Refractive limit
It is an axiomatic requirement that good eyesight and visual acuity are congruent with flying an aircraft at any level and that the limits placed on us by the regulators provide for this. However I disagree that limitations should extend to refractive error.
Visual standards should be based on visual performance rather than condition - most, if not all standards are based on this principle. If a pilot is able to meet the acuity requirements on >5.00D refractive error why should this matter? Without correction, a pilot who requires refractive corrective lenses has - for all intents and purposes - visual performance no better than that of a person outside these limits.