you can substitute spherical correction for astigmatism correction. the spherical equivalent is the normal spherical value plus 50% of the cylinder. so for -3.00 sphere -1.00 cylinder 100 axis, the spherical equivalent would be -3.50 sphere (blank cylinder, blank axis).
It makes your vision worse (because the astigmatism is really not corrected) and might trigger a myopia progression (because the glasses are too strong)
It's the normal thing to do if only spherical lenses are available. E.g. cheaper off the shelf contact lenses. Contacts with cylinder correction are relatively novel and have downsides. The lenses are not "too strong", astigmatism causes two focal points, and the spherical equivalent puts you in the middle of these two.
