Colourblind people see colours differently because they do not have all the necessary information from the L, M and S cones. A simile would be to try to obtain different paint colours by mixing only two primary colours: we would never be able to obtain the full range of existing colours.

There are numerous causes for eye redness, and many of them are not serious. Begoña Domenech Amigot, professor of the Department of Optics, Pharmacology, and Anatomy of the University of Alacant, explains.

Experimental determination or detection of the physiological mechanisms underlying disease is by and large a highly complex task. This fact has turned epidemiology into the main tool for generating knowledge in the medical field.