Colorblindness-Tritanopia
Patient Information
Characteristics
Background and History
The light sensitive cells in the retina are called rods (useful in dim vision) and cones (used for color vision). Gene mutations can impact either or both types. Those that cause a dysfunction in cones result in defective color vision of various types, sometimes called colorblindness.
This is a type of colorblindness in which the retina is less responsive to short wavelength or blue light. It is among the least common forms of colorblindness.
Clinical Correlations
Individuals are generally unable to see objects with blue color although there is some variation in the amount and type of deficiency. Some people may have difficulty seeing some blue-yellow colors and these also can have some problems identifying reds and greens. However, the more blue-green color blindness found primarily in males is caused by different genetic defects and is not part of tritanopia.
Genetics
Inheritance
Tritanopia is caused by mutations in a non-sex chromosome and therefore is found in equal frequency among males and females. It is inherited in an autosomal dominant pattern and passed directly from parent to child with a 50% probability.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Diagnosis and Prognosis
This is a stable disorder present at birth with no evidence that the retinal disease is progressive. It results from a genetic defect in retinal cells in the retina (the light sensing tissue in the eye) that normally respond to short wavelength light such as blue colors. No other health problems are known to be associated and no treatment is available.
Web Resources
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