A proposed correction in the weighted method to score the Ishihara test

Area of Science:

• Ophthalmology
• Vision Science

Background:

• The Ishihara test is a standard color vision test where all plates are typically weighted equally.
• Previous research proposed a severity index but did not fully account for plate-specific performance differences in various populations.
• Accurate quantification of color vision deficits is crucial for diagnosis and management.

Purpose of the Study:

• To propose and evaluate a modified weighted index for quantifying Ishihara test results.
• To compare the modified index with non-weighted and previously proposed weighted indices.
• To assess the index's performance in distinguishing between trichromats and individuals with congenital color vision deficiency.

Main Methods:

• Evaluated 60 normal trichromats and 107 subjects with congenital color deficiency.
• Calculated three indices: non-weighted, Rodriguez-Carmona weighted, and a modified weighted index.
• The modified index incorporated hit frequency in trichromats and error frequency in colorblind individuals for each plate.

Main Results:

• The modified weighted index showed significant changes in index values compared to previous methods.
• Weighted indices reduced scores by 22.95% (trichromats), 32.92% (protan), and 35.38% (deutan) versus non-weighted.
• Receiver Operating Characteristics (ROC) analysis indicated perfect classification performance for all metrics.

Conclusions:

• The modified weighted index offers a refined method for assessing Ishihara test results.
• While the correction significantly alters index values, its overall clinical benefit requires further investigation.
• This approach enhances the quantitative analysis of color vision deficits detected by the Ishihara test.