How to Refer: Lens Conditions
Why & When to ReferAbnormal lens conditions can be potentially serious problems. Animals may present to the veterinarian with clinical signs of acute ocular pain, vision loss, ocular inflammation, or glaucoma. Prompt and accurate recognition of these clinical signs and immediate therapy may be the difference between saving vision and a blind eye. Referral to a board-certified ophthalmologist should be considered when the lens has been identified as the cause of the eye condition or if routine diagnostics and a complete eye examination fail to confirm a specific cause. The most common reasons to refer include lens luxation, lens-induced uveitis, cataract formation, and traumatic perforation of the lens capsule. Permanent blindness from conditions of the lens is often related to delay in referral or owners' inability to recognize that their pets have eye disease.
What Information to SupplyWhen referring an animal with a lens condition for evaluation and treatment, it is important to convey whether the condition is acute or chronic and its suspected severity. For example, a 12-year-old poodle with cataract progression over 4 years may be referred for cataract evaluation and surgical removal. This typically is not an emergency. In contrast, an animal with lens luxation, lens perforation, or lens-induced uveitis and/or secondary glaucoma has an ophthalmic emergency and should be evaluated by an ophthalmologist as soon as possible.1-6
The veterinarian should perform a complete ophthalmic examination to include evaluation of pupillary light reflexes, menace reflexes, Schirmer's tear test, fluorescein stain, and tonometry. A complete blood count and serum chemistry analysis may be indicated. Any specific infections or metabolic conditions should be addressed and diagnostic tests performed as deemed appropriate based upon the primary reason for referral. Convey the results of these tests to the ophthalmologist along with any known or suspected conditions the animal may have, as this information may alter either the treatment plan or prognosis. Current medications, dosage, and frequency should be reported as well.
What to RequestThe referring veterinarian should request that priority attention be given to the patient with an acute crisis that involves lens luxation (with or without glaucoma), perforating lens injury, or lens-induced uveitis. Failure to initiate aggressive medical or surgical therapy could result in blindness. The referring veterinarian should expect confirmation that the patient with an ocular emergency will be seen on a timely basis. If this is not possible, referral to another ophthalmologist should be considered. To find a board-certified veterinary ophthalmologist in your area, log onto www.acvo.org and search under "Locate an Ophthalmologist."
What to ExpectAfter the ophthalmic examination, the specialist will discuss with the owner the details of the pet's condition, recommended treatment options, and various prognoses. If an animal has an acute lens luxation and the eye is visual, emergency surgery to remove the lens is indicated.3 Surgery is generally scheduled within 24 hours of referral. The presence or absence of secondary glaucoma may alter the medical or surgical plan based upon the expected visual prognosis and whether the lens is in the anterior or posterior chamber.
In the diabetic dog, rapid onset of cataract formation is common and results in lens-associated uveitis.1 The iris, ciliary body, and choroid may exhibit varying degrees of inflammation as lens proteins leak through the intact lens capsule. With any lens-induced uveitis, aggressive medical therapy should be instituted. Topical nonsteroidal antiinflammatory drugs (NSAIDs) (Ocufen, Profenal, and Voltaren*) and systemic NSAIDs (Rimadyl, EtoGesic, Metacam, and Deramaxx*) may be used to inhibit prostaglandin-mediated inflammation by interrupting the cyclooxygenase pathway. Topical atropine 1% may be used to stabilize the blood-aqueous barrier, minimize pain from ciliary muscle spasm, and dilate the pupils. Potent topical corticosteroids (1% prednisolone acetate or 0.1% dexamethasone) may be added as they penetrate an intact cornea. Once the uveitis is controlled, surgical removal of the cataractous lens may be indicated.
An ocular ultrasound and electroretinogram are recommended prior to surgery to verify retinal health. The ophthalmologist may recommend prophylactic retinopexy to reduce the risk of retinal detachment before cataract surgery. Immediate lens removal is indicated with rupture of the lens capsule secondary to trauma or diabetic intumescence.4, 6 Early recognition and treatment of lens-induced uveitis are critical to ensure surgical success with cataract surgery as uveitis increases the risk of glaucoma and retinal detachment.5 Thus, animals referred strictly for cataract surgery that have lens-induced uveitis may be placed on topical and/or oral antiinflammatory therapy until cataract surgery is performed.
Follow-up CommunicationThe referring veterinarian should expect timely and regular updates from the ophthalmologist, including oral and written communication after both the initial examination and subsequent rechecks. The ophthalmologist will tell the owner and referring veterinarian when the pet should return for follow-up exams. Depending on the specifics of each case, the referral veterinarian may be involved in long-term examination and treatment of the condition, which may include obtaining tonometry readings and assessing vision, ocular pain, and overall clinical improvement.
It is important for the specialist and referring veterinarian to communicate routinely about the patient's progress. The specialist should be notified if any changes occur in the animal's health that could affect any aspect of the eye condition or treatment. For a trusting and long-term professional relationship to prosper, the referring veterinarian and specialist should have a mutual respect and understand that both doctors will be needed to assure the best quality of care for the patient.
LENS CONDITIONS • Michael H. Brown
References
Ocular manifestations of diabetes mellitus: Diabetic cataracts in dogs. Basher AW, Roberts SM. Vet Clin North Am Small Anim Pract 25:661-676, 1995.
Lens-induced uveitis. Van der Woerdt A. Vet Ophthalmol 3:227-234, 2000.3. Diseases of the lens and cataract formation. Davidson MG, Nelms SR. In Gelatt KN (ed): Veterinary Ophthalmology, 3rd ed-Philadelphia: Lippincott Williams & Wilkins, 1999, pp 821.4. Traumatic anterior lens capsule disruption. Davidson MG, Nasisse MP, Jamieson V, et al. JAAHA 27:410-414, 1991.5. Lens-induced uveitis in dogs: 151 cases (1985-1990). Van der Woerdt A, Nasisse MP, Davidson MG. JAVMA 201:921-926, 1992.6. Surgery of the lens. Nasisse MP, Davidson MG. In Gelatt KN (ed): Veterinary Ophthalmology, 3rd ed-Philadelphia: Lippincott Williams & Wilkins, 1999, p 827.
Resourceswww.acvo.org: Web site of the American College of Veterinary Ophthalmologists