Overview of Feline Cataracts
A cataract is any opacity of the lens of the eye. The normal lens is translucent (clear), and it transmits and focuses light onto the retina in the back of the eye. A cataract within the lens may block the transmission of light to the retina.
Below is an overview of Cataracts in Cats followed by some detailed and in-depth information about the diagnosis and treatment of this disease.
There are many causes of cataracts. Cataracts may be inherited or related to some other disease process. Most cataracts in the cat develop secondary to inflammation within the eye, from trauma or some other eye problem. Rarely, cataracts in the cat may be inherited, may arise with abnormal development of the lens, or may occur in association with nutritional abnormalities in the young cat.
Cataracts are not the same as nuclear or lenticular sclerosis, an aging change that often occurs in the feline lens and does not cause blindness. Cataracts are not as common in cats as they are in dogs. The finding of a cataract in a cat’s eye should lead to a search for an underlying problem.
Cataracts cause varying levels of vision impairment and may lead to blindness.
What to Watch For
Bluish, gray or white color change inside of the eye
Tendency to bump into things
Reluctance to use stairs or jump up onto objects
Hesitancy in unfamiliar environments
Other signs of blindness
Redness and inflammation
Pain and squinting due to the underlying cause
Diagnosis of Cataracts in Cats
Diagnostic tests are necessary to recognize cataracts and exclude other diseases. Tests may include:
A complete medical history and physical examination.
A complete eye examination. Most veterinarians have the tools with which to confirm the presence of a cataract in the lens, but it is often necessary to visit a veterinary ophthalmologist to have a more thorough examination performed using an indirect ophthalmoscope and a slit lamp biomicroscope.
Blood tests to determine underlying causes.
An ultrasound examination of the eye if the cataract is too opaque to allow examination of the retina.
Possibly an electroretinogram to evaluate the function of the retina, especially if the cataract blocks visualization of the retina.
Treatment of Cataracts in Cats
Treatment must be aimed at correcting the underlying cause of the cataract.
When cataracts are caused by inflammation (uveitis) within the eye, the inflammation may be treated with anti-inflammatory drugs and certain antibiotics.
There is no medical treatment available to reverse cataracts, to prevent cataracts or to shrink cataracts.
Cataracts that are inherited or appear to arise spontaneously may be surgically removed. Cataracts associated with inflammation in the eye cannot be removed surgically unless the inflammation is brought under control. Many cats with cataracts are poor candidates for surgery because they have inflammation within the eye.
Whether a cat is a candidate for cataract surgery can be determined by a veterinary ophthalmologist.
Home Care and Prevention of Cataracts in Cats
It is important to have all cats with cataracts examined early in the course of their disease as the cataract is frequently a sign of another underlying problem. Inflammation in the eye (uveitis) is the most common cause of cataract development in the cat, and uveitis often indicates the presence of a systemic disease; therefore, it is important to examine and perform diagnostic tests in all cats with cataracts.
Even if the cat is not a candidate for surgical removal of the cataracts, there may be other medications needed to treat underlying diseases. If your cat has inoperable cataracts, he may require help adjusting to his blindness. Be sure to keep objects around the house in a consistent place and confine the cat to the house or an enclosed porch, patio or yard. Most blind pets function extremely well in familiar environments.
There is nothing you can do to prevent cataracts.
In-Depth Information on Cataracts in Cats
Various eye diseases can cause a cloudy white appearance similar to that observed with cataracts. Many such diseases result in poor vision or blindness. Your veterinarian or veterinary ophthalmologist will be able to tell you if the white appearance and vision loss is caused by cataracts, by disease of the cornea – the clear outer covering of the eye, or the retina, which is the specialized light receptor layer in the back of the eye..
There are several causes of cataracts including:
Genetic. Cataracts can be inherited, but this occurs only rarely in the cat.
Anterior uveitis is the leading cause of cataract development in the cat. Anterior uveitis is an inflammation of the iris and ciliary body, which make up the tissue around and behind the pupil. Uveitis usually arises as part of a systemic illness in the cat, and may be caused by feline leukemia virus, feline immunodeficiency virus, feline infectious peritonitis virus, toxoplasmosis, etc. Uveitis may affect one or both eyes in the cat; therefore cataracts may be either a unilateral or bilateral condition.
Trauma. If the eye is punctured or damaged from something like a cat scratch or a stick penetrating the eye, a cataract may form. Some of these cataracts form only at the site of injury, but others can progress to involve the entire lens.
Abnormal development of the lens. Nutritional deficiencies, exposure to drugs, toxins, or other agents during the time of development of the eye in the young kitten may induce a cataract.
Other less common causes of cataracts in cats include old age, retinal diseases such as progressive retinal atrophy, displacement of the lens, exposure to concentrated microwaves or radiation therapy, electrocution, and certain rare metabolic diseases.
Veterinary care includes diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth on Cataracts in Cats
Diagnostic tests are needed to recognize cataracts and exclude other diseases. These tests may include:
A complete eye examination. Most veterinarians have the tools with which to confirm the presence of a cataract in the lens, but it is often necessary to visit a veterinary ophthalmologist to have a more thorough examination performed using specialized ophthalmic equipment. Such an examination includes fluorescein staining of the cornea, Schirmer tear test, slit lamp biomicroscopy, tonometry, and possibly examination of the retina.
Cataracts are classified as incipient (very small), immature (encompassing more, but not all of the lens), mature (encompassing the entire lens) and hypermature (the lens is beginning to shrink down and slowly resorb). The eye exam is important for staging the cataracts and for detecting underlying diseases.
Blood tests are often necessary to search for a systemic disease. Laboratory tests are also used to assess general health prior to any surgery to remove cataracts.
An ocular ultrasound is performed if the retina cannot be examined because the cataract is too opaque, and if surgery is being considered. Prior to surgery it is important to determine if the retina is normal or healthy. If a retinal detachment or changes in the vitreous (jelly-like substance behind the lens) are found, then surgery to remove the cataract may not be worthwhile.
An electroretinogram (ERG) is also frequently performed prior to cataract surgery in order to evaluate the function of the retina. An ERG is especially important in determining underlying retinal disease masked by the cataracts (if the lens is too opaque for all the retina to be examined). If the ERG is abnormal, then the cat is not a good candidate for cataract surgery.
To understand the importance of evaluating the rest of the eye and especially the retina prior to surgery, consider this analogy: A cataract is like a physical barrier to light, similar to a cover over the lens of a camera. This barrier can be physically removed by surgery. In contrast, the retina is like the film in the camera, and the rest of the eye is the camera itself. If the camera or the retina is not working properly, then removing the lens cover (cataract) will not improve the animal’s vision. The rest of the camera must be working well, and the film must be good before removing the barrier over the lens will be worthwhile.
Treatment In-depth on Cataracts in Cats
Treatments for cataracts may include one or more of the following:
Cataract surgery. At the present time, there is no laser surgery for removing cataracts in either people or animals. Phacoemulsification is the most common technique used in humans and animals to remove a cataract. Once the pupils have been dilated and your pet is under general anesthesia, a small incision is made through the cornea (clear domed front surface of the eye). The lens is housed in a small bag called the lens capsule. A small tear is made in the front capsule and a circular piece of the lens capsule is removed. The phacoemulsification instrument uses ultrasonic waves to break apart the lens and then suck it out. Most of the lens is removed by phacoemulsification, and then the lens capsule (the “bag”) is cleaned of any remaining lens material. Frequently an intraocular lens implant (a prosthetic lens) is then placed into the lens capsule.
The lens capsule acts as a bag to hold the implant in place. There are lens implants for both dogs and cats, and these prosthetic lenses return the vision as close to normal as possible. There are some situations when a lens implant cannot be inserted. When no lens implant is used, the animal’s vision is still greatly improved by cataract surgery.
The incision through the cornea is then stitched closed after the lens has been removed.
Extracapsular lens extraction. This is another cataract removal technique. It is used either when a phacoemulsification machine is not available, or when a cataract is so hard or old that the phacoemulsification instrument isn’t powerful enough to break up and remove the lens. The surgical procedure requires making a larger incision through the cornea and a larger hole in the lens capsule so that the lens can be removed from the bag as a single, whole piece. A lens implant can still frequently be inserted during this type of procedure.
Intracapsular lens extraction. This is another surgical method that involves making a large incision through the cornea and removing the whole lens within its capsule. This procedure is used when a cataractous lens has shifted out of position and is no longer held firmly in place inside of the eye. Because the lens capsule has been removed, if a lens implant is inserted, it has to be sewn into place because there is no capsular bag left to hold it in the center of the eye.
Regardless of which type of procedure is used to remove a cataractous lens, there are many postoperative medications and important home care instructions to be followed after the surgery.
Surgical Complications of Feline Cataract Surgery
Cataract surgery has a high success rate, as long as the rest of the eye is healthy. The success rate of cataract surgery is decreased if the eye has been inflamed in the past, or is actively inflamed. All uveitis must be controlled before cataract surgery can be attempted, and other eye problems such as retinal disease and glaucoma must also be ruled out.
Risks involved with cataract surgery include those associated with general anesthesia. Anesthetic risks are minimized by evaluating pre-operative laboratory tests, performing a complete physical exam, and taking X-rays of the chest. The information gathered from these tests is then used to develop an appropriate anesthetic protocol.
Anterior uveitis and glaucoma are the two most immediate and common complications encountered in the days following cataract surgery. Many cats are medicated prior to surgery to combat the uveitis that occurs once the eye is opened, and these medications are continued for weeks following the surgery. Pressure within the eye is monitored closely following surgery, and anti-glaucoma drugs are started as needed.
The most common problems that arise long-term after cataract surgery are scarring of the lens capsule that remains in the eye and detachment of the retina. Because of both short-term and long-term problems that may be encountered after cataract surgery, frequent follow-up visits are needed for sometime.
Non-Surgical Cataracts in Cats
If your pet’s cataracts are secondary to some other eye disease, removal of the cataract is frequently not indicated.
Medical therapy may be necessary to control inflammation within the eye, to combat any glaucoma present, and to treat underlying illnesses, even when the cataract cannot be removed. Periodic follow-up examinations are required to keep the eye healthy and the cat comfortable.
Home Care of Cataracts in Cats
After cataract surgery, the first one to two weeks are the most labor-intensive. The cat must be kept quiet and calm. Usually an Elizabethan collar is used to keep the cat from rubbing the eye or grooming the area around the eye.
Follow all instructions your veterinarian gives you for medications. Several topical (drops) and oral medications may be used after surgery, such as: anti-inflammatory drops (prednisone/prednisolone, dexamethasone); dilating drops (tropicamide, atropine); antibiotic ophthalmic drops; oral anti-inflammatory drugs (prednisone, baby aspirin or ketoprofen); and oral antibiotics (amoxicillin, cephalexin).