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.
UncorrectedTwo focal lines
Cylindrical LensSingle focus · on retina
Incoming distant light →Blurred
CYL −2.00 D × 90°
Steep meridian (strong) — early focusHorizontal meridian (weak) — late focusSingle sharp focus (retina)Cylindrical lens