|
| | |
Cone
Cone One of the two light receiving retinal cells (the other is the rod) that is responsible for daylight vision (e.g., color vision, high visual acuity, bright light vision). The area of the retina that provides central or reading vision, known as the fovea, contains only cones.
RELATED TERMS--------------------------------------
Retinal
Light-absorbing portion of rhodopsin. The absorption of light causes retinal to change from 11-cis to 11-trans configuration
Vision
The sense of sight.
Acuity
The highest spatial frequency rsolvable with a grating of unity contrast (i.e. the maximum possibly contrast).
Retina
A membrane lining the inside of the back of the eye that contains light-sensitive nerve cells that convert focused light into nerve impulses, making vision possible.
Central
In anatomy and medicine (as elsewhere), central is the opposite of "peripheral" which means away from the center.
Fovea
A central portion of the retina and macula that contains only cones. The fovea is the only part of the eye that is capable of 20/20 or better vision.
SIMILAR TERMS--------------------------------------
PREVIOUS AND NEXT TERMS--------------------------------------
Choroideremia
Atrophy or decay of the choroid, choriocapillaris and Bruch’s membrane of the eye, leading to a severe loss of vision. Usually progresses to light perception by 50 years of age. Leads to night blindness tunnel vision and reduced visual acuity. No treatment available.
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
This is the vascular coat between the sclera and the retina, which furnishes blood and nutrition to the outer layer of the retina.
Choroiditis
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.
Coloboma
A congenital (born with) 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). No treatment is available.
Cone
Cone Dystrophy
Also sometimes referred to as cone degeneration. The cones of the eye degenerate over time leading to visual acuity between 20/50 and 20/200 – legal blindness. There may be a progressive vision loss, abnormal color vision and photophobia. No treatment is available, except for dark sunglasses for the photophobia. Patients with cone dystrophies and cone degenerations benefit for rehabilitation services.
Cone Rod Degeneration
Also called cone-rod dystrophy. Leads to a loss of visual acuity between 20/25 to 20/400 – legal blindness. First there is a loss of cone photoreceptors followed by a loss of rod photoreceptors. Visual fields may be restricted, abnormal color vision and photophobia. No treatment is available.
Conjunctivitis
An inflammation of the thin transparent tissue layer within the eye containing blood vessels. The conjunctiva covers the outer surface of the eyeball, starting at the limbus (edge of the cornea) and extends backward to form a recess under each lid before coming forward and covering the inside surface of each eyelid. It contains mucous secreting cells that allow the eye to move smoothly in various directions. It also helps lubricate the cornea during blinking. A contagious and treatable condition.
Cornea
The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.
Cortical Blindness
A person with cortical blindness will have normal eyes and normal optic nerves but, nevertheless, will not be able to see. The cause of the blindness is with the cortex or surface of the brain that contains 32 or more sites for visual information processing. More recently, the preferred term for such individuals is cortical visual impairment, because many people will not be totally blind but will exhibit unusual visual losses; for example, they may be blind to stationary objects but be able to see moving objects.
We thank you for using the Health Dictionary to search for Cone. If you have a better definition for Cone than the one presented here, please let us know by making use of the suggest a term option. This definition of Cone may be disputed by other professionals. Our attempt is to provide easy definitions on Cone and any other medical topic for the public at large.This dictionary contains 25007 terms. |
|
|
