visual system

lesion sites in CNS

what do visual errors indicate

• Refraction of light rays by lens and cornea

• Conversion of electromagnetic energy into nerve impulses

• Impulse transmission to visual cortex

• Integration in visual association cortex

events in visual perception

visual field is what you see; retinal field is where the image lands

visual field vs retinal field

anterior chamber and posterior chamber

what does the anterior cavity of the eye consist of?

• External fibrous tunic (sclera)

• Middle vascular tunic (choroidal)

• Inner nervous tunic (retina)

name the 3 ocular layers of the eye

vitreous humor

what is the posterior chamber filled with

night vision; day

which type of vision are rods used for? cones?

specialized receptor cells

what kind of cells are located on the retina

• Fibers from the nasal (medial) retina decussate (cross over) to the

contralateral side, while fibers from the temporal (lateral) retina remain ipsilateral (uncrossed).

what happens to optic fibers at optic chiasm

Because of the crossing pattern each tract is carrying visual data from the

opposite (contralateral) visual field of both eyes

what kind of visual data are optic tracts carrying

lateral geniculate nucleus of the thalamus

where does optic tract synapse

optic radiations; conscious vision; PVC- calcarine fissure

from the LGN, what do second order neurons form? what do they convey? then where do they travel

superior colliculus

what Coordinates rapid visual reflex, sending signals to help orient the head and eyes, and gaze tracking

pretectal nucleus

what Mediates the pupillary light reflex; sends signals to Edinger-Westphal nucleus to trigger the parasympathetic constriction via CN III

suprachiasmatic nucleus

what Regulates circadian rhythms and biological day-night cycles in response to ambient light via specialized photosensitive retinal ganglion cells.

• Motor to medial rectus, superior rectus, inferior

rectus, inferior oblique

what’s the role of CN 3

motor to superior oblique

what’s the role of CN 4

motor to lateral rectus

what’s the role of CN 6

abducts, depresses, and medially rotates eyes

main action of SO

abducts eyes

main action of LR

H test

how to clinically test for extraocular muscles

T

t/f: retinal image is a reversed and inverted form of the visual field image

emmetropia

normal vision

• Inadequate lens refractive

• Focus for near objects behind retina

hypermetropia

• Strong refractive power with focus of

  • Far objects in front of retina

  • Near objects correctly on the retina

nearsightedness

myopia

far sighted

hypermyopia

homonymous

1 side of the world

monocular blindness

lesion to optic nerve

bitemporal hemianopia (tunnel vision)

lesion to optic chiasm

nasal hemianopia (inside of world is lost)

lesion pressing against temporal retina and level of chiasm

homonymous hemianopia , same half of world lost in either eye

lesion of optic tract on one side

NO

do temporal retinas cross