Physiology of Vision (1)

Slides:



Advertisements
Similar presentations
THE HUMAN EYE Gives the sense of sight. Allows us to learn more
Advertisements

THE EYE.
Extrinsic Eye Muscles Figure 15.3a, b.
4/30/2015By Dr. Rick Woodward1 April 26, 2011: Tuesday Today’s Agenda New Seating Chart A. Journal Questions: 1. Where does most nutrient absorption occur.
Structure of the Eye Outer Tunic (pg. 470) 1. Cornea 2. Sclera Middle Tunic (pg ) 3. Choroid Coat 4. Ciliary Body 5. Lens & Accommodation 6. Aqueous.
Eye- Structure and Refraction
Ranya Marrakchi Kelsey Wright Taylor Pakulla
10.9 – Sense of Sight.
Macro and Microscopic.  Protected by bony orbits of the skull  Send information to brain directly via optic nerve.
Photoreception - Vision. Eyelids (palpebrae) separated by the palpebral fissue Eyelashes Tarsal glands Lacrimal apparatus Vision Accessory structures.
Special Senses: Vision
Imaging Science FundamentalsChester F. Carlson Center for Imaging Science The Human Eye and Vision 1 (Producing The Image)
Chapter 15 Exam Six Material. Eye and Associated Structures _______________________________________ are in the eye Most of the eye is protected by a cushion.
Special Senses.
The Human Visual System The Eye. Anatomy of the Human Eye Cornea Pupil Iris Sclera Retina Optic Nerve Lens.
The Eye: Structure & Function
Senses- The Eye The human eye is the organ which gives us the sense of sight, allowing us to learn more about the surrounding world (environment) than.
Anatomy of the Eye Even though you can’t easily see it, the cornea is a very important structure in the outer avascular fibrous tunic – It’s composed of.
VISION -I Dr.Mohammed Sharique Ahmed Quadri Assistant Professor Department Basic Medical Sciences Faculty of Medicine Almaarefa Colleges 1.
Vision and Structure of the Eye
The Senses General senses of touch Temperature Pressure Pain.
Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slides 8.1 – 8.19 Seventh Edition Elaine.
Eye Exercise 24.
Special Senses Objective 2
Eye Notes You tube video below E1MvRmWg7I.
THE EYE CHAPTER 10. QOD #1: Pre-Test 1.) What are the 5 senses? 2.) T/F Of all the sensory receptors in the body, 70% are in the eyes. 3.) T/F Your eyebrows.
Human Eye  A human eyeball is like a simple camera! Sclera: White part of the eye, outer walls, hard, like a light-tight box. Cornea and crystalline lens.
Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition Elaine N. Marieb The.
The Senses Special senses Smell Taste Sight Hearing Equilibrium
Eye Notes.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture.
Receptors Receptors are part of the co-ordination system that detect the changes of the environment by means of stimuli. Two types... Interoceptors – receptors.
Lenses. Applications of Light Refraction What are some common applications of the refraction of light? Cameras Microscopes Lenses Eyeglasses Human eye.
The Special Senses A. Visual sensations 1. Accessory structures of the eye 1. Accessory structures of the eye 2. Anatomy of the eyeball 2. Anatomy of the.
The Eye and Sight Describe the relationship between the structure of the eye and sight Contrast ways in which light rays are bent by concave and convex.
The Eye.
SPECIAL SENSES. the human body is very sensitive to conditions in both its internal and external environment the nervous system collects information about.
The Eye VISION Alyssa Jimenez & Cristina Santiago.
Vision.
Psychology 4051 The Eye/Optics. Light The stimulus for vision is light energy-a small part of the spectrum of electromagnetic radiation. Other organisms.
The Eye 1. Lacrimal apparatus  Lacrimal glands Superior and lateral in each eye Produces tears Several small ducts liberate the tear continually  Excretory.
Sight Visual Accessory Organs eyelids lacrimal apparatus extrinsic eye muscles.
Chapter 9 - The eye $100 $200 $300 $400 $500 $100$100$100 $200 $300 $400 $500 Eye Anatomy Eye Physiology More Parts of the Eye Eye Problems More Vocab.
ELAINE N. MARIEB EIGHTH EDITION 8 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation by.
1. 2 EAGLE 3 FISH 4 OWL 5 RECEPTOR THE HUMAN EYE.
The Physiology of Vision. Anatomy of the eye 1- sclera: is the outer protective layer. 2- cornea : anterior, modified part of the sclera, light rays enter.
Special Senses The Eye.
PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 16 Copyright.
SPECIAL SENSES. THE EYE Properties of light External eye –Palpebra –Eyeball –Protection provided by – –Meibomian glands (eyelashes) –Conjunctiva –Lacrimal.
Vision.
Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Seventh Edition The Eye & Vision Lecture.
RECEPTOR THE HUMAN EYE.
Sensory Physiology The Vision Accommodation Blind spot.
Anatomy of the Eye.
Nervous System PNS. Incredible Human Machine  SIGHT   HEARING.
Coordination and Response in Plants and Animals
Eye anatomy.
The Eye.
External Anatomy of the Eye
Chapter 8 – Special Senses Eye sphere – 1 inch in diameter – only see 1/6 of eyeball.
SPECIAL SENSES: VISION MARTINI, FUNDAMENTALS OF ANATOMY & PHYSIOLOGY, 8 TH EDITION, CHAPTER # 17 Exercise # 21.
The Eye & Vision. The Eye and Vision  70 percent of all sensory receptors are in the eyes - only see 1/6th of eye  Each eye has over a million nerve.
Chapter 19 Special Senses: Vision
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Eye and Associated Structures  70% of all sensory receptors are in the eye 
The Eye.
The Eye.
The Eye.
The Special Senses: Part A
15 P A R T B The Special Senses.
Sight Visual Accessory Organs eyelids lacrimal apparatus
Presentation transcript:

Physiology of Vision (1) بسم الله الرحمن الرحيم Physiology of Vision (1) Dr. Abdelrahman Mustafa Department Basic Medical Sciences Division of Physiology Faculty of Medicine Almaarefa Colleges

Learning Objecetives By the end of this lecture, You should able to Describe the functional anatomy of the eye Describe the refraction of light as it passes through the eye to the retina, identifying the eye components that account for refraction of light at the center of the eye and away from the center. Describe the process of accommodation, contrasting the refraction of light by the lens in near vision and in far vision. Describe the refractive deficits that account for myopia, hypermetropia,, and astigmatism, and their correction by eyeglasses

Important of vision Definition Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye Important of vision Learning through written speech Maintenance of equilibrium

Anatomy of the Eyeball Eye ball diameter =2.5cm Consist of 3 layers 1.Sclera(outer layer ) Constitute the posterior 5/6 of the outer layer of the eye It is formed of connective tissue, It is Opaque Structure (normally it is whitish) SO does not transmit light rays Modified interiorly to become transparent and more curved to form the cornea 2.Choroid(middle layer) it contain many blood vessels and pigmented it modified anteriority to form the ciliary body and iris which is the colored part in front of the lens The iris has central round opening called the pupil 3.Retina(inner layer ) It Contains the visual receptors [rods and cones ] that respond to the light Characterized by presence of an area that lacks visual receptors called the optic disc or the blind spot FOVEA CENTRALIS

Con THE CILLIARY BODY:- Is circular structure consist of 3 parts A) Cilliary gland B) Cilliary muscles: inserted near to corneoscleral junction C) Suspensory ligaments :Joined to lens ligiment It participates in accommodation , produces the aqueous humor and maintain the lens zonules THE IRIS :- The pigmented part of the eye It contain 2 types of muscles that adjust the diameter of the pupil to control the amount of light reaching the retina These muscles are : a. dilator pupillae: contains radial muscle fibers that cause pupillary dilatation in response to symp. Stimulation b. sphinctor pupillae : contains concentric muscle fibers that cause pupillary constriction in response to parasymp. Stimulation Lens Is a biconvex, crystallins,and transparent structure bind suspensory ligaments for focusing light CILNICAL :Opacity of the lens: Cataract

Con THE RETINA :- Contains the visual receptors [rods and cones ] that respond to the light The out put from the retina in form of AP passes through the optic nerve and other structure of the visual pathway to give perception of light Characterized by presence of an area that lacks visual receptors called the optic disc or the blind spot Temporal to the optic disc there is another area known as the macula At the center of the macula is the fovea centralis , the area with the highest visual acuity [contain cones only nervous layers of the retina (1) photoreceptor layer (a) rods (b) cones (2) bipolar layer (a) bipolar cells (b) amacrine cells (c) horizontal cells (3) ganglion cell layer

Cavities of the Eye 1. anterior cavity a. posterior chamber b. anterior chamber c. aqueous humor e. canals of Schlemm 2. posterior cavity a. vitreous humor

Con AQUEOUS HUMOR :- The clear liquid that fills the space between the lens and the cornea Provides the nutrients to the a vascular parts of the eye [the lens and cornea ] and eliminates their waste products Its pressure maintains the normal convexity of the cornea Increased production or decreased its drainage leads to increased intraocular CLINICAL: Glucoma VITREOUS HUMOUR :- The clear gelatinous material that fill the space between the lens and the retina Consist of water , salts , sugars and collagen fibers It provide structural support to the eyeball and allows passage of light rays to the retina CANALS OF SCHLEMM: for venous drainage

Muscles of Eye Movement Lateral rectus–moves the eye outward, away from the nose Medial rectus–moves the eye inward, toward the nose Superior rectus–moves the eye upward and slightly outward Inferior rectus–moves the eye downward and slightly inward Superior oblique–moves the eye inward and downward Inferior oblique–moves the eye outward and upward

Nerve supply The extraocular muscles are supplied by third, fourth and sixth cranial nerves. The third cranial nerve (Oculomotor) supplies the superior, medial and inferior recti and inferior oblique muscles. The fourth cranial nerve (Trochlear) supplies the superior oblique and The sixth nerve (Abducent) supplies the lateral rectus muscle. CLINICAL : Paralysis of These Nerve= Squint

The formation of images on the retina involves three processes: 1. refraction of light rays 2. accommodation of the lens 3. constriction of the pupil

Con Refraction is the change in direction of a wave due to a change in its speed when a ray of light crosses from one material to another of different density Refractive media of the eye :- There are 4 refractive media in the eye : The cornea its refractive The aqueous humour The crystalline lens The vitreous humour

Accomodation Accommodation : Is the process by which the optical system of the eye is adjusted to see the near objects clearly Light rays are refracted by the cornea and lens to be focused on the retina

Con Accommodation : On looking to a distant object [more than 6 meter] The light rays are coming in parallel Ciliary muscle is relaxed and the lens is flat The rays are brought to a focus on the retina On looking to a near object [close than 6meter ] : Light rays are diverging They will be focused behind the retina , this is prevented by the near response which consist of : Increased convexity of the lens [accommodation ] Convergence of visual axis Pupillary constriction

From the Eye Sight website of student Kyle Keenan at Steton Hall University.

Constriction of the Pupil 1. part of accommodation reflex 2. limits peripheral light

The iris constricts or dilates to adjust size of the pupil. You are looking at an anterior view of the iris, the colored part of the eye that you can see from the outside of the eye. * The function of the iris is to constrict or dilate to adjust the size of the pupil which is the opening in the center of the iris. * Light must pass through the pupil to enter the posterior segment of the eye where the receptors are located. * The size of the pupil, determines how much light can enter the eye. * The iris constricts or dilates to adjust size of the pupil. The pupil allows light to enter the posterior segment of the eye.

Convergence of the Eyes

ERRORS OF REFRACTION Lens: Refracts (bends) light Focuses precise image on the retina (fovea) through accommodation (changing thickness) The lens is a transparent, flexible, biconcave structure which is held in place by the suspensory ligaments. * Its primary job is to refract light passing through it so that an image may be focused on the fovea centralis. * Because the lens is flexible, tension exerted by the ciliary muscles through the suspensory ligaments changes the thickness of the lens. * This adjustment in the thickness of the lens to focus images precisely on the fovea is called accommodation.

Myopia Eyeball too long Distant objects focused in front of retina Cannot see far Image striking retina is blurred Myopia * is a condition where the eyeball is longer than normal. As a result, the image is focused in front of the fovea rather than directly on it. * Thus the actual image striking the fovea is not in sharp focus. * * Individuals who are near sighted can see nearby objects clearly because the lens can accommodate sufficiently to adjust the focal point. That is not the case for things farther away. * This condition may be corrected by using glasses which have concave lenses* which are ground precisely to correct the problem. * The condition may also be corrected by laser surgery which flattens the cornea to adjust the focal point for distant objects. * Correction: Concave lens or laser surgery to slightly flatten the cornea

Hypermetropia Eyeball too short, lens too thin or too stiff. Nearby objects are focused behind retina. Needs some accommodation . Image striking the fovea is blurred. Hyperopia or farsightedness * is due to the eye being too short, the lens too thin, or the lens being too stiff to focus the image precisely on the fovea. * As a result, the image of a nearby object is focused behind the fovea * causing the image striking the fovea to be blurry. * * Farsighted individuals can see distant objects clearly. This condition * may be corrected by using a convex lens * to bring the image of nearby objects forward far enough * for the image to be focused precisely on the fovea. * Correction: Convex lens

Astigmatism Irregular Curvature in parts of the cornea or lens Causes blurry image Irregular curvatures of different parts of the lens or the cornea * may cause portions of the image on the fovea to be blurry. * This is referred to as an astigmatism. * * This condition may be corrected through the use of specially ground cylindrical lenses to compensate for the differences in curvature of the cornea or lens or through laser surgery. * This may be corrected by specially ground lenses which( cylindrical ) compensate for the irregularity or laser surgery.

Q1 The structure that Modified interiorly to become transparent and more curved to form the cornea is A)Iris B)Choroid C)Retina D)Sclera

Q2 Cataract defined as : A)Opacity of the lens B) Increase the intraocular pressure C) Errors of refraction D)Paralysis of abducent nerve

Q3 On looking to a distant object ,Which event DOSE NOT occur A) The light rays are coming in parallel B)Ciliary muscle is relaxed and the lens is flat C)The rays are brought to a focus on the retina D) Convergence of visual axis

Q4 The cause of myopia is A)Eyeball too short B)lens too thin C)Lens too stiff D)Eye ball to long

References Human physiology by Lauralee Sherwood, 7th edition Text book physiology by Guyton &Hall,12th edition Text book of physiology by Linda .s contanzo,third edition