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How to perform corneal cytology in a cat or dog | VETgirl Veterinary Continuing Education Videos

In this VETgirl online veterinary continuing education video, we demonstrate how to perform corneal cytology collection in a cat. Corneal cytology can be quite helpful in diagnosing certain disease processes, such as bacterial infection or eosinophilic keratitis. In this video, we have a 12 year old male castrated domestic shorthair presenting with conjunctivitis and corneal changes – closer examination shows a pink to white film on the cornea.  

The first step to obtain corneal cytology is to make sure the patient is comfortable and amenable to collection. In the vast majority of cases, topical anesthesia with proparacaine or tetracaine is sufficient. There are 2 good options for the instrument used to obtain the sample – the blunt end of a scapel blade works well and is readily available. Alternatively, a specialized Cytobrush works great. In addition, you’ll need glass microscope slides and routine Dif-Quik stain. As shown in the video, the assistant is properly stabilizing the cat’s head by placing one hand under the chin and the other behind the head. The clinician then uses the blunt end of the blade, or cytobrush, to gently scrape the area of cellular infiltration to obtain an adequate sample. The sample is then directly smeared onto a glass slide, stained, and then evaluated under the microscope. This feline patient had Eosinophilic Keratitis.  As can be seen under the microscope, the cytology obtained from the corneal infiltrate contained corneal epithelial cells and numerous white blood cells, including neutrophils and notably eosinophils!
 
VETgirl’s tip: Do not use cotton tip applicators – while they collect the sample well, they do not allow it to stick to the glass slide and thus the samples obtained are generally of poor quality.  We also recommend choosing your cases wisely – be sure to obtain the sample safely, and do NOT sample an ulcer if it is excessively deep or already perforated.

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