Glaucoma is a painful and potentially blinding condition due to a build-up of pressure inside the eye (intraocular pressure, IOP). The increased pressure causes damage to the optic nerve which relays vision messages from the eye to the brain. If treated promptly blindness can be prevented or delayed, with ongoing treatment required to maintain a low IOP. If identified too late, however, blindness may be permanent.
What are the clinical signs of Glaucoma?
- A hazy, cloudy or ‘blue’ appearance to the eye
- Redness of the white of the eye
- A dilated pupil that does not constrict when light is shone into the eye
- Signs of pain: sleeping more, a squinting or watering eye, being head shy or tilting the head
- Sudden blindness
What are the causes of glaucoma?
Glaucoma may be primary (inherited) or secondary to other eye conditions.
In dogs, both primary glaucoma and secondary glaucoma are common. In cats, by far the most common cause of glaucoma is secondary to inflammation (uveitis).
Primary glaucoma (inherited)
- Primary closed angle glaucoma (due to goniodysgenesis, see below)
- Primary open angle glaucoma (POAG)
Secondary glaucoma (non-inherited)
- Inflammation (uveitis)
- Cataract surgery
- Lens luxation
- Retinal detachment
How is Glaucoma diagnosed?
There are several tests we will perform to diagnose glaucoma; tests of vision, measurement of the intraocular pressure, detailed examination inside the eye and gonioscopy (this last test uses a special type of contact lens to allow us to look inside the eye in order to identify primary closed angle glaucoma). Ultrasound scanning of the eye might also be needed if we are unable to see into the eye directly.
What treatment options are available for cats and dogs with glaucoma?
Treatment can be medical (anti-glaucoma eye drops) or surgical (shunt placement or laser surgery) and the best approach to use varies between individuals- we will discuss all these options with you at your appointment.
In some cases, if treatment is delayed or proves unsuccessful, the eye may become permanently blind and painful. In such cases, surgical removal of the eye (enucleation) may be advised.
What if my pet becomes blind?
Coping with a blind pet can seem daunting, especially in the early days following diagnosis, but most dogs and cats adapt surprisingly well to life without vision.
Please see our advice sheets ‘Living with a blind dog’ or ‘Living with a blind cat’ for information, tips and internet links which should be of help to you and your pet.
Goniodysgenesis and Primary Closed Angle Glaucoma
Goniodysgenesis (also known as Pectinate Ligament Dysplasia, PLD, Pectinate Ligament Abnormality, PLA, or Iridocorneal Angle Abnormality, ICAA) is an inherited risk factor for primary closed angle glaucoma in dogs. The condition is graded 0-3 based on its severity- the higher the grade, the higher the risk of glaucoma.
Goniodysgenesis can occur in any dog but is recognised more frequently in several dog breeds in the UK.
It is important to remember that whilst a diagnosis of goniodysgenesis means that your dog is at increased risk of glaucoma, this is by no means a certainty and many dogs with goniodysgenesis will never develop glaucoma at all. However, in such cases we may recommend regular eye examinations to check the intraocular pressure, or sometimes the use of eye drops long term to try to reduce the risk of glaucoma developing.
Breeds known to be affected by goniodysgenesis:
- American Cocker Spaniel
- Basset Hound
- Border Collie
- Dandie Dinmont
- English Cocker Spaniel
- English/ Welsh Springer Spaniel
- Flatcoated retriever
- Golden retriever
- Great Dane
- Hungarian Viszla
- Japanese Shiba Inu
- Siberian Husky
- Spanish Water dog
- Welsh Terrier
In dogs with goniodysgenesis, it is important that if any redness of the eye, clouding or blindness develops (even if transient), the dog is examined by a vet in order to measure the intraocular pressure, since any delay in diagnosis and treatment of glaucoma increases the risk of permanent blindness.
Primary Open Angle Glaucoma (POAG)
POAG is also an inherited condition in dogs, but the increase in intraocular pressure is much more gradual than in primary closed angle glaucoma. This means that affected dogs do not show sudden signs of blindness or pain – instead, the loss of vision is slower in onset, taking months or even years to develop. An inherited mutation has been found for this condition. Testing is available for this condition.
Breeds known to be affected by POAG:
- Basset Hound
- Petit Bassett Griffin Vendeen
- Shar Pei
Treatment of POAG is with anti-glaucoma eye drops. Lifelong treatment is necessary and regular intraocular pressure checks are required in order to ensure optimum control. However, in some advanced cases of POAG it is not possible to reduce pressure and in these cases surgical treatment may be required.