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Cytology & Clinical Signs of Eosinophilic Keratoconjunctivitis in Cats

Kathern E. Myrna, DVM, MS, DACVO, University of Georgia


May 2022

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In the literature

Lucyshyn DR, Vernau W, Maggs DJ, Murphy CJ, Leonard BC. Correlations between clinical signs and corneal cytology in feline eosinophilic keratoconjunctivitis. Vet Ophthalmol. 2021;24(6):620-626.


Feline eosinophilic keratoconjunctivitis is a common disorder of the cornea and conjunctiva characterized by inflammation and plaque formation with eosinophils. The etiopathogenesis is unknown, but an immune-mediated component has been proposed.1 Cytology of raised corneal lesions or plaques is critical for diagnosis, and the presence of one eosinophil can confirm diagnosis. 

This study sought to correlate clinical and cytologic findings in cats with eosinophilic keratoconjunctivitis. Corneal cytology slides from 18 eyes (15 cats) were retrospectively examined and compared with clinical images of the patient. Slides and clinical images were scored with a standardized system. Cell types (including eosinophils, mast cells, neutrophils, globule leukocytes, small lymphocytes, and plasma cells) were recorded and compared with degree of conjunctival inflammation and discharge, corneal inflammation, and fluorescein uptake. 

Larger conjunctival discharge scores were correlated with higher cytologic scores for eosinophils and neutrophils; higher neutrophil scores were associated with increased corneal opacity area scores. A wide variation in cell type combinations was also seen on cytology. 

Future studies should investigate potential disease subtypes of eosinophilic keratoconjunctivitis and the ability to correlate cytologic changes with medication choices or clinical prognosis.


Key pearls to put into practice:


Diversity of cell types found on cytology in cats with eosinophilic keratoconjunctivitis suggests there may be several subtypes of this disorder that are currently categorized as one group. This may account for differences in clinical course and treatment response.


Number of eosinophils found on cytology does not correlate with overall severity of clinical disease. Only a few eosinophils or mast cells may be noted despite substantial clinical disease.



Globule leukocytes may be present on cytology, but this has not been previously reported, and the clinical significance is unknown.


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