Chicken has pupil that is completely constricted

[grnidone]

She acts completely normal otherwise.

I’m unsure if I should treat it or if it is too late to treat?

 

[Eggcessive]

That type of pupil could be a sign of the ocular/eye form of Mareks disease, but I would guess that it might also be possible with a peck injury to the eye. Is the iris eye color more gray in her eye? She is probably blind. Chickens can have ocular Mareks without having other forms.

 

[Eggcessive]

Here is a good article about Mareks:
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/

If you scroll down to post 6 in the thread below, there is a similar eye pictured:
https://www.backyardchickens.com/threads/ocular-mareks-symptoms.1144846/

 

[grnidone]

It doesn’t look grey, it’s just constricted. I think she can see some light, but she does seem to be blind otherwise in that eye.

I had some eye ointment for my dog and out that in the eye.

 

[Eggcessive]

Usually with ocular Mareks the other pupil becomes the same over some time. So, it is good that her eye color is normal at this time. Hopefully, that means it is not Mareks but an injury.