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The Eye > Eye > Flashcards

Eye Flashcards

1
Q

Human eye

A

Photoreceptors detect light and are concentrated in the eye

- the eye is responsible for your sight

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2
Q

Position

A

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

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3
Q

Structure

A
  • 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
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4
Q

What are the 3 layers of the eye

A
  • Outter fibrous layer
  • Middle vascular layer
  • Inner light sensitive retina
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5
Q

Outter fibrous layer

A

●Sclera
●cornea
●conjunctiva

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6
Q

Sclera

  • Structure
  • Function
A

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
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7
Q

Cornea

  • Structure
  • Function
A

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
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8
Q

Conjunctiva

  • Structure
  • Function
A

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

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9
Q

Middle vascular layer consists of

A
  • Choroid
  • Ciliary body
  • Lense
  • Iris
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10
Q

Choroid

  • Structure
  • Function
A

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

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11
Q

Ciliary body

  • Structure
  • Function
A

-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

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12
Q

Lense

  • Structure
  • Function
A
  • 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
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13
Q

Iris

  • Structure
  • Function
A

-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

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14
Q

Inner light sensitive retina consists of

A
  • Retina
  • photoreceptors
  • yellow spot
  • optic nerve
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15
Q

Retina

A

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

FUNCTION
-dark pigment absorbs light rays and prevents internal reflection

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16
Q

Nerve tissue layer

A

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.

17
Q

Yellow spot

Function

A

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

18
Q

Optic nerve

A

Function

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

19
Q

Anterior cavity

Subdivided into anterior and posterior chamber

A

Infront of lense filled with watery fluid the aqueous humor

20
Q

Anterior chamber

A

Anterior chamber
Situated between the cornea and iris

Posterior chamber
Between iris and lense

21
Q

Posterior cavity

A

Behind the lense filled with jelly like vitreous humor

22
Q

Pupilary mechanism

A
  • 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
23
Q

In bright light

A
  • 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
24
Q

In dim light

A
  • 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
25
Q

Accommodation

A

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

26
Q

Distant object

Is unaccomodated

A
  • 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
27
Q

Nearby objects

Is accommodate

A
  • 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
28
Q

Binocular vision

A
  • 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
29
Q

Significance of binocular vision

A
  • Helps with performance skills such as catching and locomotion
  • Allows us to walk up and down stairs
30
Q

What are the visual defects

A
  • Short sightedness
  • long sightedness
  • Astigmatism
  • Cataracts
31
Q

Short sightednes

A
  • 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
32
Q

Long sightedness

A
  • 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
33
Q

Astigmatism

A
  • 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
34
Q

Symptoms for Astigmatism

A
  • Headache
  • Tiredness
  • Squinting
35
Q

Cataracts

A
  • 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
36
Q

Stereoscopic vision

A

Ability to see 3d images

37
Q

Short sightedness and long sightedness can be called

A

S=Myopia

L= hypermetropia

The Eye (1 decks)

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