I have the genetic condition Retinitus Pigmentosa and as a consequence for the last few years have driven on a medical licence renewable each year following a test at Specsavers.. I was very sceptical about them especially as my sight is monitored at my local eye hospital.each year. However they have been very efficient and reassured me during rather nervous times as clearly each year I worry about loosing my licence. DVLA pay the costs so it's free to me.
So Specsavers are good but the system wasteful of public money. The only difference between the tests they take and the tests at the eye hospital is that Specsavers test both eyes together whilst the hospital tests each eye separately.
Andy