I read that in eye tests red and green colors are used. For example:
But in Snellen/Eye chart, these are not background colors. These are lines only. What is the purpose of it?
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Sign up to join this communityThese two lines can be used to detect color blindness in which red cannot be distinguished from green (deuteranopia). The person tested, often a child in that case, must be able to name the colors of the lines. (Reference: Ellen M. Chiocca, Advanced Pediatric Assessment, p 314):
Otherwise, it is also certainly a convenience to allow the test taker to say which line they are comfortable with, e.g., I can read the letters just above the red line but not the ones under it.
Its for a 'Red-Green duochrome test'.
A primary task of the eye care professional is determining the refraction, or optical correction, of a patient. The duochrome red-green test is a standard tool for verification of the final refraction. Traditionally, it is recommended for use both prior to and subsequent to determining the cylindrical or astigmatic component of the refraction.