Birgit LohmannDr. Birgit Lohmann studied veterinary medicine in Ghent, Belgium, and at the JLU in Giessen, Germany. Six years she was an employee in the eye department of the surgical veterinary clinic. Wrote her dissertation on "Biometry on the canine eye using the A-mode ultrasound technique". She was awarded the additional title of ophthalmology with authorization for further training in the specialty of ophthalmology. The veterinarian has been running the veterinary practice for ophthalmology since 1995. Dr. Birgit Lohmann is a member of the DOK (Dortmunder Kreis), the FVO (Fortbildungsgemeinschaft Veterinarophthalmologie), the ESVO (European Society of Veterinary Ophthalmology) and the ISVO (International Society of Veterinary Ophthalmology).
Veterinary practice for ophthalmology
Progressive retinal atrophy (PRA) – hereditary disease in the dog's eye
The term PRA is the abbreviation for Progressive Retinal Atrophy and describes a hereditary disease in the eye of the dog, in which the affected dogs slowly progressively go blind.
Anatomy of the canine eye
For a better understanding I would like to give a short insight into the anatomy of the dog's eye: The retina is the innermost thin layer lining the eye and consists of countless nerve cells. There are nerve cells for seeing in the dark (the rods). Nerve cells for seeing in daylight (the cones). Put simply, light stimuli are processed into electrical impulses in the retina, then transmitted via the optic nerve to the brain, where they are processed into "images". Thus the retina plays an essential role in the visual process.
PRA can generally occur in any breed. Since the disease is hereditary, the affected animal already carries the predisposition to blindness at the time of birth, but only becomes ill at a later stage. For every trait, every characteristic and also every disease there are two genes in the body, which are responsible for the respective expression. The inheritance of PRA is autosomal recessive in all breeds, which means that both male and female animals can fall ill equally. For the outbreak of PRA it is necessary that the affected animal carries two pathological genes. If only one gene is altered, the animal does not contract the disease but is a carrier of the diseased gene and can pass it on to its offspring. Accordingly, two clinically healthy parents that are PRA carriers can give birth to sick offspring. Diseased animals always pass on the disease to their offspring. Due to the recessive inheritance and the late appearance of PRA in the life of the affected animals, the disease can reappear even after several generations. Mixed breed dogs can also suffer from PRA, if they have inherited the genes from pedigree dogs.
No rule without exceptionPRA is inherited gonosomal recessive, bound to the X-chromosome, in the Siberian Husky and the Samoyed.h. all males will be affected, females will only be affected if both X chromosomes carry the abnormal gene.
Early and late forms of PRA are known, in which the first noticeable changes in the sense of a deterioration of vision occur at the age of 1-2 years, in the majority of cases obvious visual impairments begin at 3-5 years of age. However, there are also late forms, in which the first symptoms begin only with 6-8 years. However, all forms have in common that they are not curable or stoppable and usually from the time of the first symptoms to complete blindness ca. 3-6 years pass.
In classical PRA, the "rods" responsible for night vision begin to degenerate first, or rather, the "rods" become degenerated. to die off. This process is not painful. In the early stages, it is noticeable that the animals move unsteadily in dim light or in the dark, are fearful and bark at unknown objects or people. Sometimes the animals bump into things they do not know or do not leave their owner's side. Another sign is the incomplete closure of the pupils in incident light and a stronger "glow" of the eyes in the dark than usual, which is a sign of a thinning retina. This makes the layer under the retina, the luminous tapetum lucidum, more prominent. These symptoms then worsen over the following months to years, leading to a noticeable deterioration of vision even in bright light, as the "cones" then also begin to degenerate. This process is also not painful. The time between the first symptoms and complete blindness is usually 3-6 years. Rarely there are PRA forms, in which first the cones and then the rods degenerate. Then exactly the opposite case occurs and the animals go blind first in bright light and then also in darkness, these are special forms and unfortunately also always end with the complete blindness of the animal. A frequent secondary disease of PRA is the cataract cataract (cataract or clouding of the lens). As a consequence of the cataract, after a few years the glaucoma (increase of the intraocular prere) occur. Glaucoma is one of the most painful diseases of the eye. May lead to loss of the entire eyeball. For this reason, animals suffering from PRA should be given approx. be presented once a year for a control examination of the eyes, so that further consequential damages can be recognized early and then be treated, in order to avoid painful conditions.
A veterinarian specialized in eye diseases (Veterinary Ophthalmologist) can make the diagnosis of PRA on the basis of the typical symptoms and the findings as soon as the disease has clinically broken out, d.h. as soon as even slight signs of visual impairment become noticeable. In individual cases where z.B. the cataract prevents the vision of the retina, the diagnosis can also be made with the help of a Electroretinogram (ERG) can be asked. The ERG is an examination of the retinal functions, which can be compared with an ECG (electrocardiogram) of the heart.
In the last decades Genetic testing The first test has been developed, with which it is possible to prove in an animal, which has no signs of a PRA disease, whether it is genetically free of PRA, whether it is a carrier of the gene or whether it will fall ill. For the genetic test blood is taken from the animal. Subsequently examined in special laboratories. The catch is, however, that the genes that transmit PRA are breed-specific, so that a genetic test is usually only meaningful for one breed. If the gene for a breed is known, then it can be determined in the respective dog whether it is genetically free or carrier or will become diseased. This is of course a very great progress in the breeding control of this disease. Nevertheless, the experience of the last 40 years shows that there are always new spontaneous mutations of the genes and so sporadically "new" PRA forms can appear in addition to the already known forms in any breed. Therefore, a genetic test can never replace the regular eye examinations, which are recommended and/or prescribed for different breeds, but optimally complement them. The combination of genetic test. Eye examination is therefore advisable.
The affected animals are very well able to adapt to the changed situation in almost all cases because of the slow progression of the disease and because of their distinctive sense of smell and hearing."
Unfortunately, it is not possible to cure, stop or prevent the onset of PRA by medication or surgery. For this reason, in the interest of the health of our dog population, it is important to support the breeding measures of the respective breed clubs (regular eye examinations, preparation of a genetic test not only of breeding animals). The diagnosis of PRA is for most owners, from my experience, always a shock. Of course, it is very sad and a great pity when a dog goes blind, but: the affected animals are in almost all cases very well able to adapt to the changed situation because of the slow progression of the disease and because of their distinct sense of smell and hearing. PRA itself is not painful, but the possible sequelae of cataracts and glaucoma should be taken seriously and treated because of the possible severe pain. In no case should be bred with the affected animal. Dogs that go blind due to PRA have the possibility to recover slowly, z.T. to get used to the new situation over years. Depending on the character of the animal, it may take some time until it gets used to its handicap.
In the phase when the vision in the light is still working and the vision in the dark is already missing, it can be a bit more difficult for the animal, because it does not know why it "sometimes sees and sometimes does not". Here the owner can help the animal, z.B. to take a flashlight with you for walks in the twilight for the orientation of the animal or to leave a small light on at night in the room in which the dog is staying. In a familiar environment it is almost always the case that the animals cope very well, know their way around and move safely and freely. In addition, experience has shown that animals do not resent their fate, but rather "accept" it than we humans, i.h. they can also forget how it was in the sighted state and accept their blindness as a now changed life circumstance. Nevertheless, some things should be taken into account in order not to make things unnecessarily difficult for the dog or to put him in danger.
– Furniture in the apartment/garden/yard should be moved as little as possible, water barrels, swimming pools, ponds or similar should be secured. It is also helpful for the dog to have as regular a daily routine as possible
– Dogs must always be kept on a leash/breast harness in traffic or dangerous places, in the open field or even in the forest many dogs can run free, some dogs feel safer on a leash especially in the early stages
– It can be helpful for a blind dog if there are other sighted dogs in the household, they can orientate themselves much better by them
– Likewise it is meaningful to train now more the hearing of the dog and to communicate much with it over certain commands, obstacles or situations can be announced to the animal in such a way.
– Provided the dog likes to play, toys can make the sounds (z.B. (e.g. bells, rattles) can be easier to locate.
– It is also important that other people are made directly aware of the dog's handicap in order to avoid unpleasant situations. There are now special blind collars and cloths available in specialized stores.
CONCLUSIONPRA is a disease of the dog, which unfortunately always leads to blindness. The dog can live with it very well, even if changed. He is not allowed to reproduce, because he can transmit the disease to his offspring. The eyes should be checked regularly, due to possible painful late effects. Very important, even if sometimes difficult at the beginning, is the own positive motivation: motivate your dog, if he himself is insecure, show him that life with this handicap is just as worth living as it was before!