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physiology of the eye

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by

asmaa ali

on 21 September 2016

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Transcript of physiology of the eye

physiology of the eye
content of the prelab.:
Structure of the eye
Ocular hypertension and glaucoma
Cataract
Structure of the eye
sclera:
the white part of the eye
it gives the eye its round shape
cornea
1/6 of the outer part of the eye
transparent doma that protect the eye
first and more powerful light focusing element
conjunctiva
clear transparent mucous membrane
lines the inner surface of eyelids
continue to cover the front surface of the eye ball except cornea
the colored disc inside of the eye
between the cornea and crystalline lens
capable of stretching and reducing the size of the eye opening.
( how ?! )
the pupil:
like the aperture of the camera
the size of the pupil opening can be adjusted by dilation of the iris.
crystalline lens
transparent lens just behind the iris
the secondary light focusing element
along with cornea, it helps to refract light to be focused on retina.
accomodation for near and far vision
the lens is attached to ciliary muscles that contract and relax in order to change the shape of the lens
ciliary body:
it secretes the aqueous humor which:
contain antibodies for eye protection
nourishes the eye
the drainage of aqueous humor is:
controlled by: canal of schlemm
through: trabecular meshwork
vitreous humor
the clear gel that occupies the posterior champer of the eye and 80% of the eye ball.
located between the crystalline lens and retina
it gives the eye its rounded shape
light is transmitted through the vitreous humor to the retina.
retina
the innermost layer of the eye
like the film of the camera
nerve tissue
(sense the light and send impules)
Retina
optic nerve
(carry them to the brain)
brain
(translate into images)
macula lutea:
provides the clearest and most distinct vision.
extra ocular muscles:
6 muscles outside the eye.
responsible for the rotation of the eye.
what is Strabismus
ocular hypertension & glaucoma
ocular hypertension refers to any situation in which the pressure inside the eye is higher than normal.
normal range:
10 - 21 mmHg
ocular hypertension:
above 21 mmHg
intraocular pressure can be elevated due to:
Eye pressure is created by continual renewal of the fluids in the eye.
aging
anatomical problems
inflammation of the eye
genetic factors
as a side effect from medications
during exercise
types of glaucoma
open-angle glaucoma



angle - closure glaucoma
open angle glaucoma
( chronic glaucoma )
most common form ( 90% of the cases )
has a wide and open angle between iris and cornea.
caused by slow clogging of drainage canal, result in fluid accumulation of fluids in eye, and increasing ocular pressure.
developed slowly and it is a life time condition
has symptoms and damage that are not noticed.

angle- closure glaucoma
( acute Glaucoma )
less common form
closed or narrow angle between iris and cornea
blocked drainage canal leading to sudden ocular hypertension
very noticeable symptoms and damage
require immediate medical attention.


cataract

the lens is contained in a sealed capsule.
As old cells die, they become trapped within the capsule. Over time, they accumulate causing the lens to be cloud and make the vision blurred.
THE MAIN CAUSE OF CATARACT:
AGING.
(rarely, may be present shortly after birth)
factors accelerate cataract:
smoking
exposure to toxic materials
eye injury
metabolic diseases e.g. diabetes
medications e.g. cortisone
innervation of the eye:
they are two types of receptors in the retina:
rods: long slender receptors
cones: shorter and thicker receptors

they operate differently:
rods: sensitive to light than cones
cones: response to higher levels of illumination (colors)
so, rods or cones are more in macula lutea?
Iris
Full transcript