The main requirement for trichromacy is three cone cell classes that are each sensitive to different wavelengths of light and therefore have different spectral sensitivities. Dichromats only express two cone classes and cone monochromats express one. For each cone missing, one of the opponent channels (red-green and blue-yellow) that are responsible for color discrimination are disabled. This is the mechanism for protanopia, deuteranopia, blue cone monochromacy and tritanopia. Even when there is trichromatic color vision and all three opponent channels are active, the size of an individuals color gamut is determined by the dynamic range of the opponent channels, which can be affected by several factors. One of these factors is the peak wavelengths of the spectral sensitivities of the three cones, namely the spectral distance between two cones contributing to an opponent channel. When this distance is smaller, the dynamic range is smaller and the color gamut is smaller, leading to a color vision deficiency. This is the mechanism for congenital protanomaly and deuteranomaly, though not of tritanomaly. The opponent channels can also be affected by the prevalence of certain cones in the retinal mosaic. The cones are not equally prevalent and not evenly distributed in the retina. When the number of one of these cone types is significantly reduced, this can also lead to or contribute to a color vision deficiency. This is one of the causes of tritanomaly. Simple colored filters can also create mild color vision deficiencies.
Primary dysmenorrhea usually begins within a year or two of menarche, typically with the onset of ovulatory cycles. Perimenstrual pain is often included as a component of premenstrual syndrome (PMS). Secondary dysmenorrhea is the diagnosis given when menstruation pain is a secondary cause to another disorder. Conditions causing secondary dysmenorrhea include endometriosis, uterine fibroids, uterine adenomyosis, and polycystic ovary syndrome. Rarely, congenital malformations, intrauterine devices, certain cancers, and pelvic infections cause secondary dysmenorrhea. If the pain occurs between menstrual periods, lasts longer than the first few days of the period, or is not adequately relieved by the use of non-steroidal anti-inflammatory drugs (NSAIDs) or hormonal contraceptives, this could be a sign for secondary causes of dysmenorrhea.When laparoscopy is used for diagnosis, the most common cause of dysmenorrhea is endometriosis, in approximately 70% of adolescents.Other causes of secondary dysmenorrhea include leiomyoma, adenomyosis, ovarian cysts, pelvic congestion, and cavitated and accessory uterine mass. Risk factors
Genetic factors, stress and depression are risk factors for dysmenorrhea. Risk factors for primary dysmenorrhea include: early age at menarche, long or heavy menstrual periods, smoking, and a family history of dysmenorrhea.Dysmenorrhea is a highly polygenic and heritable condition. There is strong evidence of familial predisposition and genetic factors increasing susceptibility to dysmenorrhea. There have been multiple polymorphisms and genetic variants in both metabolic genes and genes responsible for immunity which have been associated with the disorder.Three distinct possible phenotypes have been identified for dysmenorrhea which include "multiple severe symptoms", "mild localized pain", and "severe localized pain".