Glossary

Screening Scheme Description

Pectinate Ligament Abnormality (PLA)

What is primary glaucoma?

Primary glaucoma is an inherited condition and is divided into two types: primary open angle glaucoma (POAG) and primary angle closure/closed angle glaucoma (PCAG). In both types, glaucoma results from reduced drainage of the fluid that is made within the eye, resulting in a build-up of pressure inside the eye, leading to pain and blindness.

Clinical signs of acute PCAG include cloudiness at the front of the eye, a reddened eye, a dilated non-responsive pupil and vision loss. Your dog may be very depressed and show signs of eye pain, such as excessive blinking and may avoid bright light.

What is Pectinate Ligament Abnormality?

PCAG is associated with defective development of the drainage angle, which is termed Pectinate Ligament Abnormality (PLA), also known as goniodysgenesis (gonio = angle, dysgenesis = defective development).

How is glaucoma inherited?

PLA is inherited in several breeds. The precise mode of inheritance of PCAG 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 is gonioscopy?

PLA is tested for using a screening technique called gonioscopy. Gonioscopy involves examination of the drainage angle with a special lens (goniolens) and is separate from routine eye examination. Gonioscopy enables the drainage angle to be assessed in those breeds in which PLA is recognised.

How is PLA graded?

A simple grading scheme (0-3) for PLA was agreed by the Eye Panel Working Party in 2016; it is being piloted from July 2017 with the aim of being formally adopted, with or without any revisions, if analysis of the results supports this approach. In this pilot study PLA is graded from 0-3; where 0 is a normal angle, 1, is mildly affected, 2 is moderately affected and 3 is severely affected.

The grading scheme will be used to complement - and may ultimately replace - the ‘Clinically Unaffected’ or ‘Clinically Affected’ classification that currently records the results of examination.

How often should your dog be screened?

It was originally believed that the degree of PLA did not progress after birth and so a ‘one-off’ test before breeding was advised for dogs of certified breeds. However, recent research has provided evidence of progression of PLA with age in several breeds, namely the Flat Coated Retriever, Welsh Springer Spaniel, Dandie Dinmont Terrier, Basset Hound and Leonberger. In consequence, the advice on gonioscopy has been updated for all breeds in which gonioscopy is performed.

It is advised that for Schedule A breeds gonioscopy should be carried out every 3 years, unless any evidence to the contrary emerges.

At what age can your dog be screened?

The first test can be performed in dogs from 6 months of age onwards and current advice is that gonioscopy is performed at approximately 1, 4 and 7-8 years of age. Repeat testing should provide much needed longitudinal information about the risk of developing glaucoma in later life and, in conjunction with Breed Clubs, will enable breed-specific recommendations to be developed.

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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