Up to how many dioptres is laser eye treatment possible?

That varies depending on the laser eye treatment method.

Trans-PRK:

Short-sightedness: up to -8.00 dioptres corneal curvature: up to 6.00 dioptres long-sightedness: up to +3.00 dioptres

Femto-LASIK:

Short-sightedness: up to -10.00 dioptres corneal curvature: up to 6.00 dioptres long-sightedness: up to +4.00 dioptres