Primary lens luxation
Primary lens luxation (PLL) is a painful and potentially blinding inherited canine eye condition. Lens luxation occurs when the ligaments supporting the lens weaken, displacing it from its normal position. Signs of lens luxation may include red, teary, hazy, or cloudy, painful eyes. PLL can cause eye inflammation and glaucoma, particularly if the lens shifts forward into the eye. If left untreated, anterior (forward) lens luxation can lead to blindness and is treated as a medical emergency requiring prompt intervention.
Causes
The lens is a structure in the eye located behind the iris (the colored portion of the eye) responsible for focusing light onto the retina for visualization. It is suspended in the eye by multiple ligaments called zonules. PLL is caused by an inherited weakness and breakdown of the zonules, displacing the lens from its normal position in the eye. The direction that the lens luxates can be either forward (anterior) or backward (posterior). Anterior lens luxation is the most damaging and considered an emergency as it can rapidly increase pressure inside the eye, known as glaucoma, causing pain and potentially blindness. Posterior lens luxation leads to milder inflammation, and glaucoma is less likely to develop.
PLL most commonly develops in dogs between the ages of three and eight. However, structural changes in the eye may already be evident at 20 months of age, long before lens luxation typically occurs. Both eyes are often affected by PLL, but not necessarily at the same time. This differs from secondary lens luxation, which can more commonly only affect one eye and is usually caused by a coexisting ocular disease such as glaucoma, inflammatory conditions of the eye (uveitis), cataracts, eye trauma and eye tumors.
Breed Predisposition
Many terrier breeds are predisposed to PLL, such as Jack Russell Terriers, Miniature Bull Terriers and Yorkshire Terriers. Other predisposed breeds include Australian Cattle Dogs, Border Collies, Shar Pei and more.
Clinical Signs
Anterior lens luxation typically has many more clinical signs than posterior. Signs can range from mild redness and discomfort in the eye to extreme pain with vision loss.
Seek veterinary care whenever there is a sudden change in the appearance of your dog's eye or the following signs:
- Red eye
- Sudden change in the size and shape of the pupil
- Squinting, holding the eye closed
- Cloudiness or haziness to the eye
- Frequent pawing at the eye
- Enlarged eyes
- Increased tearing or blinking
- Visual impairment or blindness
Diagnosis
Early detection of lens luxation is crucial. Your veterinarian will diagnose primary lens luxation by performing a complete eye exam. They may measure your dog’s eye pressure for secondary conditions like glaucoma. You may be referred to a veterinary ophthalmology specialist where additional testing could include an eye ultrasound to evaluate the internal structures of the eye.
Treatment
Treatment options vary by stage of disease and position of the lens. When diagnosed early, the most common treatment for anterior lens luxation is surgery to remove the lens by a veterinarian specializing in ophthalmology. Topical eye medications may be needed long-term, even after surgery.
If glaucoma develops suddenly, this requires emergency management and may include medication to decrease eye pressure, followed by referral to a veterinary ophthalmologist. If the eye has uncontrolled glaucoma, is permanently blind, or there is pain or inflammation, it may be necessary for the affected eye to be surgically removed (enucleation).
Treatment for posterior lens luxation may include topical medications to help prevent the lens from shifting forward and causing more severe damage to the eye.
Outcome
Primary lens luxation most commonly progresses to affect both eyes. For this reason, regular and in-depth ocular examinations are recommended in at-risk dogs. Anterior lens luxation left untreated or not addressed immediately often has a poor prognosis for saving the eye.
Dogs that receive surgery early for anterior lens luxation can often preserve some vision but may have diminished vision that is more blurred up close. However, this doesn’t generally appear to affect everyday life. Surgery is not without risk of complications, and often, patients require lifelong topical eye medications.
Genetics
A variant in the ADAMTS17 gene causes primary lens luxation (PLL). It is inherited in a codominant or additive fashion, meaning dogs with two copies of the variant are at the highest risk of developing the disease. Testing for this gene can help breeders select appropriate mating pairs. Dogs with one copy of this variant are at increased risk compared to dogs with no copies but are at a much lower risk than dogs with two copies. The risk of developing PLL in dogs with one copy of the variant depends heavily on their breed. Dogs that develop lens luxation should not be bred.
This health topic was developed as part of a collaboration between the Cornell Richard P. Riney Canine Health Center and Embark Veterinary, Inc. You can learn more about the hereditary risks of other canine health conditions by exploring our genetics articles.