cataracts

Cataracts in the German Shepherd

By Fred Lanting

Cataracts - This is a disorder of that part of the eye that looks like the double-convex glass disk in the telescope, binocular, microscope, magnifying glass, etc. The lens is clear and transparent in the normal dog, is filled with a viscous fluid, and is situated between the outer "skin-like" cornea and the main part of the eyeball containing the vitreous humor, another fluid. At the back of the eye, the retina is the site of a shallow depression where images focused by the lens are received and transformed into electrical impulses carried by the optic nerve to the brain, where they are interpreted. The word cataract is used for any cloudiness or opacity of the lens and in some dogs, especially Labrador Retrievers and Samoyeds, it occurs secondary to Progressive Retinal Atrophy (PRA). Although rare, cataract in German Shepherds is believed to be due to a recessive gene; in a few dogs it results from a different, dominant gene. True cataracts may not be detected simply because some are minor, and a dog doesn't need reading ability vision to get around and doesn't complain about things looking dim or fuzzy. If you suspect cataracts in an old dog you are probably wrong; the bluish colour beyond the pupil and lens is seldom a true cataract, but rather the normal result of old age. There is opacity that is occasionally found on the lens, which may be diagnosed as a cataract by a non- opthalmologist, and that is called fibrillar nuclear opacity. There are a number of terms that overlap in meaning and may be confusing to the dog owner. Some are hardly noticeable, some may cause total blindness, others somewhere in between in severity. Further complicating the picture is the fact that some cataracts are definitely hereditary, some are acquired, some noticed early, some not identified at first, some late-onset. Location, progression, and other descriptions run the gamut in size, type, permanence, and other characteristics. Congenital means present from birth (usually though not absolutely always inherited) even though many owners don't see the lesion until the dogs and their eyes are larger. "Juvenile" cataracts (a misnomer) might not start until as late as six years of age. Juvenile cataracts are also referred to as "developmental" cataracts. In the German Shepherd Dog, most cataracts are the congenital, progressive, and autosomal-recessive type. That latter term means it is not linked with the gene determining gender, so it will affect and be carried by either sex; it also means that both parents must be carriers (or afflicted, of course, though that's not likely). In Chessies and Goldens, a dominant gene causes cataracts, so it's a bit easier to “cull the culprits.” Juvenile cataracts may be the same as congenital, depending on how closely the eye is examined, so if the term is used in connection with a GSD, you might best consider it to be the inherited, congenital form, especially if it gets worse with time.

In the GSD, at least, it is hard to differentiate acquired from congenital cataracts. The possible environmental causes are many: nutritional/metabolic, exposure to toxins, inflammation associated with disease organisms, and trauma, mostly. Diabetes, DMSO ("horse" liniment), and DNP (a formerly popular injectable wormer) are others. They may be progressive, too, but are less likely to be so than is the certain worsening within a year of the inherited/congenital type. Orphan pups on a milk replacer sometimes develop cataracts, probably due to an arginine amino acid deficiency; just add a little powdered gelatin to the formula to reduce risk. Often, acquired cataracts are reversible by removing the causative agent.

Other opacities may appear on the cornea over the pupil or slightly off-center, and the novice might think the dog has cataracts. For example, an allergic reaction or some other cause may show up as a small spot, the opacity varying from slightly translucent to more white. The size is usually less than 5mm across, round, oval, or horseshoe-shaped. Most eye specialists refer to this type of opacity as "corneal dystrophy"; the spots do not interfere with vision. In my experience the spots have faded away in a few years after reaching maximum size. Corneal dystrophy appears to be genetic, but is not serious. Probably less than one percent of the breed is affected. I once had a bitch that developed very small oval opacities, one on each cornea, after she was about four or five years old. They finally and gradually disappeared (shrunk to nothingness) by the time she was about ten years or more. At least one of her sons had the same condition, appearing in maturity and going away without treatment by old age. This bitch also developed atopic (allergic-type) problems marked by itching feet and sometimes parts of the skin, but most noticeably by an assumed feeling of excess phlegm in the throat. To get rid of this mucus, she would eat "scratchy" non-foods such as dried pine needles, bark, sand, fabric (on hidden parts of furniture) and even fibreglass curtains. I had to administer about 1-2ml of prednisone every 4 weeks to control this "itch" and to keep her from extreme discomfort and destructive/unwanted behaviour; a month was too long, and I mistrust steroids enough that any more frequently was undesirable. The steroids almost undoubtedly contributed to her sudden death, probably of mesenteric capillary haemorrhage, about six weeks following an operation for gastric torsion when she was 12 years old. One of her many sons developed the same transient and minor corneal defects.

Copyright, Fred Lanting, 1998. Reprints, forwarding, website or magazine use must have the author's permission in writing (e-mail approval OK). Send complete description of proposed use and medium to:
Mr.GSD@juno.com
Fred Lanting, "All Things Canine" Consulting, behaviour analysis, evaluations, seminars, Lectures; Author, "The Total GSD", "Canine HD"