What are cataracts?
A cataract is a clouding of the normally clear lens of the eye. The lens is enclosed within a clear sac (the lens capsule). A cataract is not a film or coating on the eye, but a fogging of the contents within the lens. When a cataract develops, partial or complete loss of vision may occur. Clouding of the lens may affect a small portion of the lens, or the entire lens. If the cataract progresses, the pupil, which normally appears black, may undergo noticeable color change and appear to be bluish or white.
all cataracts lead to blindness. The cataract can progress slowly (over many
years) or very rapidly (sometimes leading to blindness within a few days or
What causes cataracts?
There are many types
of cataracts. While
cataracts in humans are generally associated with aging, cataracts are seen in
animals of all ages, even in newborns.
In dogs, inherited cataract
is a major cause of cataracts, and can cause blindness in dogs as young as 1-4
years of age. Dogs with a genetic predisposition for cataract development include the Cocker Spaniel, Poodle,
Siberian Husky, Schnauzer, Old English Sheepdog, Samoyed, Golden Retriever,
Labrador Retriever, Maltese, Boston Terrier, and Yorkshire Terrier.
common causes for cataract formation include diabetes, aging, trauma, and
secondary to retinal degeneration.
What you should do if a cataract is suspected ...
If decreased vision or clouding of the eye is noticed by you or your veterinarian, your pet should be examined by a veterinary ophthalmologist for a comprehensive eye examination. It is best to have your pet's eyes examined before the cataracts cause complete blindness, because then all of the intraocular structures (especially the retina) can be examined. Once diagnosed, minor cataracts will be rechecked periodically to see if they progress, and antiinflammatory drops may be prescribed to reduce inflammation caused by the cataract.
vision is impaired or if the cataracts are progressing, then cataract surgery
can be performed to restore/improve vision. Thanks to advances in
medications and surgical techniques, cataract surgery is now performed routinely
as outpatient surgery on thousands of veterinary patients each year.
What is cataract-associated inflammation?
When a lens becomes cataractous, some of the lens protein becomes liquefied, and may leak through the lens capsule into the eye. This will cause intraocular inflammation (uveitis) and is called cataract-associated intraocular inflammation (or lens-induced uveitis). This inflammation must be treated with anti-inflammatory drops, because otherwise the inflammation can cause complications such as glaucoma, retinal detachment, or the development of intraocular adhesions. If cataract surgery is being considered, it is especially important to keep the eyes uninflamed prior to cataract surgery, because preoperative inflammation can lower the success rate for cataract surgery.
Even if a patient never undergoes cataract surgery,
anti-inflammatory drops are usually continued long-term to reduce chances of complications that might result from the
How are cataracts removed?
Surgery is the only effective way to remove the cloudy lens from the eye. There is no known medical or preventive treatment for cataracts. Eye drops, ointments, pills, special diets, vitamins, or eye exercises have not been proven to dissolve or reduce a cataract. Surgery is performed to remove the cloudy lens, and in many cases, an artificial lens is then implanted into the eye to restore normal vision.
Surgical removal of the cataract is performed under general anesthesia by making a small (2-3 mm) incision into the eye. A thick viscoelastic gel is injected into the anterior chamber to prevent the eye from collapsing during surgery, and to protect the inside of the cornea. A special needle-like ultrasonic instrument is then inserted into the lens. The needle tip vibrates at a very fast rate (about 40,000 vibrations per second), which ultrasonically fragments and removes the cloudy lens. This surgical procedure is called "phacoemulsification" and is the same technique used to remove cataracts in people.
During surgery, the cloudy lens is removed from the sack-like outer membrane (lens capsule). In most cataract surgery patients, an intraocular lens implant (commonly called an IOL) is then placed inside the emptied lens capsule to replace the eye's natural lens. The IOL is a tiny, lightweight, clear, plastic or acrylic disc, and restores normal vision to the eye. Unlike contact lenses that must be removed daily or periodically for cleaning, an intraocular lens implant is permanent.
In some patients, or in older animals, the lens attachments may be loose, or the lens may be too hard to be broken up with the phacoemulsification technique. In these patients, the entire lens (including the outer lens capsule) is removed, in which case an artificial intraocular lens implant cannot be placed inside the eye. These patients will still see after surgery, but their vision will not be as well-focused compared to patient with an intraocular lens implant. With time (several weeks or months), most of these patients adjust well to aphakic ("without a lens") vision, and have good functional vision.
Cataracts cannot be removed with a laser. Lasers are sometimes
used to improve vision by removing opacities within in the eye several weeks or
months after cataract surgery, but are not used to remove the cataract itself.
Should my pet have cataract surgery?
If your pet's quality of life is diminished due to decreased vision from cataracts, then cataract surgery can be performed to restore/improve vision. Few veterinary surgeries are as profound or as immediately gratifying as restoring a pet's vision through cataract surgery.
In the past, cataract
surgery was often delayed until the patient was completely blind. However, we
now know that cataract surgery is more successful if surgery is
performed sooner rather than later, for several reasons.
First, mature (complete) cataracts are more likely to cause intraocular
inflammation, which can cause vision-threatening complications before or after cataract
the surgery itself is more difficult when the cataract is mature, or has been
present for a long time (this causes the lens to become hardened, which makes
phacoemulsification more difficult).
Third, the normally-clear outer lens capsule may become
calcified when the cataract has been present for a long time.
This can make surgery more difficult, and can also cause decreased vision
after cataract surgery. However,
cataract surgery can still be performed successfully on many mature cataracts.
Is my pet a good candidate for cataract surgery?
Your pet's general health needs to be completely assessed before surgery to ensure that there are no internal problems that may interfere with a successful surgery, or that might increase the risk of general anesthesia. A preoperative physical examination and preoperative tests will be performed by your regular veterinarian (these tests will include blood and urine analysis, and sometimes chest x-rays, EKGs, or other procedures as recommended by your veterinarian). Age alone is not a deterrent to cataract surgery. With the use of modern anesthetic agents, surgery is successfully performed on dogs and cats as old as 17-18 years of age. Diabetic dogs are excellent candidates for cataract surgery, but their diabetes and any cataract-associated inflammation must be well-controlled before surgery.
There may be reasons for vision loss other than the cataract, especially conditions affecting the retina or the brain. An electroretinogram (ERG) is performed before surgery to ensure that good retinal function exists. An ocular ultrasound examination is performed to ensure that the retina is not detached. If the retina is not healthy, then cataract surgery is not performed (because the patient will not be able to see even if the cataract is removed). Some older patients are affected with cognitive disease (canine "Alzheimer's"). If cognitive dysfunction is present, cataract surgery may not improve vision at all, because the brain cannot process and interpret visual signals properly.
Your veterinary ophthalmologist will tell you if your pet is a good
candidate for cataract surgery or not.
Diabetes and cataract surgery
Diabetic cats rarely develop cataracts. However, most diabetic dogs (regardless of how well their diabetes is managed or how early the diabetes is detected) will develop diabetic cataracts and become blind, usually within 6-12 months of the onset of the diabetes. Most diabetic dogs are excellent candidates for cataract surgery, but their diabetes and any cataract-associated inflammation must be well- controlled prior to surgery.
If you have a diabetic dog, it is important that your pet be closely monitored for development of diabetic cataracts, so that anti-inflammatory treatment can be started as soon as the cataracts start to form. This is because diabetic dogs frequently develop rapid-onset cataracts, which can cause severe cataract-associated inflammation.
Cataract-associated inflammation must be treated with antiinflammatory medications to prevent complications (such as retinal detachment or glaucoma), and to ensure that the patient remains a candidate for cataract surgery (significant cataract-associated inflammation prior to cataract surgery is associated with a reduced success rate, any may even prevent cataract surgery from being performed).
Click here for more information on cataract-associated inflammation
Surgery on one eye versus two eyes
The decision on
whether to operate on one or both eyes is yours to make. At our hospital, cataract
surgery is usually performed on both eyes at the same time. Advantages of
operating on both eyes at the same time include:
Can cataracts return after surgery is performed?
the cataract is removed, it will not "regrow."
However, in all cataract surgeries, not all of the lens cells can be
removed from within the capsule. Sometimes
these lens cells will attempt to make new lens material, or will migrate across
the posterior lens capsule and cause mild cloudiness and wrinkling of this
capsule. This is similar to frost covering a window, and is called a secondary
cataract. In humans, secondary cataracts can be removed by
making holes in the posterior capsule with a laser.
However, intraocular lens implants usually prevent clouding of the lens
capsule, so that laser treatment is rarely necessary in dogs. Another
way to prevent secondary cataracts in dogs is to make a small hole in the
posterior lens capsule when cataract surgery is performed, so that the posterior
capsule cannot become cloudy.
What pre- and post-operative care is required for cataract surgery?
Before surgery, it is recommended that you train your pet to wear a cone collar, and become used to confinement. Exercise and barking must be completely restricted for at least 3-4 weeks after surgery (excessive activity and barking increase the risk for postoperative retinal detachment and suture breakage). Exercise restriction after surgery is best accomplished by kenneling your pet in a portable airline kennel, or confining your pet to a single room or part of the house.
Preoperative treatment consists of the application of anti-inflammatory eye drops, which are used once or twice a day for at least several weeks before surgery. Four days before surgery, drops are increased to 4 times daily. After surgery, oral medications (antibiotics and anti-inflammatory medication) are given twice daily, and eye drops are administered 4 times daily, for another 2 weeks. Eye drops are then continued, 1-3 times daily, for 4-6 months after surgery. The protective Elizabethan (cone) collar must be worn by the patient for 4 weeks after surgery.
In general, post surgical reevaluations are performed 1-2 days, at 1 and 4 weeks, and at 5-6 months following surgery. Periodic reexaminations are then recommended every year or so (based on the patient's progress).
you are unable to perform the pre- and postoperative treatments, return for
periodic reexaminations, if your pet will not accept limited activity
after cataract surgery, or permit you to apply medications to the eyes,
then cataract surgery is not recommended for your pet.
Success rates of cataract surgery
Specialized training, modern techniques, and advances in medications have greatly improved success rates in animals in the past 10 years. Fortunately, cataract surgery is usually successful, and 85-90% of patients who undergo cataract surgery regain useful vision.
One of the most important considerations in selecting a cataract surgeon for your pet is how many times the doctor has performed the surgery. Cataract surgery is the most common surgery performed at the Animal Eye Care Clinics. Dr. da Silva Curiel has performed several thousand cataract surgeries since beginning her career in veterinary ophthalmology in 1987.
For any patient, complications can occur during or after surgery, and a good result cannot be guaranteed. Certain breeds are more at risk for developing postoperative complications. For example, the risk of retinal detachment is slightly greater in the Boston terrier, Bichon Frise, and Havanese breeds, and Cocker Spaniels are more at risk for developing glaucoma.
For any intraocular surgery, there is always a slight risk of the development of complications such as infection, glaucoma, retinal detachment, chronic inflammation, or the formation of intraocular scarring. In general, surgical success rates are better for cataracts removed in uninflamed eyes, or in the earlier stages of cataract formation.
Surgical success rates are reduced in patients with advanced ("hypermature") cataracts, or in patients in which the eye has been significantly or chronically inflamed before surgery. In some of these patients, retinal cryopexy is sometimes recommended prior to cataract surgery. Retinal cryopexy involves freezing several sites in the peripheral retina - this creates small scars in the peripheral retina to "spot-weld" the retina into place, which can reduce the chances of the retina detaching after cataract surgery.
Sometimes cataract removal does not result in complete improvement in vision, because sight is dependent on many other factors (such as the health of the retina and optic nerve, normal brain function, and if other presurgical eye diseases are present). Rarely, complications will require that additional surgical procedures be performed. Complications are uncommon, and it is not possible to predict if they will occur.
can improve the chances of a successful outcome of cataract surgery for your pet by
following all pre-and postoperative medication instructions and treatments,
returning for postoperative reexaminations, and by calling us immediately if you
notice any postoperative problems, or have any questions about your pet's
What does cataract surgery cost?
The cost of surgery
is variable, depending on whether one eye or both eyes are operated on.
The surgical fee includes the first two postoperative examinations. The costs
of preoperative laboratory testing, medications, additional postoperative examinations,
and treatment of postoperative
complications are not included.
Su-Ling is a delightful ShihTzu dog who has diabetes, and consequently developed diabetic cataracts. Su-Ling had cataract surgery performed at the Animal Eye Care Clinic in February 2003. In gratitude for being able to see again, Su-Ling commissioned her human companion, Patricia Varnum of Nipomo CA, to make a beautiful quilt for the Animal Eye Care Clinic. This quilt depicts Su-ling and five canine companions brightly gazing out at the world! "Su-Ling's" quilt is proudly displayed in our hospital's reception area. Click here to see Su-Ling's quilt.
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