Health Matters » Eye Disorders
The Eye Examination
An detailed eye examination will be performed by a veterinary ophthalmologist (someone who has expertise in diseases and treatment of the eye). The pupils of the dog are dilated with eyedrops, and once the pupil is fully dilated, the vet will illuminate the eye to look for major problems. The different structures of the eye which are examined include the eyelids, globe as a whole, cornea, conjunctiva, sclera, anterior chamber, iris, lens, retina, choroid, and optic nerve.
A slit lamp biomicroscope is usually used next to examine the eyes in detail. This instrument will detect even minute abnormalities in the structures of the eyes. Before the exam is over, the retina is examined with an ophthalmoscope, which provides a clear view of all the areas of the retina. An indirect ophthalmoscope sits on the vet's head, providing optics and a light source, while a focusing lens is held in the examiner's hand to visualize the retina. A CERF exam is conducted in the same manner as is described here, but it is done by veterinary ophthalmologists who are board certified by the American College of Veterinary Ophthalmologists and who records the observations on a CERF (Canine Eye Registry Foundation) form. Other veterinary ophthalmologists who are not board certified by the American College of Veterinary Ophthalmologists may have been board certified in their own countries, and may be seen to be equally qualified in conducting these exams and providing you with the findings.
There are differences between the normal eye structures of humans and of dogs. It is thought that dogs are near-sighted and have rather poor visual accommodation, which means they cannot see things sharply and in focus. They also do not have many specialized retinal cells which distinguish colours; they see black, white, various shades of gray, and perhaps some colour, but not nearly as much as primates, including humans, can. By the same token, dogs have larger pupils and wider visual fields than do people, and can see better in the dark. Due to their wide field of vision, dogs are quite adept at following moving objects. Dogs also have a third eyelid or haw (nictating membrane), which is an added protective device not found in humans. This third eyelid is capable of sweeping across the surface of the eye, thus cleaning and lubricating it.
First Group Of Eye Conditions
Since there are so many diseases which have been known to affect Cavaliers, the discussion of these diseases will be started in this article and completed in Part II.
Corneal dystrophy (also known as corneal lipidosis)
Lipid (fat) deposits occur under the surface of the cornea when dogs are two-four years old. This is a condition which is thought to be inherited, probably with a polygenic mode of inheritance modified by environmental influences. These deposits appear as non-painful opaque whitish, silver, or gray blemishes, which usually occur bilaterally (affecting both eyes). They are usually seen in or around the centre of the eye.
The opacities created by the deposits are non-inflammatory (not caused by an infectious process), are progressive on a variable basis, are not associated with systemic disease, and are NOT thought to impair vision. Occasionally they will regress in size or disappear, but there is no medical therapy available to reduce lipid deposition in the deeper layers of the cornea. The opacities are composed of a combination of calcium and/or lipids (cholesterol and others). Diet may contribute. Both males and females are affected.
A corneal ulcer is a break in the outer layer (epithelium) of the cornea. It is dangerous and should be treated promptly. Large ulcers may be seen by the naked eye as dull spots or depressions on the surface of the cornea. Smaller ones are usually seen after the eye has been stained by fluorescein (an orange-red powder used to make dyes, which is used in solution applied topically to the eye to detect injury to the cornea). By definition, uncomplicated ulcers, while usually painful, should heal in three-four days with appropriate treatment (usually antibiotic ointment, but not one with cortisones in it, as the cortisone could delay healing and predispose to rupture of the eye) - check with your vet before administering treatment.
Ulcers that last longer than three-four days are usually seen to be complicated ulcers. There are two broad categories of reasons of why ulcers fail to heal. The first category is ulcers that fail to heal due to external causes. These external causes can include ongoing trauma due to other eye conditions such as entropion (the abnormal rolling in of the eyelid); or trichiasis (facial hair in contact with the eye as a result of facial conformation); or foreign bodies lurking behind the third eyelid, embedded within the eyelid, or within the cornea itself; or abnormally placed eyelashes. Also unresolved infections in the conjunctiva, glands of the eyelid margin, or within the tear duct may cause corneal ulceration. Unless these external causes are also treated, the corneal ulceration will not heal.
The other category of why ulcers fail to heal deals with internal reasons, such as other eye diseases and primary tissue healing problems.
A number of diagnostic instruments and techniques are used to properly diagnose the reasons for a complicated corneal ulcer. It is important to note that if an ulcer becomes very deep, it will need to be treated quite aggressively in order to save the eye. As corneal ulcers are a frequent problem in veterinary medicine, you are encouraged to seek appropriate treatment rather than dismissing it.
A cataract is defined as an opacity of any size in the lens. The lens of the eye is usually clear or transparent, and focuses light rays on the retina. The opacity is usually white, but can have a yellowish or grayish appearance as well, and it scatters the light rays. The extent of the vision impairment is determined by the size and location of the cataract within the lens.
The word cataract means "to break down", and is used to apply to waterfalls and rapids as well as the lens. Changes in the lens due to cataracts may appear as small, insignificant dots, microscopic blisters, with a cracked-glass look, a diffuse haze, a "pearl-like" sheen, white streaks, or a completely white lens. A cataract usually starts small and progresses to include larger areas of the lens, but the rate of progression is difficult to predict. Cataracts may develop in one or both eyes. If a large portion of the lens becomes white, it prevents formed images from reaching the retina and blurred vision results. When a light is shined into the eye of a dog with a complete cataract, the dog sees only the white light and no images.
There is the possibility of two different forms of cataracts which have been identified in Cavaliers, with evidence of inheritance in both types. In the juvenile type, young adult dogs are affected. This type of cataract is bilateral, symmetrical, progressive, and becomes total.
The other form is congenital (present at and existing from the time of birth) and associated with microphthalmos (abnormal smallness of the eyeball). The cataract is bilateral, but not necessarily symmetrical, with the two eyes often being affected to different degrees. The more severe the microphthalmos, the more extensive the cataract. Other associated abnormalities of the lens seen in some Cavaliers with this type of cataract include lenticonus (the conical protrusion of the substance of the lens of the eye) and lentiglobus (exaggerated curvature of the lens of the eye, producing a spherical bulging).
During a two year period in the early 1980s, 144 Cavaliers were screened for eye problems in Sweden, and 11 cases of congenital ocular defects were found. Posterior lenticonus, cataracts, and microphthalmia were discovered in the affected dogs, most of which were interrelated. Of the 11 dogs with problems, cataracts were found in all cases, nine of which were bilateral and two of which were unilateral.
Senile (old age) cataracts are also common, as most dogs over eight years of age have some haziness in their lenses. Even when the lenses appear opaque, there may still be a considerable amount of useful vision left. Cataracts may also result from some injuries to the eye or internal diseases such as diabetes mellitus. However, inheritance is the major cause of cataracts in cats or dogs, and if a breeder knows that a tendency towards cataracts is in your lines, your breeding stock should be screened very carefully before being bred.
The only treatment for cataracts is surgical removal, and generally is only contemplated for dogs with severely impaired vision caused by mature cataracts in both eyes who are otherwise in good health. The biggest risk of surgery is the side effects of the anesthesia. Following surgery, the dog will not completely regain all vision, but will regain some vision.
Distichiasis and Other Eyelash Abnormalities
When referring to people, the term distichiasis refers to a second row of eyelashes. Seeing as dogs usually do not have eyelashes on the lower lid, the term refers to extra lashes. The excessive lashes generally arise from the upper lids bilaterally. Severe distichiasis can be responsible for corneal ulceration in the upper portion. If these extra lashes are causing discomfort or more serious problems, medical intervention is warranted. Cryotherapy (therapeutic use of cold) or electrolysis is often successful, as is surgery. Plucking of the extra lashes may be done as well, although the benefit may be temporary and only last up to six months.
The term trichiasis refers to a third row of lashes and is used to describe misdirected lashes. Lashes which grow on the inside or outside of the eyelid are known as ectopic cilia. These abnormal lashes may even arise from the conjunctival surface, are usually short and stubby, and may cause extreme pain and profound squinting and tearing.
means excessively long eyelids, which expose large amounts of sclera (the whites of the eyes) around the cornea. The effect is to reduce the amount of protection the eyelids provide for the eyeball and to expose the eyeball to the environment and render it more vulnerable to any number of damaging conditions. Bradycephalic (flat-faced) breeds are more prone to being affected, and it may not occur until adulthood. Owners become concerned due to increased ocular redness caused by excessive exposure of the conjunctival surfaces (delicate membranes lining the eyelids and covering the eyeballs) due to the enlarged eyelid opening, or may complain about the poor cosmetic appearance due to the large amount of visible sclera. In the worst case scenario, the eyeball can roll forward out of the orbital socket. If this occurs, it is an emergency requiring veterinarian intervention.
This is the failure of one or both eyelids to open in young pups, and needs to be monitored by attentive breeders. Normally the eyelids of newborn pups will remain fused for about 10 to 15 days after birth, but then they will open completely. The danger of the eyelids not opening in the normal time span is the possibility of the pup developing a bacterial infection, most commonly with staphylococci, beneath the closed or partially closed eyelids. Pus which forms in response to the infection gathers under the eyelids, causing a bulging of the eyelid surface. Holding off on treatment could result in ulceration and scarring of the cornea, or even corneal perforation with subsequent loss of vision.
The breeder may apply warm, moist compresses at home and very gently attempt to separate the eyelids with the fingertips. An appropriate antibiotic should also be given. If these measures fail, surgery may be required to separate the eyelids and remove the pus.
Second Group Of Eye Conditions
Retinal Folds (related to Retinal Dysplasia)
Retinal folds are a form of retinal dysplasia (an abnormality of development) that occur on the retina. Retinal dysplasias are present at birth, and are recognized to occur in three forms:
Folds: defined as linear, triangular, curved or curvilinear foci of retinal folding that may be single or multiple in appearance. They may occur in one or both eyes. Microscopic study of the tissues demonstrates the formation of tubular structures called rosettes. Retinal folds, while they may be a mild form of dysplasia, are also thought to occur through a more benign process of unequal growth rates in the retina and its underlying tissues, the choroid and sclera.
Geographic: defined as any irregularly shaped area of abnormal retinal development (larger areas of true disorganization), representing changes not accountable to simple folding.
Detachment: defined as either of the above described forms of retinal dysplasia associated with separation (detachment) of the retina. The two latter forms are associated with vision impairment or blindness. Retinal dysplasia is known to be inherited in many breeds, but the genetic relationship among the three forms of the disease is not yet certain. As a rule of thumb, the breeding of dogs with folds only is seen to be at the option of the breeder, whereas the breeding of dogs diagnosed with geographic dysplasia or retinal detachment is not advised.
There is no question that retinal folds occur more commonly in puppies than in adult dogs. According to Dr. Lionel F. Rubin, an American veterinary ophthalmologist, the folds typically occur in certain locations on the retina, are usually not associated with other abnormalities, usually do not progress, and may in fact disappear with maturity. As stated by Dr. Rubin, it has been assumed that the mode of inheritance is recessive (both parents are carriers), and affected animals are not to be considered to have normal eyes. Both affected and unaffected dogs have been seen in litters with unaffected sire and dam. In his opinion, if the condition is to be eliminated, affected individuals should not be bred. He does note that as vision is not thought to be affected, the condition can be considered to be a blemish, and should not by itself cause the removal of an otherwise sound animal from one's breeding program. As one writer on the internet wisely noted, if a breeder does choose to breed a bitch who has folds (or was known to have them as a puppy), that breeder would be wise to ensure the male used not only is clear of folds at the time of mating, but also had been given an eye examination at about one year of age (or less) which also showed him to be clear of folds.
Interestingly, Cynthia S. Cook, DVM, PhD, has written that animals with folds alone will be issued CERF (Canine Eye Registry Foundation - see Appendix for more detail) numbers, except the Samoyed, Labrador retriever, and English Springer Spaniel; in these breeds, there is definite genetic evidence that the folds alone may represent a significant genetic entity.
Progressive Retinal Atrophy
Abbreviated PRA; this disorder is sometimes also known as Progressive Retinal Degeneration (PRD). According to the website (www.netrover.com/~eyevet/pra.html) provided by Dr. Michael Zigler, ophthalmologist in practise in Oakville, Ontario, in all animals with PRA, the outcome, age of the dog, and what the veterinary ophthalmologist sees are the basis for the classification of exactly what type of condition the patient has. This particular condition has been seen in almost every registered breed and in mixed breed dogs as well, although it is an unusual condition to affect Cavaliers.
As the name implies, a slow death of the retinal tissue takes place. The disease progresses gradually, and the earliest signs may be overlooked, as it is not a painful condition. The earliest signs include night vision difficulties that in most cases will progress to day blindness. Dogs may appear to be disoriented when going out in their yards at night, or may be afraid to go into a dark room. Other behavioural changes may be noticed later, such as a dog being willing to go up, but not down, stairs. Some owners may notice an abnormal shine coming from the dog's eyes; this is due to the pupils being dilated and not responding as quickly to light as do pupils of normal dogs. Cataracts may occur and generally occur later in the disease. Diagnosis is confirmed when a test called ERG is given; the dog is anesthetized and a special instrument is used. There is no known treatment for this disorder.
Dr. Rubin has indicated that while the mode of inheritance has not been positively established, it is assumed the condition is recessive. It is recommended that not only should the affected dog be withdrawn from any breeding programs, but so should both parents and all littermates.
Excessive Tear Staining
Blockage of tear-ducts will lead to an overflow of tears from the inner corner of the eye. While most obvious in white-faced dogs, because the overflow of tears leads to tear staining, as Cavalier owners know, this is not an uncommon problem in our breed. The problem is that while the dog's tears are secreted in normal amounts, they are not adequately drained away (nasolacrimal occlusion). Small or absent tear-duct openings will lead to this condition, but it can also occur if the ducts are blocked with pus or mucous during eye infections. If there is an inflammation, redness and/or signs of discomfort will be seen, along with increased tear production. Other possible causes include scarring of the ducts or their openings, or a foreign body (such as a grass seed) becoming lodged anywhere in the drainage system.
Blocked tear-ducts may be diagnosed by placing a drop of fluorescein dye onto the surface of the eye. If the tear-ducts are normal, green drops will appear at the nostrils within a short period of time; failure of the dye to appear indicates there is a blockage in the corresponding duct.
Surgical intervention may be attempted, although if the duct openings are absent, very little can be done. If the openings are present, special probes may be used and various flushing techniques are tried to highlight the site of obstruction. Often the flushing techniques in themselves remove the problem. Antibiotics and steroids may be required to reduce the inflammation.
As in people, this is an inflammation of the conjunctiva. It is very common in dogs, and causes the white of the eye to appear red. It can vary from mild to very severe. When the condition is mild, the only observable symptoms may be a slight redness and irritation with increased tear production. When the condition is severe, the eye is very red and painful, and there will be considerable discharge, which may vary from watery to a thick, grey/green pus. The eyelid may be closed (blepharospasm), and the dog will not like having its eye examined.
Causes can include viruses, bacteria, chemicals, allergies, trauma, or foreign bodies. If both eyes are affected, it might mean there is a more general disease process underway. The usual treatment is to bathe the eyes with warm sterile water and to apply antibiotic and/or anti-inflammatory drops or ointment. If the owner has eye medications left over from other episodes, and wants to start treatment immediately (don't these things always start at 11 p.m. Saturday night on a holiday weekend?), be sure to honour the following cautions:
- Check the expiry date (usually on the label for drops and on the crimp of the tube for ointments) and discard any medication that is past that date;
- Never use medication that include anti-inflammatory drugs (cortisone) without a veterinarian's authorization (you can do more harm than good);
- Never allow the tip of the medication bottle or tube to touch the dog's infected eye;
- Wipe each eye with clean tissues (don't reuse); and
- If no improvement is seen within a day or two, don't lose any more time getting an appointment with your vet.
This condition occurs when the tear gland on the inner surface of the third eyelid enlarges due to infection. As swelling occurs, it is forced out from beneath the lid, exposing a red, cherry-like growth at the nasal corner of the eye.
The usual recommended treatment is surgery. The author of this article had personal experience when one of our Cavaliers developed the condition a few years ago. Before signing our dog up for the surgery, some good old-fashioned nursing care was applied. Using a clean washcloth each time, warm (not hot) compresses were very gently held in place on the dog's eye for 15-20 minutes, four times a day, for about four or five days. Following each session with the warm, moist compress, the prescribed antibiotic was applied (as outlined under the conjunctivitis section). To our vet's amazement, the condition responded to the treatment, and no surgery was needed. Although we were advised the condition is prone to recurrence, so far it has not happened again.
There are many individual conditions which can lead to blindness. They include diseases of the cornea (keratitis), the lens (cataract), increased pressure within the eye (glaucoma), any disease which reduces retinal sensitivity to light impulses (retinal atrophy), or any disease which affects the optic nerves or the sight-center of the brain (tumours, trauma).
Some signs which might alert owners that a dog is not seeing as well as it should include uncertainty as to where it is going, treading on articles usually avoided, bumping into furniture, and carrying the nose low to the ground. Shining a bright light into a dog''s eyes to see if the pupils constrict is not by itself diagnostic. Senses of hearing and smell can become more acute as vision starts to go.
The literature makes many suggestions as to how owners can deal with blind pets. While most of them are based on common sense, they are worth repeating here. First and foremost, when out of doors, keep the dog on a leash or in a familiar fenced yard. If there is a hot tub or pool on the property, a cover or barrier is needed to prevent the dog falling in and drowning. Keep the food and water dishes in exactly the same places every day; the area can become a site for reference if the dog becomes disoriented. Don't rearrange the furniture, and be careful about putting chairs back under the table when finished eating. Place a barrier at the top and bottom of stairs; going up and down stairs has to be re-learned by the blind dog. If you know the dog is losing its sight, take the opportunity to teach it some verbal commands, such as "stay", "wait", and "down" if it doesn't know any; such obedience training might save its life one day.
Earlier this year, Cornelia Tegart had forwarded a page on Hereditary Eye Disorders in Cavaliers to our club secretary. All of the eye disorders mentioned on the page are discussed in detail in either this article or the next one coming out. The actual author is not named; however, some of the content bears repeating here.
"As a breeder you should be aware of the occurrences of these problems in your breeding program. The only way to do this is through ophthalmic examination on a regular basis, starting from the whelping box. All progeny must be tested in order to have accurate information to plan a breeding program.
If one recognizes that with regard to heredity of genes all living things are either CLEAR, NORMAL/CARRIERS OR AFFECTED it becomes clear that testing of whole litters is the only way to be aware of those factors present in a brood bitch/stud dog. It is important to recognize also that wholesale disposal of dogs from breeding programs is not the answer, but is one area to be looked at objectively and seriously considered when breeding lines are compared.
It is essential that we all try to educate ourselves and produce Cavaliers who will live long and healthy lives. We must all do what we can to preserve the Cavalier as a valuable breed for generations to come. One way to do this is through a "wide eyed" approach wherein we personally do our best, encourage others to do their best and be totally honest toward that aim."
A Few Last Eye Care Comments
Cavalier owners know our dogs are treasured for their soft, melting facial expressions, and that their large, round, dark, protuberant eyes contribute to the classic Cavalier look. It also means that we have to take special care of these very important Cavalier assets.
Earlier in 1996, there was a discussion on the Spanie-l computer mailing list about why Cavaliers do not make good field dogs. They were never bred to be retrievers or hunters; they were bred to be companion dogs. While many enjoy accompanying their owners on hikes in the woods, care needs to be taken that the paths are not too narrow and do not have a lot of low-hanging bramble, as their eyes are more vulnerable than are those of many other breeds. Even in their own backyards, ensure they will not poke their eyes on newly pruned shrubbery. One of the most common causes for dust, dirt, vegetable matter, etc. to get into dogs' eyes is allowing them to ride in the car with their heads out the window; for Cavaliers, this method of transport is asking for trouble. So is taking an extra long walk on a very windy day.
If it has been determined that the dog does in fact need medication, here are some final pointers. First, make sure your hands are well washed both before and immediately after applying the medicine. (If the infection is particularly stubborn or messy, using disposable paper towels to minimize risk of cross-contamination is a good idea. Use a clean paper towel to turn on the tap after handling the dog's eyes, dispose, and use another clean paper towel to dry your hands.) When applying the medicine, pull the lower eyelid down and apply the ointment to the inner surface of the eyelid (the dog will try and pull away if you attempt direct application of ointment). Eyedrops may be applied directly to the eyeball; you may now gently rub the eyelid to spread the medicine. Do not assume minor eye problems will clear on their own, otherwise you may find yourself treating major eye problems.
The author has not specifically researched which preparations are most satisfactory for routine eye care, to minimize the effects of tear staining and to otherwise keep the dogs' eyes neat and tidy.
Please see the Appendix immediately following this article, which outlines in more detail how CERF would rate different conditions.
Disclaimer: Your veterinarian is the most qualified person to answer all of the questions you have about your pet's health. Nothing in this article should be construed as medical advice regarding any individual animal's condition.
© Copyright April 11, 1999.
Original Article Written by Myra Ehrman, RN, BA, BS, MScN
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