The issue with medicine isn't that you're not taking chemistry, it's that you're only taking one science subject. I think there are about 5 medical schools you'd meet the A-level subject requirements for - and if any or those are GCSE heavy you would need to write them off too.
Without physics or maths at least alongside biology you have a very limited range of medical schools you could potentially apply to.
Likewise I think most optometry courses require two sciences.