The lens of the eye is a transparent structure that helps to focus light on the retina. Lens luxation occurs when the lens is either partially or completely dislocated from its normal position. This can result in serious complications for pets, including persistent glaucoma, retinal detachment, and blindness.
Here we will look at the causes, symptoms, and treatments of lens luxation in dogs and cats.
Causes of Lens Luxation
The causes of lens luxation are either primary or secondary.
- Primary lens luxation is an inherited defect that causes zonule degeneration. Zonules are fibrous strands that hold the lens in place in the eye. Primary lens luxation usually occurs in both eyes. It is rare in cats, but it is commonly seen in terrier dog breeds as well as the Australian Cattle Dog, Border Collie, and Chinese Shar-Pei.
- Secondary lens luxation typically occurs with other eye disorders. Common eye disorders that cause zonule breakage include glaucoma, tumor, injury or trauma, anterior uveitis (inflammation of the iris and surrounding structures), and collagen disorders. It can also be idiopathic, meaning that the cause is not known.
When zonules break due to primary or secondary causes, the lens can either become completely dislocated or partially dislocated. If the lens becomes completely dislocated, it will either move forward through the pupil into the front chamber of the eye (anterior luxation) or into the rear chamber of the eye (posterior luxation). If the lens is partially dislocated -- which is referred to as subluxation -- it remains in a normal or somewhat normal position in the pupil.
Symptoms of Lens Luxation
Symptoms can vary depending on the type of luxation. Anterior luxations may appear obvious while subluxations and posterior luxations may be more difficult to identify. Common symptoms include:
- Change in appearance of the eye (abnormal lens position, eye may turn white)
- Aphakic crescent (an area of the pupil where the lens is missing)
- Inflammation within the eye
- Clouding in the eye
- Squinting or holding the eye(s) closed
- Iris or lens trembling
Treatment of Lens Luxation
Contact your veterinarian if your dog or cat is exhibiting any of the above symptoms. They will perform a thorough ocular examination as well as a series of tests to rule out other possible problems (such as corneal ulcers), check your pet’s vision, detect glaucoma, and determine the underlying cause of the condition.
Treatment will ultimately depend on the location of the dislocated lens, your pet’s vision potential, and whether or not glaucoma is present. Most luxations are considered emergencies and need to be treated immediately (within 48 hours), or else the pet could become permanently blind. Posterior luxations -- those that fall into the back of the eye -- usually do not cause discomfort and may not require any treatment.
Treatment for anterior luxations (those in the front chamber) may include:
- Glaucoma must be controlled and the intraocular pressure lowered immediately. This is typically achieved with oral or topical antiglaucoma medications, topical anti-inflammatory medications, and osmotic agents.
- Anterior luxations are usually best treated with surgery. Surgery is only carried out if the glaucoma is under control, the rest of the eye looks healthy, and the pet has the potential for vision. The procedure involves removing the dislocated lens through a small incision in the eye.
- If anterior uveitis is present, it will be treated with oral or topical anti-inflammatory medication such as Carprofen.
- The pet’s entire eye may be removed (enucleated) if the eye is blind or painful.
- The eye can also be eviscerated (the internal contents removed) and an artificial eye inserted.
Contact your veterinarian immediately if you suspect that your pet is suffering from an eye disorder.
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