Astigmatism dial check.
A classic radial line fan, tested one eye at a time. With normal vision every line looks the same. If one orientation looks darker, sharper, or bolder, it can point toward astigmatism along that axis.
Cover your left eye. Look at the center with your right eye.
Right eye
No selection yet.
Left eye
No selection yet.
This is a rough, self-administered pattern check — not a measurement. If one direction consistently looks bolder or sharper across repeat tries, mention it at your next eye exam so a doctor can measure your astigmatism axis properly.
The science behind this
Astigmatism arises when the cornea or lens is curved more steeply in one meridian than the perpendicular one — toric rather than spherical. Light then focuses to two separate line foci instead of a single point, a geometry described by Sturm's conoid.
On a radial dial, the lines aligned with the meridian that happens to focus on your retina look sharp and dark, while lines 90° away fall out of focus and look faint. So the boldest set of lines marks the meridian in best focus, and its perpendicular points toward the astigmatic axis.
What it measures
- Whether a directional focus difference is present
- The approximate orientation (axis) of that difference
Limitations
- It suggests presence and axis, not magnitude in diopters.
- Accommodation and uncorrected blur can mimic or mask the effect.
- Keratometry, autorefraction, and subjective refraction are the real measurements.