Errors reading the Ishihara pseudoisochromatic plates made by observers with normal colour vision

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Ishihara pseudoisochromatic plates are standard for detecting red-green color vision deficiencies.
• A notable percentage of individuals with normal color vision also make errors on these plates.
• Understanding these errors in normal trichromats is crucial for test refinement.

Purpose of the Study:

• To analyze the performance of normal trichromats on Ishihara plates.
• To differentiate between typical and atypical errors made by normal observers.
• To identify clinical implications for improved diagnostic accuracy.

Main Methods:

• 249 participants (161 female) with normal color vision were tested using Ishihara plates.
• The number and types of errors were systematically recorded.
• Errors were categorized as 'typical' (expected in color vision deficiency) or other types.

Main Results:

• 45% (111/249) of normal trichromats misread at least one plate.
• Females made up to six errors, males up to five, when all errors were considered.
• When only typical errors were counted, all normal trichromats made two or fewer errors.
• No significant gender differences were observed for total or typical errors.

Conclusions:

• Clinicians should prioritize counting only typical errors during Ishihara testing.
• Implementing a criterion of ≤2 typical errors could enhance the test's specificity and sensitivity.
• This approach may lead to more accurate diagnoses of normal color vision.