Impression Cytology in corneal and ocular surface pathology

Abstract

Abstract Purpose: Impression cytology (IC) refers to the application of a cellulose acetate filter to the ocular surface to remove the superficial layers of the ocular surface epithelium. The SIS presentation describes the technique and uses of IC. Methods: These cells can be subjected to histological, immunohistological, or molecular analysis. Periodic acid Schiff (PAS), Papanicolaou or haematoxylin stains are commonly employed to delineate goblet cells and epithelial cell morphology. Cells harvested by IC can also be released as a cell suspension and subjected to FACS (fluorescein activated cell sorting) analysis. Proper technique is essential as the number of cells sampled can vary considerably. Results: Generally two to three layers of cells are removed in one application but deeper cells can be accessed by repeat application over the same site. Applications for IC include diagnosing a wide range of ocular surface disorders, documenting sequential changes in the conjunctival and corneal surface over time, staging conjunctival squamous metaplasia, and monitoring effects of treatment. It is also a useful investigational tool for analysing ocular surface disease with immunostaining and DNA analysis. It is non‐invasive, relatively easy to perform, and yields reliable information about the area sampled with minimal discomfort to the patient. Complications such as removal of a full thickness sheet of corneal epithelium; subconjunctival haemorrhage due to rupture of vessels in patients with conjunctival laxity, or subconjunctival emphysema due to a tear in the conjunctiva have been encountered. Conclusions: Major ophthalmic centres should introduce this technique into routine clinical practice. A team approach should include the ophthalmologist, pathologist, microbiologist and immunologist.