Projected Color Slides as a Method

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Intern. J. Neuroscience, 115:11051117, 2005Copyright 2005 Taylor & Francis Inc.

ISSN: 0020-7454 / 1543-5245 online

DOI: 10.1080/00207450590914365

PROJECTED COLOR SLIDES AS A METHODFOR MASS SCREENING TEST FOR COLORVISION DEFICIENCY (A PRELIMINARY STUDY)

NI.MET NAY GNDOG

ANNEZI

.H DURMAZLAR

Department of Physiology

Hacettepe University, Faculty of MedicineAnkara, Turkey

KORAY GMS

Department of OphthalmologyHacettepe University, Faculty of MedicineAnkara, Turkey

PINAR GEYI.K ZDEMI

.R

Department of BiostatisticsHacettepe University, Faculty of MedicineAnkara, Turkey

AYSE GL ALTINTAS

Department of OphthalmologyTraffic HospitalAnkara, Turkey

Received 18 October 2004.

The authors thank Dr. James P. Ganley, MD, for his kind communication and express gratitude

to the Ethical Committee of Hacettepe University and to the students for their help with this project.

This study was supported by Hacettepe University Research Institute grant 01 01 101 014.

Address correspondence to Nimet nay Gndog

an, MD, Professor and Chairman of Physiology

and Pharmacology Departments, Baskent University, Faculty of Medicine, Departments of Physiol-

ogy and Pharmacology, Eskisehir Yolu 20.km Bag

hca kampus 06815, Etimesgut, Ankara,

Turkey. E-mail: [email protected]

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IRMAK DURUR

Department of RadiologyAtatrk University, Faculty of MedicineErzurum, Turkey

GLGE ACAROG

LU, MD

SSK Eye HospitalDepartment of OphthalmologyAnkara, Turkey

This article compared the efficiency of the mass screening test with projected

color slides in detecting color-blindness with the authentic classic method of

Ishihara. The study was conducted in a randomly selected lecture room with

104 students aged between 1925 years (median 21). Using Ishihara projectedslides, performed mass screening test. Re-testing was done individually with

printed Ishihara plates. Six male and one female with color-blindness were

detected. The frequency of color-blindness was 13.6% among males, with a

total incidence of 6.7%. The results of two testing methods were compared

statistically. Sensitivities and specificities of both tests were 100%. Using pro-

jected slides of Ishihara plates instead of the authentic method is an effective

and timesaving method for detecting color-blindness. This method can be sug-

gested as a mass-screening test and might be beneficial in detecting color-

blindness in large populations such as students, soldiers, and so on.

Keywords a new method for Ishihara color vision test, mass screening test

for color vision deficiencies, projected Ishihara color slides, projected slides,

timesaving test for detecting color-blindness

INTRODUCTION

The Ishihara plates have been widely used as a test for color vision originallydesigned for the purpose of detecting red/green (r/g), congenital color visiondeficiency (CCVD) and it is the most effective test for detecting CCVD (Birch,1997; Sloan & Habel, 1956; Belcher et al., 1958). It has been used confidentlyfor a long time and it has become a standard for testing color vision deficiency.Nevertheless, this individual testing consumes a considerably long time inscreening larger groups. In this regard, the Ishihara test should be improved

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PROJECTED COLOR SLIDES 1107

and standardized. For this purpose, the authors modified the Ishihara test as amass screening test and produced its color slide projections.

The goal of this preliminary study was to find out the sensitivity and thespecificity of projected slides of Ishihara plates, as a mass screening methodby comparing the results with that of the individual authentic classic method

of Ishihara. The aim was to show the potential benefits of projected slides asa mass screening method for detecting CCVD individuals in short time.

MATERIALS AND METHODS

This study was carried out at the Physiology Department of Hacettepe Uni-versity with permission from Hacettepe University Ethical Committee andwith the written consent of the subjects. The study was conducted in a ran-domly selected lecture room with 104 students aged between 1925 years(median 21). None of the students had a known history of ocular pathology,ocular operations, and occlusion or penalization therapy. Except five stu-dents, none had refractive disorders and a usage history of corrective color-less glasses. The visual acuity of all students was 20/20 in both eyes. Ishiharaspseudo-isochromatic test plates (1990, 38-plate edition), numbered 1 to 25,were used (Ishihara, 1990). Thirty-five mm-projected slides were preparedwith Kodak Ektachrome Professional PC 100 film from the Ishihara testplates. All slides were exposed by compact automatic 35 mm slide projector

(Leica P 150, Typ 627 lamp 24 V/150W), which had an automatic focusingfunction. It was kept perpendicular to the screen. The test color slides wereprojected on a clean good-quality screen.

The printed forms of the same Ishihara test plates (numbered 1 to 25)were used for re-testing the subjects with the classical individual method.Because the frequency of blue-yellow color vision deficiency in the generalpopulation is very low (0.0002%), it is found impractical to test this abnor-mality in the present study.

The inability to recognize at least 9 plates out of 24 projected color plate

slides or color printed plates was accepted as CCVD.

Application of the Mass Screening Test

First, the students were seated in the lecture room, and then the rational forthe test and the importance of color vision were clearly explained to allsubjects. It was explained that this test was just like a mirror from which theywould learn their real sense of color vision. These explanations aimed to

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build an interest in their minds for color vision, and also to ensure a curiosityfor their own ability accompanied by arousing questions in their minds suchas: How do I see the colors?, Could I see colors like the others?, and Ismy color vision normal? They were directed to write whatever they saw onthe projected slide. To increase the chance of getting reliable results for the

diagnosis of color vision ability, the subjects were told not to look at othersanswers. Following all these preparations, the color vision test examinationform was given (Table 1). Before starting the test, they filled out some de-mographic characteristics such as name, date of birth, sex, and whether theywere known to be color-blind or not. It was explained that when the slidewas flashed on the screen they might have seen Arabic numbers. In a case ofnot seeing any number on the screen, they were directed to put down an Xsign for that color plate.

All the lights of the lecture room were dimmed in order to provideenough overhead lighting to allow the students to record their written re-sponses. After the introductory plate seen by all subjects was projected, itwas checked whether they could see or not for establishing equal visionquality in the classroom. Twenty-four Ishihara slides were projected in se-quence. The subjects were told to close their eyes after each slide and toopen them again for the consequent protection. A directive was given such asopen your eyes, which meant look at the plate and write, and then closeyour eyes in order to sweep the effect of retinal image and cortical stimula-

tion for avoiding the contrasts in the visual image.The students were allowed 4 s for each plate and elapsed total time was

25 4 = 100 s. Total time to complete the test, including the explanatoryremarks, was about 1520 min.

Application of the Classical Individual Method

A few weeks after mass screening, all the same subjects were re-tested with

Ishihara test plates in classic individual method in a well-illuminated roomwith sunlight between 13.0015.00 PM. Ishihara test plates, holding themperpendicular to their eyes, were shown to the subjects from a distance of 1meter. They were asked to record the numbers on the answer form whateverthey saw. During the test, it was impossible to record the test time for eachtest plate and also for the total test time of all the test plates. Nevertheless, itcould not be possible to establish test time equality among the students dur-ing individual tests with Ishihara printed color plates.

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Table 1. Examination form for detecting color vision deficiency

HACETTEPE UNIVERSITY FACULTY OF MEDICINE DEPARTMENT

OF PHYSIOLOGY COLOR VISION TEST FORM

Name:

Date of Birth: . / . / 19

Gender: Male ( ) / Female ( )City:

Faculty:

Do you have color vision problem? No ( ) / Yes ( )

This is a color vision test answer form. You should write whatever you see at the color

plates in the corresponding box. Your answer time for each of color plate is only four

seconds. If you see numbers on the color plates please write this number on the number

response colon; if the color plates seems unmeaning to you the mix or black-white please

put the symbol (X) to the colon seen below. Please follow carefully the plate numbers

during the whole period of test.

Plate Response Sign (X) if Sign (X) if Sign (X) if

number number it is unmeaning it is mix it is black-white

1

2

3

4

5

6

78

9

10

11

12

13

14

15

16

1718

19

20

21

22

23

24

25

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Statistical Analysis

Chi-square test (Fishers Exact Test) was used to determine the relationshipbetween sex and the color vision status of the students, and Kappa statisticswere used for the concordance between Mass Screening test and classic indi-vidual Ishihara Test. The classical individual method was accepted as thegold standard in identifying the red/green color-blind subjects.

RESULTS

There were seven (6M, 1F) color-blind students. The incidence of color-blindness was 13.6% (6/44) among male population and 6.7% (7/104) for thewhole population (Table 2). There was complete concordance between themass screening test and the classical method (= 1.00,p = .000). The sensi-tivity and the specificity of the mass-screening test were both found to be100% (Table 3).

Table 2. The response of classical individual method of Ishihara

Detection of color sense ability

Not color-blind individuals Color-blind individuals

Number % Number % Total

Male 38 86.4 6 13.6 44

Female 59 98.3 1 1.7 60

Total 97 93.3 7 6.7 104

Table 3. The specificity and sensitivity of projected mass screening test method

(according to the individual classic method of Ishihara, as a gold standard).

Classical Projected slides mass screening method

method

Sensitivity (%) Specificity (%)

Number Number (true color blind) (true color normal)

Not color blind 97 97 100

Color blind 7 7 100

Total 104 104

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All subjects were able to see the introductory plate in two methods aswas expected. Four normal subjects made errors during the mass-screeningtest. One of them made three errors, one student made two errors, and theremaining two students made one error in different plates. In the classicalauthentic individual method, only one normal subject made three errors. The

errors made by these subjects were similar to the errors of color-blind sub-jects errors listed in Table 4.

The results of color-blind students obtained from two different methodswere compared in Table 5 and the numbers of wrong answers of two testsare shown in Figure 1.

Table 4. The number of wrong answers of color-blind students for each

of Ishihara test plates according to numeral range of Ishihara plates in

both methods

Ishihara Color printed plate individual Projected slides

plate number (classic method) (mass screening method)

1 0 0

2 4 4

3 2 1

4 6 7

5 7 7

6 7 7

7 6 7

8 4 6

9 7 7

10 5 7

11 6 7

12 7 6

13 6 7

14 7 7

15 5 6

16 2 4

17 7 718 0 1

19 4 2

20 4 1

21 3 1

22 4 6

23 5 7

24 7 7

25 6 7

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DISCUSSION

Color blindness (color vision deficiency) is a condition in which certain col-ors cannot be distinguished, and is most commonly due to an inherited con-dition (Swanson & Cohen, 2003; Tagarelli et al., 1999). Red/Green (r/g) colorblindness is by far the most common form, and causes problems in distinguish-ing reds and greens (Tagarelli et al., 1999).There is no known treatment for

Table 5. Comparing the results of color-blind students in two different methods

Ishiharas pseudoisochromatic color plate tests

Subjects response to Subject response to printed color

projected slides plate individual

(mass screening test method) (classic method)Plate Normal

no. response 1 2 3 4 5 6 7 1 2 3 4 5 6 7

1 12 12 12 12 12 12 12 12 12 12 12 12 12 12 12

2 8 8 3 3 8 3 3 8 8 3 3 8 3 3 3

3 6 6 6 6 6 6 5 0 6 6 6 6 6 5 5

4 29 29 20 70 20 70 70 22 28 20 0 29 70 20 70

5 57 0 65 35 67 32 32 67 35 35 0 67 32 35 25

6 5 8 2 2 2 2 2 2 2 2 2 8 2 2 2

7 3 6 5 0 6 8 3 5 5 5 0 0 6 5 58 15 15 15 0 15 19 17 17 15 0 15 17 17 17 17

9 74 21 21 21 21 21 21 21 21 21 21 21 21 21 21

10 2 2 0 0 2 0 0 0 0 0 0 0 0 14 0

11 6 6 0 0 0 0 0 0 0 0 0 0 0 35 0

12 97 0 0 0 87 0 0 0 0 0 0 0 0 0 0

13 45 45 0 0 0 18 18 0 16 0 0 46 0 16 18

14 5 0 0 0 0 0 0 0 6 0 0 0 0 0 0

15 7 0 0 0 0 7 0 7 9 0 0 0 0 0 0

16 16 16 16 0 16 16 0 16 16 0 0 0 0 0 0

17 73 23 0 0 0 78 0 79 0 0 0 0 0 0 0

18 X X X X X X X X X X X X 9 X X

19 X 8 X X X 8 2 8 X X X X 8 X 8

20 X 45 X 45 46 X 46 X 45 45 46 X 66 41 45

21 X X X 73 X 73 23 X X X X X 72 23 X

22 26 26 0 0 26 0 6 26 2 2 0 28 2 0 2

23 42 42 0 0 42 4 0 4 42 0 0 42 62 0 4

24 35 86 0 0 85 3 0 3 35 35 0 86 36 0 35

25 96 26 0 0 96 2 4 56 96 96 0 96 96 0 9

Note: Boldface numbers represent incorrect response.

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color blindness, nor is it usually the cause of any significant disability. Beingcolorblind keeps one from performing certain jobs and makes others difficult(Poole et al., 1997; Spalding, 1993). Consequently, it is crucial to detect

color-blind individuals earlier, especially before they choose their profes-sions, enabling the prevention of serious problems, possibly to be faced throughouttheir professional life. In order to do this, the best way is to organize screen-ing programs, especially among the students. However, it entails such aneffective, timesaving method, which has high specificity and sensitivity fordetecting color-blind individuals.

In the large-size classrooms with more than one hundred students, indi-vidual testing with color plates consumes considerable lecture time. It isessential to establish a color vision testing method that could screen a large

population at one session. It should be timesaving, sensitive, and easy toperform. The classical individual application of Ishihara method has somehandicaps: At first, it is not suitable for mass screening because it is a time-consuming individual method. Second, as test plates are kept together in theform of a book and the examiner who allows time for the subject to identifythe figures turn the pages, the recognition time for each plate varies individu-ally, depending on the color perception ability of every subject. The recogni-tion time of a subject with normal color vision is shorter than the one with

Figure 1. The number of wrong answers detected in two methods.

Projected slides

Printed color plates

Numberofwrongans

wers

Number of plates

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CCVD. Therefore, the test time shows considerable individual variation andleads to a time-dependant heterogeneity in the evaluation of the subjects. Onthe other hand, a projected slide method solved this time-dependant hetero-geneity problem. Reply time was kept constant for each color plate and foralso total test time. Third, in this method, the practitioner would prevent the

confounding variables arising from the place, lighting, and testing-time dif-ferences in large groups. Moreover, color hue variances in the printed testbook editions also affect the number of misreadings. The printed color plateshave a tendency to fade in time for testing large groups. But with projectedslides, a mass-screening test can be administered to a large group at once aspresenting study; the CCVD examination test took only 1520 min for 104students.

Another issue is the correction of eye refraction by wearing colored

lenses. A pair of greenish sunglasses or contact lenses lets the green but notthe red light pass through. Thus, a red digit on green background will appeardark on a bright background. It will become easily readable despite a colorvision defect. A green digit on a red background will be just as easily read.It will appear bright on a darker background (Linksz, 1971). So in the presentstudy, students were not allowed to wear colored sunglasses and coloredcontact lenses.

It is so important to eliminate the confounding effects of aging factorson the color vision deficiencies (Lakowski, 1962). In the current study, the

subjects consisted of young individuals (median age 21). All of the studentswere Caucasians. The prevalence of red-green CCVD in Caucasian maleschanges from 8% to 10% (Neitz et al., 2001; Pokorny et al., 1979; Pokorny& Smith, 1987).In the present study it was found that the prevalence of R/GCCVD among male students was 13.6% in both of the methods. It may beattributed to the widely seen consanguinity relation in the Turkish population(Tunbilek, 2001). This may be a factor for such a high prevalence of CCVDin the present study group. However, the R/G CCVD prevalence was re-ported to be as high as this study by other authors (Barna et al., 1981; Tocantins

& Jones, 1993; Poole et al., 1997). On the other hand, the incidence ofCCVD for whole population in the present study was found as 6.7%. Thisfinding is in line with other studies (Ganley & Lian, 1997; Isikli et al., 1999).The reports on the prevalence of R/G CCVD in Turkey show that Ishiharacolor plates is the only test used by the researchers to determine color visiondefects for mass screening, although their results are controversial. Gkbel etal. (1992) reported findings approximately close to the present ones. On theother hand, as can be seen in Table 6, there are several contradictory reports

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in Turkey (Isikli et al., 1999; Say et al., 1996; Tmerdem et al., 1985; Ayhan

et al., 1994). However, the error scores in these studies are not clear. Aconsensus for the interpretation of the test results should be established amonginvestigators. Although the performance of the subject in reading the Ishiharaplates is evaluated to determine color-blindness, there is not a standard crite-rion for this. Some investigators diagnosed color deficiency by using trans-formation plates (plates 29) (Isikli et al., 1999), whereas others used hiddendigit plates (plates 1821) to determine color deficiency (Birch, 1997). Obvi-ously, consensus among the investigators is very important, in order to avoidcontroversial results. For example, Birch defined a color deficient subject as

the person making 8 or more mistakes in reading plates

(Birch, 1997), al-though another researcher used a different definition such as the subject making5 or more mistakes in reading 14 plates is color deficient (Ganley & Lian,1997). Determination of error score plays a crucial role in comparing thefindings and determining the efficiency of the test. If misreading some platescauses uncertainty, further color vision tests are recommended. Standardiza-tion of the error scores for the diagnosis of CCVD is very important. Conse-quently, the current authors agree with the view of Alwis, who suggestedrearrangement of Ishihara plates combined with a new recording chat and

scoring strategy enhances the usefulness of the test (Alwis & Kon, 1992).The efficiency of the screening test can be assessed in terms of sensitiv-

ity and specificity. Sensitivity is the percentage of abnormal subjects is cor-rectly identified as abnormal. Specificity in the percentage of the normalsubjects is correctly identified as normal. According to our results, the sensi-tivity and specificity of the projected slide mass-screening test and classicalIshihara test methods were both found to be 100% (Table 3). The presentresults were similar to the results of Ganley and Lian (1997), who reported

Table 6. The studies about the prevalence of R/G CCVD in Turkish population

Case number Percentage of CCVD

Total

Author Male Female Male Female (%)

Say et al. (1996) (TR) 1900 100 5.36 0.05 5.41Tmerdem et al. (1985) (TR) 6644 5859 5.49 0.16 5.65

Gkbel et al. (1992) (TR) 402 307 7.21 0.65 7.86

Ayhan et al. (1994) (TR) 8382 7413 5.19 1.30 6.49

Isikli et al. (1999) (TR) 3345 2606 5.50 0.80 6.30

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that Ishihara projected slide mass screening test sensitivity was 100% and thespecificity was 98.1%. The present study used classical individual Ishiharatest with printed color plates as the reference or gold standard test for com-paring the results of projected slides. There was complete accordance withthe authentic Ishihara classic method. The Ishihara projected slides test can

be replaced with the classical Ishihara test method. Based on these results,projected slide could be used for detecting CCVD in large groups, underwell-designed stipulations as proposed by Ganley and Lian (1997).

CONCLUSION

The present study detected a relatively high prevalence of color-blindnessamong a randomly selected group of students. Proper guidance and counsel-

ing of the students require early detection of color vision defect. This newscreening projected slide method is quite promising to become a widely usedcolor vision test in practice because it screens large groups in a short timeand it is in complete accordance with the application of classical Ishihara testmethod. The authors developed and applied this mass-screening test for thefirst time in Turkey.

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