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Achromatopsia is a hereditary vision disorder. It only affects about 1 person out of 33,000 in the Unites States. When a person has achromatopsia they do not see in a cone field but with rod vision. Also a person with achromatopsia will be completely colorblind or almost colorblind. This disorder causes the person to have poor visual acuity.
There have been several misdiagnosis when it comes to achromatopsia. Nystagmus is a symptom that occurs with achromatopsia. Yet, now there is a medical eye condition called congenital nystagmus, which is the involuntary movement of the eyes. Another misdiagnosis is when a person has rod monochromacy and has been diagnosed with cone dystrophy. One more misdiagnosis is congenital achromatopsia, which has been confused with cone dystrophy or rod dystrophy; doctors may refer to this disorder as “stationary cone dystrophy”. Yet the actual condition is not progressive and it does not lead to blindness. There have been terms that have been used in diagnosing patients with achromatopsia. The terms show that every specialist sees this condition very differently.
In a normal eye there are 6 million cone photoreceptors by the center of the retina. There are 100 million rod photoreceptors; these rods are found by the periphery of the retina. The rods functions disable a person to see the color vision, but good detail. The actual rods saturate at the higher levels of illumination. The rods can detect shades of gray, black, and white. The cones are the ones that contain particular pigments. The cones can separate red, green and blue depending on the wavelengths they are most sensitive to. These cones are what make it so that humans can see in color. When a person does not have normal cone vision, the eyes cannot adapt to the high levels of illumination. Each achromat has a different level of severity. The reason for all the severity is because of all the variations in the complete rod monochromats, incomplete rod monochromats, and blue cone monochromats. Out of all the achromats, the people with complete rod monochromats have the most impaired vision.
There are a couple different kinds of colorblindness that can make the disorders a little more confusing. There is a red-green blindness caused by the proximity of the two pigment genes, this makes an unequal crossover in the X-chromosomes, leading to this disorder. Red-green colorblindness is when a person has trouble telling the difference between red, brown and green. Another type of colorblindness is known as blue colorblindness, which is also known as incompletely achromatopsia, the clue-cone monochromatism. This is a disorder were only the blue cones and the rods can functionally properly. The research shows that the actual signals from another type is complete achromatopsia, which is color blindness. A simple definition of this can be when there is no functioning of the cone cells. The cones and rods are traveling in different pathways to where the wavelength confusion takes place.
Achromatopsia also affects people through their visual acuity. The foveal cones are what make the acuity of the eye; an achromat’s are dysfunctional. Acuity also depends on the illumination in the environment. This disorder can be relayed to the general population because of how normal vision will consist of the rods. What does help are the textures on objects. Yet when there are shadows this can affect the perception, as well as glares from windows and etc.
If a person with achromatopsia is in a bright indoor spaces or outside just before dusk the vision level will decrease as the levels of illumination rise. A person with achromatopsia can squint, blink, or even shield their eyes, which allows their eyes to adjust to the light by the positioning they put themselves in. Most achromats will wear dark tinted sunglasses because their retinas do not process the photoreceptors.
There has been great awareness in the culture about achromatopsia. In August of 1994 a BBC film crew along with Dr. Oliver Sacks went to the small Micronesian atoll of Pingelap. There at least six percent of the population has achromatopsia. This documentary was later called the “Island of the Colorblind” by many of the PBS stations. Footage of the documentary showed the journey, as well as including information from Dr. Sack’s book also titled “Island of the Colorblind”. Often Dr. Sack’s refers to achromatopsia as “achromatopia”. Also the commonly used terms are “achromatopsia” and “achromats”. Dr. Sacks refers to an individual with this disorder as an “achromatope”. This film was shown in the United Kingdom in 1996, and the United States in 1998 as well as in certain parts of Canada.
There is no cure today. There are many advances in science trying to correct the vision disorder. The way the achromats eye works has not been discovered. Achromatopsia is more then just a simple diagnosis of being colorblind, there are many symptoms. These symptoms include photophobia, reduced visual acuity, and nystagmus. All of these symptoms truly affect a person’s life.
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