Eye

Question 1

Human eye

Answer 1

Photoreceptors detect light and are concentrated in the eye

- the eye is responsible for your sight

Question 2

Position

Answer 2

Eyes are positioned in bony eye socket at the front of the skull

Question 3

Structure

Answer 3

• More or less spherical in shape
• eyelashes and eyelid protect the eye from foreign objects
• Front of the eye is covered by a mucus membrane the conjunctiva which contains pain receptors that are stimulated by dust particals which results in the blinking reflex
• The tear gland positioned above the eyeball secrets antiseptic tears which protects the conjunctiva from dehydration and bacteria
• Each eye is equipped with 6 muscles which allows movement in all possible directions

Question 4

What are the 3 layers of the eye

Answer 4

• Outter fibrous layer
• Middle vascular layer
• Inner light sensitive retina

Question 5

Outter fibrous layer

Answer 5

●Sclera
●cornea
●conjunctiva

Question 6

Sclera

• Structure
• Function

Answer 6

Strong white inelastic fibrous layer of connective tissue forms the outter part of the eye extamds into the transparent cornea at the front of the eye

FUNCTION

• protects the internal part of the eye
• maintains the structure of the eye
• provides surface for the muscles to attach

Question 7

Cornea

• Structure
• Function

Answer 7

Transparent front part of the sclera. More convex thn the rest of the eyeball

FUNCTION

• Allows light rays to the inner part of the eye
• refracts incoming light rays

Question 8

Conjunctiva

• Structure
• Function

Answer 8

Thin mucus membrane covering the front part of the eyeball

FUNCTION

Keeps front and inner surface of the eyelid moist and lubricated so eye opens and closes easily without friction or cause the eye irritation

Question 9

Middle vascular layer consists of

Answer 9

• Choroid
• Ciliary body
• Lense
• Iris

Question 10

Choroid

• Structure
• Function

Answer 10

Thin darkly pigmented vascular layer
FUNCTION
The pigmented part absorbs excess light rays to prevent internal reflection which can cause blured image
-Blood vessel supply oxygen and nutrients to the cells

Question 11

Ciliary body

• Structure
• Function

Answer 11

-thinking part of the choroid
- consists of involuntarily muscles
-attached to the lense by suspensory ligaments
FUNCTION
contracts and relaxes to change the curvature of the lense during accommodation

Question 12

Lense

• Structure
• Function

Answer 12

• Rubbery, inelastic, transparent, biconvex structure can change shape. Kept in position by the suspensory ligaments connected to the ciliary body
• Change shape by refracting light rays from far and near objects to forn a clear image on the retina

Question 13

Iris

• Structure
• Function

Answer 13

-round colored part of the eye
-contains pigment that gives colour to the eye
-continuation of he choroid
-consists of 2 involuntarily muscles
•radial muscles
•circular muscles
-opening in the middle of the iris is called the pupil allows light rays to entre the eye

FUNCTION
-regulates the amount of light rays entering the eye by controlling size of pupil

Question 14

Inner light sensitive retina consists of

Answer 14

• Retina
• photoreceptors
• yellow spot
• optic nerve

Question 15

Retina

Answer 15

-pigment layer lies on the outter layer in contact with the choroid

FUNCTION
-dark pigment absorbs light rays and prevents internal reflection

Question 16

Nerve tissue layer

Answer 16

Consists of 2 photoreceptors

• rods
• cones

FUNCTION
-rods are stimulated in low light which gives rise to black and white vision

-Cons are stimulated in high light intensity which gives rise to intense high bright colour vision.

Question 17

Yellow spot

Function

Answer 17

Located on the retina consists of mostly cones and very few rods. The middle of the yellow spot you’ll find the fovea which consists of only cons

FUNCTION
where most accurate images are formed

Question 18

Optic nerve

Answer 18

Function

Sends nerve impulses to the cerebral cortex of the brain where it gives sensation of sight

Question 19

Anterior cavity

Subdivided into anterior and posterior chamber

Answer 19

Infront of lense filled with watery fluid the aqueous humor

Question 20

Anterior chamber

Answer 20

Anterior chamber
Situated between the cornea and iris

Posterior chamber
Between iris and lense

Question 21

Posterior cavity

Answer 21

Behind the lense filled with jelly like vitreous humor

Question 22

Pupilary mechanism

Answer 22

• Is a reflex action
• response automatically to stimulus of amount of light that enters the eye
• size of pupil controls amount of light that enters the eye

Question 23

In bright light

Answer 23

• pupil constricts limiting the amount of light that enters the eye to prevent damage to the retina
• radial muscles relax
• circular muscles contract
• pupil constricts

Question 24

In dim light

Answer 24

• pupil dilates to try and get as much light in as possible to rich the retina to form a clear vision
• radial muscles contract
• circular muscles relax
• pupil dilated

Question 25

Accommodation

Answer 25

Process in which the lense changes its shape to allow you to focus on objects that are nearby(6meters) or far away(6meters)

Question 26

Distant object | Is unaccomodated

Answer 26

* Ciliary muscle relax * Ciliary body moves furtheraway from the lense * Suspensory Ligaments are taut * Elastic lense becomes less convex * Less refraction of light rays by flattening the lense * Sharp focused image falls on the retina

Question 27

Nearby objects | Is accommodate

Answer 27

* Ciliary muscles contract * Ciliary body moves closer to lense * Suspensory ligaments slacken * Elastic lense become more convex * More refraction of light by thickening lense * Sharpe focused image falls on the retina

Question 28

Binocular vision

Answer 28

* Ability to focus on an object with both eyes creating a single image allows is to see more indepth 3D objects * Left and right eye both form own image of observed object. * Brain combines the 2 images to form 2D image * Binocular vision provides wider field of vision and creative particular depth * Stereoscopic vision is ability to see in depth 3D vision

Question 29

Significance of binocular vision

Answer 29

* Helps with performance skills such as catching and locomotion * Allows us to walk up and down stairs

Question 30

What are the visual defects

Answer 30

- Short sightedness - long sightedness - Astigmatism - Cataracts

Question 31

Short sightednes

Answer 31

* Near objects seen clearly but distant objects are out of focus * Usually caused by elongated eyeball or  abnormal curvature of cornea * Objects near the eye are in clear focus focal point of distance of object lies infront of retina resulting in an unclear image * Myopia can be corrected by glasses with concave lense or laser surgery

Question 32

Long sightedness

Answer 32

* Distant object seen clearly but near objects are out of focus * Caused by shorter eyeball or an abnormally flat corner * Clear focus of objects at a distance  but focal point of near objects lie behind the retina * Long sightedness can be corrected by glasses with convex lense or go for laser surgery

Question 33

Astigmatism

Answer 33

* Caused by irregular shaped cornea or lense * Cornea with Astigmatism I'd ovul shaped but normal one is round in shape * Irregular cornea causes incoming light to be refracted in two ways * Light rays focus on more than one focal point. This creates unclear image

Question 34

Symptoms for Astigmatism

Answer 34

* Headache * Tiredness * Squinting

Question 35

Cataracts

Answer 35

* Clouding of the eyes clear transparent lense which prevents light reaching the retina and cause blured image * Lense consists of mainly water and protein * With aging protein may clump together clouting small area of lense * Can result in loss of vision * Can get eye surgery by removing lense and replacing with a clear one

Question 36

Stereoscopic vision

Answer 36

Ability to see 3d images

Question 37

Short sightedness and long sightedness can be called

Answer 37

S=Myopia | L= hypermetropia