How is corneal cytology performed?

• A. Swab
• B. Blade stub scraping or cytobrush
• C. Impression smear
• D. Needle biopsy

Answer: (B)

Corneal cytology relies on collecting superficial epithelial cells from the corneal surface to evaluate cell morphology, inflammatory cells, and any infectious elements, without penetrating into the stroma. The best way to achieve a reliable cytology sample in horses is a gentle scrape of the corneal surface using a sterile blade or a cytobrush. The collected cells are then smeared onto a glass slide, fixed, and stained for microscopic examination. This method yields a good number of intact epithelial cells with minimal trauma, providing clear diagnostic material for cytology.

A swab tends to yield fewer cells and is more suited to culture than cytology. An impression smear can be used, but it often gives variable cell yield and can distort cells. A needle biopsy would sample deeper tissue and carries a high risk of perforation, so it’s not appropriate for routine corneal cytology.