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Special sense Physiology > Contiune vision > Flashcards

Contiune vision Flashcards

1
Q

بسم الله الرحمن الرحيم
“قل إني أمرت أن أعبد الله مخلصا له الدين “
The ability of retina to adapt its sensitvity to different light intensities ?

A

Retinal adapation
Dark + Light adapataion

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2
Q

Compare between dark and light adapation in Definition

A

Dark adapation :
INcreased sensitivity and decreased threshold
Light adapation :
Decreased sensitvity and inccreased threshold

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3
Q

Compare chemical changes in light and dark adapation

A

Light adapation :
Bleaching is more than regenration so less photosenstivie pigment
Dark adapation :
Regenration is more than bleaching so increased concentration of photosensitive pigments

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4
Q

Compare non-chemical neuronal changes in ligh and dark adpaation

A

Light adapation :
Miosis to allow light to fall on central retina for cones
Maximal lumincity to yellow green (550nm)
Decreased singal intensity in bipolar - amacrine - horizontal - ganglion cells
________________________________
Dark adapation :
Mydriasis to allow light to fall on peripheral parts of retina for Rods
Maximal lumincity to green-blue (505nm)
Increased signal intensity in bipolar amacrine horizontal + ganglion cells

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5
Q

Dark adapation curve explain compnents

A

Rapid small compnent : cones 5-10m to be filled with pigments
Slow Large components : rods 20 -45m to be filled with pigments

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6
Q

In dark adpation which shares more in incraesing senstivity
chemical or nerutonal changes
which is faster ?

A

Chemical adapation takes 40 minutes for filling rods with pigments increasing sensitivity by thousands folds
Neuronal adapation : takes fractions of one second increasing sensitivity by few folds

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7
Q

Explain Von Kries Theory

A

Duplicity Theory :-
Vision occurs by 2 alternating mechanisms are:
Photopic Vision + Scotopic vision
Photopic vision = day vision for day vision by cones detecting details boundaries and Colors
Scotopic vision = dark vision dim light by rods cannot detecting colors detalis or boundaries

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8
Q

Explain purkinje shift phenomenon
concentrate on the name ! it is not purkinje sanson phenomenon

A

It is the shift from photopic cone to scotopic rod vision
_________________________________
During photopic : light wavelengthes appeas as different colors of which most luminous is Yellow green 550nm
During Scotopic : all wavelengthes and colors appear shades of grey
Most luminous is green-blue 505 nm
__________________________________
Red and blue are bright in phoptopic while in scotopic you can distinguish blue not red

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9
Q

What results from optic nerve lesion ?

A

Ipisilateral blindness
Lost Direct LR
intact consensual LR amaroutic pupil

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10
Q

amaroutic pupil occurs in case of ?

A

optic nerve lesion
Ipisilateral blindness
Lost Direct LR
intact consensual LR amaroutic pupil

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11
Q

BiTemporal heteromynous hemianopia causes ?

A

Central part of optic chiasma lesion
LR = Hemanopic pupil
when light falls from temporal field no response
but from nasal field LR occurs

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12
Q

What happens in case of lesion to peripheral parts of optic chiasma

A

Binasal heteromynous hemianopia
Hemanopic pupil

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13
Q

Left (crossed)homonymous hemianopia+hemanipic pupil why occurs>

A

Right ant2/3 optic nerve lesion
with Hemianopic pupil

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14
Q

left(crossed) homonyomus hemanipopia +spared light reflex

A

right post 1/3 optic tract lesion

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15
Q

What happens in cases of right optic radiations lesion

A

Crossed left homonymous hemianopia+
Preserved intact Light reflex

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16
Q

Left homonymous SUPERIOR quadrantanopia occurs in case of?

A

Lesion in Rigt Temporal radiation with intact Light reflex

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17
Q

Left homonymous SUPERIOR quadrantanopia occurs in case of?

A

Lesion in Right Temporal radiation with intact Light reflex

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18
Q

Right homonymous Inferior Quadrantanopia occurs in case of ?

A

Left Pariteal Radiation with intact Light reflex

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19
Q

Compare between lesion in Superior and inferior 1ry viusal cortex

A

Superior part: parietal radiation lesion =
inferior quadrantanopia
INferior part = Temporal radiation lesion = Superior quadrantanopi

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20
Q

Compare between lesion in Superior and inferior 1ry viusal cortex

A

Superior part: parietal radiation lesion =
inferior quadrantanopia
INferior part = Temporal radiation lesion = Superior quadrantanopia with macular SPARING !
both normal light reflex

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21
Q

Mention results of lesion of tip of visual cortex unitlateral

A

Hemianopic scatoma only macula !
loss of half of cental vision corssed homonymous
if right visual cotex tip lesion =
Left homonymous hemanopic scatoma
NORMAL LIGHT REFLEX

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22
Q

Mention results of lesion of tip of visual cortex bilaterally

A

Bilateral loss of central vision
CENTRAL SCATOMA
Normal light reflex

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23
Q

Visual agnosia occurs due to ? does it affect lIGHT REFLEX?

A

Damage to visual association cortex
Light reflex is intact

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24
Q

Peripheral vision loss with sparing mascular central vision due to ?

A

Large represnation area
separate represnetaion
Double blood supply

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25
Q

1-Ipsilateral blindeness + Light reflex consnesual intact while direct is damaged
2-Bitemporal hetero hemanopia
3-binasal hetero hemanipia
4-Crossed homo hemianopia
5-Central scatoma with loss of central vision

A

1-OPtic nerve lesion
2-Central chiasma
3-preipheral chiasma
4- optic tract - optic radiation - LGB - ALL visual cortex except maucla
5-Bilateral Lesion to tip of visual cortex

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26
Q

The ability of eye to discrimnate different colors by cones ?

A

Color vision

27
Q

Mention type of cones

A

Red cones : maximal absorption 570 nm
Green cones : maxinal absosption 535 nm
Blue cones : maximal absorption 445 nm

28
Q

When White is seen ??

A

When Cones are stimulated equally

29
Q

Colors when mixed gives white?

A

Complemntary color
Yellow + blue
Red + green

30
Q

Explian qualities of colors

A

Hue: acutal color with specific wavelength
Brightness lumisisty: The amount of light in the color : dark color : light color
Satuartion : purity of color the amount of white in the color

31
Q

Any color is seen by stimulation of different 3 cone types .
The Retina is responsible for perception of colore
The Visual cortex is resopinsilbe for Descrimination and interpretation of colors
Pereceving different frequencies from all 3 stimulated cones
White = equal stimulation
this is called ?

A

Young Helmholtz theory
Trichromatic theory

32
Q

Neural mechanism of discrimation of colors explain

A

Cones stimulated
stimulates bipolar to
parvocellular ganglion cells ( broad band + Single opponent + double opponent )
________________________________________
to parvocellular neurons in LGB to blobs of visual cortex color sensitive neurons

33
Q

 Special columns of neurons in 1ry visual cortex
 Stimulated by colors
 The primary areas for coding colors.

A

Blobs

34
Q

Inability to discrimnated colors ?

A

Color blindiness

35
Q

Mention causes of Color blindness

A

X linked
8% men ,4% women

Acuired : optic neuriris + DM + Glaucoma

36
Q

Mention types of Color blindess

A

Anomolaus tirchrmotus ;
Protanaomaly red
Duetranomaly green
Tritranomaly blue
________________
Dichromatic :
Protanopia red lost
Deutranopia green lost
Tritanopia blue lost
___________________
Monochrmoatic :-
oNE system only

37
Q

Mention types of Test of color blindess

A

colored wool test
Ishiara test
Eridge green lantern test

38
Q

the ability to see images of both eyes withoud diplopia

A

Binocular vision

39
Q

because there is overlap in the …part
of visual field of both eyes

A

central

40
Q

Corresponding ponints define

A

The points on both retina where image fall to be seen binocularly as Fovea centralis

41
Q

The peripheral parts of the temporal field of vision of each
is area of ……………. i.e. seen by one eye

A

monocular vision

42
Q

Mention requirements of binocular vision

A

SMC
Sensroy:
intact refreactive power + Lens + Retina +Visual pathway for sharp equal clear images of object
MOtor :
Extraocular muscles intact nerve supply
Cortical :
intact visual cortex area 17 for images fusion

43
Q

Developent of Binocular vision

A

6weeks : Macular vision
6 months : Binlcualer fixation
6 years : Binocular complete development

44
Q

Mention grades of Binocular vision

A

Grade 1 : perceprtion of Both images
Grade 2: Fusion of Both images
Grade 3: steroscopic for 3D dimensions

45
Q

Mention advantages of Binocular vision

A

1-Larger viusal field
2- Optical defect of one eye is compensated by the other normal eye
3-Better steroscopic vision

46
Q

Test of Binocular vision

A

Ambyloscope

47
Q

Visual sensation after removal of a stimulus

A

After image phenomenon

48
Q

Mention types of after image phenomenon

A

+After image : still seeing the image after closing eyes or light due to retinal after discharge
-After image : When concentratgin on a color ( yellow) then looking on white screen u will see the complementaty color (blue ) due retinal adapation

49
Q

Critical fusion frequency :

A

Continuous sensation of light from 24-60 visual stimuli /second casuing perception of motion pictures

50
Q

Critical fusion frequency direct porpotrionate to ?

A

Light intensity
it is a test for viusal function

51
Q

Sensation of separete successive visual stimuli produced by interruption of light

A

Flicker
_________
if frequency increased = movie

52
Q

all extraocular muscle 3 except SO4 LR6

A

ALL CN3 occlumotor
Superior oblique Trochlear
Lateral rectus Abducent

53
Q

explain squint

A

When there is unequal contraction of EOMs of both sides
the light falls on non Corresponding points of both retinae Causing formation of one good image and the other is bad one
the brain suppress the bad image from squinting eye becoming weak ( ambylopia exanopia )
affect 4 of children below 6

54
Q

saccades

A

Sudden jerky movments of eye during reading

55
Q

Smooth pusrsiut optokinentic nystagmus

A

fixation on tress while moving on train

56
Q

Vestibular movement

A

Maintains Visual fixation during head rotation

57
Q

Converge movement

A

Looking at near object

58
Q

Fixation movments

A

fixed eye on object on the field to see deatils

59
Q

Voluntary fixation by which area ?
involuntary?

A

Voluntary area 8
Invoulntary are 19

60
Q

Describe fundus examination

A

By opthalmoscope + system of mirrors
IMp :
1-eye diseases : Glaucoma + retinal Hge + retinins pigementosa
3-Diagnosis of Intracranial tunor
4-Determination of error of refreaction

61
Q

Visual acuity
Definition: it is the ability to see 2 points as 2 separate points.
Requirements:
1- The 2 images must fall on 2 ……separated at least by
one ……. cone. (retinal distance more than 2 u).
2- The 2 points form an angle at the …..point not less
than ….. minute.

A

CONES -unstimulated
nodal-1minute

62
Q

Facotrs affecting viusal acuity enumerate

A

1-Illumination + contrast
2-Erroes of refraction +eye diseases
3-Fovea centralis most clear

63
Q

Landlolts chart is for ?
Snellen chart

A

Testing visual acuity

64
Q

الحمدلله رب العالمين

A

Special sense Physiology (8 decks)

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