© 2017, GENASSIST, Inc.     

By Keith S. Wexler, MBA, Maternal Fetal Medicine, Prenatal Diagnosis and Biotech /Life Sciences Consultant, GENASSIST, Inc.

Paul Wexler, M.D., F.A.C.O.G., Medical Director, GENASSIST, Inc.

Clinical Professor, Department of OB/GYN, University of Colorado Health Sciences Center

Clinical Professor, Division of Genetics/Dept. of Pediatrics, Univ. of Colorado/The Children’s Hospital

Definitions:

  • Protanopia: A form of color blindness with confusion of the colors red and green or confusion of red with green or bluish green. 
  • Daltonism: Derived from the name of the chemist John Dalton (1766-1844). Color blindness of the red-green type, the most common type of color blindness. Another term for Protanopia
  • Tritanopia: Also called blue yellow color blindness. Individuals with this type of color blindness confuse blue with green and yellow with violet. Decreased recognition of blue and yellow.

Analysis:Occasionally the term Protanomaly, deuteranomaly or Tritanomaly are used interchangeably with the above terms or used to refer to an identified mutation causing the disorder.

Protanopia and Deuteranopia are believed to be sex (x) linked disorders. If an affected male, 100% of his female children will be carriers and none of his male children will be affected (since the males inherit the father’s Y chromosome and not his X chromosome).

Carrier females have a 50% risk of an affected male child and a 50% risk for a female carrier child. 

  • Up to 6% of males may have this disorder.
  • Approximately 0.25% of females may have this disorder due to incomplete inactivation of the carrier X chromosome.

Tritanopia is believed to be inherited in an autosomal dominant manner or may be acquired and is a less common form of color blindness.

  • Males and females can be affected equally.
  • A parent with this disorder will have a 50% risk of having a male or female child with this disorder.

Acquired Tritanopia has been described in individuals exposed to high levels of alcohol or organic solvents or occasionally after brain or eye injury.