CATARACT SURGERY INFORMATION

With improvements in surgical instrumentation and facilities, cataract surgery in dogs has enjoyed an improved success rate over recent years. However, cataract surgery in dogs is more prone to complications than in people since the canine lens is larger than our own and the canine eye will react more intensely to surgical intervention. The surgical technique used to remove the cataract is the same that is used in people. A small (3.5mm) incision is made at the edge of the cornea, and through that a window is cut in the front of the lens. An ultrasonic probe is then inserted into the lens and vibrates at high frequency to break up the lens (phacoemulsification) and aspirate the fragments. This leaves an empty capsular bag which used to contain the cataractous lens, and into which an artificial intraocular lens can now be inserted. See the images on the ophthalmology page.

The lens that we are currently using is an acrylic lens that can be folded and inserted through the 3.5mm incision. The lens has been designed to prevent the re-growth of the cataract across the lens capsule . We have now inserted over 200 of these lenses over a period of three years and they are successfully maintaining a clear visual pathway.

Occasionally it is not possible to insert an artificial intraocular lens if the lens capsule is unstable or if a large part of the capsule has to be removed due the presence of a cataract attached to it. In such cases the dog will still be able to see after the surgery, well enough to negotiate obstacles and to get about confidently, but vision will be more blurred than if an artificial lens has been inserted. With an artificial lens inserted into the eye vision is obviously improved and dogs with an artificial intraocular lens are able to discern small objects and recognise their owners much more readily.

Due to the reactivity of the canine eye and impact that cataract surgery has on it, there is a significant risk of post-operative complications. The two main complications are glaucoma and retinal detachment.

The glaucoma is due to an inflammation in the eye blocking the pores that allow fluid to drain away from the eye and causing the intraocular pressure to increase. There is a risk that the eye may develop glaucoma months or even years after the surgery, since the inflammation following cataract surgery can persist for years. In order to minimise the risk of glaucoma post-operatively we recommend applying topical steroid drops once daily for life; however, although this may reduce the risk of glaucoma developing it does not eliminate it entirely.

The eye is also at risk of retinal detachment following cataract surgery, since removing the cataract from the eye can result in a loss of support for the retina, allowing it to fall forward. Retinal detachment or glaucoma, although potentially treatable, will almost invariably result in blindness. Current figures in a recent survey quote a 90% success rate in cataract surgery 12 months post-operatively, but eyes that become affected with glaucoma or a detachment can be expected to become blind, and in the worst scenario a glaucomotous eye may be a source of discomfort and may need to be removed.

PRIOR TO SURGERY

Once cataract surgery has been arranged, drops and sometimes tablets will be prescribed, usually for the five days immediately prior to the surgery, to ensure that there is no inflammation or infection in the eye. Cataract patients can be fed up to and including the evening before the surgery, and water can be left down for them to drink overnight prior to their operation, but the water must be withdrawn on the morning of the operation and they must not be fed any food that morning. The routine for diabetic dogs is that they receive no breakfast on the morning of the surgery and do not receive their morning dose of insulin either. We will resume their insulin when they have recovered from the anæsthetic and are able to eat. We ask that owners of diabetic patients bring their dog’s insulin, normal food and a schedule detailing the daily routine and insulin dosage.

THE DAY OF THE OPERATION

The patients may receive their topical medication on the morning of the surgery but do not need any tablets that morning. We normally ask for them to be presented to the surgery at 9.00 a.m., on the day of the operation so that we can continue to apply topical medication and we aim to operate later in the morning or early in the afternoon. In the majority of cases we will keep patients hospitalised until the following day, so that the eye can be re-assessed. If we are happy with their progress and we can see that the eye is responding well, they can then return home that day.

POST-OPERATIVE CARE

It is necessary to apply topical medication to the eye five to six times daily post-surgery, and to administer oral tablets once or twice daily, and for dogs to wear a protective shield (“Elizabethan collar”). Patients are re-examined one week post-operatively and if making good progress the Elizabethan collar may then be removed. The topical medication is continued for a further five weeks at which time they will be re-examined, and if continuing to make good progress then the topical medication will be gradually reduced to one drop daily to be continued indefinitely. If there is an inflammatory reaction in the eye following surgery, we have the option of administering an injection into the eye at the one week check-up to break down any clots that may have formed within the eye. This injection can be given under sedation, but the patient may need to be hospitalised for 2-3 hours and owners are advised to make allowance for this when arranging their appointment.

If everything is satisfactory at the six week check-up, it is then necessary to re-examine the eye every six months to monitor the intraocular pressure. The topical medication can be supplied by post in the interim period if necessary, or it may be possible for your own veterinary surgeon to supply you with medication.