Animal Eye Clinic

The Pigmentation Continues!

animaleye — Sun, 01 Aug 2010 03:48:37 +0000

We talked about melanoma in the dog and cat in the iris and iris cysts in my last post, but what about pigment on the surface of the eye? There are a number of diseases that create pigmentation on the surface in the dog and cat that are worth exploring!

Limbal Melanoma

The junction between the clear cornea and the white sclera is called the limbus and is a circular line that separates them. Melanoma can arise from here and is also considered benign. Growth, however, can occur and is more common in young animals than in old where it may remain static. If progression is suspected and your dog, less commonly cat, is affected, you have 3 basic choices. First is to remove the affected tissue and then graft in a donor piece of sclera to replace the wall of the eye that was resected. This is the most aggressive approach and carries the benefit of the surgeon being able to hold the tumor in their hand once removed and hopefully confirm complete excision. The negative is the invasiveness of the procedure and the inflammatory reaction that must be controlled both inside and outside the eye after surgery. The second and third is ablation of the tissue using cold (cryosurgery) or heat (laser). The mass is typically debulked or shaved off and the remaining pigmented tissue is destroyed by placement of the probe over the mass and treating the area. Although you are leaving tumor behind, this treatment is very successful, less invasive and reasonably well tolerated. The negative is that you are relying on your adjunct therapy to resolve the tumor rather than knowing you have completely removed it with resection. The area retains some pigment which has to be monitored for progression but usually remains a charcoal gray color. Both laser and cryo incur an inflammatory reaction to the eye which must be managed. Cryosurgery is my typical treatment of choice. The last option, especially in older dogs, is to measure, wait and watch as clinically they may not progress or progress quickly in which case there is little risk to leaving them there.

Limbal melanom in the dog

Limbal melanoma, post-op cryosurgery

Corneal Sequestrum

One of my favorite diseases in the cat is called a corneal sequestrum where the collagen of the cornea becomes discolored and turns a dark brown or black. It usually starts with a minor, poorly defined, tea-staining of the clear cornea, usually in the central region, and then progressively organizes and becomes more dense with well defined borders. In its beginning stages, it is not uncommon to see this associated with a corneal ulceration. What causes this pigmentation? Well, three basic entities are related to sequestrum formation. The first is breed which implies a genetic predisposition. We will see these develop more commonly in the Persion, Himalayan and Burmese cat although any cat can get one. Second is due to any low-grade, chronic irritation. The most common of these would be entropion, or rolling in of the lids. As the hair around the lid is directed onto the surface of the cornea, it is not uncommon to see ulceration and subsequent sequestrum formation that lines up with the offending hairs. The last is our friend the herpes virus, the most common cause of surface disease in the cat, which creates ulcerative disease of the cornea with deposition of pigment in the ulcer bed.

Treatment of corneal sequestra involves managing the primary problem (lid surgery if entropion, antivirals if herpetic, for example) and concurrently watching to see if the pigment dissipates or organizes. If an ulcerative problem is active and resolves, sometimes the tea color will dissipate as the ulcer heals. Sometimes the sequestrum will organize, develop sharp borders and the body will try to extrude or “kick it out” like a foreign body. This may take months but if the cat is comfortable, carries anesthetic risk for removal or has other issues to contend with, time may be on your side. If viral or genetic in basis, the ulcer may be difficult to heal, the eye remains painful and then this becomes a surgical problem.

Surgery involves shaving off the pigmented region of the cornea (keratectomy) and, depending on the depth of the pigment into the corneal tissue, subsequent grafting. Grafting of the cornea is performed if we have a structural weakness due to thinning of the cornea as a result of tissue removal that is greater than 50% of the true thickness. It may also potentially decrease the chance of recurrence which is not uncommon in this disease. The method of grafting depends on the size and depth of lesion and includes conjunctival grafts and corneoscleral transpositions. These methods are highly successful and result in a relatively clear cornea at the conclusion in the cat as we try to return to a comfortable and visual state.

Corneal sequestrum in a cat

Corneal sequestrum, post-op keratectomy

Pigmentary Keratopathy/Keratitis

Chronic, low-grade irritation comes in many flavors in the dog. Usually, a combination of exposure issues, hair abnormalities, dry eyes and genetic predisposition can result in slow and steady deposition of pigment in the clear cornea. Thererfore, breeds like the Pug, Pekinese and Shih Tzu are frequent fliers to our clinic because of this constellation of problems. Surface disease may resolve but the pigmentary change may continue. Treatment involves resolution of the primary problem (lid surgery? hair removal? tear replacement?) then monitoring for progression of the pigmentary component. If advancement is obvious, then medications to try to dissolve the pigment or slow its advancement are utilized. These drugs, primary tear stimulants, are the only true medications we have in our armamentarium to halt pigmentation and their response is unpredictable and often limited. Surgical removal of the pigment is only a temporary treatment since the pigment returns quickly. Thus, procedures to minimize the exposure component and improve protection of the cornea or tear distribution may be used together to try and halt vision loss in these cases.

Pigmentary keratopathy

Dense pigmentary keratopathy

As you can see, pigment in the eye comes in many forms so keep a look out and call if you notice anything that resembles these changes. Early diagnosis and intervention, as in most cases, may increase the possibility of a good outcome. Talk to you later!

Here Comes the Sun!

animaleye — Thu, 10 Jun 2010 13:14:27 +0000

I can’t believe it is almost summer! Although not technically summer, the Memorial Day weekend, especially when sunny and warm, brings out the BBQ in all of us. Swimsuits come on, picnics for graduation appear, a relative’s wedding takes a weekend and the next thing you know the whole family is spending more time outdoors. This is a favorite time of year for our family with our two active boys and a growing puppy which makes us break out the hats, bug spray and the sunscreen to protect us from the newly changing environment. Fortunately, too much sun and sunburn is not a major issue for our pets, but pigmentation changes of the eye is a common observation by owners that prompts a visit to the eye clinic. We will review some of these entities here in case pigmentation of the eye is something of concern for you and your pet.

Iris Cysts

Cysts inside the eye are a common and benign problem we see in dogs and, less commonly, cats on a regular basis. The ciliary body, which produces the fluid which bathes the front part of the eye, is lined by pigmented cells. In some instances, this tissue will bud off in the process of making fluid which causes a pigmented, fluid filled structure to peek out from behind the iris. As the processs continues, this cyst may release from behind the iris and float in the anterior chamber. As one may intuit, these cysts are typically round, see-through and mobile unless they become wedged between the clear cornea and the lens. This is a very common finding in the Goldern Retriever and Boston Terrier but can be seen in any breed. They are benign and warrant no treatment.

Iris Melanoma in the Dog

A melanoma in the iris or ciliary body of the dog is another common problem observed inside the eye. Although benign, meaning it will not spread outside of its location, it can be bad news for the eye as slow growth is expected. The presence of the mass can cause inflammation, cataract formation, retinal detachment and glaucoma. Usually, resection or laser destruction of the mass is not practical or successful unless quite small or easily approached. Therefore, removal of the eye to try and prevent it from becoming painful as well as confirming the benign nature of the mass by pathological evaluation is often advised. Eye removal sounds horrible but honestly dogs and cats do wonderfully with this surgery if warranted.

Iris melanoma

Iris Melanoma in the cat

Different than dogs, melanoma in the cat eye is determined as diffuse meaning it is not localized to a single location. The iris can become spotted with pigmentation change and does not form a visible lump like it does in the dog. Although considered malignant, meaning it can spread to distant locations, the progression to this state can take years. To confuse the matter, cats can get benign freckles on the iris that look identical and are probably an early version of the same process before the cells transform into cancer cells. In more advanced cases, the iris in the region of the pigmentation may take on a velvety look and pigmented cells may be seen floating in the fluid in front of the iris. Because of the slow development, we now take digital photos of the iris and follow for change. If these changes become concerning, eye removal may be advised if a systemic workup for metastasis is negative. Occasionally, irises that have progressed in pigmentation that are removed still receive a histopathological diagnosis of melanosis which is taken as a good sign that we may have gotten it out before it transformed to a malignancy. Below are two pictures of irises, one with melanoma and one with melanosis…..difficult to tell which is which, isn’t it?

I will talk about other diseases with a pigment component in the cornea in my next post….don’t forget to sunblock!

Iris melanoma

Iris melanosis

Hello and Welcome to Our New Website!

animaleye — Thu, 19 Nov 2009 17:30:45 +0000

NATIONAL SERVICE DOG EYE EXAM MONTH

The Animal Eye Clinic of Wilton is proud to be supporting the National Service Dog Eye Exam Month! This special month, established by the American College of Veterinary Ophthalmologists in conjunction with Merial Pharmaceuticals, has been created to allow dogs in all forms of service to be awarded a free eye exam from a board certified ophthalmologist. So if your friend is a drug sniffer or seeing eye and anything in between, they may be eligible for this service. Go to www.ACVOeyeexam.org to see if your dog qualifies for this valued service! I have posted 2 videos on our helpful resources page as well, one from the ACVO and the other from Good Morning America, that may be helpful if you think your dog could benefit from an eye exam. Call us at 203-762-9399 if you have any questions about this service of any other information that we can provide. Dogs eligible for this exam will be seen on Thursday afternoons throughout the month of May.

OUR NEW ADDITION!

Lots of new things happening here at the AEC! If you haven’t had the need to come visit us, that is probably a good thing! But if you have come by or will be coming, I think our new facilities will impress. The initial reaction from new and returning clients have been all good. The improved parking, larger and more comfortable waiting room and exam rooms decorated with warm, calming colors have all got excellent reviews. My wonderful staff remains intact even after the rigors of the move and continue to serve you as before. As always, we try to combine good service, clinical expertise and sound advice with a dose of common sense to help you make educated decisions for your pet’s eye problems.

Speaking of new pets, my family has a new addition, too! Tess is a 9 week old Australian Shepherd that has found her way into hearts and home as of March 21st. A few years ago we went from 3 geriatric cats and a dog (average age of 16!) to none about the time my two beautiful boys were getting in an out of diapers. So the family with 2 vets and no pets has finally reloaded with 2 fish and a new puppy! Tess has been a wonderful addition and has reminded my wife and I of all the joys and challenges of raising a puppy. Fortunately, she is quite smart and well behaved, so our experience has been a positive one for both parents and kids.

This prompts a note about ocular disease in puppies. Eye disease is certainly not limited to adults as congenital malformations, surface inflammation or infection, trauma and even cataracts can be noted in young dogs. If you are a breeder, hopefully you are having your puppies (and their parents) screened for genetic-related problems. A CERF exam, for the Canine Eye Registration Foundation, is a dilated exam of pups and adults. These exams are for healthy pets with no apparent ocular problems that we evaluate closely for any evidence of genetic-based disease. Small changes, such as cataracts and retinal folds, will be marked as present and the form sent to CERF to determine breeding is a good idea in the future. Call to schedule this type of exam if you want to assess your breeding recommendation or even if you are just concerned about your puppy and want to insure normal ocular health at that time. Genetic disease is not the same as congenital disease which means you may be normal as a puppy but can still develop changes as an adult that have a genetic basis. Thus, CERF exams are recommended on an annual basis and then once at the end of the dog’s career to assess for any late onset problems.

See you soon, and say hello to Tess if she is visiting while you are!

Hope to see you soon,

Chuck Stuhr, DVM, DACVO