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z. Neuro Class > Visual System ppt 25 > Flashcards

Visual System ppt 25 Flashcards

1
Q

What is cataract?

A

Clouding of the lease. most common cause of blindness world wide.

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2
Q

What are the type of Cataracts?

A

Age-Related
Congenital
Secondary
Traumatic

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3
Q

What is glaucoma

A

high interocular pressure as a result of a buildup of aqueous humor within the anterior cavity.

Most common cause of blindness in the US

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4
Q

Normal Tension Glaucoma

A

here is damage to the optic nerve with a corresponding loss of vision, even though intraocular pressure is normal

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5
Q

The image that the retina receives is

A

inverted and upside-down

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6
Q

What is accommodation?

A

the process that increases the refractory power of the lens

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7
Q

What controls accommodation?

A

Ciliary muscle contraction controlled byt parasympathetic fibers

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8
Q

What is pupil constriction?

A

Lense Bulges for close vision. Parasympathetic input contracts the ciliary muscle loosening the ciliary zone allowing the lens to bulge

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9
Q

What is Astigmatism?

A

Occurs what the shape of the cornea is oblong. Prevents light to come into a single focal point.

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10
Q

What lens is used in astigmatism?

A

Cylindrical lense

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11
Q

What is Presbyopia?

A

Lose of lens elasticity with aging. Losing its ability to curve to focus on objects that are close

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12
Q

What is Hypermetropia?(Hyperopia)

A

Far Sightedness
the eyeball is too small of the lens is too weak.
focus is BEHIND the retina.

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13
Q

What kind of lens is used for Hypermetropia?

A

CONVEX lens

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14
Q

What is Myopia?

A

Near-sightedness.
the eye is too long or increased lens power.
focus is INFRONT of the retina

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15
Q

What kind of lens is used for myopia?

A

CONCAVE

MY big CAVE ins NEAR

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16
Q

Where is the Retina?

A

3rd and inner layer of the eyeball.
lines the posterior 3/4 of the eyeball

consists of pigmented layer and a neural layer.

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17
Q

What is the optic disk?

A

the optic nerve exits the eyeball. Bundled together with the optic nerve, the central retinal artery, and the central retinal vein.

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18
Q

What is the macula lutea?

A

the exact center of the posterior portion of the retina, at the visual axis of the eye.

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19
Q

What is the Fovea Centralis?

A

a small depression in the center of the macula lutea, contains only cones.

20
Q

What are the layers of the retina?

A
  • Photoreceptor layer
  • Bipolar cell layer
  • Ganglion cell layer
21
Q

What are the two types of cells present in the bipolar layer?

A

horizontal cells and amacrine cells

22
Q

What is the blind spot?

A

The optic disc because it contains no rods or cones

23
Q

What are characteristics of cons?

A 
Low sensitivity to light. 
Day vision
Mediate color vision
High concentration in Fovea
Less numbers then rods
24
Q

What are characteristics of rods?

A 
High sensitivity to light. 
Night vision
Saturate in day light. 
Achromatic
Absent in Fovea
More numbers then cones 20:1
25
Q

Mechanism of photoreceptor

A
  1. Light hits retina. Photoisomerization. 11cis Retinal-> all trans. Makes Metrahodopsin II.
  2. Metrahodopsin II activates G PROTEIN. gmp to 5gmp. decrease cGMP.

3/4. In dark increase in cyclic GMP levels, Na + inward current. Depolarization.
in light, decrease GMP closes Na channels. Hyperpolarization

  1. Hyperpolarization of the photoreceptor membrane decreases the release of glutamate
  2. Ionotropic receptor- inhibitory
    metabotropic receptor- excitatory
26
Q

Why is Vit A important for vision?

A

Regeneration of 11­cis retinal requires vitamin A, and defciency of vitamin A causes NIGHT BLINDNESS

27
Q

Bipolar cells response to glutamate

A
  • Theoffbipolar cells are depolarized by glutamate.

- Theonbipolar cells arehyperpolarizedby glutamate.

28
Q

What is visual acuity?

A

he ability of the eye to identify two closely placed objects at two distinct point

29
Q

Optic nerve damage will cause?

A

Blindness in the affected eye. Monocular Blindness.

30
Q

Optic Chiasma damage will cause?

A

Lose of temporal visual feels on both sides.

Bitemporal Heteronymous Hemianopia

31
Q

Damage to the upper or right geniculocalcarine tract

A

Left homonymous inferior quadratic anopsia. (parietal or occipital tumor)
lower left quadrant

32
Q

Light Adaptation

A

Visual system adjusts in seconds to the brighter environment by decreasing its sensitivity

33
Q

Dark Adaptaion

A

sensitivity increases slowly over many minutes.

Maximum dark adaptation occurs in 20 mins

34
Q

Strabismic Ambyopia

A

visual axis of the two eyes are not parallel this is called strabismus

35
Q

Dichromacy Color Blindness

A

blue cone (tritanopia) is rare.

red cone (protanopia)

green cone (deuteranopia)

36
Q

Retinitis Pigmentosa

A

visual disorder encompasses a diverse group of hereditary visual defects characterized by a gradual loss of vision caused by degeneration of photoreceptors. So far, mutations of about 30 genes have been linked

37
Q

Argyll Robertson Pupil.

A

Accommodation- YES

Light reflexes- NO

38
Q

Adie’s Pupil

A

Sluggish constriction of the pupil to light.
Dilation of the pupil is delayed.

Pathological changes in the ciliary ganglion.

39
Q

Marcus-Gunn Pupil

A

Nerve not tract

lesion in the afferent limb of the pupillary light reflex (e.g., Retrobulbar neuritis of the optic nerve seen in multiple sclerosis).
● Can be diagnosed by the swinging flashlight test.


40
Q

Weber Syndrom

A

downward and outward, drooping of the eyelid, and a dilated and nonresponsive pupil on the ipsilateral side, accompanied by contralateral upper motor neuron paralysis

41
Q

Parinaud Syndrome

A

Lesions in the pretectal area.

upward gaze, a large pupil,

42
Q

What is a light reflex?

A

light is focused on one eye, the pupils of both eyes constrict

stimulated eye: direct light reflex
other eye: consensual

43
Q

What is the accommodation reflex?

A

pupils of both eyes constrict on looking at a near object

44
Q

When is direct light response impaired?

A

lesions of:

  • ipsilateral optic nerve
  • the pretectal area
  • ipsilateral parasympathetics traveling in CN III
  • pupillary constrictor muscle of the iris.
45
Q

When is consensual light response impaired?

A

lesions of:

  • contralateral optic nerve
  • pretectal area
  • ipsilateral parasympathetics traveling in CN III
  • pupillary constrictor muscle.
46
Q

When is accommodation response impaired?

A

Lesions of:

  • ipsilateral optic nerve
  • ipsilateral parasympathetics traveling in CN III
  • pupillary constrictor muscle
  • bilateral lesions of the optic tracts to the visual cortex.

SPARED: pretectal area

47
Q

How is an afferent pupillary defect detected with swinging flashlight test? Marcus Gunn

A

the flashlight is moved from the normal to the affected eye, and the affected pupildilatesin response to light

z. Neuro Class (19 decks)

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