Evolution of human colour vision opsins was increasing from 400 to 430. During this time, Ancestral Boreotherian had two long wave length opsins created by gene duplication, with one retaining the absolute max value of 560, equal to the ancestral value. This led to the creation of the modern human long wavelength sensitive, or red opsin. The other short wavelength sensitive opsin decreased its absolute max value to 530 and became the middle wavelength sensitive, or green-sensitive opsin. This occurred through mutations involving S180A, Y277F and T285A. The order that these mutations took place in the ancestral Boreotheria is currently not fully known. It is
Human eye (eye doctors/surgeons), optometrists, and opticians, are involved in the treatment and management of ocular and vision disorders. A Snellen chart is one type of eye chart used to measure visual acuity. At the conclusion of a complete eye examination, the eye doctor might provide the patient with an eyeglass prescription for corrective lenses. Some disorders of the eyes for which corrective lenses are prescribed include myopia (near-sightedness) which affects about one-third of the human population, hyperopia (far-sightedness) which affects about one quarter of the population, astigmatism, and presbyopia (the loss of focusing range during aging). Macular degeneration is especially prevalent