Yesterday, and 3 days ago, I saw yellowish white hard substance under the nitrating membrane of one of their (2 chickens) eye. It look the same thing as what I saw on my chicken's eye on february this year. They can be easily taken out. I am pretty sure, that they have eye worm since, I saw it, when I saw the hard substance. They are free range chicken since they were born which is about 2 months ago. The chicken(which is also a free range chicken on that time) that have it on february interacts with 10 other chickens, before and after I saw it, but the other chickens didn't have it up to now. I am not sure if that chicken had eye worm on that time, but it definitely have a moderate or severe eye worm infestation at least 2 months ago, since I can see the eye worms every time I look on the eye( I can see them, because under the nitrating membranes are overcrowded with eye worms). Also, two months ago, all of my free range chickens have eye worms on their eye, ranging from mild to severe infestation, but I didn't see any hard substance under the nitrating membrane. I treated all of them with injectable noromectin( generic brand of ivermectin) for 5 consecutive days, at least 5 drops per eye everyday. I didn't see any of them including the chickens that have a lot of them, after the second treatment on most chickens. I can see it on only 3 chickens on the third and fourth consecutive day of treatment. I really believe that it work, since I didn't see them anymore especially on the ones that have a lot of them( I can see it every time I look on the eye) since about 2 months ago. Their nitrating membrane are abnormally wider. What causes the yellowish white hard substance to form under their nitrating membrane? I really want to put them inside the cage few days after they are born, but they make constant loud noises on that time, which obviously irritates our neighbor. Since few weeks ago, they don't make those sounds anymore, but I don't want to put them on the cage with the other chickens, since they will contaminate the soil( I am not concerned with eye worm eggs since eye worms have indirect life cycle, but only on parasites that have direct life cycle, like roundworm, gape worm, etc.) and there are not enough coop( I need enough to use it to contain them during treatment and at least few days after treatment) for all of them.