What is a cataract? The lens is a living ocular tissue that, when healthy, is transparent. A normal lens helps focus light to the retina, the light sensitive nerve tissue located in the back of the eye. A cataract is an abnormality of that lens in which the normal composition of the lens is disrupted, its transparency is lost, and it appears cloudy and white. If a large portion of the lens becomes a cataract, it prevents formed light from reaching the retina, causing poor vision. A cataract can assume a variety of appearances such as small spots, a cracked-ice appearance, a diffused milky haze, a “pearl-like” sheen, or white streaks. The cataract may initially affect a small area and progress to involve a larger portion of the lens. Rate of progression is difficult to predict, though it tends to be more rapid in younger animals. Cataracts may develop in one or both eyes.
What causes cataracts? Most cataracts in dogs have a hereditary basis or are age related. Cataracts can also result from injury to or inflammation in the eye, or systemic diseases that can affect the eyes. DIABETES is the most common disease associated with cataracts in dogs. Although it may be difficult to name the specific cause of cataracts, generally those cataracts that develop in the eyes that are free of signs of disease (whether ocular or systemic) are assumed to be inherited. Poor nutrition is an uncommon cause of cataracts, but has been suspected in some young dogs.
What is the treatment? Medical remedies have been inaccurately advertised as effective for the treatment of cataracts. There is no proven medical treatment know to reverse or slow the progression of, or prevent the formation of a cataract. Some promoted agents actually worsen the cataracts rather than improve the condition. Surgery is the only know treatment both in animals and humans, and often provides a return of functional vision to pets.
What should you do if a cataract is suspected? First arrange to have your pet examined by a board certified veterinary ophthalmologist. Although the lens is an important component of the visual system, a complete eye examination is necessary. Early examination is always recommended especially in diabetics. The health of the retina and other parts of the eye should be evaluated prior to the formation of complete cataracts. If the cataract is entirely mature, the area behind the lens may not be able to be examined directly. In most cases, an electroretinogram and ultrasound will be recommended to evaluate the retina. The cataract will be classified by cause, area of involvement, and the stage of progression. Not all cataracts lead to blindness, and incomplete cataracts may not impair vision significantly.
Cataract surgery is a one day outpatient procedure. It begins with pet drop off in the Tulsa or OKC office between the hours of 8:00-9:30 a.m. ERG/Ultrasound tests are performed to evaluate retinal function and position. If tests are passed, surgery is performed early afternoon and your pet is normally released by 3-5 P.M. On the average, vision returns within a few days following surgery and required three to five postoperative evaluations over a three month period.
What does cataract surgery involve? The various surgical procedures available for your pet are demanding and requite meticulous and precise microsurgical techniques. Surgery is performed using an operating microscope and sophisticated microsurgical instruments. Dr. Gwin performs phacoemulsification through a 3.2mm incision. The cloudy lens is emulsified (broken up) and aspirated from the lenticular bag. A 41-diopter foldable lens is then injected into the bag replacing the cataractous lens. With todays phacoemulsification equipment, foldable intraocular lenses, etc. visual acuity in most postoperative cataract cases appears normal, just as we see after cataract removal, especially in diabetics. Although vision can be lost quickly, it is extremely pleasing to see that vision is quickly restored and old familiar habits resume after removal of the cataracts.
When is surgery indicated? Once a cataract has progressed to involve over 50-60% of the once clear lens, vision begins to be significantly compromised. It is desirable to remove cataracts before that are totally cloudy, if possible, to decrease the chance of cataract induced inflammation that can lead to potential complications, some of which can be significant. DO NOT WAIT until your pet is totally blind.
Diabetics develop cataracts in association with an “overload” of a metabolic pathway within the normally clear crystalline lens. With this overload, the normally clear lens fibers break down their normal architectural structure. The lens fibers no longer allow light to pass through the lens. A high percentage of diabetic dogs develop cloudy cataractous lens rapidly, sometimes within 1-2 weeks. Approximately 40-50% of the cataract surgeries performed by Dr. Gwin are on diabetics. The general success rate for cataract surgery in dogs is 90-95%. This success rate remains high in diabetic cataracts that have just developed and have not been complicated by cataract induced inflammation.
- Have your pets diabetic cataracts EVALUATED EARLY, preferably before total blindness occurs. Blood sugar (glucose) does NOT need to be well controlled prior to referral, so DO NOT WAIT to call for an appointment. Waiting can result in permanent blindness.
- Cataract induced inflammation is very serious. Red irritated eyes, conjunctivitis, blepharospasms, and discomfort can develop into panophthalmitis, glaucoma, retinal detachment, etc. This can happen as quickly as 2-3 days.
- In the above cases, anti-inflammatory medications, such as NPD, PredAcetate, Flurbiprofen, and Diclofenac are usually indicated.
- To schedule an evaluation by Dr. Gwin, call either of our offices in Oklahoma City or Tulsa and inform our receptionist you have a pet that is a diabetic. We do consider this a high priority. Bring our referral form filled out by your primary veterinarian and any eye medication prescribed for your pet with you to the appointment.
- We will stay in close contact with your veterinarian who will receive a written report by Dr. Gwin following each examination.
Hypermature Cataract with Lens-Induced Uveitis
Lens induced uveitis is an inflammation that is caused by liquefied protein leaking out of lens capsule or bag when a cataract become overly mature or hypermature. This is especially common in diabetics due to the rapid development of the cataract and swelling of the lens fibers. Cataract induced uveitis can have significant and sometimes devastating sequelae, including cloudy, red, inflamed eye with inflammatory precipitates in the anterior chamber. Adhesion of the iris to the lens (posterior synechia), blockage of the drain (normal outflow mechanisms) leading to increased pressure (glaucoma), detachment of the retina, even a generalized inflammatory process involving all layers of the eye (panophthalmitis).