A Look at Chicken Eyes

Recognizing Marek's Disease Symptoms and Other Common Ailments

A Look at Chicken Eyes

Reading Time: 5 minutes

By Rebecca Krebs

As we watch our flocks busily foraging in the backyard, the importance of chicken eye health becomes obvious. Whether chasing grasshoppers or courting the ladies, chickens use their eyes for every aspect of daily life. Consequently, problems with these vital organs are detrimental to the birds’ well-being, and it is crucial to recognize the symptoms of trouble so that illness can be proactively treated. 

Healthy chicken eyes are bright, wide open, and free of discharge or swelling. Normal chicken eye colors vary according to breed and age, but the eyes should always be clear with black pupils of a regular, round shape. 

Normal chicken eye colors vary according to breed and age, but the eyes should always be clear with black pupils of a regular, round shape.

In contrast, some of the first signs that a chicken isn’t feeling well are a dull or sleepy expression and squinty eyes. Discoloration, discharge, inflammation, and discomfort often characterize chicken eye maladies. Immediately isolate sick chickens from the rest of the flock to stop disease from spreading, and work to promptly diagnose and treat illness. 

Marek’s Disease in Chickens

One of the most dreaded of chicken illnesses is Marek’s, an incurable viral poultry disease spread by feather dander. It is highly contagious and typically affects young chickens that are three to30 weeks old. Symptoms of Marek’s disease in chickens include blindness, leg paralysis, and tumors. 

While birds with paralysis die quickly, those with ocular Marek’s, the form that affects chicken eyes, may survive for some time if the other symptoms aren’t present. Ocular Marek’s disease symptoms are irregularly shaped pupils, gray or cloudy eyes, difficulty seeing, and finally total blindness in one or both eyes. A chicken’s owner may realize something is wrong when the chicken doesn’t respond to human approach, or when it has trouble picking up small food items. It has more difficulty eating, drinking, and navigating as the disease progresses. Since chickens exhibiting symptoms of any form of Marek’s suffer and eventually die, the most merciful option is to humanely euthanize them as soon as the disease is diagnosed. 

Left — Normal chicken eye. Right — Eye of a chicken with ocular Marek’s disease. Photo courtesy of the U.S. Department of Agriculture.

Practicing strict biosecurity and good animal husbandry is key to preventing Marek’s disease in chickens, as well as other infectious diseases. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service provides guidelines for an effective biosecurity plan. These resources are available at www.aphis.usda.gov/publications/animal_health/2014/pub_bioguide_poultry_bird.pdf. 

Once Marek’s disease gains entrance to the flock, it is difficult to eradicate because chickens that develop immunity to it are permanent, asymptomatic carriers that shed the virus and can infect other chickens. But don’t panic if Marek’s turns up. Most flocks have been exposed to a strain of it, and there are several options to control the disease. 

  • Genetic Resistance: Chickens can develop hereditary resistance to mild strains of Marek’s within a few generations. This option is so effective in some situations that the flock experiences no losses to the disease after building resistance. Chicken breeders often choose this route to establish natural immunity in their birds. However, flocks infected with more virulent strains of Marek’s may need to be vaccinated. 
  • Marek’s Vaccination: Vaccinating for the disease is a widespread and generally reliable means of control. You can opt to have your chicks vaccinated when you purchase from most hatcheries, and you can purchase the Marek’s disease vaccine if you decide to vaccinate your own chicks (chicks are vaccinated as day-olds). Vaccinated birds can shed the virus for life, so any new chicks should be vaccinated before entering a vaccinated flock. The use of these chicken vaccines is controversial because they are believed to be responsible for the increasing virulence of Marek’s disease. Some flock owners avoid vaccination unless necessary. 
  • Complete Isolation: Chicken owners can control Marek’s by isolating vulnerable young chickens from all other poultry, including young poultry sourced from different producers. Since people and equipment easily convey feather dander between flocks, the quarantine must be extremely strict for this option to be successful. Thoroughly disinfect facilities between batches of chicks, as the Marek’s virus is infectious for at least a year after the birds leave the premises. 

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Eye Worm

The Manson’s eye worm is a species of roundworm found in tropical and subtropical regions. Chickens pick up eye worms by eating Surinam cockroaches (which host the worm’s infectious larval stage) or by exposure to wild birds. The worms live under chickens’ third eyelids, causing acute discomfort, cloudiness of the eyes, watering, and inflammation. Infected chickens scratch and rub their eyes in an effort to dislodge the worms, but they only make the problem worse by injuring their eyes. They can go blind if the parasites are not promptly removed. 

A 5% cresol solution is effective against eye worm. Several wormers and other products are also used off-label for treating eye worm. Ask your vet about their recommended treatment. 

To help prevent chicken eye worm, maintain good cleanliness of the chicken facilities, destroy the roaches, and minimize the chickens’ contact with wild birds. 

Chicken Eye Infections

Anything from injuries to debris to pathogens can cause chicken eye infections. Common signs of infection are otherwise healthy-acting chickens with sticky, swollen, or cloudy eyes. Additional symptoms such as sneezing, lethargy, or diarrhea indicate a more serious problem. 

This chicken’s inflamed eye is a sign of an eye infection. The chicken looked healthy otherwise. Photo courtesy of Joshua Krebs.
The eye of a healthy Rhode Island Red rooster. Copyright © 2020 Joshua Krebs. Used by permission.

You can treat most infections by gently washing away discharge with a damp cloth, rinsing the eye with saline solution, and applying an eye-approved antibiotic until the eye has healed. Although many chicken eye infections can be treated at home, contact a veterinarian if the problem is serious or worsens after treatment. Keeping poultry facilities clean and dust-free helps prevent infections. 


Birth defects involving chicken eyes are relatively common, but they are usually caused by incorrect artificial incubation, not genetics. Serious deformities can be debilitating or associated with other structural or mental disorders that result in poor quality of life for affected chickens. However, many chickens with minor eye defects live happy, productive lives, though as a precautionary measure they should never be allowed to breed. 

A baby turkey missing one eye. Incorrect artificial incubation causes this relatively common birth defect in poultry. Note the associated crossed beak. Photos courtesy of Joshua Krebs.

For chicken eye maladies, prevention is the best option. Instating good biosecurity and husbandry practices is the first step toward healthy, happy chickens. When a chicken does become ill — and, unfortunately, it happens despite our best efforts — taking quick action to treat the problem is essential to the chicken’s recovery. After all, we want our chickens to enjoy many years of excellent eyesight. 


Dunn, John. “Marek Disease in Poultry.” Merck Veterinary Manual. Merck & Co., Inc. October, 2019 www.merckvetmanual.com/poultry/neoplasms/marek-disease-in-poultry. 

“Eye Worm Infection.” PoultryDVM. AnimalDVM, LLC. n.d. www.poultrydvm.com/condition/eyeworms. 

Rebecca Krebs is a freelance writer and genetics aficionado who lives in the Rocky Mountains of Montana. She owns North Star Poultry, a small hatchery that breeds Blue Laced Red Wyandottes, Rhode Island Reds, and five exclusive chicken varieties. Find her farm online at northstarpoultry.com. 

Originally published in the Backyard Poultry Special Subscriber 2020 issue  Comb to Tail Health  and regularly vetted for accuracy.

4 thoughts on “A Look at Chicken Eyes”
  1. I have a Rhode island red hen. All of a sudden her right eye closed. When she is walking around it seems as if she is blind in both. She is health otherwise, but not eating. Can anyone shed light on this

  2. My 10year old head chook appears to have problems seeing. She is moulting and has gone off the lay. Her eyes look normal. Could she be going blind due to her age?

    1. She is getting too old that is why it is happening I suggest killing it we had one like that it suffered.

  3. my chook seems to be visually impaired, possibly going blind, but her eyes look normal, she is only two and is laying very regularly. this only developed after her first molt, and she has had Coccidia before, with very different symptoms. could this be an injury she has had to her eye? if so, what will help it to heal?

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