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Achromatopsia

Achromatopsia is a medical condition (also called maskun or rod monochromatism) characterized by a low cone cell count or lack of function in cone cells; these are the light receptors responsible for colour perception. It is endemic on the atoll of Pingelap and was described by Oliver Sacks in Island of the Colourblind. Sacks went there with a Norwegian who had maskun, and the book narrates his experiences on the island. more...

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People with maskun have difficulty seeing in bright daylight because their rod cells (the receptors responsible for detecting brightness) are saturated. People with normal colour vision do not perceive things in the same way as those with maskun, because they depend on colour more than on luminosity to identify objects and patterns, whereas achromatopics depend almost entirely on luminosity to identify patterns. The closest that normal-sighted persons can come to experiencing maskun-type vision is in the dark, when the rod cells become the predominant receptors for vision due to their sensitivity to variations in brightness. Achromatopsia can vary in its severity from being mild enough that it is not diagnosed to causing near blindness. It is a relatively rare condition requiring two recessive genes (CNGA3 and CNGB3). In the United States, it affects approximately 1 in 33,000 people. The condition is generally stable over the course of one's life. Many achromats function normally with the aid of darkened lenses, while others use guide dogs, canes, and are considered legally blind.

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Blind musher cleared to enter Iditarod
From Milwaukee Journal Sentinel, The, 9/20/03

Blind musher cleared to enter Iditarod

From Journal Sentinel wire reports

Saturday, September 20, 2003

A blind musher will be allowed to compete in the 2004 Iditarod Dog Sled Race, board members of the Iditarod Trail Committee decided Friday.

The board voted unanimously to waive certain rules to allow Rachael Scdoris, 18, of Redmond, Ore., to be guided by another musher to advise her of trail conditions. The board also approved use of two- way radios so the pair can communicate.

Existing Iditarod rules allow competitors to receive assistance only from competing mushers. Verbal coaching from non-competitors and use of radios and other communication equipment also is forbidden.

Scdoris has congenital achromatopsia, a retinal condition that impairs her ability to see clearly.

Scdoris is one of 81 entrants for the 2004 race so far, including 29 rookies. It begins in Anchorage on March 6.

Copyright 2003 Journal Sentinel Inc. Note: This notice does not apply to those news items already copyrighted and received through wire services or other media
Provided by ProQuest Information and Learning Company. All rights Reserved.

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