Vision 1

Question 1

What is refraction?

Answer 1

bending of light

Question 2

What are the three layers of the eye?

Answer 2

Sclera/cornea, choroid, retina

Question 3

How do we form a sharp image on the retina?

Answer 3

Light waves bend a little through the cornea.

They then bend more through the lens, to come to a point in the retina.

Question 4

What can we do to the lens to focus? What is this known as?

Answer 4

1. We change the shape - make it thicker and more powerful or thinner and weaker.
2. Pupil constricts or relaxes
3. Eyes converge
   Known as accommodation.

Question 5

How do we focus when an object comes closer in?

List the physiological steps.

Answer 5

Lens needs more bending power so it is made thicker and more powerful.

1. The ciliary muscle contract
2. reduces space
3. suspensory ligaments become lax
4. Lens is no longer under stretch so becomes thicker

Question 6

Explain how the eye performs pupillary constriction.

Answer 6

If object is close up:

1. pupil constricts to only let a few light rays in
2. Sphincter pupillae carries out the action

Question 7

What innervation is the sphincter papillae under?

Answer 7

Parasympathetic innervation

Question 8

How do the eyes perform convergence?

Answer 8

By using the medial rectus muscles.

These are THICKER than the lateral rectus muscles.

Question 9

What is the medical term for short-sightedness?

Answer 9

myopia

Question 10

What is the medical term for long-sightedness?

Answer 10

hyperopia

Question 11

What is the most common cause for myopia? Explain pathology.

Answer 11

• eyeball is too long
  This means that when the rays converge they form in front of the retina
  When object is brought closer the rays coming from it are divergent; and then this “bending power” comes to use.

Question 12

How can we correct myopia?

Answer 12

By using a biconcave lens.

Question 13

Explain the pathology of hyperopia.

Answer 13

• Eyeball too short or,
• Lens/cornea are too flat
  The image is formed BEHIND the retina
  Person automatically starts to use accommodative power and makes lens thicker - so they are using lens power for far off things.
  This means that when things are brought up close there is not enough lens power.

Question 14

How can we correct hyperopia?

Answer 14

Biconvex lens.

Question 15

What is astigmatism?

Answer 15

The surface of the eye has different curvatures in different meridians.

• Means that bending of light rays along one axis will never be the same
• image is always fuzzy.
• need laser eye surgery to correct
• or TORIC lens

Question 16

What is the name of old-age longsightedness? And what causes it?

Answer 16

Presbyopia.

• With age the lens becomes more inelastic
• When the ciliary muscle contracts, it is not as capable as before to change shape
• Treat same as hyperopia