Frequency of congenital dyschromatopsias in male population of the Split-Dalmatian County in Croatia.

A population of 9974 healthy male subjects (aged 15-45 years) was screened for congenital dyschromatopsia. The study group consisted of subjects applying for a driving license in the Split-Dalmatian County between 1996 and 1999. The aim was to establish colour vision deficiency (dichromats) and borderline deficiencies (anomalous trichromats) in candidates through complete ophthalmologic examination including the Ishihara pseudoisocromatic plates, anomaloscope Nagel II, and Hue Lanthony colour test. The frequency of congenital dyschromatopsias was 8.48%. This frequency includes 2.39% dichromats (1.49% protanops and 0.90% deuteranopes) and 6.09% anomalous trichromats (1.27% protanomals, 4.20% deuteranomals, 0.21% extreme protanomals and 0.41% extreme deuteranomals). It is important to recognise and classify dyschromatopsias according to type and severity in order to avoid misinterpretation of results and consequent unjustified limitations imposed on anomalous trichromats in the selection of a profession.