Cataracts in Animals

Transcription

1 Cataracts in Animals

2 Cataracts in Animals Cross section of the Eye WHAT IS A CATARACT? A cataract is an opacity of the lens inside the eye. The lens is usually clear and transparent. The lens helps focus an image on the back part of the eye called the retina. The same concept happens in a camera, with the lens focusing an image on the film in the back of the camera. A camera with a foggy lens is somewhat similar to having a cataract. In humans, cataracts are one of the most common causes of blindness, especially in third world countries. CAUSES OF CATARACTS Cataracts can be caused by many things. Often we cannot be 100% sure of the cause. Most cataracts seen at the Eye Clinic for Animals are inherited from the parents (in the genes) but other causes such as diabetes, injuries, inflammation, drugs and nutrition may cause cataracts too.

3 SIGNS OF CATARACTS Owners usually report deteriorating vision of their pets. Poor vision may take the form of being more clumsy around the house, having a change of personality (lethargy or aggression) and reluctance to go into the dark amongst other things. Sometimes our clients notice a white area on the pupil (the black circle in the middle of the eye), or their referring veterinarian notices the problem during a routine physical examination. TREATMENT OF CATARACTS In the past people have tried all sorts of medications to clear cataracts. With our current medical knowledge, surgery is the only cure for cataracts. This doesn t mean you must have cataract surgery on your animal, as some cataracts are too small to warrant surgery. The decision as to whether your pet should have surgery can be discussed with one of our eye specialists. ASSESSMENT FOR SURGERY Early assessment of cataracts is important for 2 reasons: Firstly to assess the retina, the light-sensitive membrane at the back of the eye, to ensure it is normal. This can be done most easily when the cataracts are not too dense, enabling us to see the retina with an ophthalmoscope. If the cataracts are too dense we may need to do a more specialised test called an electroretinogram or ERG. Secondly, with the newer surgical equipment we use today, success of cataract surgery is greater when the cataracts are still in the early stages. WHAT HAPPENS IF MY ANIMAL DOESN T HAVE SURGERY? Cataracts can be irritating inside the eye if left in place. Sometimes medications can control inflammation and help control the associated pain. In the long term however the inflammation may get so bad that glaucoma (increased pressure in the eye) and uncontrollable pain may occur. In these cases the eye may need to be removed. So even if you decide not to have cataract surgery please stay in touch with us to monitor the progression of the cataract in your animal.

4 TESTS PRIOR TO SURGERY Before considering doing cataract surgery we need to make sure that the chances of success are as high as possible. We may need to test the retina to see if it is in its normal position by ultrasound, and to see if it is functioning normally by doing an electroretinogram, or ERG. Just like a camera with a foggy lens, we need to make sure the film at the back of the camera is in its normal position, and working normally. These tests are often done at a different time to the surgery itself. If your pet fails either of these tests then surgery should not be performed. If you are not considering doing cataract surgery then there is also no point in doing these preliminary tests. CATARACT SURGERY Cataract surgery in animals is almost identical to that in humans. Some people think that cataract surgery is called laser surgery, but it actually involves the use of ultrasound energy using a process called phacofragmentation. After being anaesthetised your pet will have hair clipped from around the eye for sterility reasons. A small area on the leg will also be clipped for catheter placement. In surgery a small incision is made and a fine pencil like probe is inserted into the eye. This probe uses the ultrasound energy which acts like a jackhammer to break up the lens and remove the fragments. In some cases after the lens is removed an artificial lens may be placed in the eye. Not all dogs are candidates for an artificial lens. The decision to place an artificial lens is often a decision made by the surgeon during surgery depending on various factors. The surgery itself usually will take about one and a half hours per eye. SUCCESS RATES OF CATARACT SURGERY Published success rates for cataract surgery in both eyes at the same time so that one eye, or both, has vision at 1 year after surgery is over 90%. Success rates for doing just one eye are about 85%. This is certainly quite a high success rate compared to almost any other surgery in the body. However this also means that even in uncomplicated cataract surgeries sup to 15% of cases may not work and some animals may even require further surgery.

5 COMPLICATIONS The most common reasons for a lack of vision after cataract surgery are ongoing inflammation in the eye, retinal detachments and glaucoma. There are other less common complications and these all may contribute to the 15% cases that fail. These complications are similar to those seen in human cataract surgery. In the worst case scenario, glaucoma or infection after surgery may not only result in lack of vision postoperatively, but also uncontrollable pain with the need to remove the eye. RISKS OF GENERAL ANAESTHETIC Whether a human or animal has a general anaesthetic, there is always a risk of complications and in the worst case scenario this may include death. The published mortality incidence in animals is about 0.1% (1 in 909) in normal healthy dogs. To minimize the chances of an anaesthetic complication you may like to have pre-operative blood and urine analysis performed by your local veterinarian. For animals over 10 years we advise these tests should be performed. For some cases we can provide a specialist anaesthetist at an additional cost. Once again we are trying to maximize chances for a successful surgery. POST SURGERY Usually after cataract surgery your pet will be in hospital for up to a few days. When we do send your pet home it is essential that you use the medications we prescribe at the frequency we suggest. Failure to use the medications as directed even for as little as a day or two can result in uncontrolled inflammation, glaucoma and retinal detachments. For the first 1-2 weeks it is important to keep your animal quiet and to limit the exercise your pet has to strict leash walks, preferably with a chest harness rather than a throat collar which can increase the pressure in the eyes. You should keep your animal out of bright light as this may cause discomfort. The eye should be cleaned once daily using a warm compress. At first we may be using medications at least 4 times daily. Over time this decreases. Your first revisit will usually be 1 or 2 weeks after the surgery. After this there will usually be another at one month or so after surgery. Subsequent revisits will depend on the progress of the case.

6 VISION AFTER SURGERY If all goes well your pet may have vision as early as the next day after surgery. Some cases may however take a few weeks to fully regain vision due to the degree of inflammation present and also your pet learning to see again. COSTS The cost of cataract surgery in animals is not the same from patient to patient as each surgery might be slightly different. The microsurgical equipment eye specialists use is expensive and many of the materials we use in cataract surgery have to be imported from overseas. The cost of cataract surgery will change as a result of these and other factors. Please ask for an estimate at the time of consultation. Please understand that this is an estimate only, and not a quote. The first recheck after cataract surgery is free. After this time there will be a standard revisit fee. FINALLY Most cataract surgery patients do well after surgery. These pet owners are undoubtedly some of our happiest clients. Their now visual pet is suddenly more energetic, happy and experiences a better quality of life. Not all cataract patients have successful outcomes. There is always a risk of complications in any surgery. For the majority of our clients the incidence of complications is acceptable. Please feel free to discuss any further questions you may have about cataract surgery with one of our eye specialists.