About the astigmatism test
This astigmatism screen shows a fan of radial lines pointing in every direction. An eye with astigmatism focuses one orientation more sharply than others, so some spokes look darker, sharper, or bolder while the perpendicular ones look fainter or blurrier. Which directions stand out points to a possible astigmatic axis, tested one eye at a time.
Astigmatism comes from the cornea or lens being shaped more like a football than a sphere, which is extremely common and easily corrected with glasses or contacts. This test can suggest its presence and rough orientation, but it can't measure your prescription — only an optometrist's refraction can. Try it both with and without your usual correction: if a direction still stands out with your glasses on, that can hint at under-correction worth mentioning at your next exam.
Frequently asked questions
How does an astigmatism test work?
You view a fan of radial lines. If some directions look darker or sharper than the perpendicular ones, it suggests your eye focuses one orientation better — the signature of astigmatism.
Why do some lines look darker than others?
An astigmatic eye brings one meridian into sharper focus, so lines in that direction look crisper and darker while the perpendicular lines look fainter or blurred.
Can I really test astigmatism online?
Only as a suggestion. This can hint at astigmatism and its rough axis, but it can't measure the amount or give a prescription — that needs an optometrist's refraction.
Should I wear my glasses for this test?
Try it both ways. With correction the lines should look even; if a direction still stands out with your glasses on, it can hint at under-correction to raise at your exam.