Cloudy Eyes in Dogs: 7 Reasons

Cloudy eyes in dogs can happen for a variety of reasons—some are more concerning than others. To help you sort through possibilities, integrative veterinarian Dr. Julie Buzby explains the symptoms, diagnosis, and treatment for seven common causes of cloudy eyes.

You’ve probably heard the expression that the eyes are the windows to the soul. But did you know that looking into your senior dog’s eyes might also tell you something about his or her health? For example, cloudy eyes in dogs can point to a variety of eye problems.

The anatomy of a cloudy eye in dogs

Normal healthy eyes tend to be clear in the front. This gives you a “window” you can look through to see the iris, pupil, and other structures within the eye. Even the lens, the disc-like structure behind the iris, should be crystal clear.

In fact, the outer and inner structures should be so transparent that you can see all the way back to the shiny back part of the eye (the tapetum lucidum). This is the part of the eye that creates the “green eye glow” when you shine a light at your dog in the dark.

Any opacity or cloudiness affecting a particular ocular structure can change the overall appearance of the eye. And depending on the problem, it may even impact your dog’s ability to see. As one of my ophthalmology professors used to say, “If you can’t see in, the dog probably can’t see out.”

Locations of the cloudiness

Because there are so many different medical problems that can cause cloudiness in a dog’s eye, it is sometimes easiest to classify the causes of cloudiness based on where the opacity is occurring. There are three different segments to consider:

• The cornea—This thin clear layer is the “windshield” at the front of the eye. It is rich in nerves, which make it very sensitive to painful stimuli. If the whole cornea becomes cloudy, you cannot see into the eye at all.
• The aqueous humor—This clear fluid surrounds the iris and fills the portion of the eye in front of the lens. Sometimes the aqueous humor can contain red blood cells, white blood cells, protein, or other substances which turn it from clear to cloudy or hazy.
• The lens—This clear disc-like structure is located behind the iris. It is flexible, which allows it to alter the direction of the light as it projects on the retina (i.e. back layer of the eye which is responsible for converting the light into a nerve impulse and sending it to the brain via the optic nerve.) If the lens is cloudy, you can still see clearly through the cornea and aqueous humor. But the area behind the pupil and iris appears hazy or opaque.

7 Causes of cloudy eyes in dogs

Now that you have a little background in eye anatomy and where cloudiness can occur, it may be easier to understand some of the reasons for cloudy eyes in dogs. Next, we’ll break down seven different ocular disorders into four separate sections:

1. The cloudy cornea
2. Cloudy cornea and/or aqueous humor
3. The cloudy aqueous humor
4. The cloudy lens of the eye

Section 1: The Cloudy Cornea

The ultra-thin and normally clear cornea can have a white or bluish coloring to it when it is diseased. This occurs because the cornea must maintain a very strict water balance in order to remain clear. If something upsets that balance, excess fluid accumulates in the cornea and turns it cloudy.

Corneal edema (i.e. fluid build-up in the cornea) may occur as a result of corneal damage or a range of corneal diseases. It is a clinical sign and not a specific condition itself. This means the vet will need to investigate further to find the cause of the corneal edema.

#1: Corneal ulcers in dogs

One common cause of corneal edema is corneal ulcers in dogs (i.e. defects in the surface of the cornea). Corneal ulcers may occur if a dog scratched his or her eye, got something foreign or irritating in the eye, or experienced an eye injury. Generally, the dog will have one cloudy eye or a cloudy spot on the eye.

Symptoms of a corneal ulcer in dogs

Initially, the dog’s cornea may still appear clear if the ulcer is very superficial. Or there might be a small cloudy spot of corneal edema surrounding the ulcer. Sometimes mild ulcers can be tricky to detect with the naked eye. So, you may not know there is an issue unless your dog displays some of the following clinical signs:

• Pawing or rubbing at the eye
• Squinting the eye (i.e. blepharospasm)
• Visible red blood vessels on the cornea (i.e. neovascularization)
• Excessive tearing or watery eyes
• Signs your dog is in pain when you touch near the eye

Corneal ulcers that affect the deeper layers of the cornea can cause observable defects or holes in the cornea. They also tend to go with more widespread corneal edema and may cause more severe symptoms than superficial ulcers. Without aggressive treatment, corneal ulcers, especially those that are deep, can cause permanent damage and lead to blindness. Thus, it is important to make a vet appointment promptly if you suspect your dog has an eye ulcer.

Diagnosis of a corneal ulcer

At the appointment, your veterinarian will use a fluorescein eye stain test to visualize and diagnose the suspected corneal ulcer. This test is typically non-painful and involves applying a drop of fluorescent dye to each eye. If the dog has a corneal ulcer, the dye will stick to the defect in the cornea and glow green when the veterinarian illuminates the eye with a blacklight. If there is no ulcer, the eye will not take up any stain.

Treatment for a corneal ulcer in dogs

Superficial ulcers are often treated with topical antibiotics and oral medications for pain. However, deeper ulcers may require additional therapies such as drops of serum (i.e. the liquid portion of the blood) to promote healing.

#2: Corneal dystrophy in dogs

Alternatively, there are some edematous conditions of the eye that are heritable. Corneal dystrophy is one such condition. Affected dogs will develop corneal edema at some point in their life due to inherited corneal abnormalities.

There are three types of corneal dystrophy:

• Stromal corneal dystrophy—This variety affects the middle layer of the cornea. It is more common in younger dogs, especially Spaniel breeds and Collies.
• Endothelial corneal dystrophy—This type affects the inner layer of the cornea and typically shows up in middle-aged to older dogs. Boston Terriers, Dachshunds, and Chihuahuas are all more prone to endothelial dystrophy.
• Epithelial corneal dystrophy—This kind impacts the outer layer of the cornea and affects all dog breeds.

Some canine patients with corneal dystrophy may act normal other than having cloudy corneas. Others experience discomfort, especially since advanced cases have an increased risk of developing corneal ulcers. For this reason, your vet might still recommend fluorescein testing in order to rule out an active ulcer.

Unfortunately, there is no definitive treatment for corneal dystrophy. However, some veterinary ophthalmologists may recommend topical saline drops to help pull some of the edema away from the cornea. There is also a newer treatment for corneal endothelial dystrophy called Descemet’s Stripping Endothelial Keratoplasty (DSEK), which shows some promise.

#3: Keratoconjunctivitis sicca (i.e. dry eye in dogs)

If your dog has a cloudy eye with discharge, he or she may have a condition called keratoconjunctivitis sicca (KCS). Commonly referred to as dry eye in dogs, KCS is any condition that negatively affects tear production in the eye.

Symptoms of KCS in dogs

Dry eye is problematic because tears act like a protective shield for the eye. They lubricate the eye, protecting it from trauma, and can help prevent infection from taking hold. Without adequate tear production, the eyes can become very irritated, red, cloudy, and goopy.

You may see a green or yellow, sticky, mucus-like discharge that builds up over and around the eyes. When it dries, the discharge can look very crusty or like a cloudy film over the eyes. Also, because they are so dry, the surface of the eyes can have a dull appearance. Dry eye can also lead to corneal ulceration in dogs.

Causes of KCS in dogs

The most common cause of KCS is immune-mediated (i.e. the immune system attacks the tear gland for unknown reasons). Damaged tear glands, allergies, neurologic disorders, certain medications like sulfa drugs, and endocrine disorders like hypothyroidism in dogs can also cause KCS in dogs. Additionally, there are numerous dog breeds that are more likely to develop KCS, including:

• Boston Terriers
• Cocker Spaniels
• English Bulldogs
• Lhasa Apsos
• Miniature Schnauzers
• Pekingese
• Pugs
• Shih Tzus
• Yorkshire Terriers

Diagnosis of KCS in dogs

If your dog has cloudy eyes and discharge, your regular vet may recommend a series of tests. In addition to the fluorescein eye test for detecting corneal ulcers, the vet may also recommend performing a Schirmer tear test and tonometry.

The Schirmer tear test uses a small piece of metered paper that has a dye-colored line on it. The tip of the paper is slipped beneath the dog’s lower eyelid and left in place for one minute. Any tears the dog produces will cause the colored line to move down the paper. After 60 seconds have elapsed, your vet will look at how far the dyed line has traveled. Anything less than 15 mm is suspicious for dry eye in dogs.

The other test, tonometry, is the measurement of the intraocular pressure or IOP within the eye (more on this in the glaucoma section). This test is important because sometimes canine patients with eye conditions such as glaucoma (i.e. high intraocular pressure) will get secondary KCS due to tear gland inflammation.

Treatment for KCS in dogs

Veterinarians can manage most cases of dry eye with a combination of topical lubricants and moisturizers. If the KCS is autoimmune in nature, the vet my prescribe topical immunosuppressants to protect the tear glands from further damage in hopes that the glands might produce tears again.

In special cases, a veterinary ophthalmologist may recommend a surgical procedure for dogs with KCS. It involves redirecting the flow of saliva from one particular salivary gland to the eye. However, this surgery comes with its own set of risks and complications. Your veterinary eye specialist will advise you on what is best for your dog.

Section #2: Cloudy cornea and/or aqueous humor

#4: Glaucoma in dogs

As mentioned above, glaucoma in dogs occurs when the pressure within a dog’s eye is elevated. In acute cases, it can cause a dog’s eye to be red, painful, and cloudy. And in more chronic cases, the eye may be cloudy and also enlarged, swollen, or bulging due to the high IOPs.

The cloudiness can occur on the cornea in the form of corneal edema. However, it can also occur within the front (i.e. anterior) chamber of the eye. This is called aqueous flare.

Causes of glaucoma in dogs

Glaucoma happens when aqueous humor, which is constantly being produced, cannot properly drain away from the dog’s eye. Normally aqueous humor is produced at the same rate that it exits the eye via the iridocorneal angle (ICA), a small opening between the cornea and the iris. When something disrupts this balance, the aqueous humor builds up and the IOP begins to rise.

Glaucoma may either be primary or secondary. Dogs with primary glaucoma have a genetic defect that impairs the ability of the iridocorneal angle (ICA) to drain aqueous humor. But for dogs with secondary glaucoma, the elevated IOPs occur due to some other eye issue (e.g., trauma, lens luxation, hypertension in dogs, ocular cancer, etc.) which impedes the flow of aqueous humor.

Symptoms of glaucoma

Regardless of the type of glaucoma, most of the symptoms are similar:

• Widespread corneal edema, which makes your dog’s eye cloudy and blue
• Episcleral injection (i.e. enlarged blood vessels within the white part of the eye which can make the eye look bloodshot)
• Conjunctival hyperemia (i.e. inflammation of the pink tissues surrounding the eyeball)
• Aqueous flare (i.e. a beam of light is visible when it passes through the anterior chamber because of the abnormally high protein content of the aqueous humor)
• Blepharospasm (i.e. squinting and blinking)
• Eye discharge

Sudden-onset glaucoma is a medical emergency. If you see these signs, please seek an emergency vet visit for your dog. The elevated IOPs can sometimes cause permanent retinal damage and blindness if not quickly addressed.

Diagnosis of glaucoma in dogs

Emergency clinics as well as some general practice vet clinics should have a tonometer (i.e. a tool to measure IOP). Normal values can be anywhere from 10 to 20 mm Hg, but anything higher than 25 mm Hg may indicate the dog has glaucoma.

To better differentiate between primary and secondary glaucoma, a veterinary ophthalmologist can also perform a specific type of eye exam called gonioscopy to evaluate the ICA. Additionally, genetic tests for glaucoma are available for Shar Peis, Beagles, and other dog breeds who are at a higher risk for developing glaucoma.

Treatment for glaucoma in dogs

Some pets with glaucoma respond well to topical ophthalmic medications. These may include medications like dorzolamide to slow the secretion of aqueous humor or topical steroids to relieve inflammation and pain. However, topical steroids shouldn’t be used if a corneal ulcer is present.

In some cases, veterinary ophthalmologists may also perform advanced surgical procedures to treat eyes with glaucoma. But if the eye is significantly diseased and painful or is blind, complete removal (i.e. enucleation) may be the best and most cost-effective treatment option.

Section 3: Cloudy aqueous humor

#5: Uveitis in dogs

Another reason for a dog’s eye to suddenly appear cloudy is uveitis in dogs, which literally translates to inflammation of the uvea. The uvea is toward the middle of the eye and is comprised of three structures— the iris, the ciliary body (i.e. structure behind the iris that makes aqueous humor), and the choroid (i.e. the vascular middle layer of the back of the eye).

Causes of uveitis in dogs

Some external (i.e. exogenous) causes of uveitis include corneal ulcerations and trauma. However, uveitis is most commonly caused by internal (i.e. endogenous) infections from organisms such as bacteria, viruses, fungi, or parasites. Other causes of uveitis include elevated blood pressure, lens luxation, retinal detachment, cancer, and congenital, autoimmune or endocrine disorders.

Symptoms of uveitis in dogs

In addition to having a cloudy aqueous humor (i.e. aqueous flare), which is a classic sign of uveitis, other potential symptoms include:

• Decreased IOP, which can cause the eye to appear shrunken or small
• Redness of the sclera or conjunctivitis
• Blepharospasm
• Miosis (i.e. constricted pupils)
• Light sensitivity

Diagnosis of uveitis in dogs

Often your vet can diagnose your dog with uveitis based on clinical signs and tonometry testing. Since there are many endogenous causes of uveitis, your veterinarian may recommend additional testing to look for the underlying cause. This may include blood work, urinalysis, X-rays, and perhaps ultrasound. If testing is inconclusive, your vet may refer your canine companion to a veterinary ophthalmologist.

Treatment for uveitis in dogs

Ultimately, uveitis treatment will depend on finding and addressing the underlying cause. However, to help relieve inflammation and provide pain relief, your veterinarian may recommend a combination of topical and oral medications. Dogs may benefit from topical steroids (if there is no corneal ulcer) or topical anti-inflammatory medications like flurbiprofen and diclofenac. If the vet suspects there is an underlying infection, he or she may prescribe topical and/or oral antibiotics.

Section 4: Cloudy lens of the eye

#6: Nuclear sclerosis in dogs

If you have a middle-aged or senior dog, and you catch a glimpse of his or her eyes from the side, you may notice that the lens looks cloudy and blue. This is due to a condition called nuclear sclerosis in dogs (i.e. lenticular sclerosis), which tends to affect dogs who are six to eight years of age. It is painless, doesn’t greatly affect a dog’s vision, and occurs as part of the normal aging process of the eye.

Cause of nuclear sclerosis in dogs

To understand the cause, it’s helpful to know that a dog’s lens is made up of numerous fibers, and over time, new fibers develop over the older ones. Some veterinary researchers feel that nuclear sclerosis is caused by the compression of these older fibers. This would explain why the cloudiness starts in the center of the lens and can work its way outward.

Symptoms of nuclear sclerosis in dogs

It is often easiest to see this blue-grey cloudiness of your dog’s lens when viewing the eye from the side rather than the front. It almost looks like your dog’s pupil is cloudy, but really what you are seeing is the lens.

Because the lens is located behind the iris, you won’t see any cloudiness on the cornea or in the anterior chamber unless a different disease process is also present. Also, nuclear sclerosis is not a painful condition, so there shouldn’t be any squinting, inflammation, or other clinical symptoms.

Nuclear sclerosis makes the lens a little less flexible after a while, but dogs can still see fairly well. To put it simply, if your dog was an avid reader, it would just mean he or she would need some reading glasses!

Diagnosis of nuclear sclerosis in dogs

Your vet can often easily diagnose nuclear sclerosis using a simple ophthalmoscope (i.e. a small magnifier with a light on it). If he or she can see through the lens to the back of the dog’s eye and there are no distinct areas of opacity, the dog has nuclear sclerosis. But if any opacities are present, the dog may have cataracts, which is the condition nuclear sclerosis most often gets mistaken for.

Treatment for nuclear sclerosis in dogs

There is no treatment for nuclear sclerosis. But since it is unlikely to affect a dog’s overall quality of life, treatment wouldn’t be necessary even if an effective one existed.

#7: Cataracts in dogs

Unlike nuclear sclerosis, cataracts of the lens can affect vision. A cataract in dogs is a white cloudy spot (i.e. opacity) that forms in the center of the lens and can work its way outward. The cloudiness of a cataract is much denser than that seen with nuclear sclerosis. Thus, it does interfere with the way light travels through the eye.

To conceptualize this, think about the difference between looking through two windows. One window has a piece of plastic wrap over it (i.e. lenticular sclerosis). The other window has a piece of thick construction paper over it (i.e. cataracts). As you can imagine, the difference is significant.

Causes of cataracts in dogs

Primary cataracts can occur simply due to old age. Over time, proteins that come from lens fibers can accumulate like a growing snowball in the center of the lens. However, primary cataracts are also hereditary and may more commonly affect the following breeds, even in their younger years:

• Cocker Spaniels
• Boston Terriers
• Labrador Retrievers
• Australian Shepherds

Cataracts may also occur secondary to trauma or another illness. In dogs with diabetes mellitus, the excess glucose in their bloodstream can travel to the eye. Enzymes in the lens convert glucose to sorbitol, a very large molecule that attracts a lot of water. As a result of the excess water, the lens becomes cloudy. Interestingly, diabetic dogs can develop cataracts very quickly, literally within 24 hours of their diabetes diagnosis. So, if your newly diabetic dog woke up with cloudy eyes, cataracts might be the culprit.

Symptoms of cataracts in dogs

Besides observing a white opacity just beyond the iris (i.e. the cataract in the lens), you may notice other signs of cataract formation such as redness and squinting. Additionally, your dog may suddenly have more difficulty seeing, especially at nighttime. In cases where the cataract developed seemingly overnight, uveitis (and the related signs) may show up at the same time. This happens because the immune system may release inflammatory mediators to attack the cataract as if it were a foreign invader.

Diagnosis of cataracts

Based on the clinical signs and the appearance of the lens, your vet can determine whether your dog has a cataract (or cataracts). He or she might use an ophthalmoscope to determine how big the cataract is and at what stage it might be. For example, cataracts in the incipient stage take up less than 15% of the lens while mature cataracts encompass greater than 75% of the lens.

Since diabetes mellitus can be related to cataract formation, your vet might also recommend blood and urine testing. Or he or she may recommend additional eye tests or other diagnostic tests depending on the suspected underlying cause.

Treatment for cataracts in dogs

The treatment of choice for cataracts is a specialty surgery performed by veterinary ophthalmologists. It is called phacoemulsification and involves removing the old lens and replacing it with an artificial lens. Dogs with cataracts are considered good candidates for cataract surgery as long as any other illnesses (such as diabetes mellitus) are under control and the dog’s retina is still functional.

It is very important to monitor your dog’s eye carefully after cataract surgery and follow the veterinary ophthalmologist’s instructions carefully. If your dog develops cloudy eyes after cataract surgery, or any other post-op complications, it’s important contact the surgeon immediately.

If your dog is not a good surgical candidate, or if the surgery is cost-prohibitive, topical anti-inflammatory medicines may provide some relief from any discomfort that your dog may experience. At this point, there are no medications or supplements that can definitively treat cataracts in dogs.

What should I do about cloudy eyes in dogs?

Understandably, if you suddenly notice that your dog’s eyes are cloudy, you want to do something to help your pup. Unfortunately though, the reasons for cloudy eyes in dogs can be complicated. And treating the condition isn’t as simple as reaching for a bandage from your first aid kit. While some issues like nuclear sclerosis are harmless and best left alone, other issues like deep corneal ulcers and glaucoma can rapidly become worse without medical attention.

Since that is the case, the best thing you can do is to call your veterinary clinic to schedule an exam for your dog. That way you know that your dog is getting the help he or she needs. Eyes can worsen quickly, so eye problems (especially those that come up suddenly, are painful, or involve red and/or cloudy eyes), do often require prompt veterinary assistance.

Are there any home remedies for cloudy eyes in dogs?

While I do think that eye problems are best addressed by your veterinarian, there are a few “do’s and dont’s” of home treatment for cloudy eyes in dogs that you might find helpful.

DON’T use left-over eye ointment from another pet or problem.

Even if you do have an eye ointment in your doggie medicine cabinet, generally it isn’t a good idea to apply it to your dog’s eye without veterinary guidance. For example, there are some medications that have a steroid as an active ingredient. If you apply that ointment to an eye with a corneal ulcer, it will delay healing or possibly make the ulcer worse.

DO stick to “safe” eye medications to care for your dog’s cloudy eye at home.

In general, most simple eye lubricants and eye irrigation solutions are safe for use in dogs’ eyes. Lubricants can soothe a dry eye and are usually not a problem when an infection or any other disease is present. Irrigation or saline solutions are useful for cleaning cloudy dog eyes after an injury or if there is lots of discharge visible.

However, ensure that the lubrication or flushing products you use do not have “red eye reducer” or other added ingredients. These extra active ingredients may not be safe for your dog. If in doubt, consult your veterinarian before using a product.

DO use an E-collar to protect the eye.

If your dog is rubbing at the eye or you are worried that there is a deep ulcer, put an Elizabethan collar on your dog to keep him or her from further traumatizing the eye.

DO NOT be fooled by products that claim to cure cloudy eyes.

Over-the-counter supplements or eye drops that promise to make your dog’s eyes brighter and healthier are available, but you must take these bold statements with a grain of salt. There are currently no supplements available that can fix cloudy eyes in dogs.

Some products like Ocu-GLO contain a mix of omega 3s and vitamins which have anti-inflammatory and antioxidant properties, respectively. These are safe and can help with overall eye health. But ultimately, the way to treat a dog’s cloudy eye will depend on the disorder that is present.

Take your dog with cloudy eyes to the vet

As you have learned, young, middle-aged, and old dogs can have cloudy eyes for a variety of reasons. We have discussed the top seven here, but there are other conditions that could be the culprit too.

If you notice your dog has cloudy eyes, it is best to seek immediate medical attention. Doing so can help avoid permanent damage and vision loss. Plus, since some eye conditions can be quite painful, getting to the vet ASAP means your dog can get some much-needed relief. Together, you and your vet can develop a plan to get your dog with cloudy eyes feeling, and hopefully seeing, better.

Why were your dog’s eyes cloudy?

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