Red Eye in Dogs

Redness and inflammation affecting one or both eyes can be due to a variety of issues ranging from mild allergies to glaucoma which can lead to blindness. Redness may or may not be accompanied by discharge or watery eyes. It may involve the surface of the eye, ruptured blood vessels within the eye, or an inflamed eyelid, among other causes. It is important to make a visit to the veterinarian if you notice redness of the eye persisting for longer than 24 hours. There are many different causes of red eyes in dogs and can be as simple as allergies, or more serious such as glaucoma. There are cases of disease elsewhere in the body that can lead to inflammation of the eye. If you notice redness for more than 24 hours, it is best to have your dog seen by a veterinarian to try to diagnosis the issue with the eye.

In addition to redness of the eye, signs that may also be noted include:

• Pawing at or rubbing eye on floor
• Squinting in light
• Keeping eye closed
• Cloudy cornea (surface of the eye)
• Watery tearing eyes
• Red mass appearing from under the eyelid
• Red spot on the white of the eye
• Swelling or puffiness of the eyelids
• White or green discharge from inner corner of the eye

If any of these signs are occurring, having your dog seen right away is important, as some of these can be an emergency.  

• Allergies – Irritation of the eye due to an allergen such as pollen, weeds, dust or fiber.
• Conjunctivitis – Inflamed conjunctiva (the thin transparent tissue that covers the outer surface of the eye) due to irritants, allergies or infection.
• Keratoconjunctivitis sicca (KCS) – Also known as dry-eye syndrome. Redness is due to inadequate tear production.
• Entropion – The eyelid turns inward causing the eyelashes and eyelid to rub against the eye’s surface.
• Cherry eye – Also known as 'everted nictitans', a gland inside the third eyelid becomes inflamed and protrudes out from behind the eyelid. Appears as a small red bump poking out from below the eye.
• Hyphema – Injury to the eye causes blood to pool in the front part of the eye.
• Foreign body – Material or small particle trapped in the eyelid or on the eye surface irritates the eye.
• Corneal ulcer – An open sore on the outer layer of the cornea.
• Glaucoma – Increased pressure within the eye.
• Uveitis – Inflammation of the iris or ciliary body caused by injury, infection or cancer.
• Blepharitis – Inflammation of the eyelid due to infection, irritation or allergy.
• Tumor– Benign or malignant mass growing behind or within the eye.

If you notice redness in one or both eyes of your pet, you should visit your veterinarian to obtain a proper diagnosis. The most common causes of red eye are conjunctivitis, allergies, or irritants, however more serious possibilities exist so it is important to have your pet examined. The veterinarian will take a history of the pet to discover when the redness began, the progression of the redness, and any behaviors your pet is demonstrating that indicate pain or irritation.

Ophthalmologic Exam

In cases involving the eye, the veterinarian will conduct a full ophthalmologic exam. This exam evaluates the various structures of the eye including the conjunctiva, cornea, tear ducts, retina and eyelids.

Schirmer Tear Test

A Schirmer tear test examines your pet’s tear production and helps rule out KCS or dry-eye syndrome. This test involves placing a small paper test strip in between the eyelid and the eye. The strip measures tear production. The tears are absorbed into the paper strips and a scale on the paper measures the level of tear production.

Tonometry

Tonometry incorporates the use of a device to measure the internal pressure of the eye. This test is often used to screen for glaucoma, a disease associated with abnormal eye globe pressure. The surface of the eye may be numbed prior to this test, though it is not required. A tonometer pen uses a small plastic ball that bounces quickly on and off the surface of the eye and measures the pressure. Several measurements may be taken to obtain an average.

Fluorescein Dye

This yellow-green dye is dropped onto the eye surface. Areas of damage to the surface of the eye light up (fluoresce) when a black light is shone onto the eye. This dye can indicate scratches and corneal ulcers.

Blood Diagnostics

Several underlying issues may cause the appearance of red eyes. Blood screening can measure kidney function, liver function, hormone production, hydration and electrolyte imbalances.

A variety of treatments may be applied depending on the diagnosis.

Topical Medications

Topical medications are available in ointments or drops and may need to be applied up to three times daily for a week or two until signs resolve. Medications include antibiotics, steroids, pain relievers, dilators and artificial tears.

Oral Medications

In case of infection or trauma to the eye, oral antibiotics may be prescribed. Anti-inflammatories may also be administered. If the cause of redness is associated with an underlying disease, the appropriate oral medication will be prescribed.

Surgery

Surgery may be required to address several causes of red eye. If cherry-eye is diagnosed, the veterinarian might try to manually reset the gland with medications. If the gland reappears after treatment, surgery is often used to permanently repair the issue. Entropion problems can also require surgery to reform the eyelid so it does not rub on the cornea of the eye. In some cases, red eye is caused by an untreatable problem and may require surgical removal of the eye (enucleation surgery). With this surgery, the pet often does not experience any adverse side effects besides loss of a degree of depth perception.

Correct application of drops or ointment and administration of oral medications is required to achieve proper healing. The pet may need to wear an Elizabethan collar (cone or e-collar) to prevent rubbing the eye.

Follow up appointments for eye examinations are often required weekly for a period to evaluate response to treatment.

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