Why are my dog’s eyes red?

How does a dog’s eye turn red?

Most dog owners are already familiar with what red eyes look like in dogs, and chances are they’ve already seen it in their own pets at least once. But what does happen when their eyes turn red and bloodshot?

The eyes are a highly vascularized pair of organs. The blood vessels in the eyes not only deliver nutrients to the eyes but also allow the migration of immune and inflammatory cells to keep the eyes protected from different environmental hazards and pathogens.

When the eye becomes irritated or injured, the body’s response is to speed up the migration of the immune and inflammatory cells to facilitate faster healing. This results in the small capillary vessels, which are normally not that visible to the naked eye, becoming engorged with blood, accounting for the redness.

The engorgement of small blood vessels is particularly visible in the white part of the eyes, called the sclera. This is usually what pet owners see turn red when they observe that their dog’s eyes become bloodshot. In some situations, damage to the cornea, the eye’s outer clear protective barrier, causes migration of the blood vessels to the site of corneal injury and contributes to the redness of the dog’s eyes.

Inflammation of the conjunctiva, the mucosal tissue surrounding the eye also causes it to become more red than normal and may be perceived by dog owners as redness of the eyes. Prolapse of the third eyelid gland, known as cherry eye, can also be perceived as eye redness by some dog owners. Being able to distinguish between these conditions is important in the management and treatment of the problem.

Common Causes of Red Eyes in Dogs

Eye redness can be caused by several conditions and diseases. A proper and confirmatory diagnosis is important to be able to come up with an appropriate, targeted, and effective treatment plan. Listed below are some of the most common causes of redness in dogs’ eyes.

1. Irritation due to foreign material

The dog’s eyes are very sensitive. Any contact with foreign objects will trigger an immune response from the eyes and result in the congestion of the blood vessels surrounding it.

The engorgement of the blood vessels makes the dog’s eyes bloodshot and red. This is usually accompanied by other signs such as squinting, pawing, discomfort, and pain. Treatment usually includes eye flushing to remove the foreign debris and eye drops to control the inflammation.

2. Corneal injury

Any damage to the cornea results in moderate to severe inflammation of the eye. Like with the previously described condition, this results in the engorgement of the blood vessels on the eyes and surrounding tissues, causing the dog’s eyes to turn red. This is most evident in the sclera, but the conjunctiva and the cornea can turn red as well depending on the severity of the corneal damage.

If the corneal injury is deep enough and the inflammation causes delays in healing, the body will compensate and make new smaller vessels grow towards the injury in a process called neovascularization. This allows inflammatory cells to migrate directly to the injury site to help speed up corneal healing.

Treatment for corneal injury will depend on the severity of the damage. Shallow injuries like corneal abrasions can be treated with a combination of eye drops designed to help in corneal healing and prevent secondary infection. Deeper corneal ulcers will often require systemic medications to control the inflammation, and worse cases will need temporary closure of the eyelids via surgery.

3. Glaucoma

Glaucoma is described as an increase in intraocular pressure. This happens when the drainage of the aqueous humor, the fluid in the anterior chamber of the eye providing nourishment to its components, becomes blocked leading to the build-up of pressure. This is considered an emergency because excessive pressure build-up, aside from being painful for the dog, can damage the optic nerve and cause blindness.

Along with severe pain, dogs with glaucoma can also have proptosis (eye bulge), cloudiness of the cornea, and bloodshot eyes due to inflammation from the pressure. Treatment usually includes eye drops to bring down the pressure and control inflammation along with analgesics to manage pain and discomfort.

What should I do if my dog’s eyes are red?

When you see that your dog’s eyes are starting to become red, it’s best to visit your vet immediately, especially if there are other accompanying symptoms. As mentioned above, some causes of eye redness in dogs are emergency cases that warrant immediate veterinary attention.

Your vet will perform a thorough ophthalmic examination and run diagnostic tests to arrive at a definitive diagnosis. The treatment plan will depend on the underlying cause of the eye redness.

Read more:

First Aid for Your Pet’s Eye

Dry Eye in Dogs and Cats

10 Facts About Your Dog’s Eyes

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