After the final set of measurements, the front surface of your eyes will be assessed using a temporary dye to highlight using a blue light any changes. Fluorescein dye does not sting, lasts only a few minutes and has no effect on vision or driving. However it may cause a self limiting mild allergic reaction where the eyes become red, irritated and sore but this is highly unlikely as there are no known reported cases. In the unlikely event this does happen the experienced optometrist is immediately available to manage the condition.