Impression cytology as diagnostic tool in horses with and without ocular surface disease.

The research article discusses the comparison of impression cytology sampling (ICS) and cytobrush sampling (CBS) as a diagnostic tool for ocular surface diseases in horses. It reveals that ICS method is less invasive, less irritating for the horses, and it preserves the natural cellular layout, hence, it can be recommended over CBS.

Objective and Methods of Research

• The objective was to compare two cytological sampling methods, ICS and CBS, for obtaining corneal and conjunctival cell samples, keeping in view the irritation caused to the patient, invasiveness, sample quality and diagnostic equivalent.
• The study was carried out on a prospective observational basis. Conjunctival and corneal samples were taken from five healthy horses from both sides (bilateral)
• Irritation and invasiveness were assessed with an eye irritation and an epithelial damaging score system, respectively. The quality of the sample was evaluated by a morphometric analysis graded by a board certified clinical pathologist.
• 15 eyes of 14 horses owned by clients with ocular surface anomalies were sampled by both ICS and CBS for the assessment of diagnostic equivalence. This involved comparing types of inflammatory cells and/or infectious agents detected and determining if the correct diagnosis could be achieved. Histopathology was used as a standard reference (gold standard) when available.

Results

• ICS was found to be significantly less invasive and irritating for horses. Both methods retrieved cells of high quality overall, but the quantity of cells was significantly higher in ICS.
• ICS also preserved the natural cellular layout. While there was a fair, but no statistically significant agreement between the diagnostic outcomes of both methods, CBS resulted in slightly more variability in inflammatory cell types compared to ICS.

Conclusions

• This study recommends ICS for cell sampling in fragile corneas and for experimental studies due to its lesser irritability and invasiveness.
• ICS is especially useful in situations where the preservation of cellular layout is advantageous. However, CBS samples are easier to obtain due to the smaller equine palpebral fissure and the identification of inflammatory cells within conjunctival cell samples is easier with CBS.
• Overall, despite its limitations, CBS remains an appropriate method in clinical settings.