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Inside the eye is a lens that focuses light on the back of the eye or the retina. Vision occurs at the retina. The structure of the eye is similar to a camera, which has a lens to focus light on the film. If the lens becomes opaque (Cloudy or Milky) this is called a cataract.

What causes cataracts?

The most common cause of cataracts in the dog are inherited cataract formation. Other causes include injuries to the eye or diseases such as diabetes mellitus (“sugar diabetes”). Some cataracts appear to occur spontaneously and are age related.

Will my dog go blind?

Cataracts will cause diminished vision. The greater the opacity the more affect on vision. Often cataracts will cause blindness but the progression will depend on the type of cataract, the breed and other risk factors. Since the major cause of cataract is hereditary, cataract progression varies from breed to breed and individual to individual. Cataracts will develop relatively early in life in some breeds while in others the first signs are detected when the dog is older and progression is so slow that dogs still have reasonable sight well into old age.

Treatment For Cataracts

Prior to performing cataract surgery a full clinical assessment needs to be undertaken. This includes taking the pressure of the eyes (tonometry) to rule out glaucoma; measuring the tear production to rule out complication from insufficient wetness of the eye; assessing the eyes response to light and potential ability to see by performing an ERG (electroretinogram). If there are other complications found with the eyes, these will have to be carefully considered before a decision is made to undertake surgery.

Cataract removal is performed under full general anaesthesia (unlike humans, our patients are not cooperative enough to let us perform this procedure under topical anaesthesia). A special probe is inserted into the eye and uses very high frequency sound waves to break the lens up and allow it to be removed (phacoemulcification). This is delicate microsurgery surgery that has to be performed under a high powered operating microscope. The procedure in animals takes much longer than in man as the lens in a dog’s eye is approximately three times the size of the lens in a human eye even though the dog’s eye is much smaller. The hardness (density) of the lens will also affect how long the procedure will take; as a general rule the whiter the lens the harder it will be and the longer surgery will take.

Depending on the type of cataract, some dogs may also be suitable for an intra-ocular lens implant (artificial lens placement). This will help the sight to be more like the original sight.

Due to the nature of the surgery and the response of the Canine eye post-operatively there are always risks of complications (including knocking the eye, post surgical inflammation, haemorrhage or infection), some of which can be serious. Despite this, we anticipate an 80-85% successful outcome (in a recent survey of cataract surgery over a 10 year period undertaken at a USA Ophthalmic University Department, they had achieved comfortable visual eye in 79% of cases operated on) . Operating on a dog that is already blind has everything to gain but very little to lose. The success will also depend on medication being given and restriction the dog receives, It is essential that an Elizabethan collar is used in order to offer some protection to the eye for a minimum of one week after surgery.. There will also be a number of drops and tablets which must be given to control the inflammation that is inevitable following lens removal. If you are in any doubt as to your ability to medicate or be able to do this at least eight times a day for the first one to two weeks before and after the operation, then this should be discussed further with the veterinary surgeon, as it will effect the outcome.

Cataract Surgery in Diabetic Dogs

Diabetes is a potential life threatening disease which requires lifetime monitoring and treatment (usually dietary and with Insulin). There are always increased risks in the treatment of Diabetic dogs with Cataracts. The nature of diabetes means that there are potentially complications (usually destabilisation) associated with the anaesthesia, post operatively, stress or because of the drugs that have to be used to treat the eye before an after surgery. Diabetic dogs should not be given insulin on the day of planned ERG assessment or Cataract surgery, as this could lead to Hypoglycaemia (low Blood sugars) especially as they need to have food withheld for the anaesthetic from 9 pm the night before. It is especially important that all Diabetic dogs have been stable and controlled before undergoing cataract surgery or the complications may be even more serious or even fatal.

Permission for inclusion was given by Lawton & Stoakes, for recognition of the article by themselves. This article was taken from their  newsletter.

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