What is lens luxation?
The lens is a clear structure located behind the pupil, held in place by thin fibers called zonules, which act like bungee cords to keep it stable. The lens focuses light onto the retina, allowing for clear vision. If these zonules weaken or break, the lens becomes unstable and shifts out of position.
This movement, known as lens luxation, can cause significant damage, leading to pain and potential blindness. When the lens moves freely inside the eye, it can increase intraocular pressure, potentially triggering glaucoma.
Lens luxation is an emergency condition and requires immediate veterinary treatment to prevent further complications and preserve vision.
What happens if lens luxation is not treated?
If the lens moves in front of the iris (anterior lens luxation), it can block fluid drainage, leading to a dangerous rise in intraocular pressure (glaucoma). This can cause severe pain and irreversible blindness. In advanced cases, if the damage is too great, surgical removal of the eye may be necessary to relieve pain.
If the lens shifts behind the iris (posterior lens luxation), the situation may not be an immediate emergency, but it can still lead to long-term retinal damage and glaucoma if left untreated. Regardless of the type, lens luxation requires prompt veterinary care to prevent serious complications.
What causes lens luxation?
There are two main reasons for lens luxation – primary or secondary.
Primary inherited lens luxation
- These patients are born with a genetic defect that results in a breakdown of the lens zonules.
- This usually occurs at a young age.
- The condition is common in the Terrier breeds but also occasionally seen in the Collie, German Shepherd, Shar Pei and other breeds.
- In dogs with primary lens luxation, both eyes are affected with the disease but it usually only manifests in one eye first.
- This means that if your dog is diagnosed with primary lens luxation in one eye, the second eye will become affected at some point in the future.
Secondary lens luxation
- The lens has displaced/slipped due to chronic inflammation inside the eye (we call this ‘uveitis’) or a high pressure inside the eye (‘glaucoma’) that has damaged the lens zonules (‘bungy jump strings’).
- This usually only affects the one eye.
What are the treatment options for lens luxation?
A: Best option: surgical removal of the lens under anaesthetic via large incision surgery.
B: Second best option: pushing the lens into the back of the eye with lifelong medical management.
- Pushing the lens into the back of the eye manually, usually requires sedation.
If lens luxation has occurred within the last two weeks, it may be possible to successfully push the lens to the back of the eye. This procedure is believed to work in 8/10 patients. If it does not work surgical removal of the lens will have to be considered.
- If the lens is already in the back of the eye, this is good as we will not need to push it back.
- Once the lens is in the back of the eye, then it is essential that the patient receives LIFELONG twice daily eye drops without fail. This drop is a drug that keeps the pupil small – which in turn ‘traps’ the lens in the back of the eye.
The chance that a patient retains sight in the eye ONE year down the line is approximately 50%
C: Third option If the lens is in the front of the eye and it cannot be pushed back and surgery (A) is not an option, then removal of the eye (enucleation) is the treatment of choice to provide pain relief.
What is the best treatment option fo subluxated lenses?
Subluxated lenses are lenses that are still in the correct place but are wobbly as some, but not all, of their ‘bungy jump strings’ (zonules) have snapped.a.
Best option: Removal by small incision in a similar way as cataracts are removed. This is the least traumatic way to remove an unstable lens from an affected eye.
This prophylactic small incision surgery has a high success rate and approximately 75% of patients are still sighted over 3 years after this operation.
Surgical removal of the lens via large incision surgery (as for option ‘a’ in fully luxated lenses) 50% of eyes having undergone this operation will remain sighted 2 years down the line.
Medical management with eye drops to keep the pupil small. For dogs where surgery is not the best option, an alternative approach focuses on keeping the lens stabilized at the back of the eye as it becomes more unstable. To achieve this, miotic eye drops (which constrict the pupil) are prescribed to help prevent the lens from shifting forward.
Strict Medication Schedule Is Crucial
These eye drops must be administered at least twice daily without fail. Missing a dose can cause the pupil to widen, increasing the risk of the lens becoming fully dislodged and luxating into the front of the eye (anterior lens luxation). If this occurs, the lens can become stuck, leading to sudden pain, increased intraocular pressure (glaucoma), and potential vision loss. By following a strict medication routine, this approach can help delay or even prevent complications, keeping your dog comfortable and preserving vision for as long as possible.
The success chances of this medical management of lens instability are unclear.
Long-Term management of Lens Luxation
Whether your dog’s lens luxation is treated with medication or surgery, there remains a significant risk of developing glaucoma (increased intraocular pressure) in the affected eye over time. This is because the displaced lens can obstruct fluid drainage, leading to pressure buildup. Fortunately, with early intervention and ongoing management, glaucoma can often be successfully controlled for several years using medications, laser therapy, or drainage implants to maintain normal eye pressure and preserve vision.
Lifelong monitoring and treatment
All dogs diagnosed with lens luxation will require regular veterinary check-ups and lifelong medication to optimize treatment, prolong vision, and ensure they remain pain-free. Ongoing monitoring is essential to detect any pressure changes or complications early, allowing for prompt adjustments to the treatment plan.
Personalised treatment approach
The decision between medical management and surgery depends on multiple factors, including your dog’s specific condition, overall health, and your lifestyle. Your veterinary ophthalmologist will work closely with you to determine the best course of action, providing expert guidance based on experience and the latest advancements in eye care.
While choosing the right treatment path is not always black and white, our goal is to help you make the best decision for both you and your dog, ensuring the highest quality of life and comfort for as long as possible.