Eosinophilic keratitis

From Cat
File:Fek1.jpg
Gross appearance of feline eosinophilic keratitis as white plaques that partially cover portions of the cornea. Neovascularization also is present (image courtesy of Dr. U. Dietrich).
File:Fek2.jpg
Gross appearance of eosinophilic conjunctivitis. The bulbar conjunctiva is thickened, light pink, and extends onto the cornea from the lateral limbus (image courtesy of Dr. U. Dietrich).

Feline eosinophilic keratitis (FEK) is a relatively common corneal disease of cats of any age.

This disease affects many purebred and cross-bred cats, especially the Persian, Siamese, Himalayan and Russian blue[1].

Feline herpesvirus-1 (FHV-1) has been isolated in the majority of corneal scrapings from cats with this disease[2].

Feline eosinophilic keratitis typically presents as a white to pink plaque that affects a variable portion of the cornea. The most common location of the initial lesion is at the temporal limbus, while the second most common site of development occurs at the nasal limbus. Lesions may progress to involve multiple quadrants of the eye. In addition, FEK may eventually become a bilateral condition, if left untreated. Grossly, the corneal plaque has the appearance of a thick white deposit of material that has a gritty consistency and can easily be removed by scraping. The appearance and consistency of this white plaque is pathognomonic for FEK.

Severe conjunctivitis and chemosis may accompany this condition[3].

Diagnosis of FEK is largely based on the presence of the typical corneal lesion(s) and exclusion of other causes by cytologic examination and culture such as Chlamydophila spp.

Microscopic examination of corneal scrapings usually contains an increased number of eosinophils, a few neutrophils, noncornified squamous epithelial cells, mast cells, and lymphocytes. Other cytologic findings include detritus and free eosinophilic granules[4].

Anti-inflammatory drugs are the mainstay of treatment for this disease[5].

Megestrol acetate is usually given at 5 mg orally once daily for 2 days, then reduced to every second day for 4 - 5 weeks, depending upon response.

Potential adverse reactions of megestrol acetate administration include polyphagia, behavioural changes, hair loss, diabetes mellitus and mammary hyperplasia.

Therefore, some clinicians propose to reserve the use of megestrol acetate to cases of FEK that are refractory to other treatment options such as topical dexamethasone 0.1% ophthalmic solution, prednisolone acetate 1% solution, or cyclosporine.

Corticosteroids such as prednisolone are administered two to four times daily as an anti-inflammatory treatment regimen. The frequency of treatment is reduced to once daily and then to once every other day over a two to three month time period[6][7].

Topical cyclosporine (0.5% ointment, 1-2% solution) is an alternative treatment to the use of topical corticosteroids. Cyclosporine solution is applied two to three times daily initially, with a reduction in the frequency of drug administration as long as the lesion is effectively controlled. Once again, the objective of cyclosporine treatment is to control lesion progression rather than trying to effect a cure. In any event, treatment for FEK must be continuously maintained at to the lowest effective drug dosage to prevent lesion progression[8]

References

  1. Allgoewer I, Schaffer EH, Stockhaus C, et al: Feline eosinophilic keratitis. Vet Ophthalmol 4:69-74, 2001.
  2. Glaze MB, Gelatt KN: Feline ophthalmology. In: Gelatt KN (ed): Veterinary Opthalmology, 3rd ed. Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp. 997-1052
  3. Martin C (2005) Ophthalmic Disease in Veterinary Medicine, 1st ed. Manson Publishing, United Kingdom, pp. 258-259
  4. Ketring KL (2004) Feline Herpesvirus I & II. Eosinophilic keratitis. Proc Western Veterinary Conf, Las Vegas, NV, 2004
  5. Moore PA (2005) Feline Corneal Disease. Clinical Techniques in Small Animal Practice
  6. Morgan,RV, Abrams KL, Kern TJ (1996) Feline eosinophilic keratitis: A retrospective study of 54 cases (1989-1994). Prog Vet Comp Ophthal 6:131-134
  7. Paulsen ME et al (1987) Feline eosinophilic keratitis: A review of 15 clinical cases. J Am Animal Hosp Assoc 23:63-69
  8. Prasse KW, Winston SM (1996) Cytology and histopathology of feline eosinophilic keratitis. Vet Comp Ophthal 6:74-81