It depends on the total amount of spherical and cylindrical refractive error.
Check your prescription against the Class 1 standard:
(d) Refractive error
(1) At initial examination an applicant may be assessed as fit with:
(i) hypermetropia not exceeding +5.0 dioptres;
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(ii) myopia not exceeding –6.0 dioptres;
(iii) astigmatism not exceeding 2.0 dioptres;
(iv) anisometropia not exceeding 2.0 dioptres
provided that optimal correction has been considered and no significant pathology is
demonstrated.
(2) Initial applicants who do not meet the requirements in (1)(ii), (iii) and (iv) above
should be referred to the licensing authority. A fit assessment may be considered
following review by an ophthalmologist.
(3) At revalidation an applicant may be assessed as fit with:
(i) hypermetropia not exceeding +5.0 dioptres;
(ii) myopia exceeding –6.0 dioptres;
(iii) astigmatism exceeding 2.0 dioptres;
(iv) anisometropia exceeding 2.0 dioptres
provided that optimal correction has been considered and no significant pathology is
demonstrated.
There is some discretion.
If in doubt write to the CAA medical centre with a copy of the prescription and ask for their advice.