Optometry

Question 1

Refractive status:

What is meant by the clinical term emmetropia?

Answer 1

An eye which has no refractive error or visual defect

The light which enters the eye focuses perfectly on the fovea in the retina

Question 2

Refractive status:

What is meant by the clinical term ametropia?

Answer 2

An eye which has one or more refractive errors

The light which enters the eye does not focus correctly on the fovea in the retina

Question 3

Refractive status:

What is meant by the clinical term anisometropia?

Answer 3

When a person has a significant difference between their left and right ametropia (refractive errors)

Question 4

Give 3 examples of refractive errors

Answer 4

Myopia
Hyperopia/hypermetropia
Astigmatism

Question 5

What is myopia?

Answer 5

Short-sightedness i.e., distance vision is blurred

Question 6

What abnormality of the eye causes myopia?

Answer 6

The light is focused too far in front of the retina, usually due to the eye being too long or the refractive power of the lens being too strong

Question 7

What sort of lenses are used to treat myopia?

Why?

Answer 7

-ve / concave lenses

The concave shape (thicker around periphery than in centre) of the lens causes light to pass through and diverge (spread) so that it can reach further back to the retina

Question 8

What is hyperopia?

Answer 8

Long-sightedness i.e., near vision is blurred

Question 9

What abnormality of the eye causes hyperopia?

Answer 9

The light is focused too far behind the retina, usually due to the eye being too short or the refractive power of the lens being too weak

Question 10

What sort of lenses are used in hyperopia?

Why?

Answer 10

+ve / convex lenses

The convex shape (thicker in the centre than around the periphery) of the lens causes light to pass through and converge so that it focuses earlier than its current position behind the retina

Question 11

What is a ‘diopter’?

Answer 11

A measurement of refractive power e.g., a -1.5 diopter prescription

Question 12

What is astigmatism?

Answer 12

‘Rugby-ball shaped eye’ causing blurring of distant and near vision

Question 13

What abnormality of the eye causes astigmatism?

Answer 13

Due to rotational asymmetry of the eye’s refractive power

i.e., refractive power is different depending on the meridian (longitudinal axis) the eye is lying in

Question 14

What sort of lenses are used to treat astigmatism?

Answer 14

Cylindrical shaped lenses

Question 15

If astigmatism in early life is left untreated, what may the child develop?

Answer 15

Amblyopia

i.e., lazy eye - brain develops to process inputs from the good eye and vision becomes worse in the affected eye

Question 16

What is presbyopia?

Answer 16

Age-related hyperopia (long-sightedness)

Question 17

What abnormality of the eye causes presbyopia?

Answer 17

The lens loses its ability to accommodate for close up vision

Question 18

How does the lens normally accommodate for close up vision?

Answer 18

The ciliary muscles tense to relax the suspensory ligaments and cause the lens to become more rounded

Question 19

How is presbyopia managed?

Answer 19

+ve / convex lenses

The convex shape (thicker in the centre than around the periphery) of the lens causes light to pass through and converge so that it focuses onto the retina

Question 20

When testing a patients vision, what is meant by the testing of…

• Vision
• Visual acuity
• Pinhole acuity

Answer 20

• Vision: smallest letter on the chart that can be read without the aid of glasses or contact lenses i.e., uncorrected vision
• Visual acuity: smallest letter on the chart that can be read with the best glasses or contact lenses i.e., corrected vision
• Pinhole acuity: smallest letter on the chart that can be read through a pinhole

Question 21

Why is pinhole acuity measured?

Answer 21

It gives an indication of the best visual acuity that is likely to be achieved with corrected vision

Question 22

Name two letter charts used to test a patient’s vision

What is the difference between them?

Answer 22

Snellen chart
LogMAR

Snellen: number of letters in each row increases with decreasing letter size down the chart
LogMAR: number of letters in each row decreases with decreasing letter size down the chart

Question 23

What do the line numbers on the Snellen chart indicate?

Answer 23

How far away the patient should be to be able to read the letters
e.g., line 16 - should be readable from 16m, line 5 - should be readable from 5m

Question 24

What is meant by Snellen notation 6/24

Answer 24

The patient was 6m away and could only read letters up to line 24

Question 25

What other types of vision testing may be used for…

• Children
• People unable to read English

Answer 25

• Children: picture matching tests
• People unable to read English: ‘tumbling E’ chart (the letter ‘E’ is shown in many different orientations and 3 fingers are used to indicate its orientation)

Question 26

List 3 examples of low visual aids for people with very low vision

Answer 26

Magnifying glass
Telescope
Tinted glasses (e.g., anti-glare, yellow-tinted to improve contrast in macular degeneration)