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Neuroscience > L26 Visual System > Flashcards

L26 Visual System Flashcards

1
Q

what is the fundus?

A

back portion of the interior of the eyeball as it is seen through an ophthalamoscope (fundoscopy)

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2
Q

what is mitosis?

A

constricted pupil

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3
Q

what is mydriasis

A

dilated pupil

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4
Q

what is neovascular associated with

A

abnormal new blood vessel formation

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5
Q

describe the sclera

A

continuation of the dura mater from the optic n. that wraps around and becomes the cornea anteriorly!

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6
Q

where is aqueous humor found?

A

anterior and posterior chambers

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7
Q

where is the vitreous humor found?

A

the rest of the eye (aka everything but A/P chambers)

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8
Q

which is more viscous - aqueous humor or vitreous humor

A

vitreous humor

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9
Q

through what structure does light enter the eye?

A

pupil and iris

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10
Q

what makes up the optic apperatus of the eye?

A

cornea and lens

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11
Q

what structures play a role in accomodation

A

ciliary muscles and suspensory ligaments (zonule fibers)

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12
Q

what 3 structures constitute the occular funds?

A

optic disc
fovea
macula

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13
Q

what is the optic disc and what are its characteristics

A

location of the optic n. ending/head
NO photoreceptors
Blindspot!

can see in ophthalamoscope - all vessels emerge form here

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14
Q

define photoreceptor

A

specialized type of neuron found in the retina that is capable of phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell’s membrane potential.

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15
Q

what is papilledema?

A

increase ICP = remember that optic n. has meninges and CSF so they can swell too!

decrease in venous drainage leading to dilation of retinal veins
the disc will appear white not pink (ophthalamascope)

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16
Q

where is the fovea located and what are its characteristics?

A

in the center of the retina

  • superficial layers of the retina are pushed laterally so there is easier exposure of the cones to light
  • highest density of CONES (no rods) = creates the highest point of visual acuity
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17
Q

when do rods function optimally

A

low light - dark

18
Q

when do cone function optimally

A

light and color

19
Q

what is the macula and where is it located

A

region of high visual acuity

surrounds the fovea

20
Q

define refractive power

A

inverse of the focal distance in meters = measured in Diopters “D”

21
Q

what is the refractive power of the cornea?

A

42 D - cornea is responsible for the main refractive power of the eye

22
Q

what is the refractive power of the lens

A

13D to 26D - responsible for the modulation of refractive power (plasticity) during accommodation

23
Q

Far vision - what is the state of ciliary muscle, lens, suspensory ligaments, refractive power

A

ciliary muscle - relaxed
lens - flattened
suspensory ligaments - tight
refractive power - reduced (image falls deeper into the eye)

24
Q

Near vision - what is the state of ciliary muscle, lens, suspensory ligaments, refractive power

A

ciliary muscle - constricted
lens - round
suspensory ligaments - loose
refractive power - increased (image is pulled back so the image is more forward in the eye so it can land properly on retina)

25
Q

define refractive plasticity

A

refractive power variability of the lens from 13-26D

declines with age -

26
Q

define presbyopia

A

lens looses its elasticity during aging, thereby reducing the ability to focus on near objects

the lens will stay more flattened thus better able to maintain far sight but near sight diminishes thus the use of +D reading glasses

27
Q

define visual acuity

A

ability to distinguish between 2 nearby points

high when 2 point discrimination threshold is low (high spatial resolution)

28
Q

what are the factors that visual acuity depend on?

A
  1. density of photoreceptors

2. lens accomodation

29
Q

what is the general distribution of photoreceptors?

A

best at fovea - highest visual acuity
better at macula
absent in optic disc

30
Q

what happens when lens accommodation is not working properly?

A

inability to focus image on the retina results in blurry image which decreases acuity

31
Q

define emmetropia

A

normal sightedness - the length of the eyeball matches correctly with the refractive power of the optical apparatus

32
Q

define myopia

A

nearsightedness

the lens is TOO powerful for the length of the eyeball so the image is focused before reaching the retina

33
Q

why do they call it nearsighted and farsighted?

A

nearsighted - vision is best during near vision

farsighted - vision is best during far vision

34
Q

what type of glasses will correctly place the image more posterior to match the retina in nearsightedness?

A

concave (-) D glasses

)( = concave

35
Q

define hyperopia

A

farsightedness

the lens is too weak for the length of the eye so the image is focused beyond the retina

36
Q

what type of glasses will correctly place the image more anterior to match the retina in farsightedness?

A

convex (+) D glasses

() = convex

37
Q

what does a score of 20/200 mean?

A

you can read the same number at a distance of 20 feet which a person with normal vision could read at a distance of 200 feet!

38
Q

what happens with a detached retina?

A

retina separates from the retinal pigment epithelium and those detached areas lose their function

lazer surgery can stop the detachment process but will not correct the damage that already occurred

39
Q

explain macula degeneration

A

most common cause of vision loss
often due to neovascular causes
most ppl can see enough to dress, eat, walk etc.
lazer tx is the only choice but has low effectiveness and recurrence is very common

40
Q

explain diabetic retinopathy

A

begins with development of SCOTOMAS
usually unnoticed by pt until the macula is involved - then vision REALLY decreases
retinal defects are caused by blood supply dysfunction including decreased permeability and aneurisms

41
Q

what is a scotoma?

A

pathological blind spot - ring of lost vision surrounded by ring of decreased light

Neuroscience (54 decks)

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