Color blindness
supervisor : prof.mahmoud salah
By :
Hashim al-shakhs .
Talal al-zahrani .
Zeid al-enezi.
Yahya al-faqihi
Objectives of this
seminar :
• Anatomy of the eye.
• Normal physiology of vision .
• Definition of Color blindness.
• Types of color blindness.
• Etiology of Color Blindness .
• Signs and symptoms of Color Blindness .
• Clinical examination of Color Blindness .
• management of Color Blindness .
• Summary.
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1. Sclera : Basically, this is the white of the eye. Attached to the sclera are six ………
muscles, which enable us to look left, right, up and down.
2- cornea : Although normally only half a millimetre thick, the cornea is responsible for
seventy percent of the total focusing of the eye. It is the most important layer in the refractive
procedure and, together with the lens, forms a clear image on the back of the ………… .
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3-Choroid – The choroid runs behind the retina and, at the front of the eye,
forms the ciliary body. As it contains many blood cells, the choroid supplies
the eye with nutrients and oxygen – as well as removing waste.
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4- ciliary body: The ciliary body comprises two parts – the ciliary process and
the ciliary muscle. It is the latter which causes the lens to change shape.
If the eye is focusing on a distant object the muscles relax, causing the ligaments
to tighten and the lens to lengthen. When we focus on an object nearby the muscles
tighten, the ligaments slacken, and the lens shortens.
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Basic Anatomy of the Eye
5. Iris {,diaphragm} and 6. Pupil:
The iris is the -------------- part of the eye.
The color of the iris is determined by the color of the connective tissue and ------------- cells.
Less --------- makes the eyes blue; more pigment makes the eyes brown.
The iris is an adjustable diaphragm around an opening called the -------------- .
Iris Pupil
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Iris Pupil
The iris has two muscles: ( intrinsic muscles of eye ball )
The dilator muscle makes the iris ----- and therefore the pupil ------,
allowing more light into the eye;
the sphincter muscle makes the iris ------- and the pupil -------- ,
allowing less light into the eye.
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The back of the --------- contains a deep layer of light sensitive
cells called rods and cones.
This is where the image is projected. Rods are responsible
for -------vision, while cones are responsible for ------- vision.
The cones also allow us to see in colour and detail.
The retina also contains a layer of --------- cells on the surface.
These cells connect the nerve fibres to the -------nerve.
This means that the nerve fibres actually pass over the sensitive
part of the eye,.
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Macula lutea – pigmented central region of the retina containing fovea.
Fovea – greatest capacity for fine detail discrimination.
Optic nerves – The optic nerve transmits electrical impulses from the ---------to the ---------. It
connects to the back of the eye near the ---------. When examining the back of the eye, a
portion of the optic nerve called the ------------ can be seen.
.
14. Lens
The lens is a clear, bi-convex structure about 10 mm (0.4 inches) in
diameter.
Accommodation : The lens CAN changes shape (by using muscles of
the the ciliary body 4). The lens is used to fine-tune vision.
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Conjunctiva
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Cornea
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Aqueous
Humour
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Iris
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Pupil
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Ciliary
Muscles
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Suspensory
Ligaments
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Lens
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Vitreous
Humour
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Retina
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Fovea
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Optic
Disc
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Choroid
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Sclera
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Optic
Nerve
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Physiology of the vision
Three aspects are important when discused vision :
• Optics of vision .
• Receptor and neural function of the retina .
• Central neurophysiology of vision .
1- optics of vision :
• The eye is equivalent to the usual photographic camera . It
has a lens system . A variable aperture system (pupil) and a
film ( retina ) .
• The lens system of the eye is composed of 4 refractive
interfaces :
1- air Cornea .
2- cornea aqueous humer.
3- aqueous humer lens.
4- lens vetruos humer.
Con …:
• Reduced eye :
In the reduced eye , a single refractive surface is
considered to exist , far from retina by 17 mm , and the
totarefractory power is 59 diopters .
• Formation of an image :
the eye lens is biconvex , and it can focusing the light rays on
the retina . The image is inverted and reversed with respect
to the object .
2- receptor and neural
function of the retina :
• Retina is the light sensitive portion of the eye .
Contains 2 types of photoreceptors cons ( color
vision ) and rods (night vision) .
• Retina had also a pigmented layer to prevent
scattering of light .
Cont …:
• 4 functional segments of either a con
or a rod :
- Outer segment .
- Inner segment :
Usual cytoplasm .
- Nucleus .
- Synaptic body :
Synapsed with bipolar and horizontal cells .
Cont ….
• The outer segment consist of large number of
discs (1000 in each rod or cone ) .
• In the membrane of those discs , the light –
sensitive photochemical ( rhodopsin , color
pigments ) are incorporated as a form of
conjugated , transmembrane proteins . ( 40 %).
Cont…
• Photochemistry of vision :
both rods and cones contain chemicals that decompose on expose to
light ( rods rodopsins , cones color pigments ).
- Excitation of the rods ( rhodopsin retinal visual cycle ):
In the outer segment of rods > ( 40 % rohdopsins = scotopsins + 11-cis
retinal )
Cont …
• When rhodopsins absorbed light , the photos
change the 11-cis retinal into all-trans form of
retinal , witch not fits to bound with scotopsin , so
the rhodopsins begins to decomposed into (
scotopsins and all-trans retinal ).
• One of the intermediates to reach scotopsin , is
metarhodopsin 2 activate many molecules of
transduction activate the phosphodisterase .
Cont …
• The phosphodisterase enzyme destroy cGMP
molecules. Without cGMP the sodium chanels
well closed . Less sodium influx to the rode .
• That mean more negativity on the rod, in other
words (hyperpolarization of the rod) initiate
a receptor potential action potential
along the visual pathway toward the visual cortical
areas in the occipital lope of the cerebrum .
Color vision :
• Is the result of activation of cons , there is 3
types of cones :
- Blue cone .
- Green cone.
- Red cone .
• The same cycle but the opsins are different .
Color blindness
(definition)
• Color blindness results from an absence or
malfunction of certain types of cons in the retina.
• The term "color vision problem" is often used
instead of color blindness because most people
with color blindness can see some color. Very few
people with color blindness can see no color at all.
Types ;
• The list of types of Color blindness mentioned in various
sources includes :
• Dichromasy : black-and-white vision; very rare
• Red-green color blindness : inbility to distinguish red and green
• Deuteranopia:A type of altered vision with a confusion of greens and
reds.
• Protanopia :The inability to see all four primary colours rather limited to
seeing blu and yellow.
Etiology :
# The main cause of color blindness is hereditary .
# there are some other causes but it is very rare
like:-
*Shaken Baby Syndrome .
*accidents and trauma .
*Exposure to ultra violet rays .
# causes of color
blindness
* The disease occurs almost in males but transmitted through the
females because the female X chromosome code for the
respective cones .
so…
* The female has at least one of her two X chromosome
has normal gene for each type of cone .
* The male has only one X chromosome which is usually
inherited from the mother ,so that a missing gene lead
to color blindness.
Signs and symptoms :
• The symptoms of color vision problems vary with
the severity of the condition. In some people the
problem is very minor, and they may not even be
aware that they see color differently from people
with normal color vision.
• In other people the color vision problem is severe,
and they can distinguish only a few shades (a
person with normal color vision can see many
thousands of colors). In rare cases, a person
cannot see color at all but sees only black, white,
and gray.
Clinical examination ;
• There are a few methods for Color Blindness
testing.
• The most used is the pseudisochromatic Ishihara
plates test.
• This test will use of a series of specially designed
pictures composed of colored dots, which include
hidden numbers or embedded figures that can
only be correctly seen by persons with normal
color vision .
Cont..
• It is possible for a person to have
poor color vision and not know it.
Quite often, people with red-green
deficiency aren't even aware of their
problem since they've learned to see
the "right" color. For example, tree
leaves are green, so they call the
color they see green.
Both normal and those with all colour vision deficiencies
should read the number 12.
Those with normal colour vision should read the number
8.
Those with red-green colour vision deficiencies should
read the number 3.
Total colour blindness should not be able to read any
numeral.
Normal colour vision should read the number 6.
The majority of those with colour vision deficiencies
cannot read this number or will read it incorrectly.
vedio
Management :
• There is no medical treatment for color blindness
that is inherited. Some acquired color vision
problems can be treated, depending on the cause.
• Color blindness that is acquired may sometimes be
improved by surgery. For example, if you are
having trouble seeing colors because of cataracts,
surgery to treat the cataracts may improve color
vision. If the problem is caused by a side effect
of medication, color vision may be improved when
that medication is stopped.
Cont ….
• Specially tinted contact lenses and eyeglasses
may help the patient to see differences between
colors. However, these lenses do not provide
normal color vision and can distort objects.
• Glasses that block glare (with side shields or wide
temples) are helpful because people with color
vision problems can see differences between
colors better when there is less glare and
brightness.
• Color vision problems cannot be prevented
Summary ;
• Eyeball is covered by 3 coats , fibrous ,
vascular pigmented and nervous .
• Nervous coat ( retina ) is sensitive to light.
• 2 main types of photoreceptors rods and
cons
• Cons are responsible of color vision.
• Any absence or malfunction of one or more
will lead to a type of ( color blindness).
,,, شكرا
Think you ,,,,