| Albinism |
People
with albinism have absent or reduced pigment in their eyes, skin or hair.
They have inherited genes that do not make the usual amounts of a pigment
called melanin which is essential for the full development of the retina.
Lack of melanin in development of the retina is the primary cause of visual
impairment in albinism. |
| Aniridia |
A hereditary
eye problem in which the iris, the colored part of the eye, is absent. There
is poor vision, sensitivity to sunlight, nystagmus, and a tendency to develop
glaucoma. |
| Aphakia |
Absence
of the lens, usually because of cataract extraction. |
| Aqueous |
A clear
watery fluid that fills the space between the cornea and the vitreous. It
is responsible for nourishing the cornea, iris, lens and maintaining the
intraocular pressure. |
| Canal
of Schlemm |
Responsible
for moving the aqueous from the front chamber in the eye through aqueous
veins into the bloodstream. |
| Cataracts |
A condition
of the crystalline lens, in which the normally clear lens becomes clouded
or yellowed, causing blurred or foggy vision. Cataracts may be caused by
aging, eye injuries, disease, heredity, or birth defects. |
| Chorioretinitis |
An inflammation
of the back of the eye involving the choroid and retina. It may be due to
a number of different diseases, which affect the body such as toxoplasmosis,
histoplasmosis, sarcoidosis, tuberculosis and syphilis. |
| Choroid |
A layer
of the eye found between the retina and the sclera. It contains major blood
vessels and provides nourishment to the outer layers of the retina. |
| Ciliary
Body |
Made up
of ciliary muscle which helps the accomodation of the lens and controls
the intraocular pressure of the eye. It is also where the aqueous is made. |
| Coloboma |
A congenital
problem with the eye that is related to a maldevelopment or underdevelopment
of a part of the eye. It may involve the eyelid, or interior part of the
eye (involving the choroid and occasionally the optic nerve). |
| Cones |
Light sensitive
receptor cells mostly found in the central part of the retina. It is responsible
for sharp visual acuity and the discrimination of color. |
| Conjunctiva |
A transparent
mucous membrane the covers the outer surface of the eyeball except the cornea.
It also lines the inner surface of the eyelid. |
| Cornea |
The clear
cone over the front part of the eye. It is is responsible for most of the
eyes optical power. |
| Cortical
Visual Impairment(CVI) |
A temporary
or permanent visual impairment caused by the disturbance of the posterior
visual pathways and/or the occipital lobes of the brain. The degree of vision
impairment can range from severe visual impairment to total blindness. The
degree of neurological damage and visual impairment depends upon the time
of onset, as well as the location and intensity of the insult. It is a condition
that indicates that the visual systems of the brain do not consistently
understand or interpret what the eyes see. |
| Field
of Vision |
The entire
area that can be seen without shifting the head or the eyes, including central
and peripheral fields. |
| Fovea |
Located
in the center of the macula. It provides the sharpest vision. |
| Glaucoma |
A symptomatic
condition characterized by raised intra-ocular pressure, visual field loss,
enlargement of the blind spot and changes in the appearance of the optic
nerve head. If left untreated ganglion cell axon death may be caused by
prolonged exposure of the eye to elevated introcular pressure. |
| Hemianopia |
A loss
of one-half of the field of vision; for example, all of the right side of
vision is gone. This is sometimes seen in older people with vascular problems,
in certain types of brain tumors or after head trauma. |
| Hyperopia |
Also known
as Farsightedness. This results from varying-shaped eyeballs that cause
light to focus in front of the retina. |
| Iris |
A colored
circular muscle that gives us the color of our eyes. It is responsible for
controlling the amount of light that gets into the eye. |
| Leber's
Amaurosis |
A severe
form of rod-cone degeneration present at birth. Infant's have very poor
visual acuity, photophobia and nystagmus. Infant's with Leber's will often
constantly rub their eyes with their fists and poke their eyes with their
fingers and thumb. |
| Lens |
Responsible
for bringing rays of light into focus on the retina. It is a clear oval
structure suspended behind the iris which can contract and expand as needed
to provide additional focusing power. |
| Macula |
A small
central area of the retina responsible for fine central visual acuity. |
| Myopia |
Also known
as Nearsightedness. This results from varying-shaped eyeballs that cause
light to focus behind the retina. |
| Optic
Giloma |
Inflammation
of the optic nerve; can produce a sudden, but reversible, loss of sight.
|
| Optic
Nerve |
Carries
the light impulses for sight from the retina to the brain. |
| Optic
Nerve Atrophy |
is
a permanent visual impairment caused by damage to the optic nerve |
| Optic
Nerve Hypoplasia |
Refers
to underdevelopment of the optic nerve during pregnancy |
| Retina |
The innermost
layer of the eye, a neurological tissue, which receives light rays focused
on it by the lens. This tissue contains receptor cells (rods and cones)
that send electrical impulses to the brain via the optic nerve when the
light rays are present. |
| Retinal
Detachment |
The separation
of the sensory layer from the pigment layer of the retina. |
| Retinitis
Pigementosa |
A disease
of the photoreceptors, frequently inherited, which at its most advanced
stage allows only a tiny island of central vision. |
| Retinoblastoma |
The most
common cancer in the eye occurring in early childhood. A parent or doctor
may first suspect a problem by detecting whiteness in the normally dark
pupil. Occasionally it leads to a wandering eye (strabismus). It does not
spread from one eye to the other but about 25% have a tumor in each eye.
Immediate medical treatment is necessary. Sometimes the eye(s) must be removed
to prevent spreading of the tumor into the brain. |
| Retinopathy
of Premturity (ROP) |
An eye
disorder affecting premature infants. This disorder was called Retrolental
Fibroplasia in the past. ROP affects immature blood vessels of the retina.
It occurs weeks after birth. Once development of blood vessels is complete,
a child is no longer a candidate for this disorder. |
| Rods |
Light sensitive
receptor cells mostly found in the peripheral part of the retina. They are
responsible for night vision. |
| Sclera |
The protective
outer layer of the eye. |
| Visual
Acuity |
The ability
to discern fine detail. |
| Vitreous |
A clear
jello-like substance between the lens and the retina that provides the structural
support to the eye. |
