How (and When) to Safely Get a Corneal Cytology Sample [VIDEO]

1. First, determine if you need a sample.  Examples of good candidates are stromal ulcers or plaque like lesions on the corneal surface.

If the eye looks like it may rupture or is ruptured, do not attempt to get a cytology!

2. Once you have decided you want to get a sample you’ll need:

• Topical anesthetic such as Proparacaine or Tetracaine
• Glass Microscope Slide
• Adequate restraint, however, you should not need sedation
• Your preference of cytology sampling tool (See Figure 1)
  • I use a 6400 Beaver Blade (you probably don’t have those but they’re super cute)
  • I recommend the blunt (non-cutting) end of any stainless-steel blade (#10, #15, #11)
  • Cytology brush
  • Kimura spatula
• Topical antibiotic to apply after

Proietto, L, Beatty, SS, Plummer, CE. Comparison of 3 corneal cytology collection methods for evaluating equine ulcerative keratitis: Cytobrush, kimura platinum spatula, and handle edge of scalpel blade. Vet Ophthalmol. 2019; 22: 153– 160. https://doi.org/10.1111/vop.12574 

3. If you are submitting to a clinical pathologist, please follow their suggestions on whether you should stain before submission or send unstained

4. If you are looking at it yourself, stain with diff quick and look away! 

What should you see on a slide? 

You should see epithelial cells with or without pigment but there will probably be some pigment if it’s a brachycephalic dog!  You may also see a few red blood cells and the occasional (rare) white blood cell if there is some granulation or vascularization present at the sampling site.

If you see organisms (rods, cocci or fungal hyphae) or loads of neutrophils and macrophages then you’ve got an infection and now you can treat accordingly!

If it’s a proliferative lesion in a cat and you see eosinophils…what is your diagnosis? Eosinophilic keratitis!

Figure 2: Corneal cytology with rod bacteria

Figure 3: Corneal cytology with cocci bacteria

Figure 4: Corneal cytology with branching fungal hyphae

#practicepearls #videotutorials

About the Guide: Kristin Miller Fischer, DVM, DACVO

Dr. Kristin Fischer is a board-certified veterinary ophthalmologist. She graduated from the University of Tennessee College of Veterinary Medicine in 2007 and completed a rotating general internship at VCA Alameda East Veterinary Hospital in Denver, CO. She then returned to Knoxville in 2009 to complete her ophthalmology residency at UTCVM. Dr. Fischer practices in South Carolina and works at Animal Eye Care of the Lowcountry. She loves the challenge of the complicated cases and the frequent connection between ophthalmology, internal medicine and neurology. Her favorite thing is returning sight to blind animals and then seeing them greet their families post-op!