Chapter 3- Refractive error (1)

Question 1

What is emmetropia?

Answer 1

Somebody that doesn’t have any refractive error

Question 2

What is ametropia?

Answer 2

Inability to produce a sharp image on the retina. When refractive error is present.

Question 3

In what units do we measure the amount of refractive error?

Answer 3

In dipotres

Question 4

What is the cornea?

Answer 4

Transparent membrane that sits over the iris

Question 5

What is the iris?

Answer 5

A flat, coloured ring shaped membrane behind the cornea of the eye with the pupil in the centre.

Question 6

What is the lens?

Answer 6

Sits behind the iris and bends light to allow us to focus images onto the retina.

Question 7

What is the retina?

Answer 7

Contains photoreceptor cells that transmit signals to the brain which allows us to form an image.

Question 8

What happens to light with people with emmetropia?

Answer 8

Light is bent through the cornea and forms an image clearly and in focus on the retina.

Question 9

What is myopia?

Answer 9

Short sightedness

Question 10

How do distance objects appear to people with myopia?

Answer 10

They appear blurred

Question 11

For people with myopia, the eye is too powerful for what?

Answer 11

The eye is too powerful for its axial length

Question 12

What is the axial length?

Answer 12

Distance from the cornea to the retina

Question 13

Myopia could be due to what?

Answer 13

1- Axial myopia- axial length is greater than the standard 22.2 mm

2- Refractive myopia- power of the eye is too strong. Greater than the standard +60D

Question 14

For myopia, where does the images focus?

Answer 14

In front of the retina

Question 15

For emmetropia, where do the images focus?

Answer 15

The image focuses on the retina.

Question 16

What is hypermetropia?

Answer 16

Long sightedness

Question 17

For hypermetropia, where is the image formed?

Answer 17

Behind the retina

Question 18

For hypermetropia, what is too weak for weak for its axial length?

Answer 18

Unaccommodated eye is too weak for its axial length

Question 19

Hypermetropia could be due to what?

Answer 19

1- Axial hypermetropia- axial length is less than the standard 22.2 mm

2- Refractive hypermetropia- power of the eye is less than the standard +60D

Question 20

How do we correct myopia and hypermetropia?

Answer 20

With spectacle lenses and contact lenses.