What Is An Astigmatism Test?
When they test for astigmatism they first determine if you have any distortion in your visual field. Initial testing can even be done at home.
You can use the online astigmatism test chart to get started:
- move 1 meter (3.3 feet) away from the screen
- cover one eye with your hand (don't press hard)
- look with your open eye at the center
- check if any lines appear blacker or lighter grey
=> take not of the lighter grey lines. These indicate at what degree your astigmatism my be.
Then repeat with the other eye.
The other way to test yourself for astigmatism at home is when you look at an object. A street sign or the sign of a business will do.
You can simply look at the sign and check if you can see the same thing twice. If you see the same object double. For example, the outline of the street sign appears double in your visual field.
When you look at the object of your choice, take note of how distorted the background is.
Now move closer to the object. Does the background clear up? If yes and the object is still doubling up, you may need to get your eyes tested for astigmatism by an optometrist or optician.
How Is Astigmatism Tested?
An optometrist initially tests for astigmatism in a very similar fashion like the graphic above. After they tested you with astigmatism they may progress to check whether it's corneal astigmatism or lenticular.
How Do Astigmatism Tests Work?
Plus, the initial test can reveal at what angle the distortion appears.
The reason for that is that a refractive error causes the light to bend incorrectly. Therefore the light doesn't focus properly on the retina. That refractive error is one of the astigmatism causes. It requires vision correction to focus correctly again.
If you have a history of keratoconus or another corneal eye disease an eye doctor will have to test your cornea's shape.
What Test Is Used For Astigmatism?
To start with an optometrist or optician can test for astigmatism with the same equipment they to test for near- and farsightedness. The eye specialist can determine the amount of astigmatism by using the lenses to check for myopia and presbyopia.
That's the old school procedure known as retinoscopy.
This test is replaced with modern test machines today. This type of testing can deliver very fast starting results for testing refractive errors.
The reason the test is so similar is that all these conditions are based on a refractive error. That is the definition of astigmatism. The only difference is that astigmatism doesn't stem from an elongated eyeball or one that is too short. Astigmatism is due to a corneal distortion or a lenticular distortion.
How Do Doctors Test Corneal And Irregular Astigmatism?
The astigmatism testing is a pretty straight forward process as long as the problem is the lens. When the distortion is due to a misshaped lens that's known as lenticular astigmatism.
As soon as an eye doctor determines that you have irregular corneal astigmatism the testing becomes more involved. In that case, you will need to undergo a process called corneal topography (also known as photokeratoscopy or videokeratography).
It's a way of imaging your cornea to determine where your cornea is distorted. It analyzes the surface curvature of your cornea and with that the outer structure of the eye.
As a result,t the eye doctor gets a 3-dimensional image (corneal topography) of the exact structure of the patient's cornea to see any distortions or misshaping.