Parakeet eye emergency
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That's a horrible infection either in or behind the eye. The best advice would have been to take the bird to a avian vet yesterday.
Its sunday the chances of finding a vet especially a avian vet is nearly impossible so.
Im not telling you to do this but antibiotics mixed with a little cereal then crop feed. I have lots of birds so I already have all the stuff required from baby cereal to bird safe antibiotics and I have experience on how to crop feed. Do some research online. maybe you have some penicillin in the house or some thing else (check on lines to see if its bird safe and how much is required). if you know how to feed then force feed. If you don't try to put a tiny amount in the beak and repeat until you know at least some has been ingested (most will be spat out that's fine don't over force the issue). Do not try to force feed unless you know what you are doing or you will make things worse and probably kill the bird. Then add antibiotics to the water in the cage. If the eye recovers make sure you keep antibiotics in the water for at least 14 days.
Look in the injury and cures section of the forum and look for something that can be put into the eye as a antibiotic. Some creams can be used but im not sure of the name brands.