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| This glossary contains: 19186 medical terms |
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Cone Dystrophy
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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.
RELATED TERMS--------------------------------------
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.
Acuity
The highest spatial frequency rsolvable with a grating of unity contrast (i.e. the maximum possibly contrast).
Blindness
Legal blindness is defined as: 1) visual acuity of 20/200 (only being able to see the big E on the eye chart) or less in the best eye even with the eyes corrected by glasses or contact lenses; or, 2) The peripheral visual field is reduced to 20 degrees of visual angle or less. Twenty degrees of visual angle is about the size of a one foot ruler held at arms length.
Vision
The sense of sight.
Abnormal
Not normal. Deviating from the usual structure, position, condition, or behavior. In referring to a growth, abnormal may mean that it is cancerous or premalignant (likely to become cancer).
Photophobia
Severe discomfort to bright lights. Usually a symptom of eye disease, such as glaucoma, in an infant or retinal disease in a child or adult. Sometimes treated with dark sunglasses.
Rehabilitation
The return of function after illness or injury, often with the assistance of specialised medical professionals.
SIMILAR TERMS--------------------------------------
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.
Cone biopsy
Surgical removal of a cone-shaped section of tissue from the cervix for the treatment of cervical dysplasia.
Cone opsin
Light absorbing molecule in cone cells.
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.
Cone snail
A fishing-eating snail (Conidae) that inhabits tropical coral reefs and produces toxins that immobilize their prey.
Conemaugh Memorial Medical Center
The Conemaugh Memorial Medical Center is a hospital in Johnstown, Pennsylvania, United States.
PREVIOUS AND NEXT TERMS--------------------------------------
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
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.
Cone Dystrophy
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.
Cover Test
A test for a muscle imbalance. While the person is looking at a distant object, one eye is covered and then uncovered (cover-uncover). This is repeated on the other eye. Finally it is performed on both eyes, covering one then the other (alternate-cover). If one or both eyes shift during this test, there is a problem with alignment of the eyes. The misalignment with the eyes often cannot be seen with both eyes opened.
RELATED TERMS--------------------------------------
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.
Acuity
The highest spatial frequency rsolvable with a grating of unity contrast (i.e. the maximum possibly contrast).
Blindness
Legal blindness is defined as: 1) visual acuity of 20/200 (only being able to see the big E on the eye chart) or less in the best eye even with the eyes corrected by glasses or contact lenses; or, 2) The peripheral visual field is reduced to 20 degrees of visual angle or less. Twenty degrees of visual angle is about the size of a one foot ruler held at arms length.
Vision
The sense of sight.
Abnormal
Not normal. Deviating from the usual structure, position, condition, or behavior. In referring to a growth, abnormal may mean that it is cancerous or premalignant (likely to become cancer).
Photophobia
Severe discomfort to bright lights. Usually a symptom of eye disease, such as glaucoma, in an infant or retinal disease in a child or adult. Sometimes treated with dark sunglasses.
Rehabilitation
The return of function after illness or injury, often with the assistance of specialised medical professionals.
SIMILAR TERMS--------------------------------------
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.
Cone biopsy
Surgical removal of a cone-shaped section of tissue from the cervix for the treatment of cervical dysplasia.
Cone opsin
Light absorbing molecule in cone cells.
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.
Cone snail
A fishing-eating snail (Conidae) that inhabits tropical coral reefs and produces toxins that immobilize their prey.
Conemaugh Memorial Medical Center
The Conemaugh Memorial Medical Center is a hospital in Johnstown, Pennsylvania, United States.
PREVIOUS AND NEXT TERMS--------------------------------------
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
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.
Cone Dystrophy
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.
Cover Test
A test for a muscle imbalance. While the person is looking at a distant object, one eye is covered and then uncovered (cover-uncover). This is repeated on the other eye. Finally it is performed on both eyes, covering one then the other (alternate-cover). If one or both eyes shift during this test, there is a problem with alignment of the eyes. The misalignment with the eyes often cannot be seen with both eyes opened.
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This dictionary contains 19186 terms.
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