What is gonioscopy?
Gonioscopy is a type of eye exam that looks for signs that a dog is affected by a painful and blinding disease known as primary glaucoma. How much the eye is affected is recorded and given as a grade. This grade can be used to help make health focused breeding decisions that reduce the risk of producing puppies that grow up to be affected by primary glaucoma.
What is primary glaucoma?
Primary glaucoma is an inherited condition caused by a build-up of pressure in the eye. This increased pressure occurs because the eye is not able to properly drain away enough of the fluid made inside.
Primary glaucoma can be divided into two types:
- Primary open angle glaucoma (POAG)
- Primary angle closure/ closed angle glaucoma (PCAG).
The information below relates to gonioscopy for primary angle closure/ closed angle glaucoma only.
What are the clinical effects of primary glaucoma?
Clinical signs of the primary angle closure/ closed angle glaucoma are:
- depression
- signs of eye pain, such as excessive blinking and avoiding bright light
- cloudiness at the front of the eye
- a reddened eye
- a dilated non-responsive pupil
- blindness
What causes primary glaucoma?
Primary glaucoma is caused by a build-up of pressure that occurs because some of the fluids that are produced in the eye can’t drain away properly.
Primary angle closure/ closed angle glaucoma is linked to a problem with the drainage angle. This is the angle between the iris (the coloured part of the eye) and the cornea (the clear window part of the eye). This issue with the angle is termed pectinate ligament abnormality (PLA), but is also known as goniodysgenesis (gonio = angle, dysgenesis = defective development).
How is glaucoma inherited?
How primary angle closure/ closed angle glaucoma is inherited is not fully understood, but researchers believe that it may be controlled by a number of different genes and also influenced by some factors that a dog may be exposed to during its life.
The way in which these sorts of conditions are inherited is not straight forward, and so they are called complex inherited disorders.
Is this test relevant to my breed?
Find out which health tests or schemes are recommended for your breed on our Breeds A to Z. These recommendations are suggested by breed clubs and approved by The Kennel Club's committees.
How do I get my dog graded?
Gonioscopy requires a degree of expertise and specialised equipment and so these examinations are not usually a routine part of the eye scheme. Gonioscopy may not be available from every member of the BVA/KC/ISDS Eye Panel.
Book a test
You will need to book your test through a BVA/KC/ISDS eye panellists. A list of eye panellists is available from the British Veterinary Association. When telephoning a panellist to book an appointment make sure you check that they can carry out gonioscopy.
What happens at a grading?
The eye panellist will apply some local anaesthetic drops to your dog’s eye. A type of examination lens, known as a goniolens, is put on the surface of your dog’s eye so that the drainage angle can be looked at. This test will be done on both eyes.
Some dogs may need to be sedated. The fee for sedation may be in addition to the cost of the test. Your eye panellist will give you advice on whether this is required.
What you need to bring with you
Owners of dogs registered with the Royal Kennel Club should bring a copy of their RKC registration paperwork, either in physical or digital form, to present to the panellist at the time of the gonioscopy test. If the dog has been assessed previously, a copy of the prior assessment certificate should also be provided.
Who gets a copy of the results?
The panellist will examine the dog, issue a certificate and inform the owner of the result at the time of examination. Copies of the certificate are distributed to the owner, the BVA and a copy retained by the examining eye panellist.
More about the scheme
For further information on the scheme, please visit the BVA website.
Costs
Goniscopy test costs
Routine eye examination
£72.00 per dog
Group testing (25 or more): £60.00 per dog
Gonioscopy
£72.00 per dog
Primary Open-Angle Glaucoma
£72.00 per dog
Litter screening* (5 to 12 weeks)
1st puppy: £72.00
Per puppy thereafter: £15.00
Duplicate copy of certificate: £46.00
At what age can my dog have a gonioscopy test?
Gonioscopy can be performed in dogs from 6 months of age onwards. In some breeds the grade has been shown to change with time. We therefore advise that gonioscopy is performed at approximately 1, 4 and 7-8 years of age.
What gonioscopy results can a dog have?
Important change from 1 January 2026
From 1 January 2026, gonioscopy results will be recorded using three grades: Grade 1, Grade 2, or Grade 3. Grade 0 will no longer be used.
What the grades mean:
Grade 1
- 25% of less of the drainage area is abnormal.
- These dogs are considered normal or mildly affected
Grade 2
- Between 26% and 75% of the drainage area is abnormal
- These dogs are considered moderately affected
Grade 3
- More than 75% of the drainage area is abnormal
- These dogs are considered severely affected and at risk of developing glaucoma
Important to understand:
Only dogs with severe abnormality (Grade 3) have a risk of developing glaucoma, however, not all Grade 3 dogs will go on to develop the condition. Dogs with a Grade 1 or Grade 2 result have not been shown to develop glaucoma.
Breeding advice
In general, dogs affected by inherited eye conditions should not be used for breeding. However, factors such as how common the condition is within the breed and the need to maintain genetic diversity may influence decisions.
Grade 1: Suitable for breeding in all breeds.
Grade 2: In breeds where maintaining genetic diversity is a significant concern, dogs graded 2 may be used for breeding with caution, provided they are in excellent health and have good results from all other recommended screening schemes. They should only be paired with dogs graded 1 under the new grading structure, or graded 0 or 1 under the old grading structure.
Grade 3: Should not be used for breeding.
These recommendations may be updated as further research becomes available.
Find a dog's gonioscopy score
Our Health Test Results Finder can help you find a dog's gonioscopy score, or results from any DNA tests and health screening schemes that we record. This tool can help you make informed decisions, whether you're a breeder trying to find a suitable healthy mate for your dog, or a puppy buyer wanting to know more about the health of a puppy's parents.
Questions and answers
How can I lodge an appeal?
The panellist who performs gonioscopy on your dog should be able to answer any questions that you may have about the findings.
There is a set procedure for appealing against the results of an eye examination should you wish to do so and the panellist will supply the requisite leaflet. Appeals must be lodged in writing with the BVA within 30 days of the examination.
Find out how to contact the BVA for more information on the appeals process.
There is a set procedure for appealing against the results of an eye examination should you wish to do so and the panellist will supply the requisite leaflet. Appeals must be lodged in writing with the BVA within 30 days of the examination.
Find out how to contact the BVA for more information on the appeals process.