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Cataracts in the Dog

Bartholomew,Daisy

We see a lot of patients of all species that present with a complaint of cataracts in either or both eyes. I decided to post our owner information sheet that we give out if cataracts are present and cataract surgery is a consideration. A few basic points that I thought I would stress. 1) Nuclear sclerosis is an old aging change of the lens where the lenses appear grey but are not truly opaque and are often misconstrued for cataract. This is an increase in density of the lens that we see commonly in older patients. 2) Cataracts are not just an old aging change! We see many young dogs that present with cataract that are genetic in basis and occur at an early age (3-6 years). 3) Cataracts can present rapidly and may be associated with an inflammatory response or conversely, intraocular inflammation can cause cataract formation. 4) Age does not preclude anesthesia and successful cataract removal! It is an elective surgery, however, I have plenty of old dogs that were behaving like older dogs because of vision deficits that “are acting like puppies again” after having the cataracts removed. Hopefully the following information will help if you or your veterinarian see cataracts in your dog and are referred for possible cataract surgery.

Definition:

Cataracts are opacities in the lens of the eye. Although some people mistakenly think the cloudiness is on the surface (a “film on the eye”), it is actually a physical change within the lens which is deep inside your pets eyeball. A cataract may be very small and insignificant or can involve the entire lens and cause vision loss.

Insignificant incipient cataract

Insignificant incipient cataract

Why did your dog get cataracts?

Many cataracts are inherited and are found in breeds such as the Cocker Spaniel, Bichon Frise, Poodle, Siberian Husky, Miniature Schnauzer, Golden Retriever, Labrador Retriever and a number of terrier breeds. Other causes of cataracts include those secondary to Progressive Retinal Atrophy (PRA), diabetes mellitus, trauma, inflammation, geriatric change or puppy milk replacers. Many cataracts will worsen to the point of blindness but certain types, especially in the Retrievers, can remain small for the entire life of the pet. Cataracts are not limited to old dogs, especially the genetic based ones that can develop at an early age.

Lens-induced Uveitis:

A local inflammatory reaction inside the eye due to the development or progression of a cataract (lens-induced uveitis) can occur and is not uncommon. This can occur immediately upon the development of a cataract if this process is rapid (Bichon Frise commonly do this) or due to slow release of the liquefied lens proteins outside the lens capsule. This reaction can result in many complications such as retinal detachment, glaucoma, intraocular hemorrhage and scar formation.

Topical medications to control or prevent this inflammation are commonly utilized if inflammation is apparent or for prophylaxis of this inflammation if progression is suspected. These medications have no effect on cataract development but are used only to control or prevent this inflammatory reaction while you decide if surgical intervention is appropriate for your pet. This must be controlled prior to scheduling surgery if present. Unfortunately, some eyes become so inflamed that adhesions form, the cornea becomes compromised or other changes occur that can preclude successful surgery. Our goal at that point is to try and keep the eye comfortable.

Iris adhesion to lens from inflammation

Iris adhesion to lens from inflammation

How are cataracts treated?

Small cataracts do not warrant any intervention. We typically document the size and location and follow for progression if that possibility is suspected. Many cataracts are very small and are in a location that does not create worry and thus routine follow-up may be limited to your annual visits with your primary care veterinarian.

Treatment of significant cataracts is surgical removal of the lens with implantation of a man-made lens to return visual acuity back to normal. This is an elective procedure that is performed if you think improvement in vision will improve your pet’s quality of life. The procedure may be performed in one or both eyes depending on the specifics of each pet.

Prior to performing surgery, your pet may need to have special tests performed to evaluate the health of the retina (the “film in the camera”). An electroretinogram is like an EKG for the eye and evaluates retinal function. An ultrasound is utilized to detect any retinal detachment. These two tests are not painful, are usually performed without sedation and have virtually no risk associated with them. The tests take approximately 40 minutes to perform and we get the results immediately. If your pet does not pass these tests, removal of the cataracts may not be indicated and surgery would not be performed. These tests are not done on the day of surgery in this practice in case they fail. If the tests are successful, then surgery can be scheduled if your veterinarian confirms that anesthetic risk is low. Routine blood tests in addition to a physical exam will be advised for your veterinarian to assess this risk.

Normal ERG in a dog with cataracts

Normal ERG in a dog with cataracts

Cataract on the left, normal clear lens on the right

Cataract on the left, normal clear lens on the right

The surgery is performed under general anesthesia. The anesthetics are state-of-the-art medications that are used in human hospitals. Blood pressure, pulse rate, oxygen level, blood and respiration are monitored by a technician throughout the surgery. We make every effort to avoid complications but as with general anesthesia in any species, risks including death do exist.

Routine cataract surgery is performed using high-frequency ultrasound power to break the lens up into small pieces which are concurrently vacuumed out of the eye. This process is called phacoemulsification. This is performed through a small 3mm incision and is performed in over 95% of our patients. Phacoemulsification is the same technique performed for human cataract removal. Many people believe that cataract removal is done with a laser but that is not true for the primary cataract. After removal of the cataract, a new man-made lens is implanted to bring their visual acuity back to normal. We currently use foldable acrylic lenses that can be implanted through the same small incision. Although lens replacement is routine, it is sometimes inappropriate or impossible to implant a lens due to tears in the lens capsule or a breakdown of lens ligments which does not allow support of the new lens. Vision without a lens (aphakic vision) can be surprisingly good in dogs. Their view is now unobstructed by the cataract but out of focus due to the loss of the lens.

Phacoemulsification of the cataract

Phacoemulsification of the cataract

Cataract surgery is elective and requires a significant time commitment on your part. Eyedrops must be administered before and after surgery. These drops may be as high as 4 times a day for the first week but taper quickly over the next 2 weeks barring complication. The patient must wear a protective plastic collar for 2-3 weeks after surgery to prevent self-trauma. Postoperative checkups are usually performed the next day, one week after surgery, two weeks later and one month after that. At the time of the third postop exam, the protective collar is usually removed. Long term checkups are made about 4 months after surgery and then two times annually thereafter. Some dogs may need a drop a day continually as maintenance but many do not if inflammation and pressure are normalized. Expect to be medicating for at least 4-6 months after surgery. The success rate is over 90% but as with any surgery, there are risks.

Implanted intraocular lens after cataract surgery

Implanted intraocular lens after cataract surgery

What are the complications of cataract surgery?

There are five major complications of cataract removal: 1) Intraocular inflammation will occur due to the surgical trauma and thus most of the medications before, during and after surgery are geared towards controlling this reaction. Inflammation is the linchpin of most complications and is evaluated at every recheck. 2) Glaucoma is increased pressure inside the eye and can occur at any point after surgery. Mild to moderate elevations in pressure can be treated, but if the pressure goes up and stays up, irreversible vision loss can occur. This is the worst complication because it creates a painful blind eye that may require removal if uncontrolled. The general risk is 4%. 3) Retinal detachment is a painless blinding condition that carries a 2% complication rate. This can occur if a tear in the retina is created and the retina is pulled off or if inflammation pushes it off. Reattachment surgery is not common but is currently being performed by only a handful of specialists in the US. 4) Cataract regrowth can occur in 2 forms. Lens material may form globules that can contribute to inflammation. This is most common in young animals. The capsule that is left behind and houses the man-made lens commonly has or develops cataract as well. This regrowth is seen in basically all dogs but may not contribute greatly to vision impairment. Rarely is any surgical treatment required for either of these two entities. 5) Intraocular infection is a rare complication but is disastrous if it occurs and usually leads to loss of the eye.

I hope this information is helpful as you investigate cataracts and cataract surgery in the dog. A nice video clip is in the Helpful Resources section that has some images of the procedure, client testimonials and other tidbits that may be of value. As always, feel free to call the clinic and set up an appointment if you would like your friend evaluated.

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