EYE1 Flashcards
(39 cards)
بسم الله الرحمن الرحيم وبه نستعين
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Special senses have distant teleceptors except for ?
Taste
Mention layers of Eye
Outer fibrous coat
Middle vascular pigmented coat
inner nervous coat
Describe outer fibrous layer of eye
Formed of :
Cornea the anterior tranparent 1/6
Sclera the remaining 5/6 hardest strcutre of eye
Covered anteriorly by conjunctiva
Connected to cornea at Limbus froming corneoscleral junction
Uveal tract show structures
Middle vascular pigmented coat:
1-Choroid :- 5/6 of coat vessels + melanin
2-Ciliary bodies: ciliary muscle + suspensory ligaments + ciliary process for secertion
3-Iris : perofrated disc with hole of pupil
containing muscles: constrictor + dilator pupillae
Explain retina structure
it is inner nervous coat of Eye
containing 10 layers and Rods and cones photorecpetors +
Macula lutea + Fovea centralis containing the Cones
Optic disc or blind sopt the side of exit of optic nerve
3mm from nasal side of macula
Mention contents of eye ?
Lens
Aquos humor water infront of lens
Viterous humor jelly fluid of hyalouronic acid + collagen + h2o behind the lens
Mention chabers of eye ?
Anterior chamber : between cornea and iris containing aqueous humor
Posterio chamber between iris and lens containing aqueous
Viterous chamber between lens and retina containig the Viterous body humor
Electromagnetic radiation may be:
- Short wave length e.g.?
- Long wave length e.g. ?
short x ray
long radio
the visible portion of the electromagnetic radiations
Light from 400 to 700nm
Mention imp of ultraviolet and signifcance of infraRed?
Ultraviolet ? FKD
Darkening skin
Killing bacteria
Forming Vit D
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InfraRed :
Heating effect
When light falls on object it is ?
Absorbed
Reflected
Rrefracted
according to the object
Refraction is: the change in ,,,,,,and/or ,,,,,,of light
velocity- direction
Refercation depends on ?
1-
2-
3-
?
1-Refraction index
2-Angle of incidence
3-degree of curvature
Refrative index of medium RI
?
RI = Velocity of light in air/Velocity of light on medium it is always > 1
☺1 RI of aqueous:
☺2 RI of vitreous:
☺ 3RI of cornea:
☺4 RI of Lens:
☺5 RI of air:
AQUOUS = 1.33
VITEROUS =1,34
Cornea=1.38
LENS=1,4
air = 1
If light falls:
Perpendicular:
Forming and angle:
prependicular: Only velocity changed
Angle : Veolcity + direction changed
Degree of curvature and refreaction !
a) Concave lens: →
b) Convex lens: →
Concave diverge parallel rays
Conves converge parallel rays
Center of lens = ,,,,,point
Point of focusing = ,,,,,point
Focal length =
cente= nodal
focal ponint
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focal length the distance between nodal and focal points
Power of lens = ?
1/focal length (m) =
1/object distance + 1/image distance
The focal length of whole eye = ?
so the the power = ?
17mm
60 diopeters
The focal length of whole eye = ?
so the the power = ?
17mm
60 diopeters called resting eye power
The most imp part of eye for refraction ?
-The anterior Surface of cornea: responsible for 40 Diopters
because most of refraction occurs at the air-cornea interface
any change in object distance → a change in lens dioptric power.
why?
Lens formula:
𝟏/
𝐟𝐨𝐜𝐚𝐥 𝐥𝐞𝐧𝐠𝐭𝐡 𝐢𝐧 𝐦𝐞𝐭𝐞𝐫𝐬
=
𝟏/
𝐨𝐛𝐣𝐞𝐜𝐭 𝐝𝐢𝐬𝐭𝐚𝐧𝐜𝐞 𝐢𝐧 𝐦𝐞𝐭𝐞𝐫𝐬
+
𝟏/
𝐢𝐦𝐚𝐠𝐞 𝐝𝐢𝐬𝐭𝐚𝐧𝐜𝐞 𝐢𝐧 𝐦𝐞𝐭𝐞𝐫𝐬
but image distance is constant
so any change in object distance changes the focal length
if increased the focal length decreases increasing the power of lens
Mention protective mechanisms of eye
Bony orbit for post 2/3
Eyelid for ant 1/3 and during sleep forcovering eye
Tear film moistening and protecting cornea and conjunctivaR
Eye reflexes
