What is a Cataract?
Like a camera, eyes have a clear lens inside them that is used for focusing. A cataract is any opacity within a lens. The opacity can be very small (incipient cataract) and not interfere with vision. It can involve more of the lens (immature cataract) and cause blurred vision. Eventually, the entire lens can become cloudy, and all functional vision lost. This is called a mature cataract.
What is not a Cataract?
All geriatric dogs develop a hardening of the lens (Nuclear Sclerosis) that causes the lens to have a blueish-grey appearance. This does not usually interfere with vision. This is commonly confused with a true cataract but is a normal part of the ageing process.
Why did my dog develop a Cataract?
- Most cataracts in dogs are inherited. The cataract may develop rapidly over weeks, or slowly over years, in one or both eyes.
- Like humans, dogs also develop cataracts with age (often after 8 years of life).
- Cataracts can also develop in dogs with diabetes mellitus or in orphan puppies on an artificial milk replacer diet.
How are Cataracts treated?
Once a lens has developed a cataract, there is no known method to make the lens clear again. There are a number of products marketed on the Internet for treating cataracts - despite the claims made there is no evidence that these expensive medications are useful. Immature and mature cataracts can be treated by surgically removing them.
The procedures and equipment used to remove cataracts in dogs are the same as those used in humans. A small incision is made in the eye and a hole is made in the capsular bag that holds the lens. Phacoemulsification is then performed, in which a special probe ultrasonically emulsifies and removes the cataract. After the entire lens is removed, an artificial replacement lens, called an intraocular lens or IOL, is sometimes placed in the bag. The eye is closed with extremely small sutures. Because even the slightest damage to structures in the canine eye can have disastrous effects, the surgery is performed under high magnification using an operating microscope. If both eyes are affected, both eyes can often be operated on at the same time.
How well will my dog see after Cataract surgery?
After successful cataract surgery dogs can often see close to normal. However, we cannot give dogs perfect vision. This is because only a handful of different IOLs are available for dogs and an exact replacement of the original lens is not possible. Furthermore, dogs have more inflammation in their eyes after surgery than humans and therefore have more scaring. This scaring may slightly decrease vision. Most owners notice a tremendous increase in their pets vision after cataract surgery, but they can still detect certain visual difficulties. These are particularly close vision and are more marked where it has not been possible to place an IOL.
After surgery, cataracts cannot recur. However, some dogs can have decreased vision years after cataract surgery due to formed scar tissue, glaucoma, or retinal detachment. In those dogs where it is not possible or advisable to use an IOL these dogs still see better, but are more far-sighted and close objects are more out of focus. The cornea does two thirds of the focusing of the eye, so vision is still present but not perfect if the lens (which does one third of the focusing) cannot be replaced.
Why is Cataract surgery so expensive?
Cataract surgery can cost as much as £2000-3000 per eye. The total cost depends in part on any complications present prior to surgery or arising after surgery but also on how quickly the eye recovers from surgery. Some patients will be off of all treatment by one month after surgery whilst other patients may require treatment for the rest of their lives. The surgery requires specialized, and expensive, equipment and training. The instruments used for cataract surgery in dogs are the same instruments used for cataract surgery in people. Furthermore, you are paying for the advanced training of a Veterinary Ophthalmologist.
What if Cataract surgery is not done?
Immature and mature cataracts can cause a serious reactive inflammation inside the eye (Lens Induced Uveitis, or LIU) that must be medically treated, whether or not surgery is performed. Cataract surgery is an elective procedure. If surgery is not performed, lifetime anti-inflammatory eye drops may be required, as well as periodic eye re-examinations. LIU can lead to complications such as glaucoma or a detached retina, and LIU decreases the success rate of cataract surgery. There is a best window of time in which to perform surgery. The earlier the cataract can be removed, the better.
What is involved in having Cataract surgery performed on my dog or cat?
The first step is to have your pet examined by one of the three Ophthalmologists at the eye clinic to determine if your pet is a good candidate for surgery. A pre operative blood profile, comprehensive physical exam, and assessment of anaesthetic level of risk is then performed. If your pet "passes" these tests, electroretinography (ERG) and gonioscopy testing is scheduled at our clinic, as inpatient procedures. They are performed under sedation or a short general anaesthetic, and cause no discomfort. ERG testing evaluates retinal function, as it is vital that the retina (the "film in the camera") is working, in order to perform cataract surgery. Gonioscopy evaluates the drainage angle of the eye to determine if the eye(s) are at increased risk of developing glaucoma postoperatively. If they are, additional medications will be prescribed and these medications may be administered for your pets lifetime. Ultrasonography of the eye(s) is also performed to measure the size of the lens and to look for complications such as a pre-existing retinal detachment. If your pet "passes" the ERG test, surgery can be scheduled. The eyes require at least seven days (and ideally 14 days) of medication immediately preceding the surgery day. On the day of surgery, your pet will need to arrive at the clinic early in the morning to receive intensive eye treatment before surgery. The surgery is performed and your pet is then hospitalised at our Veterinary hospital at Bradley Stoke for 2-3 days after surgery for continued intensive medical treatment and observation. It is sometimes necessary for repeat anaesthetics to be required during this period to address any complications which may arise. Your pet will not have eye patches. Vision usually improves during the first week but can be expected to improve over a 4-5 week period. Most dogs exhibit no pain after surgery. Your pet will require oral medication and several kinds of eye drops three to six times a day for the first few weeks after surgery, and on a lesser frequency for several months post surgery.
Your pet may be required to wear a cone-shaped restraint collar (E collar) the first two weeks after surgery to prevent self-trauma to the eyes. We also ask that you bring your pet back for re-examinations at one week, two weeks, one month and three months post and every six to twelve months thereafter. This re-examination schedule may change if there are post-operative complications.
What are the risks involved with Cataract surgery?
Cataract surgery is a highly successful procedure, but there are risks. Chances of your pet having improved vision after surgery are often high (85-90%). But 10% - 15% of dogs will not regain good vision due to complications, and may actually be permanently blind in one or both of the operated eyes. Some cases will have additional risk factors which make this success rate over optimistic - the Ophthalmologist will discuss these if they are identified during the pre-operative screening process. Common complications include:
- Scar tissue. All dogs develop some intraocular scar tissue. Excessive scar tissue will limit vision.
- Glaucoma. Glaucoma (increase in eye pressure) occurs in up to 30% of all dogs who have cataract surgery. Glaucoma not only can cause complete vision loss, but also may require the need for additional medications or surgery. It can be painful and cause LOSS OF THE EYE if uncontrolled.
- Retinal detachment. While re-attachment is sometimes possible, the success rate is low and this complication usually results in complete vision loss.
- Intraocular Infection. While it is rare, it can cause LOSS OF THE EYE (i.e. surgical removal of the eye) as well as complete vision loss.
Therefore, your pet has these risks if Cataract surgery is performed:
- Development of a complication. This could result in poor to no vision, or in the most severe case surgical removal of the eye (which is rare).
- General anesthesia. Anesthesia safety has progressed tremendously during the last decade. However, even healthy pets CAN DIE UNDER GENERAL ANESTHESIA. We take anesthesia seriously and use only the latest and safest medications at our clinic. All pets are monitored extensively by our surgical staff.
Although the thought of complications can be worrying the potential benefits of returning vision to a much loved pet can be enormous.