The use of impression cytology in the follow-up of severe ocular burns

Aims: To evaluate by impression cytology (IC) the expression of the MHC class II inflammatory marker HLA-DR by the conjunctival epithelium, the cytological modifications of the conjunctival surface according to the Nelson's classification, and the eventual correlation between the two after severe ocular burns. Methods: A total of 24 patients ( 24 eyes) who presented with severe ocular burns underwent IC. We compared them with 18 healthy eyes. HLA-DR expression was studied by flow cytometry as well as the conjunctival histology evaluated with the Nelson's classification from 2-24 months after the onset of burns. Results: There was a significant upregulation of the expression of HLA-DR in eyes with burns compared to the healthy population at 2 months (p < 0.001), 6 months (p < 0.001), 12 months (p=0.019), 18 months (p=0.0171) and 24 months (p=0.01766). A significant difference was found between the Nelson grade in the pathological population and those of the healthy population at 2 months (p=0.0157). HLA-DR upregulation was significantly correlated with the Nelson's grades between 2 months (r = 0.69, p < 0.0001) and 6 months (r = 0.61, p=0.0001). Conclusion: The IC technique can act as a useful tool for following-up ocular surface inflammation after severe ocular burns.