Vision 1

Question 1

What two anatomical structures of the eye have the power to bend light?

Answer 1

Cornea (45D)

Lens (15D but can accommodate)

Question 2

What is the scientific name for the bending of light?

Answer 2

Refraction

Question 3

At what distance is an object too close to focus on?

Answer 3

20cm

Question 4

What three things happen simultaneously during accommodation?

Answer 4

1. Lens changes shape
2. Pupil constriction
3. Eyes converge

Question 5

Describe the changes that occur to the shape the lens as an object gets closer?

Answer 5

Thicker and more spherical

Question 6

Describe the process that allows the lens to thicken?

Answer 6

1. Ciliary muscles contract
2. Space in the middle decreases
3. Suspensory ligaments become lax
4. Lens is no longer under stretch
5. Lens becomes thicker

Question 7

What division of the autonomic nervous system governs the ciliary body?

Answer 7

Parasympathetic

Question 8

Why do the pupils constrict when an object gets closer?

Answer 8

To only allow a few light rays from the object in question - producing a clearer image

Question 9

What muscle is responsible for constricting the pupil and what division of the nervous system governs it?

Answer 9

Constrictor pupilae - parasympathetic

Question 10

Where is the constrictor pupilae located?

Answer 10

In a concentric ring around the border of the pupil

Question 11

What muscles allow for convergence of the eye?

Answer 11

Medial rectus

Question 12

What nerve innervates the medial recti muscles?

Answer 12

CN III

Question 13

What is the colloquial word for myopia?

Answer 13

Shortsightedness

Question 14

What is emmetropia?

Answer 14

Perfect vision

Question 15

What feature of the lens produces myopia?

Answer 15

Too powerful

Question 16

What is the most common cause of myopia?

Answer 16

Eyeball too long

Question 17

Where does the image focussing relation to the retina in myopic eyes?

Answer 17

Infront of the retina

Question 18

What are some common symptoms of myopia?

Answer 18

Headaches, complaints of not being able to see

Infants/preverbal children - divergent squint

Toddlers - loss of interest in activities, more interest in books and pictures

Teachers may notice loss of interest at school

Question 19

How can myopia be corrected?

Answer 19

Biconcave lenses (glasses/contacts)

Laser eye surgery

Question 20

What is the colloquial word for hyperopia?

Answer 20

Longsightedness

Question 21

What is the most common cause of hyperopia?

Answer 21

Eyeball is too short

Question 22

In hyperopia, where does the image form in relation to the retina?

Answer 22

Behind the retina

Question 23

What are the symptoms of hyperopia?

Answer 23

Eyestrain, convergent squint

Question 24

Why does hyperopia require immediate correction?

Answer 24

To avoid lazy eye, ambulopia

Question 25

How can hyperopia be corrected?

Answer 25

Biconvex lenses (contacts/glasses) Laser eye surgery

Question 26

What is presbyopia?

Answer 26

Age related long-sightedness

Question 27

How does presbyopia occur?

Answer 27

Lens gets less elastic with age

Question 28

When does presbyopia usually present in life?

Answer 28

5th decade

Question 29

What is astigmatism?

Answer 29

Non-spherical shape of the cornea (or lens) therefore surface has different curvatures in different meridians

Question 30

How is astigmatism corrected?

Answer 30

Laser eye surgery Cylinder adjustments Toric contact lenses

Question 31

What is the process of phototransduction?

Answer 31

The converting of light into a neural impulse and ultimately a mental image

Question 32

What are cones?

Answer 32

Photoreceptors which are responsible for colour distinction and which work in high light

Question 33

What are rods?

Answer 33

Photoreceptors responsible for low light vision

Question 34

What visual pigments are contained in rods?

Answer 34

Rhodopsin

Question 35

What visual pigment is contained in cones?

Answer 35

Opsins S, M and L

Question 36

Roughly outline the phototransduciton cascade?

Answer 36

Light stimulates visual pigments Stimulates transducin Stimulates Phosphodiesterase Na+ channels close (hyperpolarisation) Stimulates retina

Question 37

What is the special feature of the resting potential of photoreceptor cells?

Answer 37

Depolarised at resting state, due to open Na+ and Ca+ channels

Question 38

How is visual pigment regenerated?

Answer 38

Dietary Vitamin A from the liver regenerates visual pigments

Question 39

Other than visual pigments, what does vitamin A also do in the eye?

Answer 39

Maintains healthy epithelium (cornea and conjunctivae)

Question 40

What pathologies can occur as a result of vitamin A deficiency?

Answer 40

``` Blindness (/night blindness) Ulceration of cornea Bitot's spots Corneal melting Corneal opacification ```

Question 41

Why does colour blindness occur?

Answer 41

Different types of cones are responsible for perception of different colours