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Online astigmatism test (radial fan)

A simple astigmatism self-check with a radial fan (Siemens star): with normal vision all lines look equally grey and sharp. If some lines (in a certain direction) look darker, sharper or blacker, astigmatism is possible. This is a guide, not a diagnosis; refraction is measured by an ophthalmologist.

Look at the centre of the fan from a normal distance. Cover one eye and answer for that eye.

Eye

How do the lines look when you look at the centre?

What astigmatism is

In astigmatism the cornea (or lens) is not perfectly spherical but slightly "oval", so light does not focus to a single point. Because of this, lines in one direction look sharper and in another blurred. Mild astigmatism is common and does not always interfere; significant astigmatism causes blur, eye strain and headaches.

How to take it

Look at the centre of the fan from a normal distance, one eye at a time:

  • cover one eye with your palm (not squinting);
  • look at the centre of the star — don’t "scan" the lines around;
  • if you wear glasses/lenses — check both with and without them;
  • note whether all lines are equally grey or some stand out.

What the result means

All lines equally grey and sharp suggests the fan reveals no obvious astigmatism. If some lines are consistently darker/sharper (especially in both eyes or in your glasses), see an ophthalmologist — correction may be needed.

A screen fan depends on the monitor and distance, so it’s a guide. The degree and axis of astigmatism are measured with an autorefractometer by a doctor.

Frequently asked questions

  • Look with one eye at the centre of a radial fan (Siemens star). If all lines are equally grey, the test shows no obvious astigmatism. If some lines are darker or sharper, astigmatism is possible — see an ophthalmologist. This is a guide, not a diagnosis.

  • Often not: mild astigmatism is common and may need no correction. Significant astigmatism causes blur, quick eye fatigue and headaches — then it is corrected with glasses/lenses. Whether you need correction is decided by an ophthalmologist from a measurement.

  • Because of the eye’s unequal refractive power in different directions (the cornea is not perfectly spherical): light in one direction focuses more precisely, in another less so, so some lines look sharper/darker. That is the essence of astigmatism.

  • Yes — most often with cylindrical glasses or toric contact lenses; in some cases laser correction is discussed. Astigmatism is not "trained away" with exercises and does not resolve on its own. Whether you need correction, and which, is decided by an ophthalmologist from a measurement of the degree and axis.

  • Yes, they can be: with uncorrected astigmatism the eyes constantly "over-focus" trying to sharpen the image — hence quick eye fatigue, headaches and discomfort when reading or driving. If that sounds like you, it is worth having your refraction checked by an ophthalmologist.

Tired eyes and headaches?

The cause can also be in your overall condition. Upload your labs — AI reviews the values and tells you what to check.

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The test is a self-check guide, not a diagnosis. A screen fan depends on the monitor and distance. The degree and axis of astigmatism are measured by an ophthalmologist.