The preliminary flow cytometric studies show that various immune cells (eg: T cells, B cells, and dendritic cells) can be quantified using minimally invasive impression membranes (Eyeprim). Clinically, the research team is experienced in measuring features of ocular surface inflammation (conjunctival redness, tear breakup times) with Oculus keratograph5M. The investigators also aim to harvest conjunctival immune cells using impression cytology and quantify specific cell types with flow cytometry. Corneal nerve morphology and dendritic cell density and distribution will be assessed using CCM; in collaboration with the group who have pioneered this technique.