A Blind Hen

Bonnie the Cream Legbar hen cautiously wanders the coop, bumping into other chickens as she goes.  Bonnie has become functionally blind.  Her left eye is opaque and gray and her right eye has a tiny constricted pupil that never changes.  Her eyes worked just fine when she first hatched, but I noticed that she had eye problems as long ago as early last summer when her pupils became tiny constricted dots and she stopped going outside.  She knew her way around the coop, but outdoors was just too chaotic for a blind chicken.

The pupil of one eye is a tiny constricted dot while the other eye is opaque.  Result:  Bonnie is functionally blind

Blindness in chickens can result from environmental factors, it can be caused by a number of infectious agents, or it can be congenital/genetic.

The main environmental cause of blindness is ammonia buildup in the coop air.  When ammonia reaches high levels it can dissolve into the moisture in a chicken’s eyes to form ammonium hydroxide.  Ammonium hydroxide is the caustic and pungent smelling stuff in glass cleaning products.  Living in high levels of ammonia is like having a constant spray of window cleaner going into your eyes.  As you can imagine, it is highly irritating to chickens’ eyes and eventually can ulcerate the chickens’ corneas and cause blindness.  Anyone who has ammonia blindness occurring in their coops needs only to look in the mirror to find the cause.  High ammonia levels occur when excessive amounts of chicken manure pile up and there’s inadequate ventilation in the coop—in other words, the cause is someone doing a really bad job of taking care of their flock.  I can scratch this off the list as the cause of Bonnie’s blindness—I’m pretty obsessive about keeping my coops clean, and ventilation has never been an issue.  Also, if ammonia was the problem, I’d be seeing issues in many hens, not just one.

There is a long list of infectious agents—bacteria, viruses, and fungi that can cause blindness.  Marek’s disease is an alarming example of a virus that can cause blindness.  Marek’s is caused by a tumor-forming herpes virus that can cause the iris to shrink and the pupil to take on a weird shape in one or both eyes.  It also affects other organs in the chicken and often leads to death.  It’s also very contagious.  The good news is that most of my flock, including Bonnie, have been vaccinated for Marek’s.  While vaccination isn’t 100% effective, I would like to think that the chances of Bonnie having Marek’s is pretty slim.

The thing about most infectious agents is that they usually cause eyes to get red and produce a discharge, and I’m just not seeing that with this little hen.  Plus, if it were an infectious agent, I would expect other hens to have symptoms of blindness.

That leaves congenital blindness.  I lean toward that diagnosis.  When Bonnie and her sisters went through their first baby molt last spring it was obvious that Bonnie was different.  The other girls all started growing tail feather and Bonnie never did.  The compact roundness of her body was also a good indicator that Bonnie was missing her tail bone, a condition referred to as “rumplessness”.  Rumplessness is not a bad thing—as a matter of fact rumplessness is a necessary standard of perfection for certain breeds, such as Auracanas.  But Cream Legbars are not rumpless, so for this condition to show up in Bonnie suggests a genetic mutation or reversion.  Bonnie is also quite petite.  Her sisters are now all much bigger than she is.  So it’s not hard for me to conclude that Bonnie’s blindness is hardwired into her genes and a result of a spontaneous mutation. 

A shot of Bonnie and her sister, Nicky, from last summer.  They could be twins except Nicky has a tail.

What’s the prognosis for a blind chicken?  My worst fear is that blindness is just one manifestation of a congenital condition and that there could be other negative symptoms that haven’t shown up yet.  So I keep track of this little hen pretty closely.  I give her a daily dose of Veterycin Ophthalmic Solution, which maybe is an unnecessary precaution.  Bonnie doesn’t like getting eye drops very much, but she stoically tolerates them.  Other than that, she just calmly lives her life in the best way that a non-seeing hen can.  She doesn’t go outside much, but she’s active in the coop.  She knows where the feeder and the water fount are, she manages to get on the roost every night, and she has no problem finding her way to the nest boxes to lay a pretty green egg every day. 

The “Raising Chickens” website suggests that one big problem with blind chickens is their interaction with the other members of the flock:  “Once vision is lost or severely impaired a chicken has little hope for survival; eating, finding water and roosting will be impossible. It’s unrealistic to expect one with serious chicken eye problems to do well in a flock setting, though chickens with one good eye seem to adapt.  Even still, such a handicapped chicken could be expected to be picked on and bullied by other members of the flock. Being allowed access to enough food by the rest of the flock is not guaranteed, so making sure a partially blind chicken isn’t slowly starving to death is important.”  A dire and pessimistic vision of Bonnie’s future, to be sure.

I prefer the scenario that Gail Damerow lays out in  “The Chicken Health Handbook”:  “A chicken can usually do relatively well despite being blind, provided feed and water are readily available, the chicken has companion chickens, and the blind bird is confined to a limited area where it won’t lose its way or be vulnerable to predation.” 

I think the difference between these two assessments may lie with the infrastructure and flock that the blind chicken finds itself in.  Bonnie lives in Coop Two, which is populated entirely with the hippie peace freaks of the poultry world.  Most of the nine chickens in Coop Two live there because they had issues in the more competitive, aggressive atmosphere of Coop One.  These are chickens who were on the bottom of the pecking order because of their small size, their meekness, or their physical shortcomings.  Snowball was the only Silkie living in a coop full of chickens much bigger than he was.  He eventually stopped leaving the roost, ever, and would have starved had I not held him on my lap and hand fed him every day.  He became the founding member of Coop Two.  Angitou the Polish Hen not only had problems seeing around her elaborate crest, but when she got pecked after running into other hens she would panic and run, which resulted in her being chased and maliciously pecked.  In Coop Two she fits right in.  Willow the Buff Orpington started getting picked on when she got old and lame.  Coop Two became her new home.    These Coop Two chickens obviously get along happily with each other.  For me to go further and suggest why they get along, would require me to do some extreme anthropomorphizing.  So let’s just say that the Coop Two chickens are incredibly nonaggressive toward each other and I’ve rarely seen any aggression aimed at Bonnie in spite of her blindness.  I would like to think that my little blind hen is going to be just fine.

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