axial chromatic aberration Chromatic aberration arising from the wavelength dependence of refraction - different colors are focused to different points along the optical axis in uncorrected lenses. Synonyms: chromatic distortion Related MicroscopyU Article Chromatic Aberration Chromatic aberrations are wavelength-dependent artifacts that occur because the refractive index of every optical glass formulation varies with wavelength. When white light passes through a simple or complex lens system, the component wavelengths are refracted according to their frequency. In most glasses, the refractive index is greater for shorter (blue) wavelengths and changes at a more rapid rate as the wavelength is decreased.