What actually is a cataract?
The lens is a clear structure inside of the eye that focuses light and images on the retina. A cataract is any opacity or cloudiness that forms within the lens. The cataract scatters or blocks light and images, preventing them from reaching the retina, resulting in decreased vision and even blindness. The lens is made up of highly organized clear protein surrounded by a very thin, clear elastic shell or capsule. When a cataract develops, it represents a permanent physical change in the protein structure of the lens. It is analogous to frying an egg: when you crack an egg, the egg whites are clear and transparent, but once heated in the pan, they become permanently opaque. There are no eye drops or medications, in either human or veterinary medicine that can dissolve or halt the progression of a cataract.
Cataracts develop in stages. In the earliest or incipient stage, the cataract may be a pin -point dot or tiny opacity in the lens, which does not noticeably diminish vision your pet’s vision. In the immature stage, the cataract involves more of the lens, but some clear protein remains, allowing some limited vision to persist. Visual impairment is more obvious, especially in certain lighting conditions or during activities, such as catching and retrieving toys. When the cataract is mature, the lens is totally opaque and blocks all vision. It is similar to looking through a pane of frosted glass or waxed paper. In pets the advanced stage cataracts, visual impairment is apparent, especially if both eyes are affected. You may notice your pet bumping into walls and furniture.
It is very difficult to predict whether a small cataract will progress and if so how fast it will progress. Each cataract is unique. Mature or hypermature cataracts usually cause inflammation to develop inside the eye (uveitis). When uveitis is severe or left untreated, the risk of glaucoma (elevated intraocular pressure) developing is significantly increases, as does ocular pain.
Signs associated with uveitis include increased eye redness, squinting, excessive tearing, cloudiness inside of the eye, and light sensitivity.
What causes a cataract to develop?
In dogs, cataract development is most often inherited. Despite the dam and sire being free of cataracts, they can still produce offspring that develop cataracts. The cataracts may be present at birth (congenital) or develop months to years later. The second most common and important cause of cataracts in dogs is diabetes mellitus. . Statistics show that 75% of dogs with diabetes will develop complete cataracts and blindness within 9 months of being diagnosed with diabetes. Early detection and surgery is especially important with diabetic cataracts, which can progress rapidly, and incite fulminate uveitis and secondary glaucoma. Additional causes of cataract development include trauma, uveitis and nutritional deficiencies. In cats, cataracts form most often as a result of uveitis or trauma, with a much smaller percentage due to inheritance.
How are cataracts treated?
Treatment of your pet’s cataracts will depend on the stage and cause of the cataract, and if any additional eye problems are present. Topical anti-inflammatory eye drops are most often prescribed to prevent or control associated uveitis, and reduce the risk of glaucoma developing. The only effective treatment for advanced cataracts is surgical removal. For early (incipient) cataracts, periodic follow-up exams are advised to monitor for progression. Without progression, cataract removal is not necessary.
What happens if my pet’s cataracts are not removed?
If you elect not to have cataract surgery, your pet may need to be placed on daily eye drops to help control the cataract-induced uveitis. When mature cataracts are not removed, there are several potential consequences. Glaucoma can develop secondary to uveitis or lens luxation, in which the lens shifts position within the eye and blocks the normal fluid out flow. Glaucoma is a painful and permanently blinding disease. Additional consequences of not removing advanced cataracts include retinal degeneration, retinal detachment, and keratitis and corneal degeneration. Over time, the eye can become phthisical or shrunken in size.
What is the first step if I think my pet has a cataract?
If you suspect your pet is developing a cataract, the first step is to schedule an examination with a board-certified veterinary ophthalmologist. Prompt examination is especially important in dogs with diabetes. The ophthalmologist will perform a comprehensive examination of the front and back segments of the eye, and determine if a cataract or nuclear sclerosis is present. All animal species develop a hardening of the lens (nuclear sclerosis) with age. This results in the lens having a grayish appearance, which increases as your pet ages. Nuclear sclerosis is not a cataract, but in older animals it reduces the quality of their vision up close (ability to focus in the near-field), as it does in humans. This is why people in their 40’s and older often need reading glasses. Dogs as a species do not have inherently good vision up close compared to people, so nuclear sclerosis does not tend to significantly interfere with their over-all vision. If a cataract is present, the ophthalmologist will describe the findings in detail, including cataract size and stage, and if any other eye problems are found. Surgery performed on immature or recently mature cataracts carries the highest success rate. Waiting for cataracts to fully mature is neither necessary nor advantageous.
How do you determine if my pet is a candidate for cataract surgery?
Prior to surgery, several diagnostics tests are required to ensure your pet is a good candidate for cataract surgery. These include, but are not limited to, an ocular ultrasound, electroretinogram (ERG), and gonioscopy (to evaluate your pet’s risk for developing glaucoma), and blood screens and urinalysis (to help us assess your pet’s overall health).
The ultrasound allows us to visualize the internal structures of the eye. We evaluate the entire cataract, the retina for attachment and the clarity and stability of the vitreous humor (gel body located behind the lens that provides support to the retina). The ERG tests the electrical activity of the retina to ensure that your pet’s retina is functioning properly prior to cataract surgery. The retina is a tissue-paper thin membrane that lines the back of the eye and is essential for vision. Considering the eye functions similar to a camera, the retina correlates to the film in a camera. If retinal function is abnormal, removing the cataract and implanting an artificial lens will not visually benefit your pet. For ERG testing your pet’s eyes are required to be “dark adapted”. We sit with them in a darkened exam room for 15-25 minutes prior to performing the test. These tests are not painful and can be done on most pets without any sedation. Both ERG and ultrasound testing will take around an hour for completion.
What is involved in the actual surgery?
Cataract surgery in animals is performed with the same equipment used by ophthalmologists for people and is the only way to restore vision following cataract development. Cataract removal is performed under general anesthesia. Surgery is begun with a very small incision made in the cornea to enter the eye and open the lens capsule. An ultrasonic hand piece (pen-like probe) is used to break up the cataract and aspirate it from the eye. Once this is complete, only the clear elastic bag (capsule) of the lens remains. An acrylic artificial lens is then implanted inside this capsule to restore your pet’s refraction. After removal of the cataracts, your pet will not develop cataracts again. Tiny stitches are placed in the corneal incision. These dissolve slowly to secure the incision during the healing process.
Cataract surgery is performed on an out-patient basis. Your pet will stay with us for several hours the day of surgery. Patients are monitored closely as they recover from anesthesia, during which time intraocular pressures are closely monitored and post-operative eye medications are administered. At the time of hospital discharge, you will receive a detailed list of care instructions, including oral medications and eye drops to treat post-op uveitis and to protect against infection. A protective Elizabethan collar will also be placed on your pet for 2-3 weeks. The collar is essential to limit the risk of self-trauma and to act as a “bumper”, preventing your pet from directly injuring the eye while vision is clearing.
10% of patients can experience one or more of the following complications:
- Persistent (chronic) inflammation
- Glaucoma (increased eye pressure)
- Retinal edema and / or detachment
- Breakdown or infection of the incision site
- Corneal ulceration
- Displacement of the intraocular lens implant
- Infection inside the eye
What will my pet see after surgery?
Most patients awake from surgery and experience improved vision immediately. Vision is initially a little foggy and typically continues to improve over 1-2 weeks following surgery as the inflammation subsides. With a successful surgery, most pets regain near normal vision.
While most patients are candidates for placement of an intraocular lens (IOL), there are situations when an IOL cannot be implanted. Once the cataract is removed, your pet will regain vision, as the lens is simply used for focusing up close. This means that your pet will be able to see very well far away. Their vision up close will be somewhat unfocused, much like a human that needs reading glasses. As our companion animals do not read or drive the difference in near and far vision is often not noticed. While IOL placement after cataract removal certainly optimizes vision, the most important aspect of the surgery is to remove the abnormal lens and to clear the line of sight.
What is the post-operative care for my pet?
Postoperative care is vital to a successful outcome from cataract surgery. Your pet’s eye should be considered fragile after surgery. All precautions should be taken so that your pet does not damage their eye(s). The protective Elizabethan collar should be worn by your pet until directed otherwise (generally for the first 2-3 weeks after surgery). For pets that tend to pull hard on their leashes, harnesses are preferred for a month after surgery to minimize pressure on their necks. Activity and vigorous head shaking should also be restricted for the first month after surgery.
Your pet’s vision depends on strict adherence to our recommendations for medical therapy and recheck examinations. The first post-op appointment will be required the morning after your pet’s surgery. Post-operative care involves eye drops as well as oral medications. Medical therapy is usually the most intensive for the first 2 weeks after surgery and involves instillation of multiple eye drops four times a day. The eye drops are typically reduced to once to twice a day for long term therapy by the 3 month recheck. Recheck examinations are scheduled one week, two weeks, 1 month and 2 months after surgery. Periodic follow-up examinations are then scheduled on a 6 month to a yearly basis to monitor your pet’s vision and over-all ocular health and comfort.