Chapter 6- Optometric instrumentation Part 1 (1)

Question 1

When are screening tests done and who does them?

Answer 1

Often done by Optical Assistant before patient sees optometrist.

Question 2

What are some of the clinical tests that are carried out during an eye test and what is used for it?

Answer 2

1- Objective refraction- when the refractive error of an eye is determined without input by the patient. An autorefractor is used for this

2- Interocular pressure- the fluid pressure inside the eye. Non-contact tonometry is used for this

3- Visual field testing- Visual field instruments

4- Corneal curvature (K readings)- Keratometry

5- Fundus image- Involves photographing the rear of an eye. A fundus camera is used for this.

Question 3

With all clinical test procedures, what should you do? (patients wise)

Answer 3

You should explain the procedure and what, how and why you are carrying it out.

Question 4

What is retinoscopy?

Answer 4

It is an objective technique to determine the refractive error of the eye (i.e, myopia, hyperopia)

Question 5

What are the advantages of retinoscopy?

Answer 5

1- It is reliably accurate

2- It is quick and easy to use

3- Requires minimal co-operation from the patient

Question 6

What is the process of retinoscopy?

Answer 6

1- We shine the light on the pupil

2- We watch the reflection from the fundus

3- The reflection tells us whether our light is focused on the fundus or not

Question 7

What is an auto refractor?

Answer 7

It is an instrument used to determine a patient’s description.

Question 8

How is a retiniscope and auto refractor similar?

Answer 8

They are both ways of determining what a patient’s refractive error is.

Question 9

What does the auto refractor process involve?

Answer 9

It involves looking into a target such as, a house at the end of the lane or a hot air balloon at the end of the road.

Question 10

What does a part of the auto refractor machine allow you to do?

Answer 10

Calculate the refractive error of a patient’s eye

Question 11

What type of radiation do auto refractors use?

Answer 11

IR radiation

Question 12

Why do auto refractors use IR radiation?

Answer 12

Because the retina reflects IR better than visible light

Question 13

Why will IR have no effect on patient comfort?

Answer 13

Because it is invisible to the human eye

Question 14

What are the advantages of the autorefractor?

Answer 14

1- Objective- requires minimal input from patient

2- Quick and easy to use

3- Accurate

Question 15

What are the disadvantages of the auto refractor?

Answer 15

1- Expensive

2- May be affected by ‘proximal accommodation’

3- Not good with very small pupils

Question 16

What is proximal accommodation?

Answer 16

Accommodation caused by knowing an object is near

Question 17

What is proximal accommodation the same as?

Answer 17

Instrument myopia

Question 18

What can proximal accommodation cause?

Answer 18

1- Overcorrection of myopia particularly in kids

2- Under correction of hyperopia

Question 19

What is tonometry?

Answer 19

Method of measuring the pressure within the eye.

Question 20

Why is it important to measure interocular pressure?

Answer 20

Because we need pressure to maintain the shape of the eye.

Question 21

What happens if the IOP (interocular pressure) is too high?

Answer 21

It can cause damage to the nerve fibres at the back of the eye leading to glaucoma and blindness

Question 22

What is the normal IOP range?

Answer 22

10- 21 mmHg

Question 23

What is mmHg?

Answer 23

Millimetres of mercury

Question 24

What is the average IOP?

Answer 24

15.7 mmHg

Question 25

Why may patients not like tonometry (the simple method)?

Answer 25

Because it involves puffing air into their eyes.