how old are they? Are they boys?
they may well be blind, but red eyed rats do have just really bad eyesight, however this won't be the reason for them biting you. you aren't frightening them in the sense that they don't know you're their, their hearing and sense of smell will make up for that.
it sounds like they are just really frightened of people. to begin with leave them to it. if you can pour their food in rather than open the door to put in in. they won't care where it is. When cleaning them out put on gardening gloves and houk them out when they're in their house, put them in a box that you can close with their house. Have another house already to put in once the cage is cleaned and then turf them out of the one they're in. they will get wise to this but they may prefer it to being houked out bodily by you lol. Get a water bottle that sits outside the cage if you don't already have one.
You need to be as patient as you can. It's not their fault, try not to get angry with them, they really can't help it.
don't try to stroke them or touch them as they will just attempt to bite you. leave them to it, speak to them, be near the cage as much as possible, get the used to you again, show them they've nothing to be scared off as all you are doing is cleaning them and feeding them. give them lots of good veggies as treats that you can poke through the bars without your fingers being in easy reach. carrots etc
it will probably take a while (we had a nibbler that never got use to us, but learned to leave us alone and learned that 'playtime' (command) meant a good run around and let us get her out for that but bit us the rest of the time, unless she was ill then she let us pick her up lmao). We;ve had babies that have taken months to get used to us and we've left them to it and eventually they come to us, it takes months sometimes. But eventually they get better, and nibble to investigate rather than bite, only occasionally do they bite us and that's due to us putting fingers through the bars lol our others don't bite so usually it's safe lmao.
Just leave them alone in the cage as much as possible but make sure you see and speak to them at least a few times a day. put there somewhere quiet if possible so they can have times where they are completely alone to do ratty things without the constant fear of being 'seen'.
If you want to see how they are getting on with you, put your hand in in a fist, thumb tucked in to protect it. keep it fingers down. if they bite at least it'll be less likely to be a soft part
try not to jerk away but take your hand away and say 'ow'. don't see nibbles as a bad thing, if its a proper bite and draws blood then they're nto ready but if it's a few nibbles, which shouldnt have much pressure at all behind it and then they run away that's a good sign. They're still scared if they nibble and run but they don't see you as as much of a threat. biting is meant to make you run away, so do it. Nibbling and them running is a sign that they're abit scared but you aren't an enemy so you can safely be ran away from. don't chase after them always let them come to you (if they run away when you're cleaning out the cage, try cleaning it out with them in there, have a spotter with you tho in case they ambush you
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the best way to figure out if they're ready to 'meet' you is if they come to see what you're doing like a normal rat would but if you get to close run away. if they follow your progress from their hiding place it means they're interested in what your doing, scared rats generally run away and hide completely, looking at you would mean that you can see them and therefore know where they are hiding which if your an enemy isn't a good thing.
just take it slowly and hopefully they'll come round. don't introduce any more rats to them, the new ones will pick up their cues from these 2 and become just as bad.
if you can get a bird water feeder instead (with an open source of water) they sit on the outside so are easy to replenish. also means they have a better water source to clean themselves, rats generally prefer these types of water troughs than the old ball and tube type.
if you need any more advice just let me know.
remember they've the intelligence of a 2 y/o they'll come round eventually. hopefully
you might find if they're quite young they will come round with old age when they mellow out, like i said, be patient, they really can't help it.