Evolution of human colour vision as 'visual purple' receptor proteins, are encoded by Rh1, OPN2 and RHO genes. They are characterized by extreme sensitivity to light and enable monochromatic human vision in low light or dim conditions. They are broken down into retinal and opsin when exposed to these conditions. Humans have 3 types of photopsin proteins found in the cone cells. Long Wavelength Sensitive Opsin (Red cone opsin) – Encoded by the OPN1LW gene with a λmax of 560 that is found in the yellow-green electromagnetic spectrum despite its name. Its sensitivity to the colour red is still known to be higher than the
Human eye correlated negatively with break-up time. This phenomenon indicates that perceived eye irritation is associated with an increase in blink frequency since the cornea and conjunctiva both have sensitive nerve endings that belong to the first trigeminal branch. Other evaluating methods, such as hyperemia, cytology etc. have increasingly been used to assess eye irritation. There are other factors that are related to eye irritation as well. Three major factors that influence the most are indoor air pollution, contact lenses and gender differences. Field studies have found that the prevalence of objective eye signs is often significantly altered among office workers in