Astigmatism · Optical Cross-Section

Why Doesn’t Light Focus to One Point?

In an astigmatic eye the cornea is not spherical but oval (toric). So two separate meridians focus light at two different points — no single sharp point forms.

Uncorrected Two focal lines
Cylindrical Lens Single focus · on retina
Incoming distant light → Blurred
CYL −2.00 D × 90°

Steep meridian (strong) — early focus Horizontal meridian (weak) — late focus Single sharp focus (retina) Cylindrical lens
Astigmatism · Vision

What Does an Astigmatic Eye See?

Blur is not equal in every direction: lines parallel to the axis stay sharp while perpendicular ones blur. Point lights stretch into a star-like streak.

Uncorrected Directional blur
Cylindrical Lens Sharp in every direction
Blurred
Fan / Clock Dial
Point Lights (Night)
Eksen90°
Axis 90°

Sharp (parallel to axis) Blurred (perpendicular to axis) Corrected image