Central Visual Pathways & Perceived Visual Field

Question 1

what is vision

Answer 1

the conscious perception of information from the eye –> processed in the occopital cortex (mammals)

visual system is part of the CNS which gives organisms the ability to process info that is contained in visible light

Question 2

why is vision assessment limited in vet med and how can it be assessed

Answer 2

because of interference of behaviour

1. observation, unfamiliar environment
2. ability to track (silent movement, cotton balls)
3. visual placing (small animal)
4. menace response (other reasons for failure)

Question 3

what is the visual field

Answer 3

total area in which objects can be seen in the peripheral vision as you focus your eyes on a central point

Question 4

what is the cross over at the optic chiasm between different species

Answer 4

humans 50%

cats 65%

dogs 75%

horses 80%

birds and fish 100%

Question 5

what is the cross over at the optic chiasm related to

Answer 5

inversely related to binocular vision

Question 6

what is the pupillary light relfex pathway

Answer 6

1. retina
2. optic nerve (CN II) = afferent
3. optic chiasm
4. optic tract
5. pretectal nucleus
6. parasympathetic nucleus of CN III = efferent
7. bilateral pupil constriction

Question 7

what is central (cortical) blindness

Answer 7

also known as amaurosis

blindness without apparent lesion of eyes

involves processing system

Question 8

where are the lesions in central (cortical) blindness

Answer 8

lateral geniculate nucleus

optic radiation

occipital cortex

Question 9

what are the clinical signs of central (cortical) blindness

Answer 9

1. normal PLR
2. absent menace response
3. blind

Question 10

what is peripheral (subcortical) blindness

Answer 10

involves collection/distribution system

Question 11

where are the possible sites for lesions in peripheral (subcortical) blindness

Answer 11

1. eye
2. optic nerves
3. optic chiasm
4. optic tract

Question 12

what are the clinical signs of peripheral (subcortical) blindness

Answer 12

1. absent PLR
2. absent menace response
3. blind

Question 13

what is the pathway of the dazzle reflex

Answer 13

reflex –> no cortical involvement

1. retina
2. optic nerve (CN II) = afferent
3. optic chiasm
4. optic tract
5. pretecta nucleus
6. facial nerve nuclei CN VII = efferent
7. bilateral blinking

Question 14

what is the menace response pathway (10)

Answer 14

response cortical involvement

1. retina
2. optic nerve (CN II) = afferent
3. optic chiasm
4. optic tract
5. lateral geniculate nucleus
6. optic cortex
7. motor cortex
8. pontine nucleus
9. cerebellum
10. facial nerve nuclei CN VII = efferent

Question 15

what is the innervation of the extraocular muscles

Answer 15

Question 16

what does the oculomotor nerve innervate

Answer 16

GSE: dorsal rectus, medial rectus, ventral rectus, ventral oblique, levator palpebrae

GVE: parasympathetic for pupil

Question 17

what does the trochlear nerve innervate

Answer 17

GSE: dorsal oblique

Question 18

what does the abducent nerve innervate

Answer 18

GSE: lateral rectus

retractor bulbi muscle in the eye