Comparison of a digital Farnsworth D15 test with the analog version

Purpose. This paper focuses on the comparison of a digital Farnsworth-D15 test with its analog version, which serves as a reference. The relevance of this is bearing on the widespread use of the D15 test as a screening method for both clinical and occupational purposes.

Material and Methods. In this study 36 healthy and phakic subjects (27 males, nine females, average age: 29.1 ± 9.5 years) took part. A total of ten subjects had a color vision deficiency. The analog and digital tests were performed by each of the 36 subjects against a black and a light background. An additional examination via an anomaloscope was carried out too. The evaluation of the results of all subjects by means of Bland-Altman plots allows a pairwise comparison between the two test versions.

Results. In total 25 subjects showed unremarkable results in all four test runs (C-index = 1.00, S-index = 1.38, angle = 62.00°). In case of the remaining eleven test persons these values diverged from the normal values in at least one test run. Generally the digital test indicated a high level of agreement (97 %) with its reference. Concerning the detailed analysis, most of the differences were more striking for the black background, which was perceived as more pleasant by the test subjects. On average the subjects performed slower on the black background compared to the light background (t(as) = 63 ± 39 sec.; t(ah) = 54 ± 32 sec.; t(ds) = 66 ± 40 sec.; t(dh) = 57 ± 37 sec.; a – analog, d – digital, s – black background, h – light background).

Conclusion. With regard to this data, the digital test can be considered as suitable for practical use, though further studies are required to make generally valid statements.