Colour vision screening in children: an evaluation of three pseudoisochromatic tests.

We examined 513 children (258 boys and 255 girls), between 3 and 11 years of age, with three pseudoisochromatic tests which involve different visual tasks. These were a selection of numeral designs from the Ishihara test, the Ishihara test for Unlettered Persons and the Velhagen Pfügertrident test. Eighteen children were found to be colour deficient. The symbol designs of the Unlettered Persons test were found to be the quickest and most effective method for examining children under 7 years of age. After 7 years of age the symbol designs of the Unlettered test and the numeral designs of Ishihara test were equally effective. The preferred numeral designs for screening children with the Ishihara plates are listed. Verbal identification always produced the most accurate results. Drawing over the figures or selecting replicas increased the viewing time and assisted children with normal colour vision to see both figures in transformation designs, especially pathway designs. The Velhagen Pfügertrident test was found to be unreliable for colour vision screening and younger children had difficulty performing the figure matching task.