[Assessment of contrast vision by the Mars letter contrast sensitivity test - which illumination should be used?]. / Bestimmung des Kontrastsehens mit der MARS-Tafel - bei welcher Beleuchtung?

BACKGROUND: For expert opinions on mesopic and contrast vision as stipulated in the recent version of the German driving licence regulations (2011), a standardised implementation of the relevant test method is crucial. DIN 58220, part 7, regulates the assessment of mesopic vision and the required parameters of evaluation are guaranteed by the respective test instruments. Because no standard exists for photopic contrast vision, it is recommended that it conform to that of DIN EN ISO 8596 for visual acuity. For test equipment with integrated viewing fields, the application of such tests may not be difficult. But if visual charts are used the question of standardised illumination arises. The present paper investigates this question when using the Mars Letter Contrast Sensitivity Test in the light of the recommendations by the producer to use a desk lamp for illumination. METHODS: The Mars Chart was illuminated by three different commercially available desk lights from different directions at a distance of 50 cm, which is the test distance recommended by the producer. The luminance distribution was measured on the chart at twelve equally distributed test points. RESULTS: For all conditions, the asymmetric illumination produced by a single light source leads to an extremely inhomogeneous luminance distribution over the chart. Adherence to the tolerance ranges for brightness, as well as the homogeneity of illumination from such light sources is left to chance and a subjective judgment of both parameters is not adequate. CONCLUSION: Illumination of the Mars Chart with a desk light only does not necessarily satisfy the requirement of reproducible test conditions that is mandatory for expert evaluations. For comparable test outcomes for contrast vision, illumination devices that produce a uniform illumination should be employed.

[Assessment of mesopic and contrast vision for driving licences: which cut-off values, which methods are appropriate?]. / Untersuchung des Dämmerungs- und Kontrastsehens nach Fahrerlaubnisverordnung: Welche Grenzwerte, welche Verfahren sind geeignet?

BACKGROUND: Hitherto recommendations and thresholds for contrast tests are available for mesopic but not for photopic methods. While mesopic tests are widespread in ophthalmology, in occupational medicine photopic contrast tests are often used. With regard to the attachment 6 of the German Fahrerlaubnisverordnung (FeV) which is relevant since July 2011 we tested the specificity and sensitivity as well as the test-retest reliability of available test devices and defined cut-off values. METHODS: We examined patients with medium opacities, healthy volunteers and a sample of employees. Optovist EU, Binoptometer 4P and Pelli-Robson charts with standardised illumination were applied for contrast sensitivity testing. All these methods were compared to the Mesotest II as gold standard. We followed the recommendations of the German Qualitätssicherungs-Kommission der Deutschen Ophthalmologischen Gesellschaft (DOG) for contrast vision testing and definition of cut-off values. RESULTS: 64 patients with cataract (age 42-70 years, median 62 years), 50 pilots (age 40-69 years, median 53.5 years) and 109 employees of a transportation company (age 40-59 years, median 50 years) were included in the trial. All contrast sensitivity tests showed a good sensitivity and specificity (AUC 0.86 to 0.99). For Optovist EU and Binoptometer 4P a threshold of 15 % Weber contrast is recommended for examinations according to FeV. The test-retest reliability was high in all methods with highly significant Pearson correlation coefficients of 0.77 to 0.94 and a repeatability coefficient between 0.08 und 0.4. The standard distance of 1 m common for the Pelli-Robson chart cannot be recommended for FeV examinations, while the results at 3 m distance are comparable to those of the other contrast vision tests. The preliminary cut-off for the Pelli-Robson chart at 3 m distance is 1.65. CONCLUSIONS: Cut-off values for the lawful assessment of applicants are now available. Both Binoptometer 4P and Optovist EU proved to be appropriate and - as expected due to comparable technical properties - the same cut-off can be recommended. At 1 m distance the Pelli-Robson chart is not sensitive enough. Because the new distance of 3 m for the Pelli-Robson chart was investigated in 55 cataract patients and 10 pilots in this trial, a confirmatory trial for this distance is planned.