Background
Cataracts are a leading cause of blindness in dogs. Although there are other potential etiologies, cataracts are most frequently the result of heredity or diabetes in dogs. The age of onset for inherited canine cataracts is variable, usually from 5-8 years of age.
When to Refer
You are urged to refer cataract patients early on rather than waiting for the cataracts to “mature,” which is an outdated practice. With modern techniques and technology of cataract extraction, early surgical intervention is recommended when possible. Surgery performed soon after cataract development, while it is in the mature or moderately advanced immature stage, is less likely to develop serious complications associated with lens-induced uveitis, retinal detachment, and secondary glaucoma. Cataract surgery is more often performed unilaterally now, without waiting for both lenses to become completely opaque, since success rate is at least 85%.
It is preferable to have your patient’s initial examination early on for multiple reasons. Among them: 1. fundus exam may be possible then to rule out retinal degeneration, 2. when topical anti-inflammatory medications are prescribed early for immature and immature cataracts they are less likely to develop complications related to lens-induced uveitis (before or after surgery) and 3. your clients have time to become adequately educated and be able to make a less pressured decision.
Cataract Surgery Technique
State of the art cataract extraction called phacoemulsification is performed routinely at Veterinary Vision and utilizes irrigation, aspiration, and ultrasound technology, to liquify and remove the opaque lens material. An opening called a capsulorhexis is created by the surgeon to allow access to the interior of the lens. The remainder of the lens capsule is left intact for placement of an intraocular lens. Extracapsular extraction is now only rarely performed, for very dense cataracts. The relative advantages of phacoemulsification include:
- a small corneal incision
- maintaining the anterior chamber with less damage to the corneal endothelium
- more thorough removal of lens fragments
Here are Three Good Resources Related to Veterinary Cataract Surgery:
Veterinary Vision’s cataract surgery video
ACVO’s Cataract Surgery Video
ACVO’s Cataract & Cataract Surgery Brochure
Intraocular Lenses
Following uncomplicated cataract extraction alone, vision is improved dramatically whether or not a replacement lens is inserted. Aphakic patients can generally navigate without bumping into things, but their near vision is fuzzy, so that they may use their other sense more when items, like toys, are very near. Occasionally a clear aphakic ey is the only good option, such as when there is a tear in the lens capsule or the lens capsule is only loosely attached due to subluxation. However, we insert replacement lenses as a matter of routine at Veterinary Vision. Evaluations of visual performance, although necessarily subjective, indicate significantly improved vision when an artificial lens is placed.
From left to right, the photos below show an actual clear dog lens, a mature cataract, and a dog eye following cataract surgery with placement of a clear artificial replacement lens.
Replacement intraocular lenses have been created which are appropriate for both dogs and cats. The refractive power needed is determined by the axial length of the globe, the curvature of the cornea, and the location of the replacement lens within the eye. In humans, a lens of 16-18 diopters is generally used; measurements in dog eyes indicates that a lens of 40-43 diopters is required. Intraocular lenses are made of inert materials like polymethylmethacrylate (PMMA) with flexible haptics to stabilize the lens within the capsular bag. Complications following intraocular lens implantation are uncommon and not usually the direct result of the replacement lens itself.
Here is some information about vision before and after cataract surgery
Client Education & Video
We have a short (approximately 10 minutes) educational video about phacoemulsification for cataract extraction. The advantages of this procedure are discussed as well as answering the most frequently asked questions about the pre- and post-operative care. Footage of an actual cataract surgery filmed through the operating microscope illustrates the technique including implantation of a replacement intraocular lens. The narration is designed to be easily understood and may be helpful to clients considering this procedure. Please call our office to request a copy.
Educational materials about cataract surgery are also available online in the client section of our site here.
What about Medical Treatment for Cataracts?
