Chapter 6- Optometric instrumentation part 1 (2) Flashcards
What is the more accurate method of tonometry?
The accurate method involves numbing the eye and touching the surface of the eye with a probe.
What is required to maintain the shape of the eye?
A positive IOP
What is pressure largely determined by?
Balance between aqueous production and outflow
Where does aqueous humour flow out through?
It flows out through the drainage angle in front of the iris. This equal flow maintains a stable pressure.
Raised IOP is the primary risk factor of what?
Glaucoma
Reducing IOP can do what?
It can slow down the progression of optic neuropathy which causes glaucoma.
The IOP is determined by three factors:
1- The amount of fluid within the eye
2- External forces acting on the eye
3- The intraocular volume
What are the physiological factors affecting IOP?
1- Age- Increases as you get older, but decreases slightly after 70 years
2- Gender- IOP is generally higher in females than in males
3- Myopia- associated with higher IOP
4- Light levels- IOP rises slightly in the dark due to pupil dilation
During what time of the day does IOP tend to be high?
In the mornings
Why may it be wise to repeat IOP measurements for a patient at a different time of day?
Becomes some patients have afternoon peaks.
What else should you record for IOP other than the IOP measurement itself?
The time of day and instrument
What are the two methods of measuring IOP called?
1- Contact tonometry- putting the probe on the surface of the eye
2- Non-contact tonometry- using air
What is required for contact tonometry?
Anaesthetic eye drops
How is IOP measured in contact tonometry?
The amount of corneal flattening produced by a known weight is measured.
How is IOP measured in non- contact tonometry?
You puff air into the eye and then measure how much of the cornea was flattened.
