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Photophobia is the phenomenon where a dog's eyes become sensitive to light. 

 There are several causes of photophobia in dogs and therefore it is important considering them on a case-by-case basis.

Dogs affected by photophobia will show signs of not tolerating any bright lights. You'll see these dogs squint and show an overall unwillingness to face bright lights. Some dogs may also hide in a dark room. 

 What is Photophobia in Dogs? 

As the name implies, photophobia is an excess reaction to ultraviolet (UV) rays from the sunlight and/or from sources of light such as indoor lights.

You can evaluate your dog's light sensitivity by observing him or her while indoors or outdoors. 

In dogs with photophobia, their eyes are abnormally sensitive to light, causing squinting and light avoidance. Your dog may also rub its face or paw at the affected eye. Your dog may also show other signs of pain, including tearing and rubbing its face.

These signs can be easily spotted in early cases and these cases require prompt intervention so to diagnose and treat the underlying cause.

The Importance of Seeing The Vet 

With eye problems, it's best seeing the vet sooner than later. Most vets advise having dogs with eye issues seen within 24 hours as some issues, left untreated, can lead to blindness. 

On top of this, consider that eye problems that cause dogs to squint and become sensitive to light are very painful too. 

Veterinarians have access to special instruments to examine the dog's eye. A vet can determine the exact cause of your dog's photophobia (fear of looking at bright lights) by looking at the eye's surface.

It's important that you keep your dog should in a dimly-lit room until the underlying cause is properly treated. 

Some dog owners find the use of "doggles" helpful for dogs with this problem, however not all dogs will tolerate wearing them. 

Did you know? Blepharospasm is the medical term for the uncontrollable urge to squint and keep closed one or both eyes. Affected dogs or people have difficulties keeping their eyes open.

This dog is keeping the eye partially closed due to presence of light.

This dog is keeping the eye partially closed due to presence of light.

What Causes a Dog's Eyes to Become Sensitive to Light?

There are several conditions that can cause a dog's eyes to become sensitive to light. Only your vet can accurately determine the underlying cause so that the most appropriate treatment can be initiated.

A Case of Uveitis

Uveitis is one of the main causes of photophobia in dogs. Uveitis is inflammation of the dog's uvea, the pigmented layer of the eye.

Symptoms of uveitis in dogs may include redness, extreme and sudden onset of sensitivity to light, and excessive pawing.

Treatment for uveitis would consist of eye drops with steroids. However, this is the worst treatment for a corneal injury, therefore it's imperative to get an accurate diagnosis so to know how best to treat.

An Allergic Reaction

An allergic reaction to something in the dog's environment may cause the dog's eye to become overly irritated and inflamed. With lots of inflammation going on in the eye, it may bother the dog to see light. 

Presence of Cataracts

 Cataracts can sometimes make dogs sensitive to sunlight and bright lights. 

A Potential Glaucoma

Glaucoma is an increase in the pressure inside the dog's eye. Dogs with glaucoma are commonly sensitive to light and can experience pain when exposed to it. This may be apparent as a general avoidance of bright lights or sun.

Upon exposure to bright light, the dog may also vocalize and rub his or her face against the floor, as if trying to alleviate the discomfort. Clouding of the clear parts of the eye (cornea) and reddening of the white parts (sclera) is often seen as well.

Glaucoma is a condition that must be diagnosed and treated as soon as possible to prevent blindness.

A Matter of Corneal Ulcers

A dog's cornea is the transparent layer that covers the front of the eyeball. Corneal ulcers take place when there is a scratch to the dog's cornea. 

Corneal ulcers are very painful and can trigger sensitivity to bright lights. 

Left untreated, a dog's corneal ulcer can become infected and cause scarring of the cornea, which could potentially impair the dog's vision. 

Presence of Pannus

Pannus, also known as chronic superficial keratitis, can cause a colored edge to the cornea. Sometimes, the affected eye appears hazy or grey.

It is often present in German shepherd dogs (but it can be seen in any breed with Border Collies, Belgian Tervurens, and Australian Shepherds impacted the most )and occurs more commonly in areas of high altitudes.

 Fortunately, it is possible to slow down its progression by using eye drops and limiting the dog's exposure to bright light.

Did you know? The sun's intensity increases by 4 percent at every 300-meter-high altitude, so dogs out on pasture at high altitudes are at a higher risk for pannus.

Genetic Causes 

If you have recently rescued a new dog who is showing signs of light sensitivity, consider that there may be some genetic causes at play. 

For instance, among the eye problems in merle dogs are starburst pupils in one or both eyes. The changes in the standard pupil shape can result in various levels of light sensitivity.

Iris Atrophy

 This is a condition where there is degeneration of the colored portion of the dog's eye (the iris). It is seen in elderly dogs. 

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A dog's iris acts like a camera lens meant to control the amount of light that is transmitted to the retina of the eye, but in this case, it no longer works well as it should since there is age-related thinning and weakening of the iris.

 Iris atrophy can cause dilated pupils, "eye shine" and can also include increased sensitivity to light, as well as decreased vision.

Other Possible Causes

Sometimes, squinting caused by photophobia can be seen in cases of toxic ingestions. Make sure your dog hasn't ingested anything toxic.

 It can also be a sign of canine distemper or meningitis.

Photophobia may be present too as a result of being given medications such as benzodiazepines, chemotherapy, and benzodiazepines.

Sometimes light sensitivity may stem from underlying neurological issues that impact the ability of the pupil to constrict normally.

Picture of dog squinting the eyes

Picture of dog squinting the eyes

Light Sensitivity in Dogs With Hair Covering the Eyes 

For quite a while there has been belief that the purpose of keeping the hair long over the eyes in certain breeds of dogs was to protect the eyes from the effects of sunlight.

This belief has been further reinforced by the fact that when the hair is lifted to expose the eyes, the dog's eyes reflexively respond to the light by blinking and tearing.

This natural, photophobic reaction has therefore led owners to come to the erroneous conclusion that the eyes need to be left covered, when in reality these dogs are reacting in such a way to bright light because of the hairs constantly covering the eyes in the first place, explains world-known veterinarian, Michael W. Fox.

Another physical effect of the hairs covering a dog's eyes is the constant irritation to the eyes which are prone to developing chronic conjunctivitis, corneal ulcers and other eye problems. Discover more about this: problems of dogs with hair covering the eyes. 

 Eyes Tests for Dogs 

As mentioned, your vet is well equipped to carry out various tests. The most common eye tests performed by your veterinarian include the following:

  • Fluorescein Stain test to check for ulcers
  • Schirmer Tear test to check for dry eyes
  • Eye pressure test (Tonometry) to check for glaucoma
  •  Fundic exam - an examination of the back of dog's eyes using an ophthalmoscope

Based on these findings, the vet is better equipped to form a diagnosis and what type of eye medication to send home. Complicated cases may require a referral to board-certified veterinary ophthalmologist. 

Treatment of Photophobia in Dogs

The first step in dog photophobia treatment is to understand what causes the condition. Your vet may use an ophthalmoscope, or slit lamp, to look at your dog's entire eye, including the iris, sclera, and conjunctiva.

Photophobia treatment may vary based on the underlying cause and may include special eye drops and may even involve surgery to correct any underlying problems.

Did you know? Photophobia is the term used to depict an aversion to light. Photosensitivity is a term used to depict virtually any sort of reaction to light, but in the medical field, it is primarily used to mean skin reactions to light.

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