The following are health and medical definitions of terms that appear in the Color Blindness article.
Achromatopsia: An hereditary disorder of sight due to a lack of cone vision - that type of vision provided by the cone photoreceptors in the retina. In the normal eye, there are some 6 million cone photoreceptors; they are located largely in the center of the retina. Lacking cones, persons with achromatopsia have to rely on their rod photoreceptors. There are about 100 million rod photoreceptors which are located mainly around the periphery of the retina. Rods saturate at higher levels of illumination and do not provide color vision or good detail vision. See the entire definition of Achromatopsia
Blindness: Loss of useful sight. Blindness can be temporary or permanent. Damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. There are numerous (actually, innumerable) causes of blindness. The current politically correct terms for blindness include visually handicapped and visually challenged.
Colorblindness: The inability to perceive colors in a normal fashion. The most common forms of colorblindness are inherited as sex-linked (X-linked) recessive traits. Females are carriers and males are affected. As a result, approximately 1 in 8 males is colorblind as compared to less than 1 in 100 females. See the entire definition of Colorblindness
Cone: A type of specialized light-sensitive cell (photoreceptor) in the retina of the eye that provide sharp central vision and color vision. See the entire definition of Cone
Genetic: Having to do with genes and genetic information.
Lens: The transparent structure inside the eye that focuses light rays onto the retina (the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain). The lens was named after the lentil bean because it resembled it in shape and size. See the entire definition of Lens
Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another. See: Nervous system.
Pigment: A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.
Red-green colorblindness: A form of colorblindness in which red and green are perceived as identical. This is the most common type of colorblindness. It is inherited in an X-linked recessive manner and affects 6% of males. It is also known as deutan colorblindness, deuteranopia, and Daltonism. See the entire definition of Red-green colorblindness
Retina: The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. There is a small area, called the macula, in the retina that contains special light-sensitive cells. The macula allows us to see fine details clearly. See the entire definition of Retina
Retinal: Pertaining to the retina, the extraordinary layer of neurons (nerve cells) that line the back of the eye, which can sense light and create impulses capable of voyaging through the optic nerve to the brain where the impulses are recognized as an image. See the entire definition of Retinal
Genetic disease is a disorder or condition caused by abnormalities in a person's genome. Types of genetic inheritance include single inheritance (for example, cystic fibrosis, sickle cell anemia, Marfan syndrome, and hemochromatosis), multifactoral inheritance, chromosome abnormalities (for example, Turner syndrome, and Klinefelter syndrome), and mitochondrial inheritance (for example, epilepsy and dementia).
Blindness is the state of being sightless. Causes of blindness include macular degeneration, stroke, cataract, glaucoma, infection and trauma. Symptoms and signs may include eye pain, eye discharge, or the cornea or pupil turning white. Treatment of blindness depends upon the cause of the blindness.
Blindness is defined as the state of being sightless. A blind individual is
unable to see. In a strict sense the word blindness denotes the condition of
total blackness of vision with the inability of a person to distinguish darkness
from bright light in either eye. The terms blind and blindness have been
modified in our society to include a wide range of visual impairment. Blindness
is frequently used today to describe severe visual decline in one or both eyes
with maintenance of some residual vision.
Vision impairment, or low vision, means that even with eyeglasses, contact
lenses, medicine or surgery, you don't see well. Vision impairment can range
from mild to severe. Worldwide, between 300 million and 400 million people are
visually impaired due to various causes. Of this group, approximately 50 million
people are totally blind. Approximately 80% of blindness occurs in people over 50 years old
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