Cataracts are opacities that form in the lens of the eye, leading to visual impairment or blindness. They can occur in dogs due to various reasons, including age-related changes, genetic factors, trauma, toxins, dietary deficiencies, and diabetes mellitus. Understanding the nature of cataracts and available treatment options is crucial for pet owners.
Anatomy of the Lens
The lens of the eye is responsible for focusing light onto the retina, allowing animals to see. It is normally clear and suspended by tissue fibers (zonules) just inside the pupil. As animals age, the lens becomes more compact with fibers, leading to a cloudy-eyed appearance in older dogs, known as nuclear sclerosis. However, nuclear sclerosis does not affect vision and is not considered a cataract.
Cataracts and Diabetes Mellitus in Dogs
Cataracts can be caused by various factors, including diabetes mellitus in dogs. In diabetic dogs, excess sugar in the eye fluids leads to the production of sorbitol within the lens, drawing water into the lens and causing an irreversible cataract.
Symptoms and Diagnosis
Cataracts appear as opacities in the lens, and an affected pet may show signs of vision loss. However, it's essential to differentiate cataracts from other eye conditions that may cause cloudiness on the cornea. A complete eye examination by a veterinarian or veterinary ophthalmologist is necessary for an accurate diagnosis.
Why is it Bad to Have a Cataract?
Cataracts can cause partial or complete blindness in one or both eyes. In some cases, cataracts can luxate, moving out of their normal position and leading to complications such as glaucoma or blockage of fluid drainage, causing pain and permanent blindness. Long-standing cataracts can begin to dissolve, causing inflammation (uveitis), which can lead to glaucoma.
Treatment Options
Cataract treatment typically involves surgical removal or physical dissolution under anesthesia. Surgery is invasive and expensive and is only considered when it can restore vision or alleviate pain. Pets with one normal eye may not require surgery if the other eye has a cataract and vision in the unaffected eye is good.
Determining Eligibility for Cataract Removal
A pet must be in good overall health to undergo surgery, and diabetic dogs should have their condition well-regulated before surgery. A good candidate for surgery should also have a temperament suitable for receiving post-operative eye drops. Various tests, such as an electroretinogram and ultrasound, are performed to assess retinal function and look for retinal detachments.
Types of Cataract Removal Surgery
Cataract removal can involve surgically cutting into the eye and physically removing the lens (lens extraction) or using phacoemulsification, which involves breaking apart the lens using sound waves and suctioning it out. An artificial lens is usually implanted after cataract removal to improve vision.
Complications and Success Rate
Some degree of inflammation (uveitis) is common after cataract surgery, and pre-operative anti-inflammatory eye drops may be prescribed to reduce inflammation. Other complications include opacities on the remaining lens capsule, bleeding, and glaucoma. The overall success rate of cataract surgery is approximately 95 percent immediately after surgery, with about 80 percent having long-term vision success.
Living with Untreated Cataracts
A cataract alone may not require treatment, and a blind pet can still have a good quality of life with proper care and a familiar environment. However, some animals may become anxious or aggressive when they lose their vision, and restoring vision may be considered. Eye drops containing N-acetylcarnosine have been marketed to dissolve cataracts, but they do not have this effect on mature cataracts.
Cataracts can lead to vision loss or blindness in dogs. Timely diagnosis and evaluation by a veterinarian or veterinary ophthalmologist are crucial. Cataract removal surgery can restore vision and improve a pet's quality of life in suitable candidates, but it is essential to consider the potential risks and expenses associated with the procedure. Consulting with a veterinarian can help pet owners make informed decisions about the best course of action for their furry companions.
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