I wouldn't recommend regularly cleaning out the cage as has been mentioned above. It doesn't matter that he can not see, blind hamsters live normal lives because their sight is quite poor anyway - they rely more heavily on their senses of smell and sound. Their enviroment is very important to them, more specifically the way it smells. Frequent and thorough cleaning is very stressful for a hamster, as is being moved around too much. Instead you should only remove small areas of obviously soiled bedding and nesting material and leave most of the bedding for as long as it doesn't smell. Then when you do clean the cage, put back some of the old bedding anyway.
It does just sound like old age and there is nothing you can do but make them comfortable, give them treats and softer foods and watch them. If they do suddenly go downhill and develope symptoms that suggest they might have something such as a respiratory infection - then they should really see a vet. Things like clicking when breathing and mucus around the nose. If they survive the infection for several days before they die, then it is likely that they suffered needlessly. Hamsters usually die within 24 hours if they were too weak to survive the illness even with antibiotics (usually, but not always). Painkillers and antibiotics can be given to help them if they are ill (rather than just generally de-generating with old age), it's a myth that there is nothing you can do so should just leave them for days on end.
Vets in the UK are pretty cheap (compared to the US), if you go within working hours it should only be between £5-20. This is only if they become clearly sick, on top of their old age.