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This form of color blindness is sometimes referred to historically as daltonism after John Dalton, who had congenital red–green color blindness and was the first to scientifically study it. In other languages, daltonism is still used to describe red–green color blindness, but may also refer colloquially to color blindness in general.
Research has shown that scores below twelve indicate color vision deficiency, and twelve or more correct indicate normal color vision, with 97% sensitivity and 100% specificity. The sensitivity of the Ishihara test varies by the number of plates allowed to pass, which can vary by institutional policy.
Myopia or Nearsightedness: When the refractive power is too strong for the length of the eyeball, this is called myopia or nearsightedness. People with myopia typically have blurry vision when viewing distant objects because the eye is refracting more than necessary.
Transmittance of EnChroma color correcting lenses (indoor and outdoor) superimposed onto the normalized spectral sensitivities of the cone opsins of a color normal observer. Glasses with a notch filter (e.g. EnChroma glasses) filter a narrow band of light around 590 nm that excites both the L- and M-cones (yellow-green wavelengths). [12]
Tinted glasses (e.g. Pilestone/Colorlite glasses) apply a tint (e.g. magenta) to incoming light that can distort colors in a way that makes some color tasks easier to complete. These glasses can circumvent many color vision tests, though this is typically not allowed. [62]
Anaglyph 3D glasses have a different colored filter for each eye, typically red and blue or red and green. A polarized 3D system on the other hand uses polarized filters. Polarized 3D glasses allow for color 3D, while the red-blue lenses produce an image with distorted coloration. An active shutter 3D system uses electronic shutters.
A duochrome test is a test commonly used to refine the final sphere in refraction (undercorrection and overcorrection), which makes use of the longitudinal chromatic aberration of the eye.
In glasses with powers beyond ±4.00D, the vertex distance can affect the effective power of the glasses. [4] A shorter vertex distance can expand the field of view, but if the vertex distance is too small, the eyelashes will come into contact with the back of the lens, smudging the lens and causing annoyance for the wearer.