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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
Mechanism of photoreceptor
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 5. Hyperpolarization of the photoreceptor membrane decreases the release of glutamate 6. Ionotropic receptor- inhibitory metabotropic receptor- excitatory
26
Why is Vit A important for vision?
Regeneration of 11­cis retinal requires vitamin A, and defciency of vitamin A causes NIGHT BLINDNESS
27
Bipolar cells response to glutamate
- The off bipolar cells are depolarized by glutamate.  | - The on bipolar cells are hyperpolarized by glutamate. 
28
What is visual acuity?
he ability of the eye to identify two closely placed objects at two distinct point
29
Optic nerve damage will cause?
Blindness in the affected eye. Monocular Blindness.
30
Optic Chiasma damage will cause?
Lose of temporal visual feels on both sides. Bitemporal Heteronymous Hemianopia
31
Damage to the upper or right geniculocalcarine tract
Left homonymous inferior quadratic anopsia. (parietal or occipital tumor) lower left quadrant
32
Light Adaptation
Visual system adjusts in seconds to the brighter environment by decreasing its sensitivity
33
Dark Adaptaion
sensitivity increases slowly over many minutes. | Maximum dark adaptation occurs in 20 mins
34
Strabismic Ambyopia
visual axis of the two eyes are not parallel this is called strabismus
35
Dichromacy Color Blindness
blue cone (tritanopia) is rare. red cone (protanopia) green cone (deuteranopia)
36
Retinitis Pigmentosa
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
Argyll Robertson Pupil.
Accommodation- YES | Light reflexes- NO
38
Adie's Pupil
Sluggish constriction of the pupil to light. Dilation of the pupil is delayed. Pathological changes in the ciliary ganglion.
39
Marcus-Gunn Pupil
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
Weber Syndrom
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
Parinaud Syndrome
Lesions in the pretectal area. upward gaze, a large pupil,
42
What is a light reflex?
light is focused on one eye, the pupils of both eyes constrict stimulated eye: direct light reflex other eye: consensual
43
What is the accommodation reflex?
pupils of both eyes constrict on looking at a near object
44
When is direct light response impaired?
lesions of: - ipsilateral optic nerve - the pretectal area - ipsilateral parasympathetics traveling in CN III - pupillary constrictor muscle of the iris.
45
When is consensual light response impaired?
lesions of: - contralateral optic nerve - pretectal area - ipsilateral parasympathetics traveling in CN III - pupillary constrictor muscle.
46
When is accommodation response impaired?
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
How is an afferent pupillary defect detected with swinging flashlight test? Marcus Gunn
the flashlight is moved from the normal to the affected eye, and the affected pupil dilates in response to light

z. Neuro Class (19 decks)

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