Clinical advice on refraction for the purposes of the sight test

We are seeking expert clinical advice to understand: how the sight test is delivered by commercial providers of optical services across the four nations of the UK; the possible impacts where the refraction, binocular vision and eye health checks are not carried out by the same person, both with and without the oversight/supervision of an optometrist or registered medical practitioner; the possible impacts where the refraction, binocular vision and eye health checks are not carried out at the same time or in the sam...