I have come across a number of pigeons that are missing an eye. One that was born without one eye, some that have lost their eyes to predator, some that have had an infection.
As first aid I wash the eye with warm sterile saline as sold in Boots.
I will usually take a pigeon with eye problems to the vet, to determine whether antibiotics or surgery is needed.
In her book Homeopathic Treatment for Birds Beryl M Chapman Aconite 6 given for three or four days , four times a day only if the eye is inflamed.
If an eye is infected with pus she recommends Euphrasia 3 for three days (this is also recommended for an inflamed eye that does not respond to Aconite. If there is a lot of pus she recommends Argentum Nit 6 instead of Euphrasia, dosage and length of treatment are the same.
The big question is "Can a one eyed bird be released back into the wild?" Technically, yes, because unlike raptors one eyed pigeons will have no difficulty finding and eating food so they will cope in the wild BUT their life expectancy is limited because they will be blindsided by predators, traffic and people that kick pigeons for fun.
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