Glossary

Screening Scheme Description

BVA/KC/ISDS Gonioscopy

Gonioscopy involves examination of the drainage angle with a special lens (goniolens) and is separate from routine eye examination. The technique is used to detect goniodysgenesis (defective development of the drainage angle); an abnormality of the eye which predisposes to primary angle closure/closed angle glaucoma. Gonioscopy enables the drainage angle to be assessed in those breeds in which goniodysgenesis is recognised and is graded from 0-3; where 0 is a normal angle, 1, is mildly affected, 2 is moderately affected and 3 is severely affected. Gonioscopy can be performed in dogs from 6 months of age onwards and, because of potential age-related progression, current advice is that gonioscopy is performed at approximately 1, 4 and 7-8 years of age.

Details about the disease

Glaucoma is characterised by increased pressure in the eye, which is caused by inadequate drainage of fluid (aqueous humour) produced inside the eye. If left untreated the optic nerve and retina become permanently damaged, resulting in blindness.

Primary glaucoma is an inherited disease of the eye without antecedent ocular disease, whereas secondary glaucoma is associated with demonstrable ocular disease such as severe inflammation or lens luxation. Primary glaucoma is subdivided into open angle, where the drainage angle is of normal appearance and angle closure/closed angle, the type outlined here, where the drainage angle may be of abnormal appearance either because the pectinate ligaments (the fibres that span the drainage angle) are abnormal, or because the drainage angle is narrower than usual, or both.

What are the clinical effects of glaucoma?

Clinical signs of acute angle closure/closed angle glaucoma include cloudiness at the front of the eye (corneal oedema), a reddened eye (episcleral congestion), a dilated non-responsive pupil and vision loss. Your dog may be very depressed and exhibit the classical signs of ocular pain, such as excessive blinking and avoidance of bright light.

How is glaucoma inherited?

The precise mode of inheritance of primary angle closure/closed angle glaucoma has not been determined for affected breeds, but clear breed and line predisposition indicate a genetically determined cause with what is likely to be a complex mode of inheritance.

What advice can be given to breeders?

Breeding advice can be found at the link below

www.thekennelclub.org.uk/media/1159316/gonioscopy-breeding-advice.pdf

Where can I find more about primary glaucoma and Gonioscopy?

Further information can be found at:

www.bva.co.uk/Canine-Health-Schemes/Eye-scheme/

 

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