By comparing the luminosity of a color with and without a filter (or between two different filters), the color can be estimated. This is the premise of monocular lenses and the SeeKey. In some US states, achromats can use a red filter while driving to determine the color of a traffic light. To alleviate photophobia stemming from hemeralopia, dark red or plum colored filters as either sunglasses or tinted contacts are very helpful at decreasing light sensitivity. To manage the low visual acuity that is typical of achromatopsia, achromats may use telescopic systems, specifically when driving, to increase the resolution of an object of interest. Epidemiology
Achromatopsia is a relatively uncommon disorder, with a prevalence of 1 in 30,000 people.However, on the small Micronesian atoll of Pingelap, approximately five percent of the atolls 3,000 inhabitants are affected. This is the result of a population bottleneck caused by a typhoon and ensuing famine in the 1770s, which killed all but about twenty islanders, including one who was heterozygous for achromatopsia.The people of this region have termed achromatopsia "maskun", which literally means "not see" in Pingelapese. This unusual population drew neurologist Oliver Sacks to the island for which he wrote his 1997 book, The Island of the Colorblind. Blue cone monochromacy
Blue cone monochromacy (BCM) is another genetic condition causing monochromacy. It mimics many of the symptoms of incomplete achromatopsia and before the discovery of its molecular biological basis was commonly referred to as x-linked achromatopsia, sex-linked achromatopsia or atypical achromatopsia.
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External links

Achromatopsia at MedicineNet
Achromatopsia at Merriam-Webster
Achromatopsia at NCBI
The Achromatopsia Network - an archive of information about Achromatopsia and advice on coping with the condition.