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As our four-legged friends get older, the potential for eye-related problems increases and our pooches find themselves at the vet’s office more and more.
We all want to keep our furry friends “bright-eyed and bushy-tailed,” but how can we protect them from factors that we have no control over, such as genetics or old age?
Dislocated eye lens, or lens luxation, occurs when the “Lens capsule separates 360 degrees from the zonules (the fiber-like processes that extend from the ciliary body to the capsule of the lens of the eye) that hold the lens in place, resulting in the total dislocation of the lens from its normal location,” according to petmd.com.
Lens luxation typically occurs when zonules become weakened or stretched, and the separation can be complete or partial. However, if the lens detaches from the zonules completely, it is a luxated lens, but if the lens only detaches partially, it is known as a subluxation, according to cedarvethospital.com.
What Causes Lens Luxation?
According to petmd.com, there are a variety of factors that can lead to lens luxation in dogs. Tumors in their eyes may push the lens out of position or cause chronic inflammation, which can lead to zonular degeneration.
Trauma rarely causes a normal lens to become dislocated, but it can occur if your pooch has severe uveitis, or swelling and irritation of the uvea, the middle layer of the eye.
“Primary lens luxation is an inherited disorder in which the zonules or suspensory fibers degenerate. Typically both eyes are prone to dislocation in this case. The condition occurs mainly in the Terrier breeds, but can occur in other breeds sporatically,” according to petplace.com.
Here are a few of the breeds that are prone to primary lens luxation according to cedarvethospital.com and petplace.com:
Parson Russell Terrier
Australian Cattle Dog (blue heeler)
In contrast, secondary lens luxation usually occurs after some type of eye disorder and may only involve a single eye. Here are a few of the disorders that may be associated with secondary lens luxation:
Anterior uveitis (an inflammation of the iris and adjacent structures).
Glaucoma and enlargement of the eye with breakage of the zonules.
Trauma to the eye.
Disorders that affect the strength of collagen such as Ehlers-Danlos syndrome, which result in weakening of the zonules.
Congenital (present at birth) deformities of the lens.
Idiopathic luxations, which means there is no known cause.
What are the Symptoms of Dislocated Eye Lenses?
A tumor in the eye may physically move the lens out of position or cause chronic inflammation, leading to zonular degeneration.
The inheritence pattern of primary luxation is uncertain, but it may occur concurrently with primary glaucoma in some breeds.
Trauma rarely causes a normal lens to luxate, though it can occur when there are signs of severe uveitis, especially chronic lens-induced uveitis, or hyphema.
These are the four main types of lens luxation in dogs according to petmd.com:
Subluxation - partial separation of the lens from its zonular attachments; the lens remains in a normal or near-normal position in the pupil.
Primary luxation – due to a pathologic alteration in the ciliary zonules, including abnormal development or degeneration; may be bilateral (both eyes).
Congenital luxation – often associated with microphakia (abnormally small lens of the eye).
Secondary luxation – due to rupture or degeneration of the ciliary zonules as a result of chronic inflammation, buphthalmia (increase of intraocular fluid and consequent enlargement of the eyeball), or a tumor within the eye.
Here are a few of the symptoms that you should keep an eye out for, according to petmd.com and petplace.com:
Sudden change in the appearance of the eye; it may appear to turn white.
Pain, with squinting, holding the eye closed, and increased tearing.
Uveitis or inflammation within the eye (redness and cloudiness).
Acute or chronically painful reddened eye with diffuse corneal swelling, especially if glaucoma is also present, or the luxation is in the front of the eye.
Iris trembling (iridodonesis).
Lens trembling (phacodonesis).
Abnormally shallow or deep anterior (front) chamber.
Abnormally positioned clear part of the lens.
Aphakic crescent — an area of pupil devoid of the lens.
How are Dislocated Eye Lenses Diagnosed?
Your vet may recommend a complete medical history and physical examination, along with a thorough eye exam, because there are several possible causes for luxation.
“Visual diagnostic techniques may be used to diagnose the cause of the luxation. Thoracic X-rays and abdominal ultrasound may be indicated if the luxation is secondary to an intraocular (within the eye) tumor, and ocular ultrasonography is useful if corneal edema (swelling) or cloudy ocular media prevent a useful examination,” according to petmd.com.
According to petplace.com, here are a few of the diagnostic tests that your vet may adminster when you bring your pooch in:
Thorough eye examination.
Fluorescein staining to rule out corneal ulcers.
Tonometry to detect glaucoma or low intraocular pressure (IOP).
Examination with a slit lamp to localize the position of the lens and the depth of the anterior chamber.
Assessment of the front portion of the eye for signs of inflammation (uveitis).
Examination of the retina.
A complete blood count and serum biochemistry tests.
Serology/immunologic tests for the various causes of uveitis in dogs.
Electroretinogram (ERG) to assess the potential for vision in animals with glaucoma.
How are Dislocated Eye Lenses Treated?
According to petplace.com and petmd.com, there are a few ways to treat lens luxation in your pooch:
Control of glaucoma - IOP (pressure within the eye) must be lowered immediately within a few hours with osmotic agents, topical or oral antiglaucoma medications, and topical anti-inflammatory agents.
Surgical removal of the lens – utilized if the lens is in the front chamber of the eye, especially once the glaucoma is under control.
Control of the anterior uveitis - treatment of uveitis often involves the use of topical anti-inflammatory agents, and oral anti-inflammatory agents such as carprofen.
Enucleation or removal of the eye - may be necessary if the eye is blind and painful.
Alternative to enucleation - For blind dogs, evisceration or removal of the interior contents of the eye and insertion of a black prosthesis inside the eye may be considered.
Can I Prevent My Dog from Getting Dislocated Eye Lenses?
Sadly, most cases of lens luxation cannot be prevented and it is recommended that affected dogs not be used for breeding purposes.
Find A Vet HOW TO articles are intended for informational purposes only. You should always consult with your veterinarian about any health issues affecting your dog.
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