Diagnosing Astigmatism
We know that astigmatism can be treated with laser eye surgery, but how do we initially diagnose the condition? The ophthalmologist or optometrist may use the following tools to examine the eyes:
Visual acuity test – this involves reading letters on a chart. The letters become progressively smaller on each line.
Astigmatic dial – this is a chart showing a series of lines which make up a semi-circle. People with perfect vision will see the lines clearly, while those with astigmatism will see some more clearly than others.
Keratometer – also known as an ophthalmometer. This device measures the reflected light from the surface of the cornea. It measures the radius of the curvature of the cornea and can assess the degree of abnormal curvature of the cornea.
Keratoscope – also known as Placido’s disk – this device is marked with lines or circles and observes corneal reflex. It uses light to project rings on the cornea. By measuring the spacing between the rings it calculates the variations of curvature, which in turn calculates the degree of astigmatism. A videokeratoscope is a keratoscope fitted with a video.
The importance of regular eye tests
Astigmatism is very common – experts say most of us are born with a degree of astigmatism. Most children who are born with astigmatism will not realize they have it until they have an eye test. Reading and concentrating at school may be affected if a child has undiagnosed astigmatism. Therefore, regular eye tests are important.
In the UK babies have an eye test soon after they are born. They have a follow-up test about six weeks later. Doctors recommend that children receive a comprehensive eye test when they are four years old; and then every year up to the age of 16. Adults should have an eye test every couple of years.
