Visual System Flashcards
(20 cards)
What is the difference between visual field and retinal field?
Visual field- what the patient sees
Retinal field- what region of the retina onto which the image is projected.
What effect do pupils have on images as they pass through it?
Pupil inverts image
What structure of the retina is responsible for color and high resolution/ detail.
Cones
What area of the retina is responsible for low resolution and movement?
Rods
What region of the retina is one blind?
Blind spot- point of exit of ganglion cell axons
Which retinal neuron gives rise to fibers of the optic nerve?
Ganglion cell axons
Name three structures in which primary visual fibers terminate
Hypothalamus suprachiasmatic nucleus- circadian rhythms
Amygdala- transmission of emotionally significant images
Lateral geniculate body- visual info: achieve a three-dimensional representation of object space as well as obtain information for controlling the precision optical system of the visual modality.
What is retinotopic organization?
The neurons in primary visual cortex are organized “retinotopically”. This means that different parts of the visual field (what you can see) are laid out in an organized manner in the visual cortex, and this retinotopic map is repeated several times in the early visual areas.
Describe the location and function of secondary and tertiary visual areas.
Located in brodman areas 18-19.
Color and stereopsis.
V5/MT (middle temporal area)
Movement: direction and velocity
MST (medial superior temporal area)
- perceived motion of stationary targets as observer moves
What happens with a right optic nerve lesion?
Complete blindness in the right eye. Unilateral blindness
What happens with a optic chiasm lesion?
blindness in the right half of the right eye and left half of the left eye. Bitemporal hemianopsia
What happens with a right optic tract lesion?
Blindness is the left half of both of the right and left eyes. Left homonymous hemianopsia.
What happens with a geniculocalcarine tract lesion?
No one knows
What happens with a primary visual cortex lesion?
Retention of ability to determine object location by vision but denial of blindness.
What happens with a fusiform face area lesion?
Prosopagnosia. Loss of ability to name faces.
What is the “what” system.
Midget parvocellular retinal ganglion cells.
Identification of visual image.
Processed as part of visual stream.
What is the “where” system
Parasol magnocellular retinal ganglion cells.
Location and movement of visual image.
Processed as part of dorsal steam.
Visual agnostia is what?
Loss of secondary and or tertiary visual cortex especially on one side that results in the inability to recognize objects based on vision or know what an object is used for.
Anton syndrome is what?
Loss of primary visual cortex and vision. Denial of loss.
What is Charles bonnet syndrome?
Visual hallucinations associated w age and reduced vision. (Amusing or disturbing but not emotional).
