Signs and Symptoms
The syndrome is frequently noticed first in children around six months of age by their photophobic activity and/or their nystagmus. The nystagmus becomes less noticeable with age but the other symptoms of the syndrome become more relevant as school age approaches. Visual acuity and stability of the eye motions generally improve during the first 6–7 years of life (but remain near 20/200). The congenital forms of the disorder are considered stationary and do not worsen with age.
The five symptoms associated with achromatopsia/dyschromatopsia are:
- Achromatopia
- Amblyopia (reduced visual acuity)
- Hemeralopia (with the subject exhibiting photophobia)
- Nystagmus
- Iris operating abnormalities
A sixth symptom associated with achromatopsia/dychromatopsia is seldom reported. Many sufferers are unaware of the three-dimensional aspect of their visual system. They frequently fail to observe any of the stereographic features of a scene.
The syndrome of achromatopsia/dyschromatopsia is poorly described in current medical and neuro-ophthalmological texts. It became a common term following the popular book by the neuroscientist Oliver Sacks, "The Island of the Colorblind," in 1997. Up to that time most color-blind subjects were described as achromats or achromatopes. Those with a lesser degree of color perception abnormality were described as either protanopes, deuteranopes or tetartanopes (historically tritanopes).
Achromatopsia has also been called rod monochromacy and total congenital color blindness. Individuals with the congenital form of this disorder show complete absence of cone cell activity via electroretinography at high light levels. There are at least four genetic causes of congenital ACHM, two of which involve cyclic nucleotide-gated ion channels (ACHM2/ACHM3), a third involves the cone photoreceptor transducin (GNAT2, ACHM4), and the last remains unknown.
Read more about this topic: Achromatopsia
Famous quotes containing the words signs and, signs and/or symptoms:
“The LORD brought us out of Egypt with a mighty hand and an outstretched arm, with a terrifying display of power, and with signs and wonders; and he brought us into this place and gave us this land, a land flowing with milk and honey.”
—Bible: Hebrew, Deuteronomy 26:8.
“When it is evening, you say, It will be fair weather, for the sky is red.’ And in the morning, It will be stormy today, for the sky is red and threatening.’ You know how to interpret the appearance of the sky, but you cannot interpret the signs of the times.”
—Bible: New Testament, Matthew 16:2,3.
“Social movements are at once the symptoms and the instruments of progress. Ignore them and statesmanship is irrelevant; fail to use them and it is weak.”
—Walter Lippmann (1889–1974)