[Comparison of the Lithander (Kolt test) pediatric visual acuity test with the standardized Landolt ring test]

The visual acuity values obtained with the four test figures of Lithander's "Kolt-test" have been compared with Landolt ring acuity under standardized conditions which meet the requirements of DIN 58,220 and ISO/DIS 8596/7. For a given test figure size, the Kolt-test optotypes turned out to be somewhat easier legible than the Landolt ring. On average, visual acuity measured with the Kolt-test exceeded Landolt ring acuity by 0.08 log (angle of resolution) units. Thus, according to DIN and ISO criteria, the legibility of the Kolt-test is not equivalent to the standard Landolt ring. Equal acuity values could be obtained by increasing the observation distance proposed by the manufacturer of the Kolt-test by 19%. The legibility of the four optotypes differs on adult subjects: "circle" is more difficult, "cross" is easier legible than "square" and "triangle". Confusion of Kolt-test figures is basically restricted to two pairs of two optotypes ("cross" - "triangle", "square" - "circle").