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800-532-2890

A Closer Look at Eye Care

 

© 2012 Sheryl Krohne

No portion of this article may be reproduced without permission of the copyright holder. Reprinted with permission from Sheryl Krohne.

Vision and eye disease are very important to people and dogs. Dogs don't have the same acuity of vision that people have and see colors differently. However, they certainly rely on their eyes and good vision when going about their daily routine, as well as in performance and show activities. They see movement more quickly and accurately than we do and see much better in dim light and the dark. They are able to coordinate their senses of hearing and smell with vision, which allows them to be acutely aware of their surroundings and the other animals that share their environment.

Different breeds have been bred for better acuity of vision with the sight hounds having the best vision. However, all breeds of dogs see well if their eyes are normal. This article will give you a brief overview of ho

w veterinary ophthalmologists (veterinarians who are certified by the American Col

lege of Veterinary Ophthalmology - ACVO) can examine your dogs and evaluate and certify your dogs' vision and eye health. It will also discuss the most common genetic eye diseases diagnosed in Kerry Blue Terriers. Luckily, Kerries are a relatively "eye healthy breed, and the Foundation should be proud of this.

Sheryl, Lexie and Styx on the agility fieldHowever, regular eye exams should be done in all breeding animals to maintain eye health in the breed and to diagnose and treat the individuals who have diseases. Eye problems may occur which are not genetic and need to be treated since they can cause pain and/or vision loss if not controlled.

How are eye exams in dogs performed?

Dogs can be evaluated for visual acuity using the same techniques that are used to evaluate babies and young children who can't read eye charts. The most common technique used is called streak retinoscopy. This exam is not part of the typical complete eye exam done by veterinary ophthalmologists, but can be done on request if you are concerned that your dog does not have normal vision. It may also be recommended as a further test after the initial exam, in addition to other tests.

The initial complete exam done by veterinary ophthalmologists typically includes subjective vision tests (menace, maze and tracking), measuring the tear production and intraocular pressure (lOP), evaluating papillary light responses, and examining the dog's eye using several special instruments with illumination and magnification. These instruments are the same as those used by a MD ophthalmologist when a person has an eye exam. Their use is important so that small tissues, blood supply, and parts of the eye can be seen clearly and evaluated as many diseases are located at microscopic levels in the eye. Also, special instruments are needed to look into the posterior part of the eye and evaluate the retina - which is a dark area unless illuminated.

These instruments include transilluminators (portable handheld halogen lights), head loupes, slit lamp biomicroscopes and indirect ophthalmoscopes to look at the retina and vitreous body. The lOP may be measured with an instrument that touches the front of the eye (cornea) or with a metal scale that is placed on the eye after topical anesthetic drops are used. All of these examinations and instruments are well tolerated by almost all dogs and do not need tranquilizers or sedatives to be used during the exam.

An eye examination performed by Dr. Betbeze, one of Dr. Krohne's former residents.Occasionally, a soft muzzle is used if the patient is anxious or will not hold its head still.

The muzzle focuses the dog's attention and protects the ophthalmologist who must get very close to the patient's face. Part of this examination is done in a lighted room and part is done with the lights out. 

A maze test may be set-up to test your dog's navigation, especially if he/she has been having vision problems. Traffic cones or chairs are typical obstacles used for the test. After the eye examination is completed, other tests may be recommended based on the results of the initial complete eye exam. These can include blood tests to evaluate the entire body and specific organ function, a complete physical exam, other eye tests such as electroretinogram (ERG), ocular ultrasound, or gonioscopy. Streak retinoscopy may be used (as mentioned earlier) to assess your pet's visual acuity.

A dog's normal retina shown in the examination lens.


These tests can help to diagnose the cause of eye disease in your animal. Your ophthalmologist will explain each test and what they hope to accomplish through the testing. Ophthalmologists in your area of the country can be found at the website www.ACVO.org There is a button at the website for locating an ophthalmologist using your address.

Canine Eye Registration Foundation

(CERF) Exams: These exams are a specific type of eye exam done to evaluate dogs for genetic disease. This exam can only detect genetic disease that has produced an abnormality in the eye at the time of the exam. It does not look at the genes or DNA of your dog to determine if it is a carrier of a genetic disease. The results of the exam can be used to register your dog with the Canine Eye Registry (CERF). These exams typically take about 3-4 minutes to perform, after the pupil has been dilated using tropicamide. It takes 20-30 minutes for the dilating drops to work in most dogs. It is required by CERF to dilate the pupil for these exams or the exam result is not valid.

These exams do not test for vision but are used to examine the anatomy of both eyes and the eyelids and to list any abnormalities in the structure of the eye on a special CERF form. Dogs that have no abnormalities will be marked as normal on the form and will be certified by CERF when the form is sent in. Some types of abnormalities may be found at the exam which will still pass certification because they are minor or they are not genetic. These abnormalities will also be marked on the form. Dogs that have minor genetic abnormalities will be certified by CERF with a "Breeder Option (BO) recommendation. This means that the breeder has the option to breed the dog. It is recommended that a dog with this clearance not be bred to another individual with the same abnormality. They may be bred to a dog with a different diagnosis or abnormality in the "Breeder Option section, as there are several diagnoses that may have this breeding recommendation in any breed. The exact BO diagnosis will be marked on the CERF certificate for that dog.

The ophthalmologist will give you a copy of the special exam form with the results of the exam marked on this form and signed and dated by the ophthalmologist. It is up to the owner to send the form in to CERF to register the results of the exam and receive the CERF certificate from CERF. There are instructions on the form detailing how to do this. Your CERF certificate will come back from CERF after you mail your exam form in to them. If your dog has abnormalities which do not allow it to be registered by CERF, they will send the form and your money back to you with an explanation of why your dog could not be certified. If you have questions about this decision or the diagnosis on the CERF examination form, you can call the CERF office and speak to the veterinary ophthalmologist who works at the office about your dog's diagnosis. This is a free service from CERF. You may also ask breeding advice and help with any eye disease questions from CERF. The ophthalmologist who works for them is available for consulting.

When your dog is certified by CERF, he/ she will be assigned a certification number which he/she keeps for life. However, the certification is only valid for one year, and there is a date assigned to the number on the certificate and on the CERF website where all the clearances can be found. (You can go to the CERF public website and find every dog that has passed CERF - www.VMDB.organd use the CERF button). The reason that CERF exam results are not good for the life of the dog is that many genetic eye diseases can occur in mid-life without any sign in the eye when the dog is younger. An example of this is juvenile cataracts (in dogs under 8 years of age) which may show up at 4 or 5 years of age for the first time. If the dog was examined at age 2 years and was clear of all genetic eye disease, this diagnosis would be a new one at time of the most recent exam. This dog would not be certified by CERF using the most recent exam. It is very important when breeding that CERF clearances are checked on the CERF website and dogs only bred that have been cleared within a year of breeding. Many breeders/owners are not aware that hereditary eye disease may occur in a dog that is already CERF cleared or registered. It is recommended to have breeding dogs examined at least once each year by an ophthalmologist.

Eye Diseases That Are Genetic in Kerry Blue Terriers

There are 5 diseases diagnosed in KBT that are listed in the genetic eye disease book published by the ACVO and used by CERF for certification. I have included each below with their description from the book (in quotes). The recommendations for breeding are included from the book. I have added the frequency these are diagnosed from CERF exam data, and a few remarks about the disease.

1. "Distichiasis

These are extra eyelashes (an additional row or several) that are abnormally located on the eyelid margin which may cause ocular irritation. Distichiasis may occur at any time in the life of a dog. It is difficult to make a strong recommendation with regard to breeding dogs with this entity. The hereditary basis has not been established although it seems probable due to the high incidence in some breeds. Reducing the incidence is a logical goal. When diagnosed, distichiasis should be recorded; breeding discretion is advised.' This disease passes CERF with a Breeder Option recommendation and occurs in approximately 1% of KBT having CERF exams. It is not blinding, but can cause squinting, tearing and sometimes corneal ulcers or scratches.

2. "Corneal dystrophy

- epithelial/stromal - A non-inflammatory corneal opacity (white to gray) present in one or more of the corneal layers. Corneal dystrophy implies a probable inherited basis and is usually bilateral." This disease does not usually interfere with vision but appears as a small whitish spot on the eye. It is not progressive, passing CERF with a Breeder Option recommendation. It occurs in 0.6% of KBT having CERF exams.

3. "Persistent pupillary membranes

(PPM) - Persistent blood vessel remnants in the anterior chamber of the eye which fail to regress normally in the neonatal period. These strands may bridge from iris to iris, iris to cornea, iris to lens, or from sheets of tissue in the anterior chamber. The last three forms pose the greatest threat to vision and when severe, vision impairment or blindness may occur." This disease is accepted for CERF certification in the KBT with Breeder Option recommendation. It occurs in approximately 2% of KBT having CERF exams. It does not cause pain. It can present with a corneal gray or white area if severe.

4. "Cataract

- A partial or complete opacity of the lens and/or its capsule. In cases where cataracts are complete and affect both eyes, blindness results. The prudent approach is to assume cataracts to be hereditary except in cases known to be associated with trauma, other causes of ocular inflammation, specific metabolic diseases, persistent papillary membrane, persistent hyaloids or nutritional deficiencies. Cataracts may involve the lens completely (diffuse) or in a localized region." A cataract diagnosis will not pass CERF and dogs with cataracts should not be bred. This disease occurs in approximately 5% of KBT having CERF exams.

5. "Vitreous degeneration

-Aliquefaction of the vitreous gel which may predispose to retinal detachment and/or glaucoma. Either condition may cause blindness." Vitreous degeneration passes CERF with a Breeder Option recommendation. This disease occurs in approximately 1.5% of KBT having CERF exams.

The presence of only 5 documented hereditary eye diseases in KBT means that the eyes are very healthy in your breed. Some breeds have as many as 18 different genetic eye problems. Also, the percentages of affected individuals are very low, based on the CERF data. This does not mean the KBT should not have eye exams. The opposite is actually true - continued vigilance will ensure that the breed stays eye healthy! Updates on genetic eye diseases can be researched on line and genetic testing (evaluating DNA) at the Optigen sitewww.optigen.com There are no genetic tests yet for eye disease in KBT.

Non-genetic Eye Diseases

Any dog can get other eye diseases such as a corneal ulcer, seasonal allergic conjunctivitis, dry-eye, age related cataracts, ocular trauma and many others. The principle signs to monitor for with any eye disease are squinting (holding eyelids closed), change in the color of the eye from normal, redness in the white of the eye, any type of discharge (tearing, mucous, pus), and any decrease or change in vision. These signs are very specific for eye problems and your veterinarian or veterinary ophthalmologist will be able to sort out the specific cause of the symptom for you and your pet. Eye disease may be an urgency or emergency and you should not put off consulting your veterinarian. They can do the initial exam and refer you if necessary. Many of the problems are not vision threatening, but you will not know until the cause of the symptom is diagnosed. Delaying examination may threaten vision. If there is no improvement within a few days, a visit to the veterinary ophthalmologist is recommended. Also, many veterinary ophthalmologists do not require or request referral, so you can see them on your own.


About the Author

Dr. Sheryl Krohne has been a veterinary ophthalmologist for 28 years. She works at the Animal Eye Clinic of Spokane, part of the WSU Veterinary Specialty Training Center at Riverpoint Campus in Spokane. Sheryl has retired from Purdue University Veterinary School where she worked for 25 years seeing patients and teaching veterinary students about ophthalmology. Asice from working, Sheryl enjoys agility/ obedience training with her standard poodles, knitting, cross-country skiing, kayaking and running. Their home includes a wire-haired pointer and husband Dave.

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