John Daltons original hypothesis for his deuteranopia was actually that the vitreous humor of his eye was discolored:

I was led to conjecture that one of the humours of my eye must be a transparent, but coloured, medium, so constituted as to absorb red and green rays principally... I suppose it must be the vitreous humor. An autopsy of his eye after his death in 1844 showed this to be definitively untrue, though other filters are possible. Actual physiological examples usually affect the blue-yellow opponent channel and are named Cyanopsia and Xanthopsia, and are most typically an effect of yellowing or removal of the lens. Tetrachromacy in carriers of CVD
Females that are heterozygous for anomalous trichromacy (i.e. carriers) may be tetrachromats. These females have two alleles for either the OPN1MW or OPN1LW gene, and therefore express both the normal and anomalous opsins. Because one X chromosome is inactivated at random in each photoreceptor cell during a females development, those normal and anomalous opsins will be segregated into their own cone cells, and because these cells have different spectral sensitivity, they can functionally operate as different opsins. This theoretical female would therefore have cones with peak sensitivities at 420nm (S cone), 530nm (M cone), 560nm (L cone) and the fourth (anomalous) cone between 530nm and 560nm (either M* or L* cone).If a female is heterozygous for both protanomaly and deuteranomaly, she could be pentachromatic.
Brands
Seasonale is produced by Duramed Pharmaceuticals, a subsidiary of Barr Pharmaceuticals; Barr Pharmaceuticals also produces the same medicine as a generic called Jolessa. Quasense is the generic version produced by Watson Pharmaceuticals. Seasonale contains 30 micrograms of ethinylestradiol and 150 micrograms of levonorgestrel in each active pill. Seasonale reduces the frequency of menstrual periods from thirteen per year to four per year by changing the regimen of active pills from 21 to 84. Each package has 84 active pills and seven placebo pills to be taken at the end of the active cycle. It was first developed by Barr Pharmaceuticals, in collaboration with Eastern Virginia Medical School, under an agreement. The U.S. Food and Drug Administration (FDA) approved Seasonale in the United States on September 5, 2003. Barr Pharmaceuticals, its manufacturer, claimed at the time of Seasonales approval that it would cost one dollar per pill. Health Canada approved Seasonale in July 2007, and Paladin Labs began distributing it in Canada on January 4, 2008.Seasonique, also produced by Duramed Pharmaceuticals, has active pills and packaging identical to Seasonale, but replaces the placebo week with a low-dosage week of estrogen. Lybrel is produced by Wyeth Pharmaceuticals. It contains 90 µg levonorgestrel and 20 µg ethinylestradiol in each pill, and is designed to be taken continuously with no placebos. The FDA approved Lybrel for human consumption on May 22, 2007. References
Further reading
Elsimar M. Coutinho; Sheldon J. Segal (1999). Is menstruation obsolete?. Oxford: Oxford University Press. ISBN 0-19-513021-9. Susan Rako (2006). The Blessings of the Curse: No More Periods?.