farsightedness; ability to see distant
objects more clearly than close
objects; may be corrected with glasses
or contact lenses.
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INTRAOCULAR PRESSURE (IOP)
Pressure of the fluid inside the eye;
normal IOP varies among individuals.
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IRIS
See the iris!
The colored ring of tissue suspended
behind the cornea and immediately in
front of the lens; regulates the amount
of light entering the eye by adjusting
the size of the pupil.
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LACRIMAL GLAND
(LAK-rih-mul)
The small almond-shaped structure
that produces tears; located just above
the outer corner of the eye.
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LEGAL BLINDNESS
In the U.S.,
(1) visual acuity of 20/200
or worse in the better eye with
corrective lenses (20/200 means that a
person must be at 20 feet from an eye
chart to see what a person with normal
vision can see at 200 feet) or...
(2)
visual field restricted to 20 degrees
diameter or less (tunnel vision) in the
better eye.
NOTE: These criteria are
used to determine eligibility for
government disability benefits and do
not necessarily indicate a person's
ability to function.
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LENS
See the lens!
The transparent, double convex
(outward curve on both sides)
structure suspended between the
aqueous and vitreous;
helps to focus
light on the retina.
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LOW VISION
Visual loss that cannot be corrected
with eyeglasses or contact lenses and
interferes with daily living activities.
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MACULA (MAK-yoo-luh)
See the macula!
The small, sensitive area of the
central retina; provides vision for fine
work and reading.
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MYOPIA (my-OH-pee-uh)
Nearsightedness; ability to see close
objects more clearly than distant
objects; may be corrected with glasses
or contact lenses.
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NIGHT BLINDNESS
Poor vision at night or in dim light. Causes of this include
Retinitis Pigmentosa, and a lack of Vitamin A.
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OPTIC CUP
The white, cup-like area in the center
of the optic disc.
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OPTIC DISC / OPTIC NERVE HEAD
The circular area (disc) where the
optic nerve connects to the retina.
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OPTIC NERVE
See the optic nerve!
The bundle of over one million nerve
fibers that carry visual messages from
the retina to the brain.
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PERIPHERAL VISION (per-IF-ur-al)
Side vision; ability to see objects and
movement outside of the direct line of
vision.
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POSTERIOR CHAMBER
The space between the back of the iris
and the front face of the vitreous; filled
with aqueous fluid.
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PRESBYOPIA (prez-bee-OH-pee-uh)
The gradual loss of the eye's ability to
change focus (accommodation) for
seeing near objects caused by the
lens becoming less elastic; associated
with aging; occurs in almost all people
over age 45.
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PUPIL
See the pupil!
The adjustable opening at the center
of the iris that allows varying amounts
of light to enter the eye.
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REFRACTION
A test to determine the best
eyeglasses or contact lenses to
correct a refractive error (myopia,
hyperopia, or
astigmatism).
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RETINA (RET-in-nuh)
See the retina!
The light-sensitive layer of tissue that
lines the back of the eyeball; sends
visual messages through the optic
nerve to the brain.
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RETINITIS (ret-i-NI-tis)
An inflammation of the retina.
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RETINITIS PIGMENTOSA (ret-i-NI-tis pig-men-TO-sa)
A form of hereditary degeneration of the retina which
begins as night blindness, but which produces a gradual loss of vision which may be complete.
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RETINAL PIGMENT EPITHELIUM (RPE) (ep-ih-THEE-lee-um)
The pigment cell layer that nourishes
the retinal cells; located just outside
the retina and attached to the
choroid.
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RODS, ROD CELLS
One type of specialized light-sensitive
cells (photoreceptors) in the retina that
provide peripheral vision and the ability to
see objects in dim light (night vision).
Also see CONES.
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SCHLEMM'S CANAL
The passageway for the aqueous fluid
to leave the eye.
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SCLERA (SKLEH-ruh)
The tough, white, outer layer (coat) of
the eyeball; with the cornea, it protects
the entire eyeball.
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STRABISMUS
An abnormal condition in which the eyes do not move together or are "crossed".
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TRABECULAR MESHWORK (truh-BEC-yoo-lur)
The spongy, mesh-like tissue near the
front of the eye that allows the
aqueous fluid (humor) to flow to
Schlemm's canal then out of the eye
through ocular veins.
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UVEA, UVEAL TRACT (YOO-vee-uh)
The middle coat of the eyeball,
consisting of the choroid in the back of
the eye and the ciliary body and iris in
the front of the eye.
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VISUAL ACUITY
The ability to distinguish details and
shapes of objects; also called central
vision.
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VISUAL FIELD
The entire area that can be seen when
the eye is forward, including
peripheral vision.
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VITREOUS (VIT-ree-us)
See the vitreous!
The transparent, colorless mass of gel
that lies behind lens and in front of
retina.
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ZONULES (ZAHN-yoolz)
The fibers that hold the lens
suspended in position and enable it to
change shape during accommodation.
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