VISION Flashcards
IN a snellen, The letter at the top of the chart subtends ________
at a distance of 200 ft
5 min of an arc
________ is reported as a nonmathematical fraction
that represents the patient’s ability compared to
that of a person with normal distance vision
Acuity
The clarity of these
media can be determined ophthalmoscopically, and a
complete examination requires that the pupil be dilated
to at least ________ in diameter. This is accomplished by
instilling two drops of _____________ in each eye after the
visual acuity has been measured,
6 mm
- 5 percent phenylephrine and/ or
- 5 to 1.0 percent tropicarnide
Rarely, an attack of __________
(manifesting itself by diminished vision, ocular pain,
nausea, and vomiting) may be precipitated by pharmacologic
pupillary dilatation
angle-closure glaucoma
The rod cells
contain ____________ a conjugated protein in which the
chromophore group is a carotenoid akin to vitamin A.
rhodopsin,
The rods function in the perception of visual stimuli in
subdued light___________ and the cones
are responsible for color discrimination and the perception
of stimuli in bright light ____________
(twilight or scotopic vision),
(photopic vision).
The fibers derived from macular cells
form a discrete bundle that first occupies the _________of the disc and optic nerve and then assumes a more
_____________within the nerve (papillomacular bundle).
temporal side
central position
Damage to the papillomacular
bundle produces the ____________(extending
from fixation to the blind spot).
“cecocentral” scotoma
Lesions at the junction of the
optic nerve and chiasm, generally compressive in nature,
may cause a small contralateral superotemporal quadrantic
defect in addition to the expected central scotoma
in the ipsilateral eye _________
(“junctional scotoma
if
the lesion has an anterior extension to the junction with
one optic nerve there is a loss of full-field vision in that
_________
eye and a partial loss in the other (“functional scotoma”).
___________, there is an abnormality
of chiasmatic decussation, in which a majority of the fibers
cross to the other side
In albinism
Approximately __________of the fibers of the optic
tract terminate in the lateral geniculate body, a thalamic
nucleus, and synapse with the six laminae of its neurons
80 percent
Three of these laminae (1, 4, 6), which constitute the large
dorsal nucleus, __________, and three (2, 3, 5) receive ___________
receive crossed (nasal) fibers from the contralateral eye
uncrossed
(temporal) fibers from the ipsilateral eye
Selective occlusion of either component of the dual blood supply to the
lateral geniculate, consisting of the anterior and posterior
choroidal arteries, is infrequent but when it does occur,
produces a characteristic _________
“multiple sectoral field defect
Other optic tract fibers terminate in the pretectum
and innervate both Edinger-Westphal nuclei, which subserve
__________
pupillary constriction and accommodation
A small group of fibers terminate in the ____________in animals and presumably also in
humans.
suprachiasmatic
nuclei
It supplies the inner retinal layers and issues
from the optic disc, where it divides into four branches,
each of which supplies a quadrant of the retina; it is these
vessels and their branches that are visible by ophthalmoscopy.
central
retinal artery
In up to a third of the population, a small cilioretinal artery may arise from
either the_________
and supply the macula
choroidal circulation or from the circle of ZinnHaller
It must be made clear, however, that an ophthalmoscopic appearance identical to that of papilledema can be
produced by____________ and by
___________
infarction of the optic nerve head (the “papillopathy” of anterior ischemic optic neuropathy).
inflammatory changes in the intraorbital portion of the optic nerve ("papillitis", a form of optic neuritis).
In its mildest form, papilledema appears as slight
elevation of the disc and blurring of the disc margins,
especially of the________ and a mild
fullness of the veins in the disc.
superior and inferior aspects,
Because many normal individuals,
especially those with _______, have ill-defined disc margins, the early stage of papilledema may be difficult
to detect
hypermetropia
On the other hand, the presence of spontaneous venous pulsations is a reliable indicator of an
intracranial pressure below______and thus usually
excludes papilledema
200 mm H20,
More severe degrees of papilledema appear as further
elevation, or _______ of the entire disc and
surrounding retina
“mushrooming”
Purely unilateral edema of the optic disc
is indicative of a_________, but it can sometimes occur at
an early stage of increased intracranial pressure.
perioptic meningioma or other tumor
involving the optic nerve
______, while it may enlarge the blind
spot slightly, does not greatly affect visual acuity
Acute papilledema
Chronic or recurrent papilledema
may result in ________and cause a reduction
in visual acuity by that mechanism.
optic atrophy
_______
which occurs when papillitis in one eye occurs years after
an optic neuropathy of the opposite one.
“pseudo-Foster Kennedy syndrome,”
Papilledema caused by increased intracranial pressure
cannot be distinguished from combined edema of the optic
nerve and retina, which typifies _____
malignant hypertension.
Chronic papilledema, as occurs in ________ presents a special problem in diagnosis,
and represents a risk for permanent reduction in visual
acuity from secondary optic atrophy.
pseudotumor cerebri
The essential element in the pathogenesis of papilledema
is an_______
increase in pressure in the sheaths surrounding
the optic nerves, which communicate directly with
the subarachnoid space of the brain