I too am totally confused. Visual accuity is checked at every medical using spectacles. If you pass with those spectacles I do not understand why there is more to be said. You need to carry two pairs of those glasses or others with identical lenses in the cockpit.
The CAA's website states
the latest optometrist reports should be made available at each medical assessment for the AME to check.
and
spectacle wearers (who tend to have checks yearly or 2-yearly)
.
I accept contact lens wearers are separate but I see no rules stating you need to do any more than attend the medical and pass the VA test wearing your spectacles and have an optometrist's report from any time in the past. Especially for the majority of pilots who merely have age related needs for reading glasses any demand to have a new or repeat optometrical examination is ultra vires and not mandated. Every time I have one the shop gives me dreadful grief because I buy my glasses for under £10 on Amazon instead of buying their identical lenses for many times that.