The most obvious signs of pain associated with eye conditions 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 animal very sensitive to light, and the dog may try to avoid bright light. This symptom, called photophobia, is commonly associated with serious eye diseases.
It is not always easy to tell if your pet is experiencing eye pain and sometimes all you may notice are subtle behavioral changes. It is instinctual for many animals 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 his "normal" pattern of behavior.Causes
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
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
Excessive pawing or rubbing of the eyes
Swelling of the eyelids or eyeball
Protrusion of the third eyelid so that is covers part of the eye
Reduced vision or blindness
Lethargy (lack of energy)
Pain upon opening the mouth, reluctance to fully open the mouth
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 so extremely painful 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 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 medical treatment, surgical intervention, or both to resolve the painful ophthalmic condition.
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.