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11 Cards in this Set
- Front
- Back
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Distinguish between the visual acuity principles of minimum: visible, separable, and recognizable. |
Minimum visible - ability to detect smallest stimulus without recognizing it; function of brightness; 1 arcsecond
Minimum separable - relative location of 2 features; "hyper acuity"; 2 arcseconds
Minimum recognizable - most common form tested in adults; distinguish optotypes; 30 arcseconds |
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When testing visual acuity, 2 points are discriminable as long as what happens? What is the associated distance between them? |
2 separate cones are stimulated.
30 arcseconds or 2.5 um |
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Explain RAPD. |
Relative afferent pupillary defect - normally both eyes constrict. Abnormally, both pupils dilate when swing the light to the other eye after 3 seconds.
It indicates unilateral optic never dysfunction. |
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Know the location of optic nerve lesions and the corresponding vision loss for: nasal step, arcuate scotoma, altitudinal defect, and cecocentral scotoma. |
Second the image on the second to last slide on Page 5 of the notes. |
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What is hemianopia?
Distinguish between homonymous and heteronymous. |
Loss of one half of visual field to either side of the vertical.
Homo - lesions posterior to the chiasm produce visual field defect to the same side of the vertical in both eye.
Hetero - lesions on opposite sides of the vertical in each eye. Bi-temporal hemianopia are diagnostic of lesions of optic chiasm. |
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What are the 3 components of optic tract syndrome? |
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Name some different efferent conditions in each of the 4 categories that could affect vision. |
Muscle disease - myopathy
Junction disease - myasthenia gravis
Nerve disease - 3rd, 4th, 6th CN palsy
Brainstem disease - stroke, tumor, MS |
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Evaluate a case of acute 3rd cranial nerve palsy. |
It is an emergency due to possible pressure on the nerve from an expanding Posterior Communicating/Superior Carotid artery aneurysm.
If the pupil is spared, it could be from diabetes.
If more than 1 CN invovled, it is a lesion of the cavernous sinus or skull base. |
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Briefly describe the nerve supply to the 3rd cranial nerve. |
Pupillary constrictor (iris sphincter) - parasympathetic from 3rd CN (starting with the Edinger-Westfall nucleus)
Pupillary dilator - sympathetic from sympathetic autonomic nerves |
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What are the 4 components of Horner's syndrome? |
Ptosis - upper lid drooping slightly due to paresis of Mueller's muscle. Maybe some lower lid elevation.
Miosis - Pupil is abnormally small
Anhidrosis - face, forehead
Facial/conjunctival flushing |
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What are 5 other disorders that can cause visual hallucinations and illusions? |
Classic migraine (scintillating scotoma), occipital seizures (sparkles, stars), temporal seizures, Charles-Bonnet syndrome (like 'Phantom limb), Lewy body dementia |
