Comparison of cytologic and histologic evaluations of the conjunctiva in the normal equine eye.

This research focuses on comparing the cell types found in the conjunctiva (the membrane that covers the front of the eye) of a healthy horse through two different methods: cytologic (study of cells) and histologic (study of tissues). The goal is to understand the cell types recovered through conjunctival brush cytology (CBC), a less invasive method compared to histological examination.

Research Methodology

• The study was conducted in three distinct parts.
• Firstly, conjunctival brush smears were collected from 20 healthy horses, with cell types identified using May Grünwald-Giemsa (MGG) smears.
• Next, a similar process was carried out on the whole eyes of five horses obtained post-mortem, followed by a histological examination of their conjunctiva.
• Lastly, cytobrush smears were collected from another group of five healthy horses and analyzed using the MGG and periodic acid Schiff (PAS) staining.

Results

• The primary cells identified were deep and intermediate epithelial cells with only a small number of superficial and goblet cells.
• The study found a stratified columnar to cuboidal epithelium covering most of the conjunctiva, with a stratified squamous type observed at the palpebral and bulbar edges.
• Areas with high mucus cell indices were found from the nasal to the temporal edge of the equine inferior conjunctiva in the upper palpebral segment near the fornix and in part of the nasal fornix.
• No mucus cells were identified in MGG smears, but they were numerous in PAS smears and were primarily cylindrical cells.

Conclusions

• The predominant cell types in the cytobrush smears from healthy horses were polyhedral and cylindrical cells, with a lesser presence of squamous cells.
• Cylindrical cells may be mucous cells and are likely originating from the main stratified columnar to cuboidal epithelium.
• This investigation acts as a foundation for further comparative studies between healthy and diseased equine eyes, aiding in the diagnosis and treatment of ocular diseases in horses.