Final answer:
The Ishihara test assesses color perception, and to have color vision within normal limits, a patient must correctly identify a majority of the 14 color plates.
Step-by-step explanation:
The Ishihara test is designed to evaluate color perception and is often used to identify color vision deficiencies. To be considered as having color vision within normal limits, a patient should be able to correctly identify a majority of the 14 color plates. The plates consist of dots in various sizes and colors that form shapes, such as numbers, against a background of contrasting colors. The ability to discern these numbers indicates the functioning of the color-sensitive cones in the eye. In line with the trichromatic theory of color vision, individuals with normal color vision have three types of cones, each sensitive to different wavelengths of light corresponding to red, green, and blue colors.
Individuals who do not identify the majority of the plates may have a color vision deficiency, with the most common form being red-green color blindness. Though the exact number of plates needed to pass may vary by the test administration, a strong performance typically indicates normal color vision.