[colliebird]

Yesterday morning she was fine, or wasn't showing any particular signs of vision problem. In the afternoon I noticed she wasn't moving around with the others and was laying down a lot of the time.  At bedtime, she accidentally (?) went in the goose house and literally climbed the 6' high wire mesh panel that separates the hens and geese sleeping quarters.  I had to help her down the other side and put her on the perch to roost for the night.
This morning part of one eye is white, (not cloudy) and she is "high stepping" as if she's feeling her way around and it's obvious her vision is seriously reduced.  She also feels very light.  No lice, and this morning for the first time, there aren't any mites on the perch.
I've never had a hen that needed glasses  and wondered if anyone knows of a reason why this could happen so quickly?
She's young, about 15 months old, and is the hen who went broody then left her eggs after 3 weeks just around the time the Monstrous Mites appeared.
They all get layers pellets, mixed corn and/or some wheat as a treat in the afternoon, and maybe some dry bread when there is any, as they all like that.
Any suggestions as what it might be?
(I haven't sprayed when the hens have been in the coop.)

[themagicaltoad1]

Can't give you any advice other than a word with the vet might be a good idea.

[iwantanallotment]

I'd agree with toad, to take her to the vet for a quick check over.

I posted this here once before, and it might not apply but still.........
One of my brother's dogs went blind overnight & white eyes - it was an infection behind the eye & quickly sorted with antibiotics. Hope that's all it is for your hen, too 

[colliebird]

I'd agree with toad, to take her to the vet for a quick check over.

I posted this here once before, and it might not apply but still.........
One of my brother's dogs went blind overnight & white eyes - it was an infection behind the eye & quickly sorted with antibiotics. Hope that's all it is for your hen, too 

It got worse and she was falling over and couldn't get up. Saw vet, he thinks it was a neurological/locomotion problem and unlikely to get better. Says it sometimes happens which could be due to anything. Auto immune problem, trauma and that antibiotics wouldn't help.  Hen is now in chookie heaven 
It happened more or less overnight.