Color blindness is a condition, of predominantly genetic in nature, characterized by alterations in color perception. It affects about 8% of the population and mainly male individuals are affected (the frequency in women is around 0.4 – 0.5%).
Man perceives the external world not only through the vision of objects but above all, with the various shades of color that make them up.
All that we see in nature, in fact, contains photosensitive substances which, when hit by sunlight or artificial light, emit radiation, which are captured by the retina of the human eye.
These photoreceptors, i.e. cones and rods, are fundamental: they are in fact cells sensitive to light radiation. In particular, rods are responsible for sight in the dark, therefore they are insensitive to light, and cones are responsible for color vision. The latter can be of three types, sensitivity respectively to red, green and blue light.
When color blindness is inherited, it affects both eyes but there are some cases where it can affect only one.
FORMS OF COLOR BLINDNESS
There are mainly two types of color blindness.
Achromatopsia is characterized by the absence of perception of all, or almost all, the colors, due to a lack or alteration of all types of cones. The symptoms experienced by the patient are photophobia, loss of visual acuity, nearsightedness and color vision defect.
Dyschromatopsia, on the other hand, is characterized by the lack of perception of only some colors, therefore they are due to the lack or alteration of one or two groups of cones. They can be further divided into subcategories: protanomaly (difficulty in distinguishing red), deuteranomaly (difficulty in distinguishing green), deuteranopia (blindness in green), protanopia (blindness in red) and, finally, tritanopia (blindness to blue).
The main cause of color blindness, as mentioned above, is genetics.
Some patients, however, are not born with the anomaly but acquire it later due to some diseases such as: cataracts, multiple sclerosis, alcoholism, head injuries, maculopathy or other pathologies that affect the eyes.
The diagnosis of color blindness occurs through the Ishihara test: this consists in the use of colored plates on which a number of different colors is reported with respect to the background. The type of dyschromatopsia will be distinguished according to the type of perceived number.
There are also other types of tests, such as the Farnsworth test, which probes the accuracy of color perception. The subject examined is asked to order the shades of some colored tablets.
Unfortunately there is no cure to color blindness, therefore the therapy is purely symptomatic and represented by the use of glasses for color blind people. In four out of five cases, the glasses allow for a more correct perception thanks to filters that are able to eliminate some wavelengths to make other colors predominant.