What is astigmatism?
Astigmatism means the front of your eye (the cornea) or the lens inside it is curved more in one direction than the other, a bit like a rugby ball instead of a basketball. Light focuses unevenly, so things look blurry or stretched at any distance. It's very common, often present from birth, and frequently comes with nearsightedness or farsightedness.
Typical signs are blur at both near and far, eye strain, headaches after screen work, squinting, and glare or streaks around lights at night.
How the clock dial astigmatism test works
The dial has groups of lines at every clock position, all printed equally dark. An eye without significant astigmatism sees them evenly. An eye with astigmatism focuses one direction better than the others, so those lines look bolder or blacker. Noting which clock hours look darkest also hints at the axis, which an optometrist would measure precisely.
Cover one eye, sit at arm's length, look at the center of the dial and wear your usual glasses. Then switch eyes.
What to do if lines look uneven
Book an eye exam. Astigmatism is easily corrected with glasses, toric contact lenses or, for some people, laser surgery. If you already wear glasses and still see uneven lines, your prescription may need updating.