EOSINOPHILIC KERATOCONJUNCTIVITIS IN A CAT

History

A four year old, male neutered, common domestic short haired cat presented seeking a second opinion having had an ongoing corneal lesion in its left eye for 6 months. It was originally believed to have been a scratch on the cornea and enucleation had been recommended due to its progressive nature.

Examination

A full clinical examination was undertaken along with an ophthalmic examination as per Appendix 1. All relevant findings are recorded below.

OU: - PLR, indirect and direct - brisk and normal

- Menace normal

- Lids unremarkable

- Fundic examination unremarkable

OD: - Ocular examination unremarkable

OS: - Cornea - a fleshy, irregular area filling the dorsolateral corneal quadrant, with a white, gritty surface plaque. This was protuberant from the corneal surface and extended over the limbus into the adjacent conjunctiva which was hyperaemic. Sparse neovascularisation was present with a rim of corneal oedema (fig. 24).

- Mild conjunctivitis including the third eyelid

- Mild blepharospasm with serous ocular discharge

- Fluorescein dye retention negative.

STT L=12mm/minute, R=14mm/minute

A corneal scrape was taken for cytology.

Diagnosis

A diagnosis of eosinophilic keratoconjunctivitis (EKC) was made based on clinical appearance and confirmed by cytology.

Cytology Report (Idexx Laboratories)

A single submitted air dried smear indicated to be from the cornea contains a few squames and squamous epithelial cells. There are eosinophils present. No infectious agents are seen.

Comment - The cytological preparation is of low cellularity but the features are consistant with slight eosinophilic inflammation. The primary consideration should be eosiniphilic proliferative keratoconjunctivitis. Treatment for this condition, with continued monitoring, is recommended.

Treatment

Carbomer 980 (Viscotears, Novartis AG) TID OU

Prednisolone acetate 1% solution (Pred Forte, Allergan) QID OS

Follow up

10 days later - 80% resolution of the lesion (fig. 25)

- STT L= 18 mm/min, R= 19 mm/min

- Due to the improvement in the STT values the ocular lubrication was stopped 30 days later

- The lesion had continued to improve however there was a persistent opaque area but this was no longer fleshy in character (fig. 26)

- STT L=19mm/min, R=21mm/min

- The cat was becoming intolerant to application of topical medication so a change of medication route was necessary for 100% resolution.

- Megestrol acetate (Ovarid, Novartis AG) started, at 2.5 mg q72hrs PO

30 days later - 100% resolution of the corneal lesion (fig. 27).

All treatment ceased.

Update

A minor recurrence occurred at the same site 2 years later. This was treated with prednisolone acetate 1% QID and resolved within 3 weeks.

Discussion

Eosinophilic keratoconjunctivitis is a poorly understood condition that is seen uncommonly in cats and even more rarely in horses. It has been suggested that it may be associated with UV light exposure, being more common in cats living at altitude (1). It has also been shown that cats with EKC have a much higher incidence of Feline Herpes Virus (FHV-1) (76.3%) compared with ophthalmologically normal cats (5.9%) (2). This strongly suggests that FHV-1 is involved in the aetiology of this condition. FHV-1 does not normally induce an eosinophilic inflammatory response within the cornea so the pathogenesis of the condition remains uncertain.

This is a slowly progressive and usually unilateral disease at first but will affect both eyes if left untreated. Initially this condition presents as corneal oedema with neovascularisation. Signs of pain or ocular discharge, which would usually be expected to accompany such corneal changes, are very variable. It has a typical site of occurrence at the dorsal temporal or dorsal nasal limbus but can occur anywhere around the limbal circumference (3).

The granulation tissue and white plaque lesions are usually taken to show evidence of chronicity. The white plaques are formed from degenerate cells and nuclear debris with amorphous eosinophilic material. There is eosinophilic stromal infiltrate on histological examination with a chronic granulomatous inflammatory reaction. Demonstrating eosinophils on corneal scrape or biopsy is therefore diagnostic, especially with the typical clinical signs (4). The histology is similar to the lesions seen with feline eosinophilic granuloma complex however no link has been established between skin lesions and ocular lesions.

Historically megestrol acetate was given as a very effective treatment for this condition but due to concerns about its safety, especially long term, its use is now discouraged. Its use can precipitate iatrogenic Addison's disease, pyometra and diabetes mellitus (5). Topical prednisolone is now taken to be the treatment of choice. Megestrol acetate was used in this case to resolve the last recalcitrant remnants of the disease once the cat had become intolerant of topical treatment. Megestrol acetate has the benefit of being in a very palatable base and therefore easy to give to cats.

Recurrence can occur, as in this case, however rapid recognition allowed early treatment and resolution. Ongoing monitoring of these animals is warranted to prevent establishment of a chronic lesion. Recurrence of these lesions may help support an FHV-1 associated aetiology as it is well documented that FHV-1 latency may occur.

References

1. Slatter D (2001) Fundamentals of Veterinary Ophthalmology 3rd ed. WB Saunders, 288-290.

2. Nasisse MP, Glover TL, Moore CP, Weigler BJ (1998) Detection of feline herpesvirus 1 DNA in corneas of cats with eosinophilic keratitis or corneal sequestration. American Journal of Veterinary Research July 59 (7) 856-858.

3. Paulsen M, Lavach JD, Severin G, Eichenbaum J (1987) Feline Eosinophilic Keratitis: A Review of 15 Clinical Cases. Journal of the American Animal Hospital Association 23 (63-69).

4. Prasse KW, Winston SM (1996) Cytology and Histopathology of Feline Eosinophilic Keratitis. Veterinary and Comparative Ophthalmology Vol. 6, No 2, (74-81).

5. Tennant B (1999) BSAVA Small Animal Formulary 3rd ed, BSAVA, 153.

Figure 24: On presentation.

Figure 25: Ten days into treatment.

Figure 26: Thirty days into treatment.

Figure 27: Lesion fully resolved, after sixty days of treatment.