As far as eyesight is concerned just the colour blind test. Might be worth trying to get tested before the medical, it did delay things slightly after I failed the initial medical as I had to get an optician appointment, order 2 pairs of glasses that met the standards, go back and be retested, then I passed the medical. Took about a month to sort it all out. I found this online which should help.
Train drivers, like pilots, are responsible for large numbers of passengers. Similar visual standards are therefore required, as well as the ability to distinguish coloured signal lights. Their requirements are at least 6/9 corrected in the better eye, 6/12 in the worse seeing eye, and 3/60 in each eye unaided. Colour vision is assessed with a standard set of Ishihara plates. London Underground drivers must meet similar requirements, except their vision must be at least 6/60 in each eye unaided. These visual standards are tested at renewal for licences, and this is done every three years for those <55, and every year thereafter