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| This glossary contains: 19186 medical terms |
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Cone opsin
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Cone opsin Light absorbing molecule in cone cells.
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.
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 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 dystrophy
A disease of the cones, the specialized light-sensitive cells that act as photoreceptors in the retina of the eye, providing sharp central vision and color vision. The cone dystrophies are a form of genetic macular degeneration characterized by progressive deterioration of the cones that leads to the distinctive triad of loss of color vision, photophobia, and reduced central vision. Cone dystrophy genes have been mapped to chromosome regions 6p21.1, 6q25-q26, 17p12-13, and Xp21.1-p11.3. In region 6p21.1, mutations have been found in the gene that encodes GCAP1, a key component in the recovery of photoreceptor cells to the dark-adapted state after exposure to a light stimulus.
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--------------------------------------
Closed-Loop control
A control system in which the output is continuously modified by feedback from the environment.
Color opponency
When a cell is excited by one part of the visible spectrum and inhibited by another. First observed in ganglion cells in the retina.
Color opponent channel
Pathway that begins with the midget (parvo) ganglion cells in the retina and terminates within the parvocellular layer of the LGN. Conduction slower than that of Magnocellular Pathway.
Complex cells
Cells in the primary visual cortex (V1) that responding either to an edge, a bar or a slit stimulus of a particular orientation falling anywhere in its receptive field. The exact location of the stimulus within the receptive field is not as critical. Have receptive fields longer than those of simple cells. The cell behaves non-linearly, responding to a drifting cosine grating with a uniform increase in activity with no sinusiodal modulcation (i.e. insensitive to phase). For a historical perspective see Simple Cells.
Concentric field
A receptive field divided into an inner circular region and an outer ring-shaped region. Light falling in each of the two regions has opposite effects on the response of the cell.
Cone opsin
Contrast sensitivity function
The reciprocal of the threshold contrast required to obtain a criterion response from a cell or a human subject as a function of spatial frequency. Falls off in sensitivity as the spatial frequency of the test pattern increases.
Coplanar ratio hyphothesis
An hypothesis by Gilchrist in which the visual system does not use retinal contrasts to determine relative lightnesses but uses depth information to determine which regions are at the same depth (coplanar) and uses their contrasts to deteremine the lightness perceived. This hypothesis has come under recent attack.
Correspondence problem
In Stereopsis: the challenge of matching elements in one eye with elements in another eye. Also known as the Matching Problem. In Motion: the challenge of matching moving elements in one frame with elements in a succeeding frame (especially true of random dot cinematograms).
Corticaltectal pathway
Pathway from the cortex to the superior colliculi.
Cortical magnification factor
Defined as millimeters of cortex per degree of visual angle.
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.
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 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 dystrophy
A disease of the cones, the specialized light-sensitive cells that act as photoreceptors in the retina of the eye, providing sharp central vision and color vision. The cone dystrophies are a form of genetic macular degeneration characterized by progressive deterioration of the cones that leads to the distinctive triad of loss of color vision, photophobia, and reduced central vision. Cone dystrophy genes have been mapped to chromosome regions 6p21.1, 6q25-q26, 17p12-13, and Xp21.1-p11.3. In region 6p21.1, mutations have been found in the gene that encodes GCAP1, a key component in the recovery of photoreceptor cells to the dark-adapted state after exposure to a light stimulus.
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--------------------------------------
Closed-Loop control
A control system in which the output is continuously modified by feedback from the environment.
Color opponency
When a cell is excited by one part of the visible spectrum and inhibited by another. First observed in ganglion cells in the retina.
Color opponent channel
Pathway that begins with the midget (parvo) ganglion cells in the retina and terminates within the parvocellular layer of the LGN. Conduction slower than that of Magnocellular Pathway.
Complex cells
Cells in the primary visual cortex (V1) that responding either to an edge, a bar or a slit stimulus of a particular orientation falling anywhere in its receptive field. The exact location of the stimulus within the receptive field is not as critical. Have receptive fields longer than those of simple cells. The cell behaves non-linearly, responding to a drifting cosine grating with a uniform increase in activity with no sinusiodal modulcation (i.e. insensitive to phase). For a historical perspective see Simple Cells.
Concentric field
A receptive field divided into an inner circular region and an outer ring-shaped region. Light falling in each of the two regions has opposite effects on the response of the cell.
Cone opsin
Contrast sensitivity function
The reciprocal of the threshold contrast required to obtain a criterion response from a cell or a human subject as a function of spatial frequency. Falls off in sensitivity as the spatial frequency of the test pattern increases.
Coplanar ratio hyphothesis
An hypothesis by Gilchrist in which the visual system does not use retinal contrasts to determine relative lightnesses but uses depth information to determine which regions are at the same depth (coplanar) and uses their contrasts to deteremine the lightness perceived. This hypothesis has come under recent attack.
Correspondence problem
In Stereopsis: the challenge of matching elements in one eye with elements in another eye. Also known as the Matching Problem. In Motion: the challenge of matching moving elements in one frame with elements in a succeeding frame (especially true of random dot cinematograms).
Corticaltectal pathway
Pathway from the cortex to the superior colliculi.
Cortical magnification factor
Defined as millimeters of cortex per degree of visual angle.
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This dictionary contains 19186 terms.
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