09-04-2020, 03:09 PM
Most soft contact lenses (i.e. most daily and monthly contacts) will have absolutely no impact on eye tracking. Some heavily tinted contacts may make it difficult to get proper thresholding of the pupil, but these are not common. Hard contact lenses, however, will almost certainly cause problems because they are smaller than soft contact lenses and tend to float around as the eye moves. As a result, the corneal reflection may not be in a predictable location and the eye tracker can find it difficult to compute the center of the pupil if the edge of the lens is obscuring it. If possible ask participants who normally wear hard contact lenses to bring glasses instead.