|
Primary Lens Luxation (PLL) is an inherited eye condition that affects multifple breeds of
dogs, including many breeds of terrier. Primary len luxation is distinct from secondary
luxation, which can occur in any breed as a secondary result of trauma, inflammation,
glaucoma or an intraocular tumour.
The lens is a transparent structure inside the eye that is held in place by many tiny
ligaments called zonules. If these ligament break, the lens will become loose inside the
eye and eventually fall out of its normal position. There can be partial (sub-luxation) or
complete displacement (luxation) of the lens from its normal site, either forward into the
anterior chamber of the eye (in front of the pupil) or backwards into the vitreous. PLL is a
painful and serious condition, particularly if the lens luxates in the anterior of the lens
where it can cause increased pressure within the eye leading to glaucoma and possible
loss of vision.
Dr Cathryn Mellersh at the Animal Health Trust, in collaboration with Dr David Sargan
at Cambridge University, has been carrying out research to attempt to identify the
mutation responsible for PLL. Initially research began by studying the condition in
Miniature Bull terriers but has now been extended to include Lancashire Heelers, Tibetan
terriors, Jack Russell terriers and Parson Russell terriers.
Following a genome wide scan to identify genetic markers linked to the condition the
scientists are now confident they have identified a small region on one of the dogs' 38
chromosomes that harbours the mutations. The region represents less than 1% of the
dogs' DNS and Drs Mellersh and Sargan and their respective research groups are currently
combing the region to try and identify the specific mutation that causes PLL.
Once the mutation has been identified a DNA test will be developed that will enable
breeders to identify their dogs are clear, affected or a carrier of PLL. Results generated
to date indicate the same region, and in all likelihood the same mutation, is associated
with PLL in all breeds included in the study thus far.
To facilitate the final stages of the research Drs Mellersh & Sargan require additional
DNA samples from dogs of any breed affected with lens luxation. The DNA can be
collected as a simple cheek swab and should be accompanied by a 5-generation
pedigree and a copy of the dog's certificate of eye examination, to confirm diagnosis.
Anybody interested in donating a DNA sample from his or her dog should contact
Dr Cathryn Mellersh, via email, for more information.
| 
