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Why is there a thick red vein in my dog’s eye?

I will never forget looking in the mirror and discovering one of my eyes had red veins all over it. As the hours passed, part of my eye turned completely red. It was a scary situation, but it turned out it was just a mild eye hemorrhage.

Our eyes are one of our most vital, and vulnerable, organs. The same is true for our dogs. Just like us, dogs can develop a wide range of eye conditions. Just as finding something wrong with your own eyes can be a scary experience, noticing a problem with your dog’s eye is harrowing as well.  

Why is there a thick red vein in my dog’s eye?

There are many potential causes for red veins in your dog’s eyes. These range from trauma to glaucoma. As scary as it can be, in some cases it’s nothing to worry about. In others, it’s a sign that something is wrong.

Corneal Ulcer

Dogs can get corneal ulcers for many reasons. One of the most common is scratch or foreign object in the eye.  Other causes include dry eye and eyelid conditions. 

A corneal ulcer is a defect or ulcer in the cornea, which is the clear lens that sits on top of the eye. Just as broken skin can lead to a skin infection, a corneal ulcer often leads to infection. 

A corneal ulcer causes lots of inflammation, or swelling in the eye. In an attempt to heal the cornea and relieve the pressure, the dog’s body does something remarkable. 

The blood vessels in the eye grow longer, moving from the outer edges to the location of the ulcer. These blood vessels carry healing nutrients to the injury site.   

If your dog has a corneal ulcer, they may keep their eye closed or squint. The eye may be red as well. Discharge from the eye is another sign. They may also seem unwell. These symptoms can include lethargy, being less playful than normal, and loss of appetite. 


Uveitis is another potential culprit. It causes inflammation of the eye’s middle layer. It has a wide variety of causes, including trauma or injury to the eye, cancers, and cataracts.  It can also be caused by diseases. These include immune-mediated disorders, tick borne diseases, and and inflammatory conditions.

The condition causes severe swelling or inflammation within the eye. This causes the blood vessels to grow or thicken in the eye, in an attempt to heal it. You may also notice blood in the corner of the eye.

Lens Luxation

The lens is found behind the iris. It is designed to focus light rays by sending them to the retina, which is in the back of the eye. 

When the lens becomes displaced or dislocated, this is known as lens luxation. This can occur due to injury, glaucoma, or uvetis. It can also be genetic. It can move to the front or back of the eye. 

It causes severe inflammation, which leads to pain and redness. The inflammation can also cause the blood vessels to swell. If there’s a luxation, you may see the lens, which is clear, moving around in the eye. 

This can be a veterinary emergency, particularly if the lens is displaced in front of the eye. 


Glaucoma can also develop in dogs. This causes an increase in pressure in the eye, which can lead to redness or the appearance of blood vessels in the eye. 

It can occur over months or years, or begin suddenly. Acute glaucoma is particularly concerning. It causes intense pain, redness of the white part of the eye and mucus membranes surrounding the eye, and squinting.

Lethargy and decreased appetite are also common. The cornea may get a bluish tint, and your dog may have difficulty seeing .


Conjunctivitis is one of the most common problems to occur in dogs. It causes inflammation of the mucus membranes that surround the eyes. It also affects the white part of the eye, causing redness and swelling. 

It can be due to a simple viral  or bacterial infection getting into the eye. However, it can also have an underlying cause. These include parasitic infestations, tick borne diseases, allergies. Puppies can develop follicular conjunctivitis. 

Dry Eye

Dry eye is the least serious cause of a red vein in your dog’s eyes. The bad news is the condition can be life long. The good news is that it can usually be treated with eyedrops. 

As the name suggests, dry eye means the eye is too dry. On the outside of the eye is a tear film. This film provides nutrients, moisture, and protection to the eye. In dry eye, this film doesn’t have enough water to function properly. 

Dry eye can be caused by an abnormality in the eye or eyelids. More commonly, it occurs because the body attacks its own tear glands. This is a type of auto-immune condition. 

It’s typically inherited. Bull-dogs, cocker spaniels, schnauzers, and Lhasa apses are at a higher risk of developing dry eye, but any dog can get the condition. 

What to do if my dog’s eye has a thick red vein?

What to do if you see a thick red vein in your dog’s eye will depend on several factors. Some situations require immediate veterinary care, while others are not an emergency. 

When Eye Problems are an Emergency 

Some eye symptoms mean that you shouldn’t wait to get treatment. If left untreated, your pooch could experience lasting damage to their vision or health. 

One sign you need to bring your pooch in pronto is a very red eye. If the white part of their eye is cherry red, this is a cause for concern. 

Swelling is another give away something is seriously awry. Slight swelling isn’t an emergency. However, if your dog’s eye seems to be bulging from its socket, this needs immediate care. 

A closed eye is another warning sign. Generally, an eye stays closed when it’s too painful to open it, or it’s too swollen to open. 

If the vein in their eye looks very large, this is also a sign to seek care. It’s unlikely, but not unheard  of, for vessels to burst under extreme pressure. 

If you are aware of an injury to your dog’s eye, this also requires immediate veterinary attention. Even if it seems minor. The eyes are very sensitive. 

Lastly, you know your pooch. If they seem to be in severe pain, are disoriented, or acting nothing like their normal self, consider it an emergency. 

Signs You Should Call the Vet 

If these don’t apply, it’s probably safe to call the vet and get an appointment. You should know that this isn’t a “wait and see” type of call. Your vet will likely want to schedule an appointment to examine your dog, and soon. 

Still, if your pooch can see and is acting relatively normal, there’s no need to rush them to the doggie er. Any eye issue is considered urgent, but not all are emergencies. 

What Not to Do 

There are many doggie issues you can treat at home. Mild injuries like scratches, stomach upset, and even allergies can often be handled without visiting your vet. 

However, when it comes to eye issues, never try to treat the issue yourself. Don’t hesitate to bring your pooch in, or at least call your vet.