Specsavers offer free home tests by one of their team of mobile opticians to those who cannot get to a store unaccompanied. Most people living with dementia will be eligible for this service.
The eye-test is very similar to one that is performed in store but with a few adjustments to make it suitable to be done at home. The optician will ask about your eyecare history and any problems you may be having, before carrying out an eye test with specialised equipment for use in the home.
You can check your eligibility and request a home eye test here: https://www.specsavers.co.uk/home-eye-tests