Cataract surgery is one of the most common surgical procedures performed today in veterinary ophthalmology. The success rate is listed as greater than 90%. Specialty training and specialized surgical equipment and techniques have improved the success of canine cataract surgery.
WHAT IS A CATARACT?
Mature cataract and lens-induced uveitis
Cataract is an opacity of the lens. The lens is a crystalline structure that sits behind the iris and is seen in the pupil. The lens focuses light to the back of the eye onto the retina that is like the film of a camera. A camera needs to have a clear path of light to register an image onto the film. The eye must equally be crystal clear from the front of the eye to the back of the eye to register an image onto the retina. Cataracts prevent the transmission of light and with time can blind your pet.
IS MY DOG A GOOD CANDIDATE FOR CATARACT SURGERY?
An initial consultation and examination are required before any surgery is performed.
Many dogs are presented for cataract evaluation and actually have other conditions that need to be addressed.
Pre-operative testing is performed on each potential cataract surgery candidate.
CBC, blood chemistries and T4 need to be performed prior to any anesthesia. If blood tests have been done within the last 6 months by your regular veterinarian please have them fax a copy to our facility. If the dog is older than 10 years of age please have your regular veterinarian take a radiograph of the thorax (chest) and call us with the results.
Electroretinography (ERG), gonioscopy and ocular ultrasound and ultrasound biomicroscopy are some of the pre-operative tests performed. Electroretinography measures the electrical activity of the retina. A contact lens electrode is placed on the eye and two small needles are placed under the skin near the eye and the base of the ear. If your dog has normal retinal function we will see the results immediately on the computer. If the waveforms are reduced or non-existent your pet may have Progressive Retinal Atrophy (PRA) and surgery may or may not not be recommended.
Should I consider cataract surgery for my PRA-affected dog? Should my dog get an ERG before deciding on cataract surgery to assess if there is good retina behind the cataracts?
In the past, conventional wisdom was a dog with PRA was not a candidate for cataract surgery, because its retina would not be capable of useful vision even if the cataract surgery were technically successful. This assumed two premises, which were generally accepted as true at the time. First, cataract surgery should be delayed until the cataracts were mature, and the dog was essentially blind from the cataracts. Second, complications from surgery were frequent, and success rates were “modest.” However, things have changed. Success rates are higher, complication rates are lower, and the restoration of vision is better. So, a dog with PRA may in fact be a good candidate for such surgery. The decision for surgery comes down to cost vs. benefit. It could be argued that a dog with a late onset, slowly progressive form of PRA, such as prcd, and with a cataract interfering with central vision, should be considered for cataract surgery in order to best preserve whatever vision it has for as long as possible. Whether this makes financial sense is a decision for the owner. An ERG, done in a reliable fashion by an expert, will provide more information for making a fully informed cost/benefit decision regarding surgery. If the fundus (retina seen at the back of the eye) is visible, then an ERG should not be necessary. But if the fundus is not visible because the cataract is mature, then a good ERG can be useful. If surgery is considered, doing it before the cataract is mature is most helpful. Gonioscopy utilizes a contact lens prism allowing us to visualize the drainage angle of the eye. If abnormal this could indicate a potential for glaucoma post-operatively, which is blinding and painful. Finally ocular ultrasound utilizes a piezoelectric ultrasound probe that is non-invasive and provides detail of the anatomy of the eye. We cannot see beyond the lens due to cataract. This tells us if there is a retinal detachment or any other abnormalities we need to know about before doing cataract surgery. Ultrasound Biomicroscopy (UBM) uses a 35 MHz probe and gives us a detailed view of the anterior structures of the eye including the iridocorneal angle and ciliary cleft (both needed to assess your dog for glaucoma). This affords a more accurate assessment of the potential for glaucoma than gonioscopy. A copy of results is given to you upon your pet’s release and findings will be discussed with you. As well a written report will be provided with an assessment of all findings. Overall, careful examination determines which of these pre-operative tests are recommended.
WHAT IF MY DOG IS A GOOD CANDIDATE FOR SURGERY?
Cataracts cause inflammation in the eye and your dog should be treated with anti-inflammatory topical medications at least 2 to 4 weeks before cataract surgery.
Owners often want to operate as soon as possible but intraocular inflammation during surgery can be detrimental to a positive outcome. Topical glucocorticoid and non-steroidal anti-inflammatory medications are used pre-operatively. Diabetic patients need to have their blood glucose carefully monitored by your regular veterinarian in case the blood glucose becomes elevated. If the blood glucose increases then there may be a need to increase the insulin dosage under the direct supervision of your regular veterinarian. If blood glucose levels are increased above normal we can start an insulin drip during surgery to help control the blood glucose level.
WHAT DOES CATARACT SURGERY INVOLVE?
The preparation for cataract surgery begins several days prior to the actual event. You will be required to apply drops to one or both eyes three times daily for three days prior to surgery to reduce inflammation in the eye(s). Cataract surgery is performed on an outpatient basis. Pre-operative testing (electroretinogram. ERG, gonioscopy and ocular ultrasound) may be performed prior to surgery to assess the eye(s) and evaluate your pet’s chances for successful cataract surgery.
Testing can be done while awake but may require a short hospital stay for a few hours depending on what testing is needed. Some dogs will not allow testing without sedation or a short-acting anesthesia.
Bichon Frises, Labrador Retrievers and Poodles have a tendency towards post-operative retinal detachment, causing permanent blindness without retinal re-attachment surgery. Therefore, if the testing results are normal we recommend cryoretinopexy to staple the retina in place reducing the risk of retinal detachment from 92-94% to 12-14% in these breeds. These dogs require general anesthesia.
Cataract surgery is performed 2 weeks after the cryoretinopexy. Dogs that do not require cryoretinopexy can undergo cataract surgery within several days to a week after the testing if the eyes have been treated with medication for at least 2 weeks before surgery. Glaucoma can occur in some dogs if the drainage angle of the eye is abnormal. In these cases endolaser is performed as a secondary procedure to reduce the chances of post-operative glaucoma.
Boston Terrier Cataract Surgery
A recent study showed the odds of complications and blindness after cataract surgery with Boston terriers was 290 times greater than with mixed breed dogs. The most frequent complications were:
1. Glaucoma
2. Retinal detachment
3. Intraocular hemorrhage
4. Severe uveitis.
Therefore, we recommend if surgery is performed that cryoretinopexy and Endoscopic Diode Laser are performed to decrease the possibility of glaucoma.
Even with all of this being done these dogs still have the risk of complications. If retinal detachment occurs post-operatively then additional surgery to re-attach the retinal would be needed and there would be further expense for this procedure.
BEFORE HAVING SURGERY
Please have your dog groomed and bathed before having surgery. The dog cannot be bathed for at least 3 weeks after cataract surgery. Avoid soap in the eyes as this could delay surgery.
If there are any dental problems such as Periodontitis please have this take care of before having cataract surgery.
Please use the prescribed drops in the eyes 3X daily starting 3 days before the surgery
WHAT DO I NEED TO KNOW THE DAY OF SURGERY?
Take food and water away after midnight the night before surgery.
Diabetic patients should be given only ½ dose of insulin that morning.
Please place the prescribed drops in the eyes the morning of surgery.
Drop off time is 8:00 AM the day of the procedure. We will let you know what time to pick up you pet on the day of surgery.
HOW IS CATARACT SURGERY PERFORMED?
Pre-surgical drops are placed in the eye at several intervals to dilate the pupil and prevent inflammation. An intravenous catheter is placed and pre-operative medications are given to dry up secretions and prevent vomiting. Anesthesia is given intravenously and a tube is placed down your pet’s trachea to control respiration. Blood pressure, blood oxygen and carbon dioxide and electrocardiogram monitor your pet’s progress during the procedure. A highly sophisticated ultrasonic needle is used thru a small incision into the cornea. This needle gently fractures the lens and aspirates it’s fragments.
An artificial lens is placed to take the place of the diseased lens. In some cases the lens capsule is diseased and will not tolerate an artificial lens. Though vision is not as good it still is better than what the dog had before surgery. The incision is closed with suture material that is less than the thickness of a human hair.
WHAT DO I NEED TO KNOW ABOUT THE AFTERCARE?
This is an outpatient procedure: your pet goes home the same day unless there are specific health issues that necessitate further hospitalization at an emergency facility or with your regular veterinarian.
1. Your pet will want to urinate more frequently due to the intravenous fluids given the day of surgery.
2. Please take off the leg bandage 1 hour after arriving home. This is where the IV catheter was placed.
3. Wait at least 30 minutes before giving food and water and give small amounts initially.
4. Avoid your pet jumping on and off furniture, going up and down stairs, biting on hard toys and getting too excited.
5. If the dog is to excitable then sedatives may be needed over the course of the three-week post-operative period.
6. We will see you the day after surgery to re-evaluate your pet’s post-operative condition.
7.Hold the head up with the nose pointing towards the ceiling gently open the eyelids with index finger and thumb avoiding pressure on the eyeball and place a drop of medication on the cornea in the center of the eye. Any excess can be wiped away with a tissue or washcloth. When using more than one type of drop wait 10 minutes in between drops.