The results obtained in colour vision tests can be influenced by many factors. It is possible that a learning effect disguises the fact that an acquired colour vision disturbance has progressively either deteriorated or been successfully treated. Therefore, the primary object of this study was to examine whether a possible learning effect occurred if screening by the colour vision test Roth 28-hue (E) desaturated was repeated several times, and if this learning effect was age dependent. Sixty-five ocularly and generally healthy subjects participated in the study and were divided into two age groups: group A: 20-39 years, n = 35; group B: 40-59 years, n = 30. Besides their ophthalmological status (visual acuity, refraction, intraocular pressure, cup/disk ratio, central fundus), the cap-sorting test Roth 28-hue (E) desaturated was performed under standardized test conditions. The measurements were repeated after 5 +/- 1.72 days (TI), 15 +/- 3.53 days (T2), 32 +/- 6.97 days (T3), and 189 +/- 16.85 days (T4). The ophthalmological parameters of all subjects were inconspicuous. The individual evaluation of the error scores in the cap-sorting test Roth 28-hue (E) desaturated showed large-scale variations. For both age groups there was no statistically significant difference between the right and left eye at any time. The mean values of the younger group remained relatively constant after the first measurement. This age group showed a quick, clearly visible learning effect that persisted over the whole test period. With regard to the older age group the average values deteriorated, remained solid for one month increasing again after 6 months. The results showed an age-related learning effect. Therefore, it is important to repeat the colour vision test within 5 days for the age group 20-39 years. This second test result will then serve as a stable basis for further comparative examinations within a period of 6 months. The subjects of the age group 40-59 years ought to repeat a first colour vision test after 5 and again after 15 days. The result of the second repetition will then offer stable basic values for subsequent tests. (c) 2006 Wiley Periodicals, Inc.