Color Vision Abnormalities Flashcards
normal color vision
trichromatism, or trichromacy
long- wavelength
red
middle- wavelength
green
short- wavelength
blue
red
long- wavelength
green
middle- wavelength
long- wavelength
red
Hereditary congenital color vision defects - genetics
X- linked- recessive
Hereditary congenital color vision defects - color
red- green
Hereditary congenital color vision defects - epidemiology
5%–8% of males and 0.5% of females
Acquired defects - color
blue- yellow, or tritan
Individuals who need only 2 primary colors
dichromacy. It is assumed that such individuals lack 1 of the cone photopigments
An absence of color discrimination
achromatopsia
forms of achromatopsia and signs
rod monochromatism, and (2) S- cone monochromatism (blue- cone monochromatism). Both disorders typically pres ent with congenital nystagmus, poor visual acuity, and photophobia
differentiate achromatopsia from congenital motor nystagmus or ocular albinism
Electroretinography (ERG) testing helps differentiate achromatopsia from congenital motor nystagmus or ocular albinism, both of which are associated with normal cone ERGs
Rod monochromatism - other name
complete achromatopsia
complete achromatopsia - other name
Rod monochromatism
most severe form
Rod monochromatism (complete achromatopsia) have normal rod function but no detectable cone function and see the world in shades of gray.
Rod monochromatism - diagnostics
ERG pattern in patients with rod mono- chromatism shows an absence of cone- derived responses and normal rod responses. Dark adaptometry shows no cone plateau and no cone– rod break.
Rod monochromatism - genetics
autosomal- recessive inheritance
S- cone (or blue- cone) monochromatism - pathophysiology
function of rods and S cones is normal, but L- and M- cone function is absent
S- cone (or blue- cone) monochromatism - genetics
X- linked
S- cone (or blue- cone) monochromatism - diagnostics
preserved S- cone ERG responses, severely reduced cone flicker ERGs, and normal rod ERGs.
Congenital stationary night blindness - genetics
most often x-linked
Congenital stationary night blindness - features
normal to 20/200, nystagmus, may high myopia, may have paradoxical pupillary response
Congenital stationary night blindness - diagnostics
Dark-adaptometry curves reveal markedly reduced responses, negative ERG in which the bright- flash, dark- adapted ERG has a normal (or near- normal) a- wave but a markedly reduced b- wave (melanoma- associated retinopathy similar)
Fundus albipunctatus - signs
night blind from birth and usually exhibit yellow- white dots in the posterior pole extending into the midperiphery, but sparing the fovea. visual acuity and color vision are usually good
Fundus albipunctatus - diagnostics
ERG responses commonly show a cone- isolated retina pattern, with undetectable rod- specific ERG, and a severely reduced bright- flash dark- adapted ERG (arising in dark- adapted cones) that normalizes with sufficiently extended dark adaptation.
Fundus albipunctatus - differential
retinitis punctata albescens
retinitis punctata albescens - features
progressive rod– cone dystrophy, the white dots may be finer than those of fundus albipunctatus, and there may be attenuation of the retinal vessels. ERG responses are usually very abnormal
Mizuo-Nakamura phenomenon
Patients with Oguchi disease are also night blind from birth. The fundus in eyes with Oguchi disease is - normal after dark adaptation but shows a peculiar yellow iridescent sheen alteration after even brief exposure to light
