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John L Barbur, Benjamin Evans, Marisa Rodriguez-Carmona; New screener for congenital and acquired colour deficiencies. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1314.
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Purpose: Currently, there is no conventional colour-screening test that passes all normal trichromats and identifies correctly all subjects with congenital or / and acquired colour deficiency. The aim of this project was to make use of recent advances in visual displays and improved understanding of colour vision mechanisms to produce a rapid and sensitive colour vision screener that overcomes the limitations of current tests.
Methods: The screener employs the effective use of the dynamic luminance contrast noise technique developed for the CAD test (Br Med Bull. 2017 Jun 1;122(1):51-77. doi: 10.1093/bmb/ldx007) to isolate the use of colour signals. Age-matched thresholds that describe the upper normal, healthy limits of red / green (RG) and yellow / blue (YB) colour vision are employed. The difference in thresholds between the least-sensitive, normals and the least-affected, age-matched deutans and protans enables accurate screening for congenital deficiency. The screener also detects acquired loss of colour vision, even in subjects with congenital deficiency. The CAD-Screener is easy to use and takes two minutes to complete. The eight stimulus colours are randomly interleaved and the subject cannot make use of any other cues. The CAD-Screener does not require display calibration and runs on monitors that support the sRGB colour mode.
Results: The experiments carried out so far involved 120 normal trichromats, 80 deutans and 12 protans. Based on these initial findings the CAD-Screener detects all normal trichromats and all protans with 100% sensitivity and specificity. The deutans examined have also been identified as having congenital colour deficiency. Since only a small percentage of deutans (< 3%) have thresholds close to the upper, age-matched normal limit, more deutan subjects are needed to establish an accurate statistical outcome.
Conclusions: Conventional colour assessment tests are often used in schools and many occupations to screen for RG colour deficiency. The outcome is often unexpected in that normal trichromats can fail and some subjects with congenital deficiency pass. Those that pass can have severe loss of colour vision. The CAD-Screener eliminates these problems. In addition, the screener also tests for YB loss and detects the presence of acquired deficiency. The potential use of the CAD-Screener within schools and visually demanding occupations remains to be established.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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