MINIATURE BULL TERRIER HEALTH

                                               PRIMARY LENS LUXATION

This is a condition where the lens is partially or fully dislocated from the threads that hold it in position within the eye. These tiny threads, sometimes called ligaments are known as zonules and it is they that weaken and break causing this condition. How quickly and how many break determines the speed of onset of this condition. Using normal ophthalmic instruments (such as your own vet may possess) it is difficult to even see these small threads. What the experienced ophthamist (not your own vet) should also be looking for is a wobble in the lens as the dog moves his head around. This indicates that the zonules are becoming weak. Weak zonules is called subluxated , completely detached (luxated)

In our case, the regular twice yearly eye examination had occurred a month before the actual onset of the condition, therefore it is imperative that you conduct your own eye examinations as well.

Unfortunately, each eye can behave differently, so a rapid onset on one eye, may or may not lead to a gradual (and predictable) onset with the other. As this appears to be a genetic defect in dogs, then it is almost certain that eventually both eyes will be effected.

There are two directions in which the lens can go: forward and backward. Forward in called  anterior luxation. Backwards is called posterior luxation. The lens can also detach at an angle which can cause bruising of the cornea (edema of the cornea). This causes the cornea to loose its transparency in the area of contact. This may or may not be permanent.

What to look for:Forward is the usual way. In my dog�fs case, the results were obvious. The iris  (the coloured part of the eye, surrounding the pupil  (the normally dark spot in the centre of the eye)) was almost invisible: being fully open & unable to contract even in strong light. The pupil was consequently very large revealing the greenish hue (in fact, a reflection) from the back of the eye: the sort of colour exhibited by animal eyes when illuminated at night.

In addition, the eye might appear slightly swollen and the dog may have difficulty holding his eye open. These are VERY BAD signs. They indicate that pressure has already built up in the eye, possibly to damaging levels.

In the case of my dog�fs first eye, the only other symptom was shivering - due to the pain. Bull terriers have a habit of shivering for no reason in any case, but it is worth checking the eyes if he/she is shivering for no apparent reason. When the second eye went, I noticed that the dog was having trouble finding food items on the floor. I think I noticed this one almost immediately it luxated. Even so, by the time I had got the dog to the Veterinary Centre for treatment (about two hours later), the dog was just beginning to close his eye and the pressure (the IOP,intraoccular pressure) was already 51!

If the lens goes backwards, I don�ft know what the symptoms are (there may not be any) or what the prognosis is, however there is the possibility that the lens could go forward at some time and cause glaucoma and the other conditions mentioned.

               


What happens:When the lens goes forward in the eye, it usually blocks the flow of fluid (aqueous humour) which is continually produced in the normal eye by a ring of tissue (the cilary body) between the iris and the lens. The majority of this fluid normally flows out of the eye. Because the fluid cannot drain away, a condition arises which can cause irreparable damage to the eye due to the build up of pressure. This condition is known as glaucoma.

Nowadays, pressure (tonometry, the measurement of eye pressure - impress your vet with that!) is easily measured with a small hand held digital (no moving parts!) pressure gauge (a tonopen) held against the front of the eye. . Normal pressure should be in the range of 15 to 25 torr (mm of mercury). But can reach as high as 60 (with glaucoma) That is over one pound per square inch!.

At the back of the eye is the light receptive area. These cells (rods and cones) are mounted in a structure called the  retina, which is held on to the interior wall of the eye. The blood flow and information from the light sensitive cells pass out of a central area in the back of the eyeball, which contains the optic nerve (which transmits the information from the cells). Pressure build-up in the eyeball can cause permanent damage to the optic nerve itself and constrict the blood flow, which can lead to the death of the light sensitive cells. A consequence of this is that the retina detaches from the eyeball. This can be seen eventually by examination of the eye, though it might take some months to happen. Partial detachment can also occur. Detachment can be progressive. The amount of detachment relates to the level of vision available to that eye. This detachment is not in any way painful to the dog, however.

If glaucoma is allowed to remain untreated for as little as six hours, then your dog will be fully blind in that eye.It important that the dog is immediately seen by a vet who is fully knowledgeable in this subject. Most vets aren�ft, or don�ft appreciate the seriousness of the situation. This is an acute condition (requires urgent attention), not  chronic (slow).

The treatment :At first I had understood that the only treatment was an immediate operation to remove the lens. However, now I understand that there are drugs which, if given soon enough will reduce the pressure in the eye. By careful monitoring, a dog can be maintained (at the veterinary centre) until an operation is undertaken. This can be a period of some days or even weeks. Alternatively, some surgeons allow dogs to go home with the owner administering the pressure reducing treatment, until the lens has become almost completely detached and moved to a suitable position so it can be easily removed.

The lens is also attached to the vitreous humour (the jelly-like substance) in the eyeball itself. In order to remove the lens, it has to be severed from the vitreous humour. This is a delicate operation, as it is possible that the any outward pressure on the lens can move the whole of the vitreous humour forward which can detach the retina with consequent loss of vision. Some vitreous humour is inevitably removed with the lens, though in a sucessful operation the surgeon takes as little as possible because the space left by the lens and the removed vitreous humour causes an imbalance within the eye. In this situation, there is a tendency for the vitreous humour to move forward causing partial or complete retinal detachment. Some surgeons remove the lens prematurely by forcible suction, the majority hold (I believe) that this is not advisable that because the danger of retinal detachment by this method. In addition, there is usually more chance of hemorrhage (internal bleeding), more scar tissue, again increasing the likelyhood of retinal detachment.

Because stabilty of the eye has been upset, surgeons recommend that the dog does nothing that might cause the movement of the retina. For instance �erat killing�f (violent toy shaking). Even straining against a collar is considered by some to be inadvisable, so they recommend a body harness (which does not bear on the neck).

After successful treatment, the eye has no focusing ability and the light image which would (at least in humans) be inverted by the lens now falls directly on the retina. However, in dogs, apparently, the cornea (the structure in front of the lens) provides an appreciable focusing (though fixed) element to the eye and although focusing is absent, some resolution of an image should be possible. Presumably, in time, the brain will eventually learn to interpret what falls on the retina, which should give the dog the so called �eguidance vision�f.

Sometimes, the short term results are good, particularly if both eyes have retained their retinas. I have seen a dog playing and catching! the thin cord attached to another dogs lead. She obviously knew where it was, despite having both her lens removed.

However, as mentioned, prolonged glaucoma may have already caused irreparable damage to the retina. In addition, this major alteration to the structure of the eye can lead to glaucoma again! (for reasons which are not entirely understood) The eventual consequences of glaucoma require removal of the eye.

                
                                                     CONGENITAL DEAFNESS 
                                BAER TESTING HOW THE HEARING WORKS

Sound waves enter the external ear canal and strike the ear drum, which begins to vibrate. This, in turn, causes vibration of the tiny bones in the middle ear (the ear ossicles). These vibrations set up waves in the fluid of the cochlea, the spiral-shaped structure in the inner ear. The change in pressure ultimately causes vibration of the hair cells inside the cochlea which are connected to the auditory nerve. This triggers a nerve impulse via the auditory pathway to the brain. Inherited Deafness

Microscopic examination has shown that Inherited deafness is caused by degeneration of the blood supply to the cochlea in the first few weeks of life. This is followed by destruction of the hair cells and ultimately further deterioration of components of the inner ear and nerve degeneration. The loss of the hair cells is permanent and irreversible. The passage of sound to the auditory nerve is interrupted, resulting in the dog becoming deaf. Affected puppies can be detected by 4 weeks old and one study showed no evidence of progressive hearing impairment beyond this age. Deafness may occur in both ears (bilateral deafness) or in one ear only (unilateral deafness).

Research in America has concluded that 1 in 6 white bull terriers unilaterally deaf (deaf in 1 ear) whilst 1 in 20 is bilaterally deaf (totally deaf). Not only white's but also coloured and even solid Bull Terrier can be deaf.

Although it is possible to keep a bilaterally deaf dog, the problems associated with such a decision cannot be emphasised too highly. A deaf dog is an incredible responsibility and can be a liability both to itself and others.

Deaf Bull Terriers should not be sold by breeders.

Unilaterally deaf dogs make excellent pets, but they carry the genetic material for deafness. As the condition is hereditary, it makes sense not to use affected individuals for breeding.

BAER TESTING

The only way in telling the exact state of a dogs hearing is to BAER test (brainstem auditory evoked response). This method can distinguish between a totally deaf dog, a dog that is unilaterally deaf or a dog that can hear normally.

When a sound enters the ear, tiny electrical impulses are generated by components of the auditory pathway in the inner ear and brain. These signals can be picked up by recording electrodes positioned on the head, and are in turn passed into a specialised electrodiagnostic machine. A series of approximately 500 stimuli, usually clicks, are passed into the ear through a headphone. In a normal-hearing dog a series of peaks and troughs is produced which is displayed on a small TV-type screen. Thus, the BAER can be defined as the electrical response of the brain to a series of auditory stimuli.

The test can be carried out on puppies from 5 weeks old without any sedation, adult dogs usually need to be lightly sedated.

More and more responsable UK breeders are starting to BAER test which will in the long term reduce the amount of deafness in the breed.

Unfortunatly not many veterinary centers have the facilities to do BAER testing, see the list below;

Animal Health Trust, Newmarket - 01638 552700

ChesterGates Referral Hospital - 01244 853823

Animal Medical Centre, Manchester - 0161 8813329

Hearing Assessment Clinic (mobile), Hampshire - 01962 713155

Vale Vets, Gloucester - 01453 542092

Small Animal Clinic, Midlothian, Edinburgh - 0131 6501000

Church Farm Veterinary Clince, Liverpool - 0151 3271885

Wey Referrals, Surrey - 01483 729194

                                                  HEART CONDITIONS