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ANIMAL EYE CLINIC INFORMATION SERIES! www.seattleaec.com Vitreoretinal Surgery Anatomy of the eye page 1 ANIMAL EYE CLINIC INFORMATION SERIES! WHAT NORMALLY KEEPS THE RETINA IN PLACE? As stated previously, the retina lies against the back wall of the eye. The back of the eye (vitreous cavity in diagram) is filled with a transparent gel which stabilizes the intraocular structures- much like styrofoam peanuts in a box of fine glassware. When the head moves rapidly, as when a dog shakes a toy in his or her mouth, the vitreous reduces the amount of turbulence inside the globe. The retina is fused to the inside wall of the eye over 360 degrees in the area marked pars plana in the diagram, as well as at the optic nerve. Everywhere else, the retina is held against the wall by a suction pump that pumps fluid out of the space between the retina and the wall- the retina is essentially suctioned onto the wall. WHAT CAUSES RETINAL DETACHMENT? The retina can detach for a few reasons- the suction pump can fail, allowing fluid to build up between the retina and the wall; fluid can be forced out of the wall faster than the pump can remove it; or a hole can develop in the retina. In this last example, the pump still works, but fluid simply flows in through the hole into the space between the retina and the wall, resulting in detachment. This type of detachment page 2 www.seattleaec.com ANIMAL EYE CLINIC INFORMATION SERIES! www.seattleaec.com is called a rhegmatogenous retinal detachment. While other types of retinal detachment are often treatable with medications, a rhegmatogenous detachment requires surgery if it is to get better. ! HOW DO HOLES FORM IN THE RETINA? In animal patients, we are mostly concerned with two scenarios. The first would be a dog who has inherited defective vitreous. This is called vitreal dysplasia- rather than a nice firm molded gel, the vitreous is watery with rope-like strands running through it. As the head and eyes move, the strands are swinging back and forth in the swirling liquid, pulling on the retina. This can lead to tearing of the retina, with subsequent fluid flow into the hole and separation from the wall. This type of inherited detachment is seen most commonly in certain breeds including the ShihTzu, Italian Greyhound, Parson Russell Terrier, Chinese Crested, as well as many mixed-breed dogs. The other scenario is in dogs who have developed cataracts +/- had cataract surgery. Cataract developmentespecially if very rapid in onset, can lead to inflammation. This inflammation in turn can lead to areas of adhesion between the retina and vitreous, with subsequent tearing. HOW CAN I TELL IF MY DOG HAS A RETINAL DETACHMENT? Most owners won’t recognize a problem in one eye. When the retina detaches the patient will lose some or all of the vision in the affected eye. You might notice an increased glow in the pupil as light reflects more brightly off of the bare wall in the back when the retina falls away. Sometimes a torn retina will bleed, leading to a red appearance behind the pupil or in the front of the eye. In the case of an inherited detachment most people don’t notice until the second side detaches and the patient is suddenly acting blind. In the cataractpage 3 ANIMAL EYE CLINIC INFORMATION SERIES! www.seattleaec.com associated type a detachment may be found before surgery (pre-operative ultrasound is performed to look for detachments when the cataract prevents us from directly viewing the retina), or it is seen during routine post-operative rechecks if it develops later. HOW CAN SURGERY HELP? There are different surgical options depending upon the situation and the treatment goals. 1. Complete retinal detachment or giant retinal tear: ! This is the situation with the inherited type, as well as some of the post cataract types. Basically there is a large tear in the retina, and as a result the majority of it has separated from the wall. In this case we would perform a vitrectomy. In this procedure three holes are made into the back of the eye. Fluid flows into the eye through one, a light is inserted into the second to illuminate the area, and the third is used to introduce different surgical instruments. First the vitreous is completely removed. Next a heavy fluid is introduced into the space- this flattens the retina back against the wall of the eye. A laser is then used to seal any holes or tears so the body’s own suction pump will once again be effective at keeping the retina in place by removing fluid. The heavy fluid will cause problems if left in place, so it is then removed and replaced with silicone oil- the new vitreous. This procedure is approximately 85% successful in reattaching the retina, but the amount of vision that returns is variable. Success depends upon how long the retina has been separated, whether the retina has scarred while detached, and other intrinsic factors. Surgery can be unsuccessful- problems can occur during or after- page 4 ANIMAL EYE CLINIC INFORMATION SERIES! www.seattleaec.com ward leading to failure. These include severe hemorrhage inside the eye while transferring fluids (expulsive choroidal hemorrhage)- the most common intraoperative complication. Post operative complications include: infection, glaucoma (increased pressure in the eye), cataract formation (often this can be removed via cataract surgery), recurrence of the retinal detachment, and leakage of silicone oil into the front of the eye or into the tissues surrounding the eye. Some of these complications can be addressed with medications or additional surgery, but not all. In the worst case scenario, an eye might even require removal to restore comfort if painful. ! Post operative care: your dog would be discharged the same day. The eyelids are often partially closed with a temporary stitch as they may not blink fully for the first few days after surgery. This stitch is removed at the first recheckusually 3-5 days later. There would be some eyedrops for a few weeks, and oral medications to reduce inflammation, maintain comfort, and prevent infection. An Elizabethan collar is kept on at all times for 2-3 weeks. Vision recovers slowly, and the amount of vision that returns varies between patients. It can take as much as 6 weeks to see any improvement, although most will show evidence of returning vision earlier. Some may not recover vision at all (uncommon), others appear to function normally. The most common successful outcome is a return of functional, but not normal vision. These dogs do better in brightly lit surroundings. They seem to have better distance vision than close vision. They can avoid objects, find doorways, navigate well and confidently. If a toy is tossed they will see that it was thrown, but not be able to pinpoint the spot from where they sit. 2. Small tear with partial detachment: ! Sometimes in this situation we can use a laser to “wall off ” the detached area in hopes of preventing further spread of fluid between the retina and wall. This is called a barrier retinopexy. The chances of success page 5 ANIMAL EYE CLINIC INFORMATION SERIES! www.seattleaec.com depend upon the specific situation- your doctor would discuss more fully during the appointment. 3. Inherited vitreal dysplasia with retinal detachment in one eye, but currently no tears in the second: ! In this case, the eye without any detachment has a significant risk of detaching later. We do not know how great this risk is as studies have not been performed, and we don’t know how many dogs have detached one side without their owner’s knowledge. In human patients, the recommendation is to laser the periphery of the retina in order to lower the risk of tears leading to detachment later- prophylactic retinopexy. This likely reduces future risk, but, again, no studies have been done in dogs. It is painless post-operatively, so very low-impact for the patient. There is a small risk that the inflammation in the immediate post operative period can actually lead to detachment- especially in a very active patient. For this reason it is best to keep your dog quiet for 7-10 days afterward. Otherwise there are no other complications associated with this procedure, but it may not work- i.e. tears and detachment can still happen, although they are presumably less likely to occur. WHAT IF I DECIDE NOT TO DO SURGERY? There aren’t any right or wrong decisions. Long term, the presence of a retinal detachment in an eye can lead to glaucoma. This is increased pressure inside the eye. It can lead to vision loss, although most eyes with retinal detachment will already be without vision. The concern would be comfort as increased pressure can cause a headache sensation. Affected dogs rarely squint or rub at the eye, rather they sleep more and play less. If the pressure increases, the eye might become more cloudy, or it may bulge and slowly enlarge. If any of these changes occur, see your ophthalmologist right away. Otherwise it would be a good idea to monitor pressure over time to watch for any increase. If both eyes are detached and your dog has lost vision completely, he or she can still have an excellent quality of life. It is important to keep in mind that most blind dogs have an excellent quality of life as long as comfort is maintained. Not only are they in a protected and loving environment, dogs use vision very differently than humans with their other senses far more developed than ours. Sudden vision loss will take a longer period of adjustment than a gradual decline, but in either case most owners report that their pets adapt remarkably well. page 6