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Visual System (26)
Which structure of the eye is continuous with the dura mater?
Which meningeal layers cover the optic nerve?
What cells connect the photoreceptors to the retinal ganglion cells?
bipolar cells; 1
Axons of which cells make the optic nerve?
retinal ganglion cells; 1
What part of the eye does not contain photoreceptors?
optic disc; 100
What structure marks the center of the retina?
Explain why the fovea has the highest visual acuity?
Light directly hits the fovea's photoreceptors only because other cells are displaced laterally.
Which photoreceptors populate the fovea?
What area surrounds the fovea?
What area is medial to to the fovea?
nasal hemireteina; 2
What area is lateral to the fovea?
temporal hemiretina; 2
Which hemiretina contains the optic disc?
nasal hemiretina; 2
Light from the _____ side of the visual field hits the blind spot.
How does a concave lens affect light rays?
light rays scatter; 3
How does a convex lens affect light rays?
light rays converge; 3
What structure of the human eye provides the majority of refraction?
What is the focal length?
distance between refractive surface and focal point; 4
What is refractive power equal to?
reciprocal value of the focal length (m); 4
What muscles control the shape of the lens?
Describe the state of the suspensory ligaments and ciliary muscles when the lens is flattened.
Why does light from a near source produce a blurry image on a flattened lens?
light rays converge behind the retina; 6
How do the suspensory ligaments and ciliary muscles adjust for near vision? How does this affect the lens?
suspensory ligament loosen
ciliary muscles contract
greater refractive power (26D)
*eyes must also converge for near vision; 7
Where are the cell bodies of the preganglionic parasympathetic neurons for the ciliary muscle located?
Edinger-Westphal nucleus; 8
Where do the pre- and postganglionic parasympathetic neurons of the ciliary muscle synapse?
ciliary ganglion; 8
What parameter declines with age--leading to a decrease in accommodation ability?
What is presbyopia?
refractive plasticity decline with age
What happens to focal length in presbyopia?
too great; 9
What type of lens can be used to correct presbyopia?
Visual acuity is high when 2-point discrimination threshold is _____.
High density of receptors leads to _____ spatial resolution.
Review the relationship between distance across the retina and the receptor density.
Describe the pathway for pupillary constriction.
parasympathetic control; 11
Describe the pathway for pupillary dilation.
sympathetic control; 11
What is myopia?
concave corrective lens (subtract D); 13
What is hyperopia?
convex corrective lens (add D); 15
What is normal vision?
What does 20/800 vision mean?
what the patient can read at 20 feet, an individual with 20/20 vision could read at 800 feet.
Name 3 symptoms of increased ICP.
What is diabetic retinopathy?
degeneration of blood vessels of the eye that can lead to blindness
*leading cause of acquired blindness in U.S.
Describe the progression that leads to detached retina.
vitreous humor becomes more liquid with age, retinal tear can occur
retinal detachment occurs due to fluid buildup
Deficiency of what structure leads to macular degeneration?
*normally cleans the shed parts of the rods and cones
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