Pass rates for the Farnsworth D15 colour vision test

Test time affects Farnsworth D15 outcomes in practiced, but not unpracticed, subjects with color vision deficiency

SIGNIFICANCE

Imposing a time limit on the Farnsworth D15 test may prevent patients from compromising the test.

PURPOSE

This study aimed to investigate the effect of test time on the Farnsworth D15 color vision test in unpracticed and practiced subjects and determine an optimal test time.

METHODS

Twenty-one subjects (mean/standard deviation age, 33.1/9.3 years) with a range of congenital color vision deficiency participated in the study. Pseudoisochromatic plate screening, Farnsworth D15, and anomaloscope testing were performed for classification purposes. At each of 2 visits, 10 trials of the Farnsworth D15 were performed with a range in test times from 30 seconds to 10 minutes. Between visits, subjects practiced the test. Major crossovers were used as the outcome measure. A repeated-measures analysis of variance compared the scores across trials. Post hoc Dunnett's testing analyzed the pairwise data.

RESULTS

Although no significant difference in the mean number of major crossovers was found across the 10 trials for the first visit ( F (9, 180) = 1.30, p=0.24), a significant difference was found for the second visit ( F (9, 180) = 4.77, p<0.001). The range of mean number of major crossovers for the second visit was 1.71 to 5.1, with the 30-second trial resulting in the largest number of major crossovers and the longest trial resulting in the smallest number of major crossovers. Analysis showed that a 2-minute time limit resulted in a Farnsworth D15 outcome that would be expected based on the anomaloscope for a majority of subjects.

CONCLUSIONS

In this study, test time was found to affect performance in practiced subjects but not in unpracticed subjects. Based on this study, we recommend enforcing a time limit of 2 minutes to discourage those who try to pass the Farnsworth D15 through practice. Additional measures, such as recording patient behavior, can also be taken.

Evaluation of colour vision impairment during acute hypobaric hypoxia in aviation medicine: a randomized controlled trial

The digitization of aircraft cockpits places high demands on the colour vision of pilots. The present study investigates colour vision changes upon acute exposure to hypobaric hypoxia. The digital Waggoner Computerized Color Vision Test and the Waggoner D-15 were performed by 54 healthy volunteers in a decompression chamber. Respective altitude levels were sea level, 10,000 or 15,000 ft for exposure periods of 15 and 60 min, respectively. As for 60 min of exposure a significant decrease in colour perception was found between subjects at 15,000 ft as compared to the control group as well as between subjects at 15,000 ft as compared to subjects at 10,000 ft. No significant difference was found in the comparison within the 15,000 ft groups across time points pre-, peri-, and post-exposure. Thus, pilots appear to experience only minor colour vision impairment up to an exposure altitude of 15,000 ft over 60 min of exposure.

Clinical analysis of the Konan-Waggoner D15 color vision test using the Surface-Pro display

This work expands on our previous comparison of the Konan-Waggoner D15 (KW-D15) and Farnsworth D15 (F-D15). Sixty subjects with normal color vision and 68 subjects with a red-green color vision defect participated in the study. The KW-D15 had good agreement with the F-D15 for both pass/fail and classification across all failure criteria. The agreement was slightly better if subjects had to pass on 2/3 trials compared with just the first trial. The KW-D15 is an adequate substitute for the F-D15, with the caveat that the KW-D15 might be slightly easier to pass than the F-D15 for deutans.

Modeling D15 test sequences in red-green anomalous trichromacy

Color arrangement tests such as the D15 test can be used to detect congenital and acquired color vision defects. However, the D15 test cannot be used as the only test to assess color vision because of its relatively low sensitivity in less severe cases of color vision deficiency. In this study, we attempted to determine D15 cap arrangements for red/green anomalous trichromats with varying degrees of severity of color vision deficiency. The color coordinates of D15 test caps corresponding to a particular type and severity of color vision deficiency were determined using the model proposed by Yaguchi et al. [J. Opt. Soc. Am. A35, B278 (2018)JOAOD60740-323210.1364/JOSAA.35.00B278]. The arrangement of the color caps was modeled by assuming that individuals with color vision deficiency would arrange the D15 test caps judging by color differences perceived by them. The proposed simulation correctly predicts the increase in severity of color vision deficiency with spectral reduction between the L- and M-cone photopigments. The type of color vision deficiency is correctly predicted with few exceptions in protanomalous trichromats.

Lanthony D15 for Occupational Testing: Short-term Repeatability

SIGNIFICANCE

The Lanthony D15 has been reported to have poorer repeatability than the Farnsworth D15. This study found that two trials of the test provide high short-term repeatability and can be administered this way for occupational testing.

PURPOSE

This study aimed to determine the short-term repeatability of the Lanthony D15 in patients with color vision deficiency. Repeated trials were used to examine if learning effects occur and to determine how many trials would be necessary to ensure the highest short-term repeatability for occupational testing.

METHODS

Twenty male subjects (mean [standard deviation] age, 27.2 [4.3] years) with congenital color vision deficiency, ranging from mild to severe, participated in this single-visit study. Visual acuity, color vision book screening, Farnsworth D15, and anomaloscope testing were performed for classification purposes. Ten trials of the Lanthony D15 were performed. Color confusion index scores from each trial were determined, and a repeated-measures analysis of variance was used to compare the scores across trials. Orthogonal polynomial analysis was performed to detect any trends across trials through the third order. The intraclass correlation coefficient was calculated.

RESULTS

No differences in color confusion index (mean [standard error of the mean], 3.57 [0.04]) were found across the 10 trials ( P = .18). Legendre polynomials showed no statistical significance (all P > .39). The intraclass correlation coefficient was 0.81 (95% confidence interval, 0.70 to 0.90). Based on the method of Shrout and Fleiss, intraclass correlation coefficients of 0.7, 0.8, and 0.9 could be achieved with an average of one, two, and four trials of the test, respectively. However, empirically, 0.9 was not achievable.

CONCLUSIONS

The Lanthony D15 test has fairly high short-term repeatability. Thus, although more trials would likely improve clinical certainty, the mean result of two trials appears sufficient for occupational testing.

Evaluation of the Third edition of the City University Colour Vision Test

INTRODUCTION

The 3rd edition of the City University Colour Vision Test (CUT) was originally based on the Farnsworth-Munsell D-15 test (D15). The first part of the test is for detecting a defect, and the second part is used to diagnose the type and severity of the defect. This study evaluates the CUT 3rd edition relative to the Ishihara and the D15 colour vision tests.

METHODS

Fifty nine colour vision normal subjects and 60 subjects with a congenital red-green colour vision defect were recruited. Subjects were tested with the Ishihara and CUT tests. Subjects who failed the Ishihara also performed the D15 test.

RESULTS

The agreement between the Ishihara and CUT screening plates was marginally higher when using the CUT failure criterion of >1 error compared with using >2 errors. If the diagnostic plates were included with the screening plates in determining the pass/fail outcomes, the agreement between the Ishihara and CUT was high, with a first-order agreement coefficient (AC1) of 0.90. The AC1 coefficient agreement between the D15 and CUT diagnostic plates in terms of pass/fail was 0.81 when using the D15 failure criteria of >1 or >0 crossing.

CONCLUSION

The level of agreement between the 3rd edition of the CUT and D15 was lower than the 2nd edition of the CUT. The primary reason for the lower agreement of the 3rd edition of the CUT was that it had a lower specificity relative to the D15 compared to the 2nd edition. Although the CUT predictive value for failing the D15 is over 90%, the predictive value for passing shows that 19%-25% of patients who pass the 3rd edition of the CUT test will fail the D15. The 3rd edition tends to misclassify protans as deutans or cannot classify the type of defect relative to the D15 and Ishihara.

Evaluation of the Waggoner computerized D15 color vision test using an iPad device

The W-D15 test, a computerized variant of the F-D15 test, is used to determine whether an individual with a color vision defect can safely perform color-related tasks. This study evaluated the performance of the W-D15 test using an iPad. Fifty-nine color normal and 61 color vision defect subjects participated. Participants were screened based on the Ishihara, City University Test, and Waggoner PIP24 tests. Different failure criteria of the D15 tests were considered. The pass/failure agreement between the two tests was relatively appropriate, with a κ-coefficient ≥0.8, for all failure criteria. The W-D15 could be an appropriate substitute for F-D15 using an iPad.

Unexplained multi-sensory neuropathy syndrome in young Tanzanian adults

Background

A unique syndrome affecting young adults of unexplained hearing loss often associated with uncorrectable poor visual acuity and lower extremity numbness is endemic in Dar es Salaam. This study characterized the hearing loss, associated it with other symptoms, and gathered information on potential causes.

Methods

Forty-seven patients (23 men, 24 women) <40 years old with a symptom consistent with the syndrome, negative syphilis test, and no head injury history were recruited from Muhimbili National Hospital. 18 controls (10 men, 8 women) were recruited from the same neighborhoods as patients. Hearing ability and cochlear outer hair cell function (distortion-product otoacoustic emissions (DPOAEs)) were assessed, as were visual acuity and color vision. Peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument (MNSI), and physical examination. Blood C-reactive protein levels and toenail trace metal concentrations were measured. Environmental exposures were elicited using a questionnaire. Patients with at least two of the following signs were defined as having the syndrome: poor hearing with normal DPOAEs, vision not correctable to better than 20/30, or a MNSI score greater than 4.

Results

29 participants met the case definition. CRP levels did not differ between groups but manganese, cobalt and tin levels were each greater in the cases than controls. No other environmental exposure differences were noted.

Conclusions

Toenail manganese, cobalt, and tin levels were higher in those with the syndrome. These metals are potential neurotoxins suggesting a possible environmental origin for this unique and debilitating syndrome.

Effect of EnChroma glasses on color vision screening using Ishihara and Farnsworth D-15 color vision tests

BACKGROUND

The prevalence of color vision deficiency (CVD) is about 0.5% in females and 8% in males. Although there is no cure for CVD, specially filtered glasses are purported to improve color contrast. One recent development is the EnChroma filter. The purpose of this study was to assess the effect of the EnChroma filter on color vision screening (CVS) using Ishihara and Farnsworth D-15 color vision tests.

METHODS

The medical records of patients with CVD were reviewed retrospectively. Responses to color vision testing with and without the EnChroma filter were evaluated using Ishihara and Farnsworth D-15 tests, and the overall scores were analyzed.

RESULTS

A total of 38 eyes of 19 patients were included. Mean error scores of no filter compared to EnChroma were significantly reduced in 17 eyes using the Ishihara test (0.88 ± 0.03 vs 0.85 ± 0.03, P = 0.017). The error score significantly reduced only in deutans (P = 0.022), not in protans (P = 0.44). The confusion index of no filter to the EnChroma filter was significantly reduced in 20 eyes using the Farnsworth test (3.30 ± 0.15 vs 2.98 ± 0.17; P = 0.01). The confusion index significantly reduced only in protans (P = 0.01), not in deutans (P = 0.19).

CONCLUSIONS

In this study cohort, the EnChroma filter significantly reduced overall error scores using the Ishihara and Farnsworth tests; error scores on Ishihara testing reduced only in deutans. Conversely, the confusion index using Farnsworth reduced only in protans. The majority of patients reported subjective increase in color perception.

Predicting the Farnsworth-Munsell D15 and Holmes-Wright-A lantern outcomes with computer-based color vision tests

This study determined the AC1 agreement values between computer-based color vision tests and the Farnworth-Munsell D-15 (F-D15) and the Holmes-Wright Type A lantern (HWA). The computer-based tests were the United States Air Force Cone Contrast Test (OCCT), Cambridge Color Test, Innova Rabin Cone Contrast, Konan-Waggoner D15 (KWC-D15), and Color Assessment and Diagnosis (CAD). Sixty-eight color-vision-defective persons participated. The KWC-D15 had the highest AC1 with the F-D15 (${\rm AC1} = {0.88}$AC1=0.88). Both the CAD and OCCT had the highest values with the HWA (${\rm AC1} \gt {0.96}$AC1>0.96). The KWC-D15 would be the best substitute for the F-D15. Either the CAD or OCCT would be appropriate substitutes for the HWA.

Limitations and Precautions in the Use of the Farnsworth-Munsell Dichotomous D-15 Test

SIGNIFICANCE

Clinicians who administer the Farnsworth-Munsell D-15 test need to pay attention to the quality and quantity of lighting and the time that they allow for completion of the test, and all repeat attempts need to be included in reports on compliance with color vision standards.

PURPOSE

The validity of the Farnsworth-Munsell D-15 has been questioned because practice may allow significantly color vision-deficient subjects to pass. In this article, we review the influence of practice and other factors that may affect the performance. These relate to both the design and the administration of the test.

METHODS

We review the literature and present some calculations on limitations in the colorimetric design of the test, quantity and quality of lighting, time taken, and repeat attempts.

RESULTS

In addition to the review of the literature, color differences and luminance differences under selected sources are calculated, and the increases in luminance clues under some sources and for protanopes are illustrated.

CONCLUSIONS

All these factors affect the outcome of the test and need specification and implementation if the test is to be applied consistently and equitably. We recommend the following: practitioners should never rely on a single color vision test regardless of the color vision standard; lighting should be Tcp '' 6500 K and Ra > 90; illuminance levels should be between 200 and 300 lux if detection of color vision deficiency is a priority or between 300 and 1000 lux if the need is to test at the level where illuminance has minimal influence on performance; illuminance should be reported; time limits should be set between 1 and 2 minutes; repeat testing (beyond the specified test and one retest) should be carried out only with authorization; and initial and repeated results should be reported. A set of test instructions to assist in the consistent application of the test is provided in the Appendix.

Can the Farnsworth D15 Color Vision Test Be Defeated through Practice?

SIGNIFICANCE

This study suggests that it is possible for some patients with severe red-green color vision deficiency to do perfectly on the Farnsworth D15 test after practicing it.

PURPOSE

The Farnsworth D15 is a commonly used test to qualify people for certain occupations. For patients with color vision deficiency, there may be high motivation to try to pass the test through practice to gain entry into a particular occupation. There is no evidence in the literature on whether it is possible for patients to learn to pass the D15 test through practice.

METHODS

Ten subjects with inherited red-green color vision deficiency and 15 color-normal subjects enrolled in the study. All subjects had anomaloscope testing, color vision book tests, and a Farnsworth D15 at an initial visit. For the D15, the number of major crossovers was determined for each subject. Failing the D15 was determined as greater than 1 major crossover. Subjects with color vision deficiency practiced the D15 as long as desired to achieve a perfect score and then returned for a second visit for D15 testing. A paired t test was used to analyze the number of major crossovers at visit 1 versus visit 2.

RESULTS

Color-normal subjects did not have any major crossovers. Subjects with color vision deficiency had significantly (P < .001) fewer major crossovers on the D15 test at visit 2 (mean/SD = 2.5/3.0), including five subjects with dichromacy that achieved perfect D15 performance, compared to visit 1 (mean/SD = 8.7/1.3).

CONCLUSIONS

Practice of the Farnsworth D15 test can lead to perfect performance for some patients with color vision deficiency, and this should be considered in certain cases where occupational entry is dependent on D15 testing.

Case Report: Invalidation of the Farnsworth D15 Test in Dichromacy Secondary to Practice

SIGNIFICANCE

The Farnsworth D15 test can be subverted by patients even with severe red-green color deficiency.

PURPOSE

To describe a case showing that perfect performance on the Farnsworth D15 is possible after practicing the test.

CASE REPORT

A 23-year-old man presented for a comprehensive color vision evaluation. He had only minor complaints with regard to color vision and otherwise normal vision and ocular health. Based on anomaloscope findings, he was diagnosed with protanopia, a form of dichromacy in which the patient does not have any functional L cones, only S and M cones. The patient practiced the Farnsworth D15 test and returned for a follow-up visit in which he performed the test perfectly four times (i.e., twice in the regular order and twice using cap 15 as the pilot cap). In addition, the patient returned a year later and again performed the test perfectly, indicating long-term learning.

CONCLUSIONS

All studies to date have shown that patients with dichromacy fail the Farnsworth D15 test. This case report shows that it is indeed possible for highly motivated patients to subvert the test through practice, and knowledge of this possibility is very important, especially in occupational testing.

Acquired color vision deficiency

Acquired color vision deficiency occurs as the result of ocular, neurologic, or systemic disease. A wide array of conditions may affect color vision, ranging from diseases of the ocular media through to pathology of the visual cortex. Traditionally, acquired color vision deficiency is considered a separate entity from congenital color vision deficiency, although emerging clinical and molecular genetic data would suggest a degree of overlap. We review the pathophysiology of acquired color vision deficiency, the data on its prevalence, theories for the preponderance of acquired S-mechanism (or tritan) deficiency, and discuss tests of color vision. We also briefly review the types of color vision deficiencies encountered in ocular disease, with an emphasis placed on larger or more detailed clinical investigations.

Occupational color vision standards: new prospects

Occupational color vision standards in transport have been implemented for 100 years. A review of these standards has taken place early this century prompted by antidiscrimination laws in the workplace and several transport accidents. The Australian and Canadian Railways have developed new lanterns to address their occupational medical requirements. The Civil Aviation Authority in the UK has adopted the Color Assessment and Diagnosis (CAD) test as the standard for assessing color vision for professional flight crews. The methodology employed using the CAD test ensures that color deficient pilot applicants able to complete the most safety-critical task with the same accuracy as normal trichromats can be accepted for pilot training. This methodology can be extended for setting new color vision standards in other work environments.

Occupational styrene exposure, colour vision and contrast sensitivity: a cohort study with repeated measurements

OBJECTIVE

Associations between occupational styrene exposures and impairment of visual functions were investigated with a view to answering three questions: (1) are the published findings for colour vision deficiencies and impaired contrast sensitivity to reproduce in a new study approach, (2) if such effects exist, are they related to current or chronic exposures and (3) if effects exist, are there reductions in the effects during an exposure-free period?

METHODS

Workers from a boat building plant were examined in groups of current low [n = 97, mean mandelic acid (MA) + phenylglyoxylic acid (PGA) = 51 mg/g creatinine], medium (n = 115, mean = 229 mg/g creatinine) and high (n = 30, mean = 977 mg/g creatinine) level exposure to styrene. Job tenure was about 6 years. In addition, subgroups chronically exposed to low-short (n = 34, lifetime weighted mean 200 mg/g creatinine for 6 years) and high-long (n = 17, mean = 660 mg/g creatinine, 15 years) styrene levels were analysed. The examinations were carried out during normal working days and during the company holidays. Colour vision was investigated with the Lanthony desaturated panel D-15d using the colour confusion index (CCI) as a relevant variable. Contrast sensitivity was investigated with the Vistech charts VCTS 6500 using frequency-related results as well as total scores as variables. Co-variance analyses with repeated measurements and multiple linear regressions were used for statistical analysis.

RESULTS

There was no evidence of significant associations between exposure parameters and CCI. This is true for the analyses with all participants as well as for those with the subgroups with high-long versus low-short exposure. Thus, no exposure related changes in the relevant variables were found during the exposure-free period. The analyses for contrast sensitivity show similar results. The largest portions of the variances in both tests were explained by age. German as mother tongue covered a considerable portion of the CCI variances. Education, long-term alcohol use and job tenure explain only partly significant portions of the test variances exhibited.

CONCLUSION

Both acute styrene exposure levels of 40 ppm (range of standard deviation up to 54 ppm) and long term exposures to 27 ppm (range of standard deviation up to 44 ppm with higher exposure levels in the past) for a period of about 15 years were not identified as causing elevated risks for the investigated parameters of colour vision and contrast sensitivity. This statement contradicts the published results for styrene-related colour vision deficiencies but it seems to be compatible with published results for contrast sensitivity due to styrene exposure.

Occupational colour vision requirements for police officers

Inclusion of public service professions in the UK Disability Discrimination Act in 2004 prompted a review of occupational colour vision requirements for police officers. Changes in the regulations which existed prior to 2003 were proposed. The aim of this study was to obtain the views of serving police officers in Northern Ireland on the importance of good colour discrimination in everyday police work and on the recruitment regulations for patrol constables introduced in 2003 in mainland UK. These views were obtained by means of a questionnaire and informal discussions. More than 65% of police officers who responded to the questionnaire considered that good colour vision was very important for effective policing. Fewer than 2% considered that colour vision was unimportant. Experienced police officers agreed that the employment of colour-deficient patrol constables, as permitted in the new regulations, would lead to reduced efficiency and organisational difficulties at the local level. A number of everyday activities were described which showed the need for accurate colour discrimination. The change in recruitment policy and the lack of clarity in the new regulations show inadequate appreciation of the needs of the occupation, of different types of colour vision anomalies and of the diagnostic function of colour vision tests. Failure to provide guidance on appropriate colour vision tests, examination procedures and counselling services is likely to result in inconsistent employment policies in different police forces. It is recommended that the colour vision standard in place prior to 2003 is reinstated at the recruitment stage. The Ishihara test should be used for screening, and colour-deficient applicants further examined with the Farnsworth D15 test as a replacement for the City University Test 2nd edition.

Failure of concordance of the Farnsworth D15 test and the Nagel anomaloscope matching range in anomalous trichromatism

The Farnsworth D15 test (D15) was developed for use in occupational guidance. People with significant color deficiency, including all dichromats are expected to fail and people with slight color deficiency are expected to pass. Pass is a circular results diagram and fail an interlacing pattern with one or more red-green isochromatic errors (Farnsworth, 1947). The Nagel anomaloscope is a “gold standard” reference test for identifying and classifying red-green color deficiency. The matching range on the red/green mixture scale indicates the severity of the discrimination deficit. Pass/fail results for the D15 are presented for 107 protanomalous and 410 deuteranomalous trichromats and compared with the anomaloscope matching range. Thirty-six percent of the subjects examined failed the D15. Protanomalous trichromats are able to utilize perceived luminance contrast to obtain good results on the D15 but 42% of these subjects failed the D15 compared with 35% of deuteranomalous subjects. Failure of the D15 was clearly related to the Nagel matching range in deuteranomalous trichromatism but not in protanomalous trichromatism. For example, 84% of deuteranomalous subjects with matching ranges > 30 scale units failed the D15 but only 2% with matching ranges < 9 scale units were unsuccessful. In comparison, 53% of protanomalous subjects with matching ranges > 15 scale units and 33% of subjects with matching ranges < 5 scale units were unsuccessful. Protanomalous trichromats with apparently minimal color deficiency are therefore shown to have poor practical hue discrimination ability as measured with this test.