The Eye

Question 1

Photoreceptors

Answer 1

The receptors that detect light stimuli

Question 2

Outer fibrous layer of eye:

SCLERA

Answer 2

• white inelastic layer of connective tissue
• protects internal parts of eye
• helps to maintain spherical shape of eye
• serves for muscle attatchment

Question 3

Outer fibrous layer of eye:

CORNEA

Answer 3

• transparent front part of sclera
• more convex than rest of eyeball
• allows light though to inner layers of eye
• NB curvature causes the refraction of incoming light rays

Question 4

Middle Vascular Layer:

CHOROID

Answer 4

• darkly pigmented vascular layer

- Pigment absorbs light to prevent internal reflection which may cause blurred images

Question 5

Middle Vascular Layer:

CILIARY BODY

Answer 5

Thickened front part of the choroid with involuntary muscles. These attach to the lens and can contract to change the curvature of the lens

Question 6

Suspensory ligaments

Answer 6

A series of fibres that connect the CILIARY BODY of the eye with the lens, keeps it in place.

Question 7

Middle Vascular Layer:

IRIS

Answer 7

• Round
• Coloured
• Has both radial and circular involuntary muscles that pull the iris open or closed
• NB THIS ALLOWS REGULATION OF LIGHT INTO THE EYE

Question 8

Lens

Answer 8

• rubbery, elastic transparent, biconvex structure (held in place by suspensory ligaments attached to the ciliary body)
• changes shape to refract light of near and far objects onto the retina

Question 9

Aqueous humours

Answer 9

Watery fluid in front of the lens, to maintain shape of the eye and holds the retina against the choroid

Question 10

Vitreous humours

Answer 10

watery fluid behind the lens, similarly to the function of the aqueous humours

Question 11

RETINA

Answer 11

pigmented layer and nerve tissue with photoreceptors that detect light stimuli and convert the stimuli into nerve impulses.

There are 2 types of photoreceptors: Rods and Cones

Question 12

Rods

Answer 12

light sensitive and give rise to black and white vision

Question 13

Cones

Answer 13

allow for bright light and color vision

Question 14

How your eye works (FRIP)

Answer 14

F - focused onto retina
R - refracted light on retina is upside down
I - info sent along optic nerve
P - processed by brain so you see it normally

Question 15

ACCOMMODATION

Distant Objects

Answer 15

concave and/or flatter
contracting ciliary muscles
suspensory ligaments relax

Question 16

ACCOMMODATION

Nearby objects

Answer 16

convex and/or rounder
ciliary muscles relax
suspensory ligaments contract

Question 17

PUPILLARY MECHANISM

-DIM LIGHT

Answer 17

radial muscles contract
circular muscles relax
pupil widens (dilates)

Question 18

PUPILLARY MECHANISM

BRIGHT LIGHT

Answer 18

radial muscles relax
circular muscles contract
pupil shrinks (constricts)

Question 19

Binocular vision

Answer 19

The left and right eyes each form their own image of am object. This provides a wider field of vision and is known as binocular vision.

Question 20

Stereoscopic Vision

Answer 20

The ability of the brain to combine the two images in the left and right eyes to form one, 3D combined image with depth perception.

Question 21

SHORT-SIGHTEDNESS

myopia

Answer 21

Caused by:

• elongated eyeball
• the cornea being too curved for the length of the eyeball
• the inability of the lens to become -less convex

When looking at distant objects, the light rays focus in front of the retina, causing blurred vision

Question 22

LONG-SIGHTEDNESS

hypermetropia

Answer 22

caused by:

• an eyeball that is too short (rounded)
• the cornea not being curved enough for the length of the eyeball
• the inability of the lens to become more convex

Question 23

Astigmatism

Answer 23

With an astigmatic cornea, light entering the eye is not focused evenly on the retina. This leads to blurred vision, headaches and squinting of the eyes.

Treatment:

• glasses with prescription lenses
• contact lenses
• laser therapy

Question 24

Cataracts

Answer 24

Cataracts occur when the clear transparent lens becomes cloudy. This prevents light from entering the eye and results in blurred vision. The cataract develops slowly and increases in size over time.

The causes could be due to congenital factors, age-related hardening of the lens, diabetes, strong sunlight, and heavy smoking.