Ординатура / Офтальмология / Английские материалы / Small Animal Ophthalmology Secrets_Riis_2002

Figure 8. The sliding conjuncti- val-corneal graft is sutured to the adjacent cornea with 8-D Vicryl. Note the central cornea now has clear tissue, but the periphery of the graft is opaque from the conjunctiva.

7.Following the surgical procedure elected, is it necessary to medicate the eye topically?

Yes, most ophthalmologists prefer to medicate a corneal wound with a broad-spectrum an-

tibiotic. Culture and sensitivity tests from the surgical site should be submitted on all keratectomy cases. The results many times are negative, possibly because the patient has been on topical antibiotics presurgically. Those that have resulted in positive cultures have a high incidence of Mi- CroCOCClIS, which usually will respond to antibiotics, such as tobramycin (Tobrex) or ciprofloxacin (Ciloxan). Ointments are preferred mainly for their longevity. Allografts and heterografts should also be treated with 0.2% cyclosporine (Optimmune) twice a day for 3-6 months, depending on acceptance of the graft. In addition to the above, topical corticosteroids (dexamethasone) should be used for regression of neovascularization once the healing has taken place.

8. Should atropine be used postoperatively?

Initially, mydriasis is indicated, so a dose of 1% atropine preand postoperatively usually lasts 3-5 days. If atropine solution is used frequently and over days to weeks, the medication causes adverse effects that outweigh the desired effects.

9.If some pigment remains in the deep stroma after the keratectomy, is that bad?

The incomplete removal of the stromal pigment does not have adverse long-term consequences.

A faint tint of brown may be the worst remaining consequence, but the healing will progress.

10.Where does the pigment come from?

It is not known for sure. It may arise from the lacrimal gland or from the conjunctival flora.

The pigment, whatever its source, can be noted in the tears. It can stain the hairs around the eyes; it can be absorbed onto tissue paper; and, if you treat an ulcerated cornea with a soft contact lens, it will densely stain the contact. Attempts to identify the stain have proven the pigment to be a protein (Fig. 9).

11. In which cat breeds are sequestra most prevalent?

The breeds of highest incidence of sequestrum occurrence are the Burmese, Himalayan, and Persian. These breeds all have shallow orbits and protruding eyes, which make their corneas particularly vulnerable to microtrauma from trichiasis, entropion, lagophthalmia, and associated diseases of the adnexa.

12. Is there anything that can be done to prevent recurrence if the diagnosis of sequestration has been made and surgical treatment instigated?

Although there are no guarantees, it is helpful to start a topical antiviral at the first indication of corneal irritation and confirmation of an ulcerative process. Also, vaccines should be main-

4.Morgan RV: Feline corneal sequestration: A retrospective study of 42 cases (1987-1991). J Am Anim Hosp Assoc 30:24-28, 1994.

5.Nasisse MP, Guy JS, Davidson MG, et al: Experimental ocular herpesvirus infection in the cat. Invest Oph-

thaImol Vis Sci 30:1758-1768,1989.

6.Pentlarge VW: Corneal sequestration in cats. Comp Cont Educ Pract Vet 11:24-32,1989.

7.Schmidt GM, Whitley RD: Management of feline corneal sequestration: Medical therapy and surgical therapy. Vet Med Report 1:258-261, 1989.

8.Startup FG: Corneal necrosis and sequestration in the cat: a review and record of 100 cases. J Small Anim

Pract 29:476-286, 1988.

9. Wilkie DA, Whittaker G: Surgery of the cornea. Vet Clin N Am Small Anim Pract 27:1067-1107, 1997.

eosinophils have released their cytoplasmic granules. The slide preparation technique may cause this traumatic fracture of the cells; a gentle blotting or rolling of the material gathered usually yields more intact eosinophils.

5.Are the eye manifestations in any way related to the dermatologic syndromes?

No, the ocular lesion is unique.

6.Is there any consistency to ocular involvement or breeds involved?

Usually, the condition presents as a unilateral problem; however, it has been seen bilaterally.

Previously diagnosed cases can re-present with the opposite eye involved. There is no breed or sex predilection.

7. What is the etiology of proliferative keratoconjunctivitis?

The etiology is uncertain, however, one study found PCR-positive results against feline herpesvirus-I (FHV -1) in 76.3% of the surgical samples taken from proliferative lesions. To add to the uncertainty, this author has diagnosed and treated specific-pathogen free (SPF) cats with proliferative keratoconjunctivitis.

8.What is the treatment for proliferative keratoconjunctivitis?

The lesions respond to corticosteroids. Depending on how aggressive you choose to be, top-

ical, subconjunctival, and oral medications all are effective. If the cat is difficult to treat and the lesions are large, all three routes can be used. Initially, give 0.1 ml of 40 mg/ml of methylprednisolone (Depo-Medrol) subconjunctivally. Oral megestrol acetate should be prescribed: 5 mg/day for 1 week, then 5 mg/every other day for 1 week, then 5 mg/every third day for 2 weeks, and tapering off after 6 weeks. Minor lesions need to be treated only with the topical medication.

9.Are there concerns over the use of megestrol acetate?

Yes, owners should be warned about possible polydipsia-polyuria signs. Most cats lose these

adverse signs once the dose is reduced or stopped. Some weight gain has also been noted on Ovaban, which is now off the market.

10. Causing a flare-up of FHV is a concern with corticosteroids use. Do nonsteroidal antiinflammatories work?

Topical 0.1 % diclofenac, 0.03% flurbiprofen, 1.0% indomethacin, and 1.0% Suprefen all reduce the neovascularization and, therefore, slow the proliferative course of the disease. These medications need to be used 4-6 times per day for several months, but the results still may not be as good as with corticosteroids. Another drawback is that cats become tired of frequent, long-term eye medications, and their owners feel they cause a bonding loss with this ritual.

11.Can a different therapy approach be used other than corticosteroids?

Yes, immunomodulators have been used.

12.Which immunomodulator has worked?

Interferon alfa-2a has been successful when used at an oral dose of 1000 IUlday/week, fol-

lowed by no treatment for 1 week, then again back on medication. This alternating schedule is continued as necessary, but eventually the treatment is completely cancelled. In severe cases, oral interferon is supplemented with topical steroids.

13.How is the interferon prepared?

Interferon alfa-2a (Roferon-A Roche Pharmaceuticals) is sold in units containing 3 million

IU. Aliquots are made up with 10,000 IU/ml and dispensed with directions to give oral 0.1 ml (1000 IU)/day.

14. Are there any adverse effects from interferon in cats?

The only reported side effect is a reduced white blood cell level, which returns once the interferon is stopped. The alternating weekly dose helps keep the white blood cell level.

BIBLIOGRAPHY

I. Bedford P, Cotchin E: An unusual chronic keratoconjunctivitis in the cat. J Small Anim Pract 24:85, 1983.

2.Larocea RD: Eosinophilic conjunctivitis, herpesvirus, and mast cell tumor of the third eyelid in a cat. Vet Ophthalmo13:221-225,2000.

3.Nasisse M, Luo H, Wang Y, et al: The role of feline herpesvirus-I (FHV-l) in the pathogenesis of corneal sequestration and eosinophilic keratitis. Proc Am Coli Vet OphthalrnoI27:80, 1996.

4.Pentlarge VW, Riis RC: Proliferative keratitis in a cat: a case report. JAm Anim Hosp Assoc 20:477, 1984.

5.Pentlarge V. Eosinophilic conjunctivitis in 5 cats. J Am Anim Hosp Assoc 27:21,1991.

6.Prasse K, Winston S: Cytology and histopathology offeline eosinophilic keratitis. Vet Comp Ophthalmol 6:74,1996.