Karteikarten
Visual disorders
Karten in diesem Stapel (17)
- 1Where does the geniculostriate pathway go? What does the optic nerve do?The eye to the optic chiasm to the LGN down the optic radiations into V1.
Carries information from the eye to V1. - 2What is a visual field defect?This refers to different types of visual field loss and how these map onto different lesion sites.
- 3Light in the eye... How does light enter the eye? What does the pupil do to reduce light? What does it do when it's dark? What is light focused by and what is it projected to?Through the pupil.
Goes smaller to reduce light.
Dilates when it's dark.
Focused by cornea and lens and projected onto the retina. - 4What is the retina lined with? Where does light from the left side of the world strike? Where does light from the right side of the world strike? Where does light from the bottom of the world strike? Where does light from the top of the world strike?Photoreceptors that detect light.
Right hemiretina.
Left hemiretina.
Top hemiretina.
Bottom hemiretina. - 5What is binocular viewing? What are the similarities between the eye and a camera? What are the differences?Seeing with both eyes.
Image is inverted, amount of light is controlled.
Eye lens changes shape rather than distance to focus, the retina is curved and not uniformally sensitive. - 6What are the photoreceptors called? What do they contain? How do they react with light? What does this process do?Rods and cones.
Contain photopigments.
Light causes a reaction with the photopigment which alters the flow of electrical current around the photoreceptor and triggers action potentials in the ganglion cells.
Translates external light stimulus into internal neural signals. - 7What is topographical organisation? How many rods and how many cones? What are rods sensitive to? Why?Means adjacent points in the visual field are processed by adjacent receptors in the retina because light travels in a straight line.
120 million rods, 6 million cones.
Low level light.
Because they pool their responses to influence the next layer of cells but in doing so, sacrifice detail. - 8When are cones less active? What are they used for? In colour vision, how long are red, green and blue wavelengths? Where are more cones?In dim light.
High acuity vision (because few receptors funnel their input into a post-synaptic cell) and colour vision.
Red-long
Green-medium
Blue-short
Fovea which is in the centre of the human retina and specialises in detailed vision. There are no rods in the fovea. - 9What's foveal vision? What's peripheral vision? What are nearly absent in the fovea and why? Name 2 features of peripheral vision. Name 2 features of foveal vision. What does this result in?To look at something that you are directly focusing on at 0 degree angle.
Outside the centre of gaze, lots of rods and few cones.
Blood vessels or ganglion cell axons so it has the least impeded vision.
Good sensitivity, poor acuity.
Colour vision/good acuity, poor light sensitivity.
Different implications if one is damaged. - 10What does the retino-geniculostriate pathway consist of? What is the retino-tectal pathway? Where does the retino-geniculostriate pathway go from?90% optic nerve neurons and controls visual perception.
Involves 10% of optic nerve neurons controlling visual attention and orienteering.
Retina-Optic nerve-Optic chiasm-optic tract-LGN-optic radiations-V1. - 11What is the LGN a sub-component of? What does it have in it? How many optic radiation loops are there? What is V1?The Thalamus.
Parvocellular and Magnocellular layers.
2.
A calcarine fissure surrounded by primary visual cortex. - 12Where is each hemifield represented? Where is the fovea in V1 represented? Where is the periphery represented? What is a visual field? What is a visual field deficit?In the contralateral hemisphere.
At the occipital pole (far edge).
More towards the middle of the brain.
Everything that can be seen whilst fixating.
An area of blindness. - 13What is quadrantanopia? What is hemianopia? What is scotoma?A quarter of the visual field is blind.
Half of the visual field is blind.
A random hole of blindness. - 14What causes visual field deficits? What can analysis of visual fields indicate? What is retinal detachment? What is macular degeneration? How can it be recovered?A variety of retinal, sub-cortical and cortical lesions/injuries.
Site of neurological damage.
Where the edges of one's retina begins to peel away. Quick attendance=reattachment. Slow attendance=cells die.
Where certain photoreceptors start to die, cones degenerate, colour and acuity decrease ad it leads to a hole in fovea/visual field, often age-related.
By using a bionic eye which uses glasses where a camera captures the image and sends the data to an electrode attached to the retina. - 15What happens with damage before the optic chiasm? Directly to the optic chiasm? After the optic chiasm? What ways are there for assessing damage? What's confrontation? What's perimeter?Will result in damage to the ipsilateral eye.
Damage to both eyes. Lose peripheral on both sides.
Damage parts of both eyes (only one hemifield).
Confrontation and perimeter.
Asking people directly, e.g. look at objects, let me know what you see.
Patient goes into a machine, they're told to fixate ahead, a light is gradually brought in and asked let me know when you see the light. - 16What happens when patients have problems seeing the whole visual scene? Patients with visual have difficulties doing what? What does predictability have a large impact on?They make hypermetric saccades which are rapid and organised eye movements.
e.g. seeing objects avoiding collisions, driving, reading etc...
How well patients cope with homonymous visual deficits. - 17Why can patients with 1 eye drive? What issues did hemianopic patients have with reading? What do extent of reading difficulties depend on? What is the recovery rate for visual deficits? What are many patients left with?Because they only lose 25 degrees of vision, whereas hemianopic lose 90 degrees.
Omission of part of a sentence/word and often substitute words.
Depends on location and size of loss.
If the reading is left to right.
If the fovea is sharing or splitting.
7-85% rarely completely recovered and maximum of 3 months before it's known as permanent.
Chronic visual field loss which negatively impacts on quality of life.
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- Beschreibung
- Degree Neuropsychology Karteikarten am Visual disorders, erstellt von kat.bridgman am 04/05/2015.
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- kat.bridgman
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