Glaucoma

There is now some evidence that repeated forceful pulling on a dog’s neck collar increases the fluid pressure inside their eyes. Dogs predisposed to glaucoma or who have already developed glaucoma in one eye may do better walked on a harness rather than a collar. – See more at: http://akcchf.petwave.com/Dogs/Health/Glaucoma/Causes.aspx#sthash.DoSkVHA9.dpuf

Glaucoma is a painful and very serious condition in which pressure builds up within the eyeball, damaging the retina and the optic nerve and so impairing vision. If not treated quickly, the pressure on the retina and the optic nerve can cause irreparable damage leading to permanent blindness.

Cells within the eye continuously produce a fluid known as the aqueous humour, which nourishes the tissues of the eye. The balance of the aqueous humour is naturally maintained by excess fluid draining from the eye into the bloodstream. The fluid drains through a mesh-like structure contained within the part of the eye known as the Drainage Angle. Glaucoma occurs when something prevents the fluid from being drained from the eye and so excess fluid builds up causing pressure (Intraocular Pressure or IOP) within the eye.

Note: The pain from advanced Glaucoma is like having a persistent migraine headache

Causes of Glaucoma:

There are two main causes of Glaucoma:

      • Primary Glaucoma
        is an inherited condition in which the drainage points within the eye are narrow or improperly formed, preventing adequate drainage of the fluid from the eye.
        Note: Certain breeds of dog are predisposed to this form of Glaucoma:
        Alaskan Malamute, Boston Terrier, Cocker Spaniel, Basset Hound, Beagle, Bullmastiff, Cairn Terrier, Chow Chow, Dalmatian, Flat-Coated Retriever, Fox Terrier, Golden Retriever, Great Dane, Jack Russell, Japanese Akita, Maltese, Miniature Poodle, Norwegian Elkhound, Samoyed, Scots Terrier, Shar Pei, Shih-Tzu, Siberian Husky, Springer Spaniel, White West Highland Terrier
    • Secondary Glaucoma
      usually results from inflammation of the tissues of the eye, caused by another underlying condition, for example, infection, cataracts, lens displacement or detachment (Lens Luxation), detachment of the retina, tumours, or trauma from injury. The inflammation causes problems with the drainage system and results in the build up of fluid within the eye which in turn causes a build up of pressure within the eye

Symptoms:

Glaucoma is often difficult to spot until it has reached an advanced stage, because the earlier symptoms also relate to a number of other eye disorders. To be certain you should take your dog to a vet as soon as possible if you notice any of the following symptoms:

  • Bloodshot eye
  • Cloudy appearance to front of the eye
  • Enlarged pupil
  • Lack of co-ordination and bumping into things, which could indicate a reduction or loss of vision
    Note: It isn’t always easy to spot vision problems in dogs if only one eye is affected, as they compensate very well with their sighted eye
  • Sensitivity to light
  • Aversion to being touched or petted near the eye, which could indicate that the eye is sore and painful
  • Excessive blinking or pawing at the eye

Eventually the pressure within the eye will cause it to bulge and distort. This means the glaucoma has reached an advanced stage and urgent treatment is needed. Unfortunately, by the time the eye has started to bulge it is too late to save the eyesight, as permanent damage will have already been done to the retina and optic nerve.

Diagnosis:

In most cases the disease starts in one eye and then develops in the other eye (known as the Fellow Eye) sometime later – on average around 8 months later. Usually Glaucoma in the first eye isn’t spotted until it reaches the advanced stage, by which time it’s too late to save the eyesight. However, the Fellow Eye can then be monitored and therefore the condition can be identified and treated early, which gives the best chance for the treatment to work. Treatment given in the early stages of Glaucoma can delay the progression of the disease for several months or more and perhaps even save the eyesight in that eye.

To check for Glaucoma the vet will use an instrument called a Tonometer to measure the pressure within the eye. This test should be done several times throughout the day to give an average reading, because eye pressure changes at different times of the day.

Once your vet is reasonably certain that your dog has Glaucoma, you may be referred to a specialist opthalmic vet.

The Specialist will carry out further tests:

  • Electroretinography to check the interior of the eye for damage. This will show if it’s possible that eyesight may be restored after treatment for the Glaucoma.
  • Gonioscopy to determine the angle at which the aqueous humour drains from the eye

Also in cases of Secondary Glaucoma:

  • X-rays and ultrasound may also be performed to check for abnormalities within the eye.
  • Blood tests to detect any underlying infection or inflammatory disease that may have caused the Glaucoma

Treatment:

The treatment given to your dog will depend upon the type of Glaucoma (Primary or Secondary) and the extent to which the disease has progressed, but it will involve application of eyedrops and/or eye ointment, probably combined with oral medication and eventually, surgery. The aim of this treatment is to reduce the pressure in the eye and keep it down so as to minimise the damage to the optic nerve and the retina and also to relieve the pain.

Medical Treatment of Glaucoma:

Once Glaucoma has been diagnosed, treatment must begin immediately to try to save whatever vision remains in the affected eye and also to delay the onset of Glaucoma in the Fellow Eye.

There are a number of different drugs that your vet may prescribe, which will reduce fluid production in the eye or increase the drainage of fluid from the eye and so reduce the pressure. Many of these drugs will be applied direct to the eye in the form of eyedrops and/or ointment and some are given orally.

Unfortunately, these drug treatments do not usually work in the long term and often don’t work at all for the eye which is already in the advanced stage of Glaucoma. These drugs are therefore mostly used as a temporary treatment to offer the dog some relief from pain and discomfort until surgery can be performed on the effected eye, and they are also used to delay the onset of Glaucoma in the Fellow Eye.

Surgical Treatment of Glaucoma in sighted eyes:

In the event that Medical Treatment of the Glaucoma is unsuccessful, there are a number of surgical options available for eyes which retain some vision:

  • Cyclocryotherapy:
    Freezing temperatures are used to damage or destroy the cells in the eye which produce the Aqueous Humour
  • Endolaser Cyclophotocoagulation (ECPC) laser surgery:
    A probe is inserted into the eye and then a laser beam is used to destroy or damage some of the cells that produce the Aqueous Humour
  • Gonio-implant:
    An artificial drainage device is implanted within the eye to drain off the fluid

Unfortunately, as with the medical treatments, these surgical procedures only delay the onset of Glaucoma and most cases will inevitably end in blindness.

Treatment for advanced Glaucoma in unsighted eyes:

Once the eye is blind there is no treatment available that can restore the eyesight and the Glaucoma will continue to be a problem and a source of pain and discomfort for your dog.

There are a number of procedures available, each with a different aesthetic outcome. The procedure chosen will very much depend upon the owner’s preference for their dog’s facial appearance, as well as financial considerations.

  • Enucleation (Removal of the Eyeball):
    The most straightforward of the procedures, which simply involves complete removal of the eyeball and then the eyelids are stitched together over the empty socket. After the healing process has completed the dog will be left with an obvious sunken appearance to the eye socket.
  • Enucleation and Orbital Prosthesis:
    Once the eye has been removed, a prosthetic ball is implanted into the empty eye socket and then the eyelids are stitched together over the implant. This prevents the sunken appearance to the eye socket.
  • Evisceration and Intraocular Prosthesis:
    The removal of the contents of the eyeball, leaving the outer part (known as the sclera) intact. The contents are then replaced with a prosthetic ball. This leaves a grey-looking eye, which is obviously blind, but it does move and blink.

Note: Although removal of the eye seems like a pretty drastic step, it will remove the cause of pain and discomfort for your dog and you will find s/he will be much happier after the surgery.

There is an alternative to actual removal of the eyeball, but it also has its drawbacks, aesthetically speaking:

  • Intravitreal Gentamicin Injection:
    (also known as Chemical Ablation or Pharmacologic Ablation)
    The antibiotic Gentamicin is injected into the eye which kills off the fluid producing cells. The eye becomes cloudy and may shrink considerably. Some eyes may bleed internally, but this isn’t painful for the dog and will stop after a while.

Prognosis (Long Term Outcome of Treatment):

The success of the treatment for Glaucoma will depend on the cause of the Glaucoma and how advanced the condition is. Usually treatment of the first eye to develop the condition is unsuccessful because the diagnosis is made too late for any treatment to be effective.

If the Glaucoma is diagnosed early enough (usually the Fellow Eye is in this situation) treatment can be effective in delaying the onset of the condition or at least slowing down the progression of the condition for several months or more.

Once the condition reaches an advanced stage and eyesight has been lost, no treatment can restore the sight and it will become necessary to remove the eye.

Note: If you are reluctant to opt for eye removal surgery, consider this – whether or not the eyeball is removed your dog will be still blind in that eye, however if the eye isn’t removed your dog will also be in pain. Milo was so much happier once his eye had been removed. He was back to his old, fun-loving self and I’ve never regretted making that choice.
Also bear in mind that the vast majority of dogs adjust very well to blindness, as eyesight only ranks third in importance of their senses – hearing and smell being much more important.

One Final Note on Caring for a Dog with Glaucoma:

Bear in mind that repeated tugging on a lead that is attached to a neck collar increases pressure in the jugular veins and this in turn increases pressure within the eyes.

Increased pressure on the jugular veins in a dog with Glaucoma, or even one that is predisposed but hasn’t yet developed this condition, can ultimately lead to a Glaucoma attack.

It is therefore advisable to avoid using a lead attached to the dog’s collar and use a harness instead.


Further information and recommended reading:

For more detailed information on this condition the following websites are well worth a visit:

              • American Kennel Club Canine Health Foundation – GlaucomaAn excellent article on Glaucoma in dogs. Easy to understand and contains detailed information on the causes, symptoms, diagnosis, treatment and ongoing care.
              • Eye Care for Animals – Glaucoma
                A detailed, yet straightforward article on Glaucoma in dogs. Probably the best article to read for those who don’t want too much technical jargon but who need to understand exactly what Glaucoma is
              • Animal Eye Care LLC – GlaucomaAn extremely detailed (but in places quite technical) article. It includes very useful illustrations along with the detailed explanations of what glaucoma is, what causes it, how it is treated, surgical procedure, the risks of surgery and much more.
              • PetMD- Glaucoma in DogsA straightforward, easy to follow article on Glaucoma in dogs.

Related reading:

Your Pets and Glaucoma
An article by Jack Stephens
Glaucoma is increased pressure within the eye.  Cells inside the eye produce a clear fluid (‘aqueous humor’) that maintains the eye’s shape and nourishes the tissues inside the eye. The balance of fluid production and drainage is responsible for maintaining normal pressure within the eye. In glaucoma, the drain becomes clogged, but the eye continue producing fluid, resulting in increase eye pressure, which can actually can cause the eye to stretch and enlarge, in addition to blinding the eye. Read more….

Canine Glaucoma- a Leading Cause of Blindness
An article by Sharon Kay
Canine glaucoma occurs in approximately 8% of dogs in the United States. It is the leading cause of blindness in middle aged dogs. Glaucoma in dogs, as in humans, is an abnormal buildup of fluid inside of the eye. The buildup occurs when the fluid does not drain properly through a filter between the cornea and sclera of the eye. The increased amount of fluid within the eye destroys the retina and optic nerve which will quickly cause blindness. Read more….

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