Vitreous Degeneration in the Italian Greyhound and Whippet

Vitreous Degeneration in the Italian Greyhound and Whippet

The vitreous is a crystal clear jelly that is the single largest structure within the eye. The health of the vitreous is important for normal ocular function. The vitreous helps give shape to the eye, provides nutrients and removes waste products, as well as giving support for the retina. The vitreous is nearly 99% water, with the remaining portion composed of a few cells, a lattice work of transparent collagen fibers and a semisolid slippery material called hyaluronic acid.

Maintenance of normal sight requires the vitreous to be clear and remain in its normal semisolid state and position. If the vitreous becomes cloudy, liquefied, or move

s from its position; vision may be impaired or lost. In addition, we know that vitreous syneresis (change from semisolid to liquid) of the normal vitreous gel can be a degenerative change associated with aging. Syneresis also occurs secondary to previous intraocular inflammation. It has also been seen as a congenital and heritable condition associated with retinal dysplasia in certain breeds, such as the Labrador retriever. In addition it can be seen in the Collie with Collie Eye Anomaly as well as in the breeds affected by primary glaucoma and/or lens luxation. Vitreal degeneration has been presumed to be inherited in the Italian Greyhound (IG) and Whippet, yet a mode of inheritance has not been defined. Lens luxation (dislocation) and glaucoma are commonly associated with vitreous degeneration; and are both devastating ocular disorders.

To date no careful study of vitreous degeneration has been done in the dog. Most information about the problem comes from Canine Eye Registry Foundation (CERF) examinations and anecdotes from owners, veterinarians and ophthalmologists. The CERF records from 1991 – 1999 indicate that nearly 18% of the IG’s and 6% of the Whippets examined were diagnosed with vitreous degeneration.

In 1996 Dr. Schoster received a 3 year grant from the American Kennel Club to do a prospective study about vitreous degeneration in the Whippet. In the first three years of the study, 13.6% of the Whippets examined were affected with vitreous degeneration. Dr. Schoster intends to follow the animals enrolled in the study for at least a full ten years.

The first step in solving any problem is to define the problem. In order to define vitreous degeneration in the Italian Greyhound and Whippet, one needs to start examining all animals starting at 8 weeks of age and then once each year there after for the life of the animal. Using that information, researchers can begin to understand the condition and have a better idea about the age of onset, the degree and rate of progression, as well as consequences in affected animals.

The research plan for Dr. Schoster’s study is as follows:

Specific Aims

1) Describe the age of onset of vitreous degeneration by examining all ages of animals and following each animal registered in the study with annual examinations for its full life. Animals can be entered in the study as early as 8 weeks of age.

2) Characterize vitreous degeneration in individual animals and illustrate chronological changes.

3) Characterize any associated or secondary ocular abnormalities.

4) Identify characteristics of the condition that may predict the advent of serious complications and those that may be benign in nature.

5) Investigate and characterize familial relationships of those affected with vitreous degeneration by means of correlation of clinical findings with familial linkage.

6) Carry out the study for the full life of the animals in order to capture the changes over time.

Research Design and Methods

It is customary for members of the Italian Greyhound Club of America and the American Whippet Club to have their animals examined by a boarded ophthalmologist periodically, either at a private clinic or at a CERF eye clinic which is usually held during a dog show.

There is a standard protocol and form for the Canine Eye Registry Foundation examination. Unfortunately this examination and data form only require a post dilation examination with the biomicroscope and indirect ophthalmoscope. It does not include the detail necessary to fully characterize vitreous degeneration and possible associated problems.

Therefore a supplementary examination protocol has been developed to accompany the main CERF data for this study.

How Can IG Owners Participate?

There are two ways a dog can be entered into the study. The dog can be examined by Dr. Schoster, or the dog can be examined by any board certified ophthalmologist.

The first way to enter an animal into the study is to have Dr. Schoster examine the dog. Dr. Schoster has been attending the Whippet National Specialty for the last several years and performing eye exams there.

In August 2000 Dr. Schoster offered an eye clinic for the first time at the Italian Greyhound Club of America National Specialty in Canfield OH. In 2001 he was not able to attend but in 2002 Dr. Kimberly Stanz, DVM DACVO will be performing the examinations.

The second way to enter a dog into the study is to have it examined by a board certified ophthalmologist at any other time or place. When scheduling an eye exam with an ophthalmologist, the owner will have the option to ask the examiner to collect the additional data needed for the study. Because the owner may find that some or all ophthalmologists will charge a fee to collect that additional data, the owner must be willing to pay any supplemental exam charges.

If dogs are to be examined by an ophthalmologist other than Dr. Schoster, the examiner needs to contact Dr. Schoster prior to the time of the exam in order to forewarn the examiner of the requirements of the supplementary examination. If the examiner agrees to comply, then the examination should follow the format requested on Dr. Schoster’s data sheet. The owner must download the examination form (data sheet) from the web site and bring it to the examiner.

The examination is the same as a CERF examination except that the eyes are examined with the biomicroscope before the dilating drops are used and intraocular pressure is also measured. At least 20 minutes after the dilating drops are placed, the biomicroscopic examination is repeated followed by the ophthalmoscopic examination and a second glaucoma test.

All completed supplementary examination forms must be returned to Dr. Schoster by the owner.

In addition, in order to evaluate the possible mode of inheritance of vitreous degeneration, Dr. Schoster needs information about the relatives of all dogs entered in the study. The familial data form should also be downloaded from the same web site. This is important information about the animal’s parents and littermates. The owner should fill out this form and mail it to Dr. Schoster.

An alternative to filling out the form is to enter the data directly into Dr. Schoster’s database through his web site.

Dr. Schoster will contact the owners after receiving pedigree information and arrange for the subsequent examinations of the relatives with himself or another boarded ophthalmologist.

Summary

In summary, this study is meant to not only identify those animals affected with vitreous degeneration, but also to determine the long-term outcome. Annual examinations for the life of the animals are the only way to know the incidence and consequences; it is also a way to determine the mode of inheritance.

Thank you in advance for participating in this important study.

**Voluntary participation in this study does represent a conjoined motivated expression of interest and concern by the owners, breed club, breeders and examiners. It is expected that if an owner agrees to have the supplemental vitreous examination performed they will be willing to support any reasonable extra charges by the examiners. In addition, owners must be willing to provide Dr. Schoster the key familial information needed to investigate familial tendencies of vitreous degeneration. Since Dr.  Schoster is the principle investigator of the grant he can waive any supplement charge to the client for the vitreous examination when he or an agent of his performs the examinations. Owners whose animals are examined as part of this study must also be willing to pay any supplemental exam charges required if the exam is performed by an ophthalmologist other than Dr.  Schoster. Please plan to discuss these charges at the time the appointment is made. Lastly, the original AKC grant had subsidized a portion of the extra costs for this data collection by a small payment to the examiner. Please inform your ophthalmologist that since the startup original grant completed its 3 years; no compensation from Dr. Schoster is currently available.

James V. Schoster, DVM Diplomate, American College of Veterinary Ophthalmologists