Contiune vision Flashcards by Omar Gazar

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 ?

Retinal adapation
Dark + Light adapataion

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Compare between dark and light adapation in Definition

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

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Compare chemical changes in light and dark adapation

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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Compare non-chemical neuronal changes in ligh and dark adpaation

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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Dark adapation curve explain compnents

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

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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Explain Von Kries Theory

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

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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What results from optic nerve lesion ?

Ipisilateral blindness
Lost Direct LR
intact consensual LR amaroutic pupil

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amaroutic pupil occurs in case of ?

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

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BiTemporal heteromynous hemianopia causes ?

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

Binasal heteromynous hemianopia
Hemanopic pupil

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

Right ant2/3 optic nerve lesion
with Hemianopic pupil

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left(crossed) homonyomus hemanipopia +spared light reflex

right post 1/3 optic tract lesion

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What happens in cases of right optic radiations lesion

Crossed left homonymous hemianopia+
Preserved intact Light reflex

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Left homonymous SUPERIOR quadrantanopia occurs in case of?

Lesion in Rigt Temporal radiation with intact Light reflex

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Left homonymous SUPERIOR quadrantanopia occurs in case of?

Lesion in Right Temporal radiation with intact Light reflex

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Right homonymous Inferior Quadrantanopia occurs in case of ?

Left Pariteal Radiation with intact Light reflex

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Compare between lesion in Superior and inferior 1ry viusal cortex

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

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Compare between lesion in Superior and inferior 1ry viusal cortex

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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Mention results of lesion of tip of visual cortex unitlateral

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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Mention results of lesion of tip of visual cortex bilaterally

Bilateral loss of central vision
CENTRAL SCATOMA
Normal light reflex

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

Damage to visual association cortex
Light reflex is intact

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Peripheral vision loss with sparing mascular central vision due to ?

Large represnation area
separate represnetaion
Double blood supply

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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

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

The ability of eye to discrimnate different colors by cones ?

Color vision

Mention type of cones

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

When White is seen ??

When Cones are stimulated equally

Colors when mixed gives white?

Complemntary color Yellow + blue Red + green

Explian qualities of colors

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

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 ?

Young Helmholtz theory Trichromatic theory

Neural mechanism of discrimation of colors explain

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

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

Blobs

Inability to discrimnated colors ?

Color blindiness

Mention causes of Color blindness

X linked 8% men ,4% women Acuired : optic neuriris + DM + Glaucoma

Mention types of Color blindess

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

Mention types of Test of color blindess

colored wool test Ishiara test Eridge green lantern test

the ability to see images of both eyes withoud diplopia

Binocular vision

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

central

Corresponding ponints define

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

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

monocular vision

Mention requirements of binocular vision

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

Developent of Binocular vision

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

Mention grades of Binocular vision

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

Mention advantages of Binocular vision

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

Test of Binocular vision

Ambyloscope

Visual sensation after removal of a stimulus

After image phenomenon

Mention types of after image phenomenon

+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

Critical fusion frequency :

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

Critical fusion frequency direct porpotrionate to ?

Light intensity it is a test for viusal function

Sensation of separete successive visual stimuli produced by interruption of light

Flicker _________ if frequency increased = movie

all extraocular muscle 3 except SO4 LR6

ALL CN3 occlumotor Superior oblique Trochlear Lateral rectus Abducent

explain squint

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

saccades

Sudden jerky movments of eye during reading

Smooth pusrsiut optokinentic nystagmus

fixation on tress while moving on train

Vestibular movement

Maintains Visual fixation during head rotation

Converge movement

Looking at near object

Fixation movments

fixed eye on object on the field to see deatils

Voluntary fixation by which area ? involuntary?

Voluntary area 8 Invoulntary are 19

Describe fundus examination

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

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.

CONES -unstimulated nodal-1minute

Facotrs affecting viusal acuity enumerate

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

Landlolts chart is for ? Snellen chart

Testing visual acuity

الحمدلله رب العالمين