Flashcards in Anatomy and Physiology of Vision II Deck (30):
Which is larger? nasal retina or temporal retina?
Nasal retina is larger than temporal retina
What is the fovea's diameter?
What makes resolution high in the fovea?
1- Anatomical structure
2- Receptor/ganglia ratio
3- types of photoreceptors
What makes the anatomy of the fovea special for visual resolution?
Few anatomical structures impede the passage of light
a- fovea is avascular
b- contains only receptors with few vascular cells
c-ganglion axons divert AROUND the fovea
What kind of receptor has higher density in the fovea? what is its ratio to ganglion cells?
What kind of vision do rods produce? In what light conditions?
Monochromatic vision, in dim light
What kind of vision do cons produce? In what light conditions?
Colour vision, in bright light
What is the ratio of photoreceptors to ganglion cells in average for the retina? the reinal periphery? Fovea?
137:1, 1000:1, 1:1
What is the main change associated with macular degeneration?
Aging changes in RPE
accumulation of metabolic debris at the layer of Bruch's membrane ---> Drusen
What pathology is associated with late stage macular degeneration?
- photoreceptors are dead, but the periphery vision is not affected
What is the role of the retinal pigment epithelium (RPE)?
Provide suitable ionic and metabolic conditions for the rods and cons
What conditions cause possible damage to the optic nerve?
Glaucoma, optic neuritis, ischemia, inflammation, and compression
What 3 areas in the brain receive visual input?
Suprachiasmatic nucleus of the hypothalamus, lateral geniculate body of the thalamus, and pretectal region of the brain.
Where is the pretectal region of the brain located?
Anterior to the superior colliculus (pretectal nucleus and Edinger Westphal nucleus)
What is the main function of the pretectal region and its nuclei?
Drives the Pupillary light reflex
Where does the image from the top visual field get delivered?
To the thalamus, through the loop of Meyer's, and to the occipital region (all contralateral)
Where does the image from the lower visual field get delivered?
To the thalamus, and directly to the occipital region
What is the name of the axons carrying visual information from lateral geniculate body to the occipital lobe?
What kind of lesion does a visual field loss respecting the horizontal midline suggest?
An optic disc (nerve)/retinal lesion (one or both eyes)
What kind of lesion does a visual field loss respecting the vertical midline suggest?
A neurologic lesion (often both eyes)
What kind of visual loss does a lesion to the right optic nerve produce?
Loss of vision in the right eye
What kind of visual loss does a lesion to the optic chiasm (pituitary tumour) produce?
What kind of visual loss does a lesion to the right optic tract produce?
Left homonymous hemianopsia
What kind of visual loss does a lesion to the left myers loop produce?
Right homonymous superior quadrantanopsia (pie in the sky)
What kind of visual loss does a lesion to the left geniculocalcarine axons produce?
Right homonymous heminaopsia
What kind of visual loss does a lesion to the right occipital lobe produce?
Left homonymous heminanopsia sparing the macula
What kind of visual loss does a lesion to the right optic nerve close to the optic chiasm produce?
Where does the visual association area lie?
Surrounds the primary visual area (para-calcarine fissue area) and occupies the occipital lobe
What percentage of the optic nerve, tract, and geniculocalcarine axons represents the fovea?