It is possible to do this by yourself if necessary, just leave yourself a block of time so you can be patient. Wrap the hen in a towel to help hold her, and if necessary lay her on her back which will help calm her. Just take your time. The pus really needs to come out or you will just be fighting a losing battle. There are a lot more videos on line on removing pus from a chickens eye, do a search, one of them might be more inspiring to you. Sometimes it will come out with some manipulation, sometimes you have to use something to help get it out. I have curettes that I use for all sorts of things on chickens, not sharp, spooned on the ends. There is no telling what the initial cause is/was, could have been viral, could have been injury or debris in the eye. I would do a good rinse, clean it out as well as you can and flush it well. Then use the terramycin twice a day. Once all the pus is out, it should start to improve. You can get a stronger eye drop, but you will need a prescription from a vet, and the pus will still need to come out.
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