Ординатура / Офтальмология / Английские материалы / Small Animal Ophthalmology Secrets_Riis_2002

10. What causes KCS?

There are many etiologies. The most commonly stated is immune deficiency disease. Other etiologies include viral distemper; congenital acinar hypoplasia (Yorkshire terrier); iatrogenic, either by drug-induced disease (sulfa class of drugs) or by removal of the secondary gland ("cherry eye") (30% of the tear film production); trauma; neurologic; endocrinopathy (thyroid, Cushing's, diabetes); and, of course, neoplasia.

11.How is KCS treated??

If the primary etiology can be determined and it is treatable, then obviously it should be

treated. For example, KCS from thyroid disease may resolve with thyroid therapy. In addition or if the etiology is not known, the eye must be kept moist. The modalities for a "wet eye" are artificial tears, cyclosporine, pilocarpine, antibiotics, and corticosteroids.

The consensus is that many KCS cases are immune related, and cyclosporine is the modality of choice for this etiology. Cyclosporine stimulates the lacrimal gland by its action as a T-cell immunosuppressant.

Artificial tears have an effective life of 8-10 minutes, so it takes a lot of applications to keep an eye moist. If both "mom" and "dad" are working 8 hours a day, not much is accomplished with artificial tears. Topical antibiotics and antibiotic-corticosteroid combinations are used to reduce infection and inflammation wherever appropriate (if there is an accompanying corneal ulcer, antibiotic-corticosteroid is contraindicated).

Pilocarpine is a parasympathomimetic that can stimulate the lacrimal gland to function, if there is any gland to stimulate. It must be given in high enough doses to have a systemic effect, and therefore it can also negatively affect the respiratory and cardiovascular systems. Some have advocated its use topically as an irritant to cause reflex tearing and as a direct parasympathomimetic. These authors are opposed to pilocarpine for KCS treatment.

12.Is KCS a hard disease to treat?

It takes a lot of work: clean-up, treating, and "staying on top of it." A 60-day trial period of

topical therapy will be enough to determine the efficacy of the therapy. If, at the end of 60 days, there hasn't been a dramatic change, then surgery is indicated. If there has been a positive change in 60 days, medication must be continued indefinitely. Cyclosporine is only effective for short periods of time and must be given continuously. Other supportive therapy is also necessary.

13.Are some KCS cases just not responsive to cyclosporine treatment?

A few breeds of dogs seem to be unresponsive. The German shepherd, samoyed, and West

Highland terrier top the list.

CONTROVERSIES

14.Is cyclosporine indicated when the etiology of KCS is known not to be immune deficiency? Probably no more than 60-70% of the patients treated with cyclosporine respond significantly.

15.Is surgery a good option for KCS?

Surgery to treat KCS involves transposing the parotid gland duct (PDT) from the mouth to

the inferior cul-de-sac so the animal in effect "spits" in the eye. This keeps the affected eye "wet." The question then becomes, Is an excessively "wet eye" from PDT surgery better than a dry eye that needs constant medication? Many authors say that the surgery has insurmountable side effects. Others, including these authors, believe it is better to deal with the minimal problems of a wet eye than having to deal constantly with a nonresponsive dry eye. This applies to the cat as well. Before the advent of cyclosporine, PDT surgery was frequently performed. Because cyclosporine is not the "wonder drug" it was once thought to be, surgery is once again being performed with some degree of regularity.

BIBLIOGRAPHY

I. Gilger B, Allen 1: Cyclosporine A in veterinary ophthalmology. Vet Ophthalmol 1:181-187, 1998.

2.Moore CP: Qualitative tear film disease. Vet Clin N Am Small Anim Pract 20:565-58\, \990.

3.Morgan R, Duddy 1M, McClurg K: Prolapse of the gland of the third eyelid in dogs: A retrospective study of 89 cases (1980-1990). 1 Am Anim Hosp Assoc 29:56-60, 1993.

4.Salisbury MA, Kaswan RL, Ward DA, et al: Topical application of cyclosporine in the management of keratoconjunctivitis sicca in dogs. J Am Anim Hosp Assoc 26:269-274, 1990.

Figure 1. This 7-year-old female shih tzu dog suffered proptosis of the left globe after being attacked by a larger dog. Lateral deviation of the globe is evident with medial rectus muscle avulsion, but the anterior segment is clear and there is minimal orbital hemorrhage. The globe was salvaged but was not visual.

These patients show intact pupillary light reflexes or a miotic pupil in the affected eye with an indirect pupillary response to the contralateral eye. Minimal or no hyphema and minimal orbital hemorrhage are present in patients who continue to have useful vision following proptosis. Intact visual responses with a normal-appearing fundus confer a favorable prognosis.

8.When is the prognosis for vision grave?

When severe trauma resulted in globe displacement and it is accompanied by marked hy-

phema, vitreal hemorrhage, or retinal detachment, the prognosis for future vision is grave.

9. Are there any ancillary tests that can be done to determine the prognosis for vision?

Most veterinary referral centers provide ultrasound imaging of the globe and orbit. Hyphema in the absence of marked vitreal hemorrhage and retinal detachment would suggest a better prognosis compared with vitreal hemorrhage and complete retinal detachment. Blindness following proptosis, however, is frequently the result of optic nerve injury. Visual evoked potentials can be measured with specialized equipment, indicating the transmission of electrical signals from the retina to the occipital (visual) cortex. This type of testing requires a clear ocular media and is rarely considered in the emergency situation, but it can be useful in combination with electroretinography after the globe has been salvaged to determine amount of vision present (see Chapter 1).

10.Is it always possible to salvage the globe?

Some patients present with severe tissue damage to the globe and orbit. Patients with rupture

of the cornea, collapse of the globe, complete loss of extraocular muscle attachments to the orbit (Fig. 2), or excessive corneal injury associated with drying and exposure are often scheduled for

Figure 2. This 8-year-old male Yorkshire terrier dog was attacked by a German shepherd dog resulting in proptosis of the left eye. No extraocular muscle attachments remained intact, and marked orbital hemorrhage is evident. The eye was enucleated shortly after presentation.

enucleation as soon as the patient is able to withstand general anesthesia. Enucleation can be considered at any time during the course of treatment, however, and because of this most clinicians attempt initially to salvage the globe. The prognosis for vision should be discussed with clients, because some will prefer enucleation to rapidly resolve the medical situation if there is no hope for future vision. Even if the globe is salvaged, chronic medical treatment may be necessary to keep the patient comfortable.

11.Is there any danger of injury to the contralateral eye?

Most dogs with proptosis of the globe exhibit unilateral injury. There are case reports of

blindness in the contralateral eye that shows no visible evidence of displacement or traumatic injury. It is assumed that optic nerve tearing at the level of the optic chiasm results in contralateral injury. Excessive traction on ocular tissues, especially in cats, can result in further optic nerve injury with potential involvement of the second eye. Some degree of vision loss in the contralateral eye may occur more frequently than is realized because there is no easy way to assess partial vision loss in veterinary patients.

12. What steps are taken to reposition the globe into the orbit?

General anesthesia is required in most cases to reposition the globe. If proptosis develops as a result of restraint, the hairs can be grasped on the lids and pulled out away from the globe, allowing the eye to fall back into the orbital space. In this situation, anesthesia may not be necessary. With most traumatic cases of globe proptosis, excessive tissue swelling and orbital hemorrhage will complicate globe repositioning and necessitate chemical restraint. Blood and debris are removed from the periocular tissues prior to globe replacement.

When excessive tissue swelling and orbital hemorrhage are evident, a lateral canthotomy not only will ease repositioning of the eye but also will immediately relieve vascular stasis to the globe. Various techniques have been described for globe replacement. Essentially the eyelid margins must be elevated and rotated away from the globe while gentle pressure is placed on the cornea. Stay sutures can be placed in the eyelid tissue near the lid margin to allow manipulation of the eyelids, or tissue clamps (Allis) can be used. Split-thickness mattress sutures of 3--0 to 4--0 nonabsorbable material supported with stents are preplaced and gradually tightened to close the lids around the displaced globe. Caution is used while placing sutures to avoid needle contact with the cornea. Just prior to lid closure, all debris should be thoroughly flushed from the conjunctival fornices using sterile saline. Most clinicians leave a gap medially or laterally for placement of antibiotic and atropine ophthalmic ointments. If a lateral canthotomy is made, it is closed routinely after eyelid closure and stabilization of the globe.

13.Should there be supportive medical treatment after closure of the eyelids?

Following recovery from general anesthesia and in the absence of other severe injuries, most

patients with proptosis can be released for home care soon after replacement of the globe. An Elizabethan collar is often necessary and recommended to prevent self-injury or removal of the sutures. Supportive medical care should include rest, oral antibiotics, and oral corticosteroids. Corticosteroids are used at the anti-inflammatory level to help resolve panuveitis and optic nerve injury in addition to orbital inflammation and swelling. If an opening was left between the eyelids to facilitate application of medications, triple antibiotic ophthalmic ointment is applied 3--4 times daily and atropine ophthalmic ointment is applied I or 2 times daily to control pain associated with ciliary spasm and anterior uveitis. Atropine ointment should be used judiciously because it will contribute to sicca, which is frequently a complication of proptosis in dogs.

If the cornea is ulcerated at the time of globe replacement, evaluation of the ocular discharge emerging from the medial or lateral eyelid opening is an important way to monitor for secondary corneal bacterial infection. If copious white discharge emerges from the opening and the patient shows excessive and progressive discomfort, the sutures can be temporarily removed to further assess the condition of the cornea. Microscopic evaluation of debris collected from the ulcer bed can categorize the inflammation and aid in appropriate changes in antimicrobial therapy.

14.How long should the eyelids be left closed after repositioning ofthe globe?

In general, the eyelids should be left closed for at least 2 weeks. Clients should be instructed

to evaluate the lid closure daily. As tissue swelling resolves, gaps may develop between the upper and lower eyelid margins, allowing suture contact with the cornea. This may necessitate altering the tension on the sutures or replacing them. After 2 weeks, the sutures are removed and the globe is assessed for vision and any other irreversible injury that is evident. If excessive lagophthalmos and exophthalmos persist, the lids should be closed again for an additional 2 weeks.

15.What complications are commonly encountered after the eyelids are opened several weeks following the injury?

Common complications following ocular proptosis include strabismus associated with extraocular muscle injury, both ulcerative and nonulcerative keratitis, keratoconjunctivitis sicca, lagophthalmos, and blindness. Traumatic cataract, iris bornbe glaucoma secondary to hyphema, retinal detachment, and phthisis bulbi can occur additionally.

16.Why does strabismus occur following proptosis?

The medial rectus muscle frequently is torn from the globe at its insertion when the eye is ac-

celerated forward. This results in lateral strabismus in most dogs following proptosis. Reportedly, the strabismus improves with time, presumably associated with readjustment of tension on the remaining viable extraocular muscles (Fig. 3). Although clients have requested reattachment of the medial rectus muscle, finding and reattaching fragments of torn muscle is not likely to be successful following proptosis injury.

Figure 3. This 3-year-old female Pekingese dog suffered proptosis of the right eye 6 weeks prior to this photograph. The final outcome of treatment is evident with lateral strabismus but a quiet, comfortable eye. The strabismus will probably partially resolve in the following months.

17.Why is keratitis frequently a problem following proptosis?

Ulcerative keratitis develops rapidly secondary to exposure after injury. Following treatment

of proptosis using a temporary tarsorrhaphy, keratitis can result from poor tear production and lagophthalmos. Poor tear production can result from direct injury to lacrimal glands or as a result of nerve damage or vascular damage supplying these structures. Treatment with ophthalmic cyclosporine ointment (Optimmune) mayor may not improve tear production because sicca following traumatic proptosis of the globe is frequently neurogenic in origin.

Anesthesia of the cornea is common following proptosis, presumably associated with loss of function of the cranial nerve five sensory endings in the cornea. This also contributes to lagophthalmos and sicca because blinking and tearing are at least partially controlled by reflexes originating in the corneal stroma. Lack of sensation in the cornea in addition to exposure and sicca will promote ulcerative keratitis, referred to as neurotropic keratitis. Ulcers associated with anesthesia of the cornea frequently are very slow to resolve with supportive treatment alone, and other surgical procedures may be necessary.

18.Are there any steps that can be taken to prevent proptosis?

Dogs that experience proptosis with minor trauma frequently have exaggerated brachy-

cephalic anatomic features that provide little support or protection for the globe. Reduction of the excessive palpebral fissure size with lateral or medial canthoplastic procedures can reduce the chances of proptosis in the future. After loss of vision in one eye, many veterinary clients will consider palpebral reduction surgical procedures to protect the second eye.

CONTROVERSIES

19. Should the medial rectus muscle be reattached during globe replacement to minimize postoperative strabismus?

For repair of the medial rectus muscle: Repair of the medial rectus muscle prior to globe replacement can minimize or resolve strabismus, which is common following proptosis injury in animals. After induction of general anesthesia, a lateral canthotomy can be immediately performed to reduce vascular stasis to the globe. Medial rectus muscle is reattached to the sclera at its insertion prior to performing the temporary tarsorrhaphy.

Against repair of the medial rectus muscle: Traumatic proptosis of the globe in animals is usually associated with marked orbital edema and hemorrhage, which prohibits identification of medial rectus fragments for attempted repair. It is questionable whether or not the extended anesthetic time required for extraocular muscle repair and further manipulation of an already traumatized eye is warranted when repositioning of the globe and stabilizing of the patient are of paramount importance. Emergency clinic veterinarians and primary care veterinarians are more likely to initially manage ocular proptosis cases than specialists, and these individuals are not likely to have available specialized surgical instrumentation for strabismus surgery.

20.Should every effort be made to salvage the globe for a cosmetic appearance?

For salvage of the globe whenever possible: Emergency clinic and primary care veterinarians

initially manage the majority of cases of ocular proptosis in animals. If the eye is irreversibly damaged, enucleation is discussed and recommended. In all other situations the eye is replaced in the orbit in hopes of future vision. Specialists later become involved in case management, and with more sophisticated equipment the prognosis for vision can be clearly established. Emergency and primary care veterinarians are reluctant to recommend enucleation in the absence of such information.

Against salvage ofthe globe when blindness is inevitable: Most veterinary ophthalmology references indicate that every effort should be made to salvage the globe even if enucleation may be necessary at some later point. This advice may be hard to justify in light of the overall poor prognosis for vision in most cases of traumatic proptosis of the globe. The recommendation becomes even more difficult to justify when consideration is made of the time of patient discomfort following salvage versus enucleation and when medical expenses are considered for the various approaches to treatment. Obviously, enucleation is not recommended if there is any hope for vision, but enucleation perhaps should be considered early on for hopelessly blind eyes when clients are more concerned with patient discomfort and/or medical expenses than the final cosmetic appearance. Following enucleation of the globe, most animals have fully recovered from inflammation and discomfort 5 days after surgery. Traumatized eyes may be inflamed and painful for weeks or months after injury. Most veterinary clients are not well informed on the usual appearance of salvaged globes, and the "cosmetic" appearance of laterally deviated and oftentimes phthisical eyes can be debated. After induction of general anesthesia to replace the proptosed globe, ultrasonography can be performed quickly.lfthis shows excessive ocular hemorrhage and retinal detachment, then enucleation can be strongly considered to rapidly alleviate patient discomfort.

BIBLIOGRAPHY

I. Fritsche, J, Spiess BM, Ruehli MG, et al: Prolapsus bulbi in smaJl animals: A retrospective study of 36 cases. Tierarztl Prax 24:55-61, 1996.

2.Gilger BC, Hamilton HL, Wilkie DA, et al: Traumatic ocular proptoses in dogs and cats-84 cases (1980---1993). J Am Vet Med Assoc 206:1186-1190,1995.

3.Kern TJ: The Canine orbit. In Gellatt K (ed): Veterinary Ophthalmology, 2nd ed. Philadelphia, Lea & Febiger, 1991, pp 243-244.

4.Lindley DM, Ringle M, Moorthy R, et al: Efficacy of lateral canthotomy and cantholysis in orbital hemorrhage. Vet Pathol 29:473, 1992.

5.Ramsey DT, Fox DB: Surgery of the orbit: Surgical management of ocular disease. Vet Clin North Am

27:1244-1247,1997.

6.Slatter DH: Ocular emergences. In Fundamentals of Veterinary Ophthalmology. Philadelphia, W.B. Saunders, 1990, p 538.

7.Spiess BM, Wallin-Hakanson N: Diseases of the canine orbit. In Gellatt K (ed): Veterinary Ophthalmology, 3rd ed. Philadelphia, Lippincott Williams & Wilkins, 1999, pp 520---522.