Which test utilizes chromatic aberration to verify the final sphere component of a refraction?

Which test utilizes chromatic aberration to verify the final sphere component of a refraction?

• A. JCC
• B. Astigmatic dial
• C. Duochrome
• D. Worth 4 Dot

Answer: (C)

The duochrome test uses the eye’s chromatic dispersion to fine‑tune the final spherical refraction. Different wavelengths focus at slightly different depths in the eye, so red and green images fall at different planes on the retina. With a correct spherical correction, letters on both red and green backgrounds should be equally sharp. If one color looks clearer, the spherical power isn’t balanced for both wavelengths, and you adjust the sphere until the red and green letters are equally clear. This test specifically checks the spherical component, unlike the other methods, which target cylinder, axis, or binocular status.

The duochrome test uses the eye’s chromatic dispersion to fine‑tune the final spherical refraction. Different wavelengths focus at slightly different depths in the eye, so red and green images fall at different planes on the retina. With a correct spherical correction, letters on both red and green backgrounds should be equally sharp. If one color looks clearer, the spherical power isn’t balanced for both wavelengths, and you adjust the sphere until the red and green letters are equally clear. This test specifically checks the spherical component, unlike the other methods, which target cylinder, axis, or binocular status.