The eye

Question 1

What is the consensual light reflex?

Answer 1

• Change in pupil size changes in both eyes if only one eye is stimulated
• Due to both Edinger-Westphal nucleus being innovated by sensory input from one eye

Question 2

What is the function of the iris

Answer 2

• Contains muscles which control pupil size

Question 3

What is the pupillay constrictor?

Answer 3

• Smooth, circular muscle on the inside of the iris
• Contracts to make pupils smaller
• Regulated by parasympathetic NS

Question 4

What is esotropia?

Answer 4

• Convergence of the eyes

- Weakening of the outside muscles

Question 5

What is glaucoma?

Answer 5

• A build-up of aqueous humor due to slowed uptake
• Increases intraocular pressure
• Compression of the optic nerve and blood vessels
• Progressive loss of vision from the periphery inwards

Question 6

What is exotropia?

Answer 6

• Divergence of the eyes

- Weakening of the inside muscles

Question 7

What is the difference between the light rays from near and distant objects by the time they reach the eye?

Answer 7

• Distant - almost parallel, requires less refractive power by the lens
• Near - not parallel, require more refractive power by the lens

Question 8

What is the lens of the eye?

Answer 8

• Transparent structure behind the iris
• Can changes shape to adjust refractory power
• Connected to cillary bodies by zonal fibres

Question 9

What is hyperopia?

Answer 9

• Longsightedness (can’t see close)
• Eye is too SHORT
• Light convereges after the retina
• Requires a convex lens to fix (converge light rays more)

Question 10

What is the conjunctiva?

Answer 10

The membrane underneath the eyelids which connects to the sclera

Question 11

As you get older are you more likely to get myopia or hyperopia?

Answer 11

Hyperopia as the refractive power of the lens decreases with age

Question 12

What is cateracts?

Answer 12

• Clouding of the lens due to changes in the composition of the aqueous humor
• Not supplying the correct nutrients
• Increase with age, diabetes M, smoking
• Treatment is lens replacement

Question 13

What are the zonal fibres?

Answer 13

• Ligaments which attach the cillary body to the lens

- Allows the lens to change shape and change refractive power

Question 14

What is the optic disc?

Answer 14

• The ‘blind spot’ of the eye
• No photoreceptos
• Origin of blood vessels and the optic nerve

Question 15

What is the sclera?

Answer 15

• The tough white part of the eye which is continuous with the cornea

Question 16

What is refraction and when does it occur?

Answer 16

• Bending of the light as it travels from one transparent material to another
• Light travels easier in air than water
• Tries to bend light perpendicular to the interface
• Happens when light enters the aqueous humour, in order to focus light on the retina

Question 17

When does pupil size change?

Answer 17

• Low light = large pupil

- Bright light = small pupil

Question 18

What is the foeva?

Answer 18

• The centre of the macula
• Where the retina is the thinnest
• High concentration of cones found here

Question 19

What is the focal distance?

Answer 19

• Distance between the cornea (refractive substance) and the retina (where the light rays converge)
• May be different in people - highlight disorders

Question 20

What is the function of the pupil?

Answer 20

• Lets light into the eye

- Size changes

Question 21

What happens to the lens when focusing on nearer objects?

Answer 21

• Ciliary muscles contract, zonal fibres relax, lens is more spherical
• Lens has more refractive power

Question 22

Where does the most refraction occur in the eye?

Answer 22

In the cornea - 80%

Rest occurs by the lens - 20%

Question 23

What is emmetropia?

Answer 23

• Ciliary muscles are relaxed, zonal fibres are stretched, lens is flattened
• When the eye is focused on an object more than 6m away (distant)

Question 24

What is the vitreous humor?

Answer 24

• Viscous liquid inside the eyeball which keeps the eyeball spherical

Question 25

Where is the aqueous humor secreted from?

Answer 25

The ciliary body (muscle)

Question 26

What is the macula?

Answer 26

• Devoid (free of blood vessels) area

- Region of the retina for central visual processing

Question 27

What is light?

Answer 27

Electromagnetic radiation in the visible region

Question 28

What is the aqueous humor?

Answer 28

• Watery liquid infront of the lens and iris

- Providing nutrients to the lens and the cornea

Question 29

What regulates light levels into the pupil?

Answer 29

The pupillay constrictor and pupillar relaxor muscles in the iris

Question 30

What is refractive power measurements?

Answer 30

Diopters

Question 31

What is the pupillay dilator?

Answer 31

• Smooth, radial muscle on the outside of the iris
• Contracts to make pupils larger
• Regulated by sympathetic NS

Question 32

Where is the aqueous humor absorbed?

Answer 32

By the canal of schlemm (between the cornea and the sclera

Question 33

What is myopia?

Answer 33

• Nearsightedness (can’t see far objects)
• Eye is too LONG
• Light converges before the retina
• Requires a concave lens to fix (to diverge light rays more)

Question 34

What nerves is eye movement controlled by?

Answer 34

Oculomotor (III)
Trochlear (IX)
Abducens (XI)

Question 35

How is refractive power calculated?

Answer 35

1/ focal distance(m)