Cataracts in Dogs
Veterinary care includes diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth of Cataracts in Dogs
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 ancillary or underlying diseases. Blood tests are necessary to search for diabetes and other underlying systemic diseases. Laboratory tests are also used to assess general health prior to cataract removal surgery. 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 for Dogs with Cataracts
Treatments for cataracts may include one or more of the following:
Cataract Surgery for Dogs 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 both 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 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 where a lens cannot be inserted. When no lens implant is used, an 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 whole. 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 in its capsule. This procedure is generally 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 going to be used, 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 surgery.