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| This glossary contains: 19186 medical terms |
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Photopic
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Photopic Bright light conditions where only the cones are functional.
SIMILAR TERMS--------------------------------------
Photocoagulation
Using a special strong beam of light (laser) to seal off bleeding blood vessels such as in the eye. The laser can also burn away blood vessels that should not have grown in the eye. This is the main treatment for diabetic retinopathy.
Photodynamic radiation therapy
A light sensitive drug is given through a vein and concentrates in the tumor. Then, during a surgical procedure, a special light activates the drug. The activated drug kills tumor cells.
Photofrin
Photofrin is a prescription or over-the-counter drug which is (or once was) approved in the United States and possibly in other countries. Active ingredient(s): porfimer sodium.
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.
Photoreceptor
A light sensitive neuron. Photoreceptors interact with light which produces changes in their electrical properties which are communicated to other neurons. They constitute the first stage in the physiological process which underlies vision. The human retina, like the retina of most vertebrates, contains two broad classes of photo-receptors, rods and cones.
Photoreceptor mosaic
The spacial arrangement of photoreceptors in the retina.
Phototherapy
The use of ultraviolet light to treat newborns with jaundice.
PREVIOUS AND NEXT TERMS--------------------------------------
Pattern adaptation
The perceived width and orientation of a grating pattern can be altered by first adapting to grating pattern of different frequencies and orientations. After adapting the contrast sensitivity to stimuli near the frequency or orientation of the adapting pattern is reduced. Suggests the existence of neurons tuned for frequency and orientation at are fatigued by the adapting pattern.
Perceptive field
Area of the retina or visual space that when stimulated by a visual stimulus produces a change in behavioral response.
Perceptual constancy
The phenomenon that the perception of an object remains constant despite changes in the its size, lighting conditions and orientation.
Perceptually lossless compression
An image processing technique with loses some information about contents of the image, but the distortions produced by the loss aren't visible to the human image processing system.
Peri-Stimulus time histogram
Plot of the average number of action potentials at each moment in time following a brief test flash.
Photopic
Photoreceptor mosaic
The spacial arrangement of photoreceptors in the retina.
Pigment epithelium
Cells lining the back of the eye containing melanin which resynthesize photopigment for photoreceptors.
Pointspread
A measure of optical blur produced by natural imperfections of the lens of the eye. The response to a point of light produces a certain amount of blur, the amount of this blurring is known as the pointspread.
Poles (of optic flow field)
The two points in the optic flow field surrounding an observer moving through the environment at which there is no flow of optic texture. One is the point toward which the observer is moving and the other is the point away from which the observer is moving.
Pool hypothesis
Hypothesis for the mechanism for stereopsis. Suggests the visual system contains three pools, one for crossed disparities, one for uncrossed disparities and one for non-zero disparities. A particular depth is signaled by the relative activity of crossed and uncrossed pools rather than by a sharply tuned neuron coding a particular depth.
SIMILAR TERMS--------------------------------------
Photocoagulation
Using a special strong beam of light (laser) to seal off bleeding blood vessels such as in the eye. The laser can also burn away blood vessels that should not have grown in the eye. This is the main treatment for diabetic retinopathy.
Photodynamic radiation therapy
A light sensitive drug is given through a vein and concentrates in the tumor. Then, during a surgical procedure, a special light activates the drug. The activated drug kills tumor cells.
Photofrin
Photofrin is a prescription or over-the-counter drug which is (or once was) approved in the United States and possibly in other countries. Active ingredient(s): porfimer sodium.
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.
Photoreceptor
A light sensitive neuron. Photoreceptors interact with light which produces changes in their electrical properties which are communicated to other neurons. They constitute the first stage in the physiological process which underlies vision. The human retina, like the retina of most vertebrates, contains two broad classes of photo-receptors, rods and cones.
Photoreceptor mosaic
The spacial arrangement of photoreceptors in the retina.
Phototherapy
The use of ultraviolet light to treat newborns with jaundice.
PREVIOUS AND NEXT TERMS--------------------------------------
Pattern adaptation
The perceived width and orientation of a grating pattern can be altered by first adapting to grating pattern of different frequencies and orientations. After adapting the contrast sensitivity to stimuli near the frequency or orientation of the adapting pattern is reduced. Suggests the existence of neurons tuned for frequency and orientation at are fatigued by the adapting pattern.
Perceptive field
Area of the retina or visual space that when stimulated by a visual stimulus produces a change in behavioral response.
Perceptual constancy
The phenomenon that the perception of an object remains constant despite changes in the its size, lighting conditions and orientation.
Perceptually lossless compression
An image processing technique with loses some information about contents of the image, but the distortions produced by the loss aren't visible to the human image processing system.
Peri-Stimulus time histogram
Plot of the average number of action potentials at each moment in time following a brief test flash.
Photopic
Photoreceptor mosaic
The spacial arrangement of photoreceptors in the retina.
Pigment epithelium
Cells lining the back of the eye containing melanin which resynthesize photopigment for photoreceptors.
Pointspread
A measure of optical blur produced by natural imperfections of the lens of the eye. The response to a point of light produces a certain amount of blur, the amount of this blurring is known as the pointspread.
Poles (of optic flow field)
The two points in the optic flow field surrounding an observer moving through the environment at which there is no flow of optic texture. One is the point toward which the observer is moving and the other is the point away from which the observer is moving.
Pool hypothesis
Hypothesis for the mechanism for stereopsis. Suggests the visual system contains three pools, one for crossed disparities, one for uncrossed disparities and one for non-zero disparities. A particular depth is signaled by the relative activity of crossed and uncrossed pools rather than by a sharply tuned neuron coding a particular depth.
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This dictionary contains 19186 terms.
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