Diagnosing Light Sensitivity in Dogs

Light sensitivity, or photophobia, may occur in dogs and can indicate a disease. The light sensitivity may be accompanied by other symptoms which must be considered when diagnosing the dog. Light sensitivity can signal damage to the eye, eye problems, toxicity, an abscess or canine distemper. It can cause pain and discomfort in your pet, so it should be diagnosed as soon as possible.

Causes of Light Sensitivity

Light sensitivity in dogs can be caused by a number of conditions that may or may not be related to the eye. The main causes of light sensitivity include:

• Cornea damage; the cornea is the external clear membrane of the eye
• Retinal damage
• Problems of the oculomotor nerve, leading to the inability of the pupil to constrict normally
• Eye ulcer
• Eye cataracts
• Congenital abnormalities of the dog’s eyes
• Conjunctivitis or pink eye
• Uveitis
• Papillary dilatation, which can be natural or induced by the presence of certain irritant chemicals
• Toxicity
• Abscess that affects the ocular nerve
• Canine distemper
• Shock or trauma
• Meningitis
• Respiratory infections or colds
• Rabies
• Neurological diseases

Medications such as benzodiazepines or chemotherapy can also lead to light sensitivity. The onset of the light sensitivity can be sudden or the dog can gradually become sensitive to light.

You will notice that your dog will hide whenever there is strong light, or he has a negative reaction to light. He may hide in dark rooms and may also be lethargic. You can easily detect if your dog has light sensitivity by exposing him to light and observing his reactions. Dogs that don’t suffer from photophobia will not be bothered by light.

Diagnosing Light Sensitivity

The vet will perform a thorough ophthalmoscopic examination on your dog: the eyelids will be examined, along with the conjunctiva, the sclera, the iris and the cornea. The vet may use a slit lamp machine to get a closer look at the dog’s eyes.

• If the vet suspects optical nerve damage or a neurological problem, he will perform the swinging-flashlight test. This test may also reveal any pupil abnormalities the dog may have.
• The intraocular pressure (IOP) may also be measured to detect any other ocular problems.
• Blood tests may be performed if the vet suspects toxicity or a possible abscess that may affect the ocular nerve.
• If there are ocular discharges, the vet will analyze a sample to diagnose a possible conjunctivitis or pink eye.

Let the vet know if your dog has any additional symptoms or if you suspect any disease. If your dog hasn’t been vaccinated against canine distemper, let the vet know.

A dog with light sensitivity should be kept in low light until the underlying condition is treated. The early detection of a possible disease that may cause sensitivity to light is important, as some infections can lead to the loss of sight if left untreated.