Birds eye

Small eye pupil in chicken

source: Victoria Roberts
Country Smallholding November 2002
p18

Chickens may suffer from eye disease which results in the pupil of an eye becoming very small. This could be the result of a viral infection. The pupil sometimes recovers, though not always, and affected birds appear to retain some vision. Chickens may be otherwise healthy, but could become targets for bullies in the flock. There is a possibility that the condition could be inherited, so it is best not to use affected hens as breeders.
CH,HD