Overview
Color blindness may be a hereditary condition or caused by disease of
the optic nerve or retina. Acquired color vision problems only affect
the eye with the disease and may become progressively worse over time.
Patients with a color vision defect caused by disease usually have
trouble discriminating blues and yellows.
Inherited color blindness is most common, affects both eyes, and does
not worsen over time. This type is found in about 8% of males and 0.4%
of females. These color problems are linked to the X chromosome and are
almost always passed from a mother to her son.
Color blindness may be partial (affecting only some colors), or complete
(affecting all colors). Complete color blindness is very rare. Those who
are completely color blind often have other serious eye problems as
well.
Photoreceptors called cones allow us to appreciate color. These are
concentrated in the very center of the retina and contain three
photosensitive pigments: red, green and blue. Those with defective color
vision have a deficiency or absence in one or more of these pigments.
Those with normal color vision are referred to as trichromats. People
with a deficiency in one of the pigments are called anomalous
trichromats (the most common type of color vision problem.) A dichromat
has a complete absence in one cone pigment.
Signs and Symptoms
The symptoms of color blindness are dependent on several factors, such
as whether the problem is congenital, acquired, partial, or complete.
The symptoms of more serious inherited color vision problems and some
types acquired problems may include:
Detection and Diagnosis
Color vision deficiency is most commonly detected with special colored
charts called the Ishihara Test Plates. On each plate is a number
composed of colored dots. While holding the chart under good lighting,
the patient is asked to identify the number. Once the color defect is
identified, more detailed color vision tests may be performed.
Treatment
Consult an Eye Specialist.
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