Lanthony's new color test--part III. The neutral zone.

With the New Color Test (NCT) the neutral zone was studied in hereditary and acquired dyschromatopsias. Acquired type III blue-yellow defects with neutral zone occurred in heredo-atrophies of the optic nerve, in edematous maculopathies, in choroidal atrophy, in myopia, in glaucoma and in retinitis pigmentosa. With exclusion of the autosomal dominant inherited cases, the type III neutral zone in retinitis pigmentosa becomes complicated by a type I neutral zone when the visual acuity dropped to 0.2.