Ophthalmology - Special Services, Technology, & Information
Cataract Surgery in Dogs
Cataracts are a leading cause of visual impairment in dogs and frequently progress to cause total blindness. Fortunately, the vision of affected dogs can often be restored to a normal state by surgically removing the abnormal lens and substituting an artificial lens in its place.
What is a cataract?
A cataract is opacity or clouding of the lens within the eye. The lens' function is to focus light rays on the retina, and cataracts decrease vision by interfering with light reaching the retina. Advanced cataracts are a leading cause of blindness in dogs and are generally recognizable by pet owners as a decrease in the dog's vision or by a cloudy, whitish-blue appearance to the eye. Cataracts must be distinguished from a normal aging change in the lens termed "lenticular sclerosis," which causes a bluish appearance to the eye but generally does not interfere with vision.
What causes cataracts in dogs?
The majority of cataracts in dogs are the result of a genetic, or inherited, defect involving the lens. Many types of purebred dogs are predisposed to inherited cataracts, which may be present at birth or develop later in young to middle-aged animals. Dogs affected with inherited cataracts should not be used for breeding purposes. Cataracts are also associated with diabetes, advanced age, trauma, and retinal disorders. Depending on the cause, cataracts may or may not progress to total blindness. The rate of progression is often predictable and can be determined by a thorough examination by a veterinary ophthalmologist.
How are cataracts treated?
Currently, the only effective treatment for cataracts is through surgical removal of the defective lens. Lens removal is done under general anesthesia by making an incision in the eye and using special equipment to ultrasonically fragment and remove the diseased lens material. In most cases, an artificial intraocular lens is implanted to replace the diseased lens. Due to the optical properties of the artificial lens, light can once again be focused on the retina. Lasers are not used to remove cataracts but are occasionally used several months after standard cataract removal to cut away debris that can develop around the intraocular lens. Surgery is generally recommended when the cataracts cause diminished vision, or for progressive cataracts where vision loss is anticipated. The surgical success rates for cataracts in the early stage are higher than for advanced cataracts that have been present for months to years. The preoperative evaluation by a veterinary ophthalmologist will include an ocular examination to screen for other eye disorders, and a laboratory analysis of blood and urine samples to help determine the general state of the dog's health. An ultrasound evaluation of the eye and a special diagnostic test called an electroretinogram will also be performed to screen for any retinal disorders that could interfere with a successful outcome.
How successful is cataract surgery?
The success rate of uncomplicated cataract surgery with intraocular lens implantation in dogs is approximately 95% or, in other words, 95 out of 100 eyes will have functional vision after surgery. The outcome may vary, depending on the overall "health" of the eye. After examination and testing, the ophthalmologist will assess the risks and benefits of surgery with the owner to help determine the best decision for the dog.
What are the risks and complications of cataract surgery?
There are inherent risks involved with any surgical procedure under anesthesia. Owners should discuss these risks with their primary veterinarian and the veterinary ophthalmologist. The current rate of complications following cataract surgery in dogs is approximately 5%. When an eye suffers from a complication, usually this simply means it does not regain vision and additional intervention is unnecessary. Some complications may require long-term medical therapy, or even additional surgery to correct. If both eyes have cataracts, we often recommend performing surgery on both eyes at the same time because the likelihood that the animal will suffer from a complication in both eyes following surgery is only 1-2%. Significant complications include:
- Retinal Detachment is a condition where the retina separates from the underlying tissue. Total retinal detachment causes vision loss, but sometimes it is possible to correct this complication with surgery.
- Excessive Inflammation, or uveitis, is a potentially serious problem. Patients with eye inflammation prior to surgery are more likely to develop this problem. Increasing the frequency of medical therapy can sometimes correct this complication.
- Glaucoma refers to higher than normal intraocular pressure. Some dog breeds are predisposed to glaucoma and may be more likely to develop it after surgery. Medical and surgical therapy can often control this complication.
- Capsular Opacification, or "secondary cataract," refers to the cloudiness of a membrane in the eye that surrounds the prosthetic lens (once a cataract is removed, it cannot truly return or recur). This opacity rarely occurs to such an extent that it causes visual problems. A laser procedure may sometimes be used to correct this complication.
What to expect after surgery
The patient is discharged the day after surgery wearing a special collar to protect the eyes from irritation for 2 weeks. The dog's exercise and activity need to be restricted to prevent injury to the eye. Topical medication will need to be instilled into the eye 4-5 times daily for several weeks. Reevaluation by the ophthalmology service at NCSU is required at 2-week, 6-week, 3-month, and 6-month intervals after surgery to observe the eye and attempt to correct or prevent any complications. With a successful surgery, vision is often restored immediately although this is sometimes difficult to appreciate in dogs for the first 1-2 weeks after surgery.
The primary veterinarian's role
The dog's regular veterinarian plays a key role in the proper maintenance of overall ocular health, and their role in the successful management of cataracts is no exception. Early detection of cataracts by the primary veterinarian, with subsequent referral to a veterinary ophthalmologist, can have a positive influence on the eventual outcome. Owners should also actively seek the advice of their veterinarian when considering cataract surgery for their pet. Surgery is not indicated in every case; however, it often restores useful vision to dogs whose sight is lost or impaired due to cataracts.