Visual, Auditory, and Vestibular System Flashcards
What is visual acuity a function of?
Central vision involving the macula
What is color vision a function of?
Macula
Improved acuity when looking through a pinhole suggests the problem with visual acuity is ___. If it does not improve, what should be suspected?
Ocular; lesion of the optic nerve or macula
The normal blind spot abnormally enlarges in size in the presence of what pathology?
Papilledema
What are scotomas?
Pathological, abnormal blind spots elsewhere in the visual field of one eye, where vision is lost or decreased
Causes of scotomas?
Retinal lesions (infections or inflammation, macular degeneration, retinal detachment) or optic nerve lesions (demyelination or ischemia)
Patients with constricted or contracted visual fields may have underlying ___ or a ___ disease.
Glaucoma; retinal degenerative
Tunnel vision is usually due to what type of problem?
Psychiatric
Describe how vision is transmitted from the outside world to the cortex.
Visual image in the R side of the patient’s world is detected by the L halves of each retina
Transmitted by optic nerve fibers which, beyond the optic chiasm, are continued as a pathway through the L optic tract, then the L optic radiations, ending in the L occipital visual cortex
Presentation of post-chiasmal lesions on the left?
R-sided visual impairments
A visual image in the uppermost part of the patient’s world is detected by the ___ portions of the retinae, and these fibers continue past the optic chiasm as the ___ of the temporal lobe.
Inferior; inferior optic radiations
Presentation of a temporal lobe lesion involving the inferior optic radiations?
Contralateral deficit in the patient’s superior visual world
Presentation of a L optic nerve lesion (excluding ocular/retinal causes)?
Blindness of the L eye
Presentation of an inner optic chiasm lesion?
Bitemporal heteronymous hemianopsia
Presentation of a L outer optic chiasm lesion?
R sided nasal heteronymous hemianopsia
Presentation of a L inferior optic radiation lesion (temporal lobe, Meyer’s loop)?
R superior homonymous quadrantanopsia
Presentation of a L superior optic radiation lesion (parietal lobe)?
R inferior homonymous quadrantanopsia
Presentation of a L occipital lobe lesion?
R homonymous hemianopsia with macular sparing
Congruence of visual field deficits increases when the lesion is more ___.
Posterior (occipital lobe, superior and inferior optic radiations)
In summary, optic ___ lesions produce scotomas or monocular blindness. Optic ___ lesions produce heteronymous visual field defects. Lesions of the ___ or ___ or ___ cortex produce homonymous visual field defects.
Nerve; chiasm; tract; radiations; occipital
Causes of acute unilateral optic nerve lesions in younger and older adults?
Younger - demyelination (MS, etc.)
Older - ischemia
Presentation of optic neuritis?
Sudden blindness of part (scotoma) or all of one eye, which may feel achy or tender with eye movement; pupils constrict poorly or not at all with light shined into the involved eye, but constrict normally with light shined into the normal eye
Optic disc appears swollen with indistinct, blurry margins
Weeks to months after acute optic neuritis, vision has recovered completely or partially. What residual deficits may remain?
Residual scotoma with or without impaired visual acuity or color vision; possible relative afferent pupillary defect
Presentation of optic atrophy (due to loss of ganglion cell axons)?
Optic disc appears more white or pale with sharply defined edges