When I was a kid, we had the sweetest cat ever. One day we found him half dead in the backyard; he had been mauled by the neighbors doberman pinschers (they were so mean, one of them chewed the other's leg off). We took him to the vet, who said he was lucky to be alive. One of his legs was partly chewed off and had to be in a cast for a couple of months, he lost part of an ear, and had gashes all over the place. He was never the same after that.
Not long after we got our cockatiel, I let her out to stretch her wings and heard a strange squawk. I looked at her and she looked fine, but she had scratched her eye on something. Since she has pink eyes, it was hard to tell that the eye was irritated until she started scratching at it and it began to water profusely. It was 9 pm in rural NC and no vets were open; I got ahold of an emergency vet in Raleigh and they told me of a vet in the area that handled birds. I made a plastic bell guard out of the top of a coffee can and took her to the vet the next day. He put some antibiotic drops in her eye and told me she might lose sight completely in the eye. She had to wear the guard for about a week, and she had great difficulty eating with it. She became very thin and I was worried she was going to die. She pulled through though, her eye is fine, and she's still the little snot she has always been