Ocular (Eye) Pain and Squinting in Dogs

Overview of Eye Pain and Squinting in Dogs

The most obvious signs of pain associated with eye conditions in dogs are squinting and holding the eyelids closed. Squinting may occur from both external and internal irritation of the eye. Other potential signs of ocular pain include tearing, pawing at the eye, rubbing the face, reluctance to eat hard foods or fully open the mouth, and reluctance to be petted. Eye pain may make the dog very sensitive to light, and the dog may try to avoid bright light. This symptom, called photophobia, is commonly associated with serious eye diseases.

Below, we will give you possible causes of eye pain and squinting in dogs, followed by detailed and in-depth information on how to determine the underlying cause.

It is not always easy to tell if your dog is experiencing eye pain and, sometimes, all you may notice are subtle behavioral changes. It is instinctual for many dogs to withdraw and become more reclusive when they are experiencing eye pain or discomfort. Behavioral changes, such as sleeping more, hiding, decreased appetite, reduced playfulness, and an aggressive disposition are often more subtle demonstrations of eye discomfort. The realization that these subtle expressions are connected to eye disease may only occur after the eye condition has resolved and the pet has resumed there “normal” pattern of behavior.

Causes of Canine Eye Pain

There are many different causes of eye pain. A few are described below:

• The cornea and conjunctiva have a rich concentration of pain fibers (nerves), with the highest proportion located near their surfaces. This nerve fiber distribution is the reason why large, superficial ulcers of the cornea may be more painful than smaller, deeper ulcers. A corneal ulcer or scratch can also cause reflex pain and spasm of the iris inside of the eye. When this occurs, the pupil constricts (miosis), and the iris becomes swollen and the conjunctiva reddened (bloodshot). A specific ophthalmic medication, called atropine, is used to treat this type of pain.
• Foreign material on the surface of the eye is often painful.
• Dogs that develop anterior uveitis (inflammation of the iris) may also show signs of eye pain. There are numerous causes of uveitis.
• Glaucoma or elevated pressure in the eye can be very painful to the dog.
• Trauma to the face, eyelids, the eye itself, and the tissues behind the eye may result in dramatic pain.
• Infection behind the eye and within the eye socket (orbit) are commonly painful and the animal may try to avoid fully opening its mouth with these conditions.
• Inadequate tear production, or dry eye, can cause a gritty, painful sensation on the surface of the eye.

In contrast to the cornea, conjunctiva and iris, the retina and optic nerve have no pain sensation. Therefore, diseases such as retinal degeneration, retinitis (inflammation of the retina), and optic neuritis (inflammation of the optic nerve) do not cause outward signs of pain.

What to Watch For

• Squinting or holding the eye closed
• Excessive tearing
• Mucoid or pus-like ocular discharge
• Bloodshot or reddened conjunctiva
• Cloudiness or bluish haze or film covering the eye
• Dilated, constricted, or unequal pupil sizes
• Photophobia
• Excessive pawing or rubbing of the eyes
• Swelling of the eyelids or eyeball
• Protrusion of the third eyelid so that it covers part of the eye
• Reduced vision or blindness
• Lethargy (lack of energy)
• Decreased appetite
• Pain upon opening the mouth, reluctance to fully open the mouth
• Hiding

Diagnosis of Eye Pain and Squinting

Veterinary care includes diagnostic tests to determine what is causing the eye pain and to direct subsequent treatment. Your veterinarian may do any of the following:

• Complete medical history and physical examination
• Complete ophthalmic examination including a Schirmer tear test, fluorescein staining of the cornea, tonometry, examination of the eyelids and surface of the eye with magnification (such as slit-lamp biomicroscopy), and detailed examination of the front and back portions of the eye. A thorough eye examination may only be possible after topical local anesthetic solutions have been administered, and the squinting has been relieved (temporarily). Some dogs are in such an extreme amount of pain that ocular examination may require sedation of the animal.
• Ocular ultrasound if the eye is too opaque to allow a good examination or if diseases are suspected behind the eye
• Cytology (complete cell analysis) and culture of cells collected from corneal wounds or ulcers
• Complete blood count and serum biochemistry tests if other underlying problems are suspected
• Skull X-rays to look for fractures, metallic foreign bodies, and other conditions of the head
• Computerized tomography (CT) or magnetic resonance imaging (MRI) to assess the tissues behind and around the eye

Treatment of Ocular Eye Pain and Squinting in Dogs

• Treatment depends on the cause of the eye pain and squinting. There is no general treatment for these symptoms. Unfortunately, topical local anesthetics are too toxic to be used repeatedly on the eye and rapidly lose their ability to numb the eye with repeated applications.
• Treatment may involve medication, surgical intervention, or both to resolve the painful ophthalmic condition.

Home Care

Recommendations for home care depend upon the underlying cause of the problem. Seeking immediate veterinary medical attention is critical, as many causes of eye pain and squinting are vision threatening and most require specific medical and/or surgical treatment.

Gently clean away excessive eye discharge with a warm, moist cloth to prevent crusting and caking of the hair around the eyes. Cease all attempts if the dog becomes aggressive or if pain seems to worsen with these efforts.

If vision appears to be impaired, minimize stress and risk of injury by confining the pet to a safe area until the cause of the problem is determined. Keep your pet in a dimly lit area or room to help relieve any photophobia.

In-Depth Information on Eye Pain in Dogs

Squinting and photophobia can affect one or both eyes simultaneously. Sometimes, both eyes are squinty even if only one eye is in pain. However, the squinting is usually more dramatic in the diseased eye. It is important to monitor pets closely for subtle behavioral changes, since it is instinctual for many animals to withdraw and become more reclusive when they are experiencing eye pain or discomfort.

Numerous ophthalmic diseases result in eye pain. Diseases involving the eyelids, cornea, conjunctiva, iris, front chamber of the eye, and the orbit result in the most overt signs of eye pain. A thorough ophthalmic and physical examination is necessary to determine which diagnostic tests are needed to determine the cause of the pain.

In younger animals, ocular trauma, inherited or congenital diseases, and infections are common causes of eye pain. In older pets, chronic inflammations, immune-mediated and neoplastic (cancerous) diseases may be more common.

Causes of Eye Pain and Squinting in Dogs

The following are the most important causes of eye pain:

• Proptosis, or forward displacement of the eye out of the orbit following some sort of trauma
• Corneal scratches, lacerations, and foreign bodies
• Corneal injuries that result in surface abrasions and ulcers
• Recurrent or chronic corneal ulcers that arise from healing defects within the cornea
• Inward rolling of the eyelid margins (entropion), resulting in hair rubbing against the cornea
• An extra row of eyelashes growing from the edge of the eyelid (distichiasis) and rubbing on the cornea
• Eyelashes growing out from underneath the eyelid (ectopic cilia) and rubbing on the cornea
• Eyelids injuries and infections
• Sudden or gradual decline in tear production (keratoconjunctivitis sicca) resulting in drying of the eye
• Certain forms of inflammation of the cornea (keratitis), especially those that interrupt the top layer of the cornea
• Conjunctival scratches, lacerations, and foreign bodies
• Exposure of the eye to chemicals, smoke, fire, and other noxious materials
• Anterior uveitis from a variety of causes
• Penetrating trauma to the eye
• Bleeding in to the eye (hyphema)
• Forward dislocation of the lens (luxation), with the development of acute glaucoma
• Glaucoma (elevated pressure within the eye), especially when the pressure rise is sudden and onset
• Orbital diseases, such as orbital inflammation or infection, orbital abscess, nasal infection, or disease with extension into the orbit
• Trauma and fractures to the bones around the eye

Diagnosis

Diagnostic tests used to determine the cause of the eye pain are chosen by your veterinarian based on the findings from the ophthalmic examination, physical examination, prior history of ophthalmic disease, and response to prior treatment. Be sure to inform your veterinarian of all medications currently being administered to your pet.

• Complete medical history and physical examination. Historical information regarding both prior and on-going ophthalmic conditions is important to determine if current symptoms represent chronic or acute ophthalmic disease.
• Complete ophthalmic examination including a Schirmer tear test, fluorescein staining of the cornea, tonometry, examination of the eyelids, and surface of the eye with magnification (such as slit-lamp biomicroscopy), and detailed examination of the front and back portions of the eye. A thorough eye examination may only be possible after topical local anesthetic solutions have been administered, and the squinting has been relieved (temporarily). Some dogs are in such pain that ocular examination may require sedation of the animal.

Other Diagnostic Tests

Your veterinarian may recommend other diagnostic tests on a case-by-case basis, such as:

• Ocular ultrasound to visualize details within an eye obscured by inflammation, blood, tumor, lens luxation, cataract, or miotic (constricted) pupil. A veterinary ophthalmologist or radiologist may perform or interpret this test for your veterinarian.
• Cytology (complete cell analysis) and culture of cells collected from corneal wounds or ulcers to evaluate the presence of infectious organisms.
• Complete blood count to evaluate for presence of infection, anemia, and low numbers of platelets
• Specialized blood tests to assess the clotting ability of the blood
• Biochemistry tests to look for other organ diseases, such as secondary conditions and concurrent problems, and to minimize anesthetic risk
• Serum tests for
  • fungal infections
  • tick-transmitted infections
  • parasitic infections, such as heartworm and toxoplasmosis
• X-rays of the head and bony orbit to identify fractures in dogs that sustained head and eye injuries
• Computerized tomography (CT) or magnetic resonance imaging (MRI) of the eye and orbit
• Blood pressure testing to identify elevated blood pressure that is diagnostic for systemic hypertension

Treatment of Eye Pain

Do not delay in bringing the pet to a veterinarian for examination as many causes of a painful eye are vision threatening and require immediate medical attention. Many causes of acute (sudden) eye pain are considered medical emergencies and, in certain circumstances, require surgical intervention to preserve vision. For surgical therapy to be the most successful, time is of the essence. If vision cannot be saved, prompt presentation of the pet for medical attention increases the likelihood that the ball or globe may be preserved.

• Do not allow the pet to rub or traumatize sore or painful eyes. A protective collar called an Elizabethan collar may be necessary to prevent self-trauma and may be obtained from your veterinarian or pet supply store.
• Do not administer home remedies or human over-the-counter medicines designed to reduce eye redness or irritation, because these products may exacerbate the signs of eye pain.

It is important for pet owners of purebred dogs to be familiar with any ophthalmic diseases their breed is predisposed to develop. There are numerous inherited ophthalmic diseases known to afflict certain breeds of dogs and many of these are associated with eye pain and squinting.

Prompt medical and/or surgical therapy is indicated to preserve vision for the following potentially inherited or breed-predisposed ophthalmic diseases:

• Glaucoma
• Lens luxation (displacement)
• Entropion (inward rolling of the eyelid margin)
• Distichiasis (extra rows of eyelashes)
• Ectopic cilia (hair growing out from under the eyelid)
• Cataract
• Keratoconjunctivitis sicca (dry eye syndrome)

Breed-Specific Treatment

Brachycephalic (flat-faced) breeds of dogs are predisposed to corneal ulcerations, abrasions, and scratches. These breeds tend to have large, prominent eyes that are more prone to corneal injuries like scratches and ulcers. These breeds also have very shallow orbits or bony eye sockets, and, therefore, more commonly (and easily) displace their eyeball or globe than non-brachycephalic breeds.

• Topical antibiotics may be used to treat some corneal or conjunctival injuries and infectious processes, but the underlying cause must be also treated.
• Deep corneal ulcers and perforations must be stabilized surgically.
• Lacerations of the eyelids, cornea, and sclera also require surgical repair.
• Conformational or congenital eyelid deformities usually require surgical correction.
• Corneal and conjunctival foreign bodies are removed with forceps or surgery.
• Displaced or proptosed globes may be surgically repositioned or may require removal (enucleated) if excessive injuries to the eye are sustained.
• Anterior uveitis may be treated with topical anti-inflammatory medications, systemic medications, or both.
• Glaucoma may be treated with medications, surgery, or both.
• Lens luxations are treated with specific ophthalmic medications, surgery, or both.
• Orbital infections may be treated with antibiotics and/or surgery

Optimal therapy of any acute or chronic ophthalmic disease resulting in symptoms of eye pain depends on determining the correct diagnosis. There are a myriad of potential causes of ocular pain and squinting, and before any treatment can be recommended, it is essential to identify the underlying reason. Nonspecific therapy is not a substitute for definite treatment of the principal disease responsible for the pet’s condition. Initial therapy must be aimed at the primary cause of the eye pain.