Syftet: Syftet med studien var att undersöka hur färgade kontaktlinser påverkade färgseendet och vilka våglängder av det synliga ljuset som de släppte igenom. Metod: 30 personer i åldrarna 19-52 deltog i studien. De hade sfärstyrkor mellan +5,00 D till -10,00 D och ingen hade cylinderstyrkor över -0,75 D. En synundersökning gjordes för att få fram nuvarande styrkor och sattes i en provbåge, ögat som inte undersöktes ockluderades. Ett Farnsworth D-15 färgsorteringstest användes för att bedöma färgseendet utan och med tre plana kontaktlinser i färgerna Blue, Green och Sherry från Star-Lens AB. Med en spektrofotometer mättes vilka våglängder som passerade genom kontaktlinserna. Resultat: Det fanns en signifikant skillnad med kontaktlinsen Blue på färgseendet av medelvärdet på antal gjorda fel (p < 0,05) jämfört med utan kontaktlins. Med Green och Sherry fanns det inte någon signifikant skillnad (p > 0,05 för båda). Transmittansen genom kontaktlinsen Blue hade ett minimum vid 590 nm, Green vid 600 nm och Sherry vid både 510 nm och 540 nm. Green och Sherry sjönk även transmittansen kraftigt efter 530 nm respektive 480 nm. Slutsats: Det blev en signifikant skillnad på färgseendet med kontaktlinsen Blue, men ingen skillnad med Green och Sherry. Färgade kontaktlinser har ingen direkt påverkan på färgseendet vid mätning med ett Farnsworth D-15 färgsorteringstest. Transmittansen på kontaktlinserna sjönk mest vid respektive kontaktlins komplementärfärg, men färgerna Green och Sherry sjönk transmittansen även en del i de blåa våglängderna. / The aim of this study was to examine how tinted contact lenses affect color vision and which wavelengths of the visible light that is transmitted through them.   A total of 30 people in the range from 19 to 52 years were included in this study. They had refractive errors from about +5.00 D to -10.00 D and no cylinder power over -0.75 D. An eye exam was made and their current power was put in a trial frame, the eye that was not examined was occluded. A Farnsworth D-15 color arrangement test was made to examine color vision without tinted contact lenses and was then repeated with each of the three plano contact lenses in the colors Blue, Green and Sherry. A Spectrophotometer was used to measure the transmittance of visible light through the contact lenses.   There was a significant difference with the Blue contact lens on the mean error score (p < 0.05) compared to without contact lens. With the contact lenses Green and Sherry was there no significant difference (p > 0.05 for both). The transmittance through the Blue contact lens had a minimum at 590 nm, Green at 600 nm and Red at both 510 nm and 540 nm. Both the Green and Red contact lenses the transmittance decreased considerably after 530 nm and 480 nm respectively.   There was a significant difference in color vision with the Blue contact lens, but no difference with the Green and Red contact lenses. Tinted contact lenses have no direct effect on color vision when measuring with a Farnsworth D-15 color arrangement test. The transmittance decreased most at the complementary color of each contact lens, but with the Green and Red contact lenses the transmittance also decreased in the blue range of the visible wavelengths.

Introduction Colour codes are used extensively in railways to convey specific information governing movement of trains and equipment on the track. One such task is the railway traffic control display that uses colour coded video display terminals (VDTs) to convey information of the signal status, train movements and track status to the railway dispatcher. Because individuals with colour vision deficiencies (colour-defectives) may have problems with these colour-related tasks, questions were raised about the suitability of colour vision defectives to work as railway dispatchers. In order to answer that, a VDT based Dispatch Colour Vision Test based on the actual railway traffic display was developed previously. Purpose The main purpose of this thesis is to establish the pass/fail scores and repeatability of the VDT based Dispatch Colour Vision Test that resulted from the previous work. Secondly, the study will also examine whether clinical colour vision tests can predict the performance on the practical task. Methods The Dispatch colour vision test was divided into three parts based on the colour sets that the dispatcher had to recognize. The testing computer system used the the same RGB colour settings, graphics card and monitor as in railway dispatch centres. Subjects viewed the display colours and entered their responses by using a mouse. One hundred colour-normals and fifty two colour-defectives participated in the initial session. The test was repeated approximately after 10 days. Ninety three colour-normals (93%) and 44 (85%) colour-defectives participated in the second session. The total number of errors and time to complete the test was recorded. Results Pass/Fail on the VDT Dispatch colour vision test was based on colour-normal errors. Ignoring orange-red errors, two errors were allowed in the first session and one error was allowed in the second session. Based on this criterion, 42% of colour vision defectives could perform as well as colour normal subjects. The kappa coefficient of agreement between the sessions for the colour-defectives was 0.85. Detailed analysis between the colour differences and the errors showed only a weak correlation between the two. However, the general trend was that colour-defectives made more errors on colours that were near or along the same lines of confusions and the colours were nearly equal in luminance. Nevertheless, the interaction between luminance and location with respect to the lines of confusion was not easy to interpret. The time to complete the task for the colour-defectives who passed the test took 14% longer than colour-normals and colour-defectives who failed took 30% longer than colour-normals. All groups showed a similar learning effect with an 18% reduction in mean times to complete the task at the second session. There was no significant correlation between the number of errors and time to complete or the clinical tests and completion times for any of the groups. Clinical colour vision tests have limited value in predicting performance of colour-defectives on the Dispatch test. Logistic analysis results showed that the Farnsworth D-15 along with the Nagel was the best predictor of the VDT Dispatch colour test pass/fail results. However, these results were similar to using the Farnsworth D-15 test alone. Ninety-five percent of the individuals who failed the Farnsworth D-15 also failed the Dispatch test. However, approximately 25% of the individuals who passed the Farnsworth D-15 failed the VDT Dispatch colour test which is an unacceptable false negative rate. These results indicate the Farnsworth D-15 can only be used to predict who is likely to fail the dispatch test. Conclusions Forty two percent of colour vision defectives could perform as well as colour-normals in identifying VDT railway display colours and time to complete the task. Clinical colour vision tests were inadequate predictors of performance in practical task, overall. However, the Farnsworth D-15 was a very good predictor of who would fail the VDT Dispatch test. Hence a practical VDT Dispatch test may be needed to test individuals who would want to work as railway dispatchers.

Introduction Colour codes are used extensively in railways to convey specific information governing movement of trains and equipment on the track. One such task is the railway traffic control display that uses colour coded video display terminals (VDTs) to convey information of the signal status, train movements and track status to the railway dispatcher. Because individuals with colour vision deficiencies (colour-defectives) may have problems with these colour-related tasks, questions were raised about the suitability of colour vision defectives to work as railway dispatchers. In order to answer that, a VDT based Dispatch Colour Vision Test based on the actual railway traffic display was developed previously. Purpose The main purpose of this thesis is to establish the pass/fail scores and repeatability of the VDT based Dispatch Colour Vision Test that resulted from the previous work. Secondly, the study will also examine whether clinical colour vision tests can predict the performance on the practical task. Methods The Dispatch colour vision test was divided into three parts based on the colour sets that the dispatcher had to recognize. The testing computer system used the the same RGB colour settings, graphics card and monitor as in railway dispatch centres. Subjects viewed the display colours and entered their responses by using a mouse. One hundred colour-normals and fifty two colour-defectives participated in the initial session. The test was repeated approximately after 10 days. Ninety three colour-normals (93%) and 44 (85%) colour-defectives participated in the second session. The total number of errors and time to complete the test was recorded. Results Pass/Fail on the VDT Dispatch colour vision test was based on colour-normal errors. Ignoring orange-red errors, two errors were allowed in the first session and one error was allowed in the second session. Based on this criterion, 42% of colour vision defectives could perform as well as colour normal subjects. The kappa coefficient of agreement between the sessions for the colour-defectives was 0.85. Detailed analysis between the colour differences and the errors showed only a weak correlation between the two. However, the general trend was that colour-defectives made more errors on colours that were near or along the same lines of confusions and the colours were nearly equal in luminance. Nevertheless, the interaction between luminance and location with respect to the lines of confusion was not easy to interpret. The time to complete the task for the colour-defectives who passed the test took 14% longer than colour-normals and colour-defectives who failed took 30% longer than colour-normals. All groups showed a similar learning effect with an 18% reduction in mean times to complete the task at the second session. There was no significant correlation between the number of errors and time to complete or the clinical tests and completion times for any of the groups. Clinical colour vision tests have limited value in predicting performance of colour-defectives on the Dispatch test. Logistic analysis results showed that the Farnsworth D-15 along with the Nagel was the best predictor of the VDT Dispatch colour test pass/fail results. However, these results were similar to using the Farnsworth D-15 test alone. Ninety-five percent of the individuals who failed the Farnsworth D-15 also failed the Dispatch test. However, approximately 25% of the individuals who passed the Farnsworth D-15 failed the VDT Dispatch colour test which is an unacceptable false negative rate. These results indicate the Farnsworth D-15 can only be used to predict who is likely to fail the dispatch test. Conclusions Forty two percent of colour vision defectives could perform as well as colour-normals in identifying VDT railway display colours and time to complete the task. Clinical colour vision tests were inadequate predictors of performance in practical task, overall. However, the Farnsworth D-15 was a very good predictor of who would fail the VDT Dispatch test. Hence a practical VDT Dispatch test may be needed to test individuals who would want to work as railway dispatchers.