作者：Nimet ünay Gündogan Nezih Durmazlar Aysegül Kocak Altintas , Koray Gümüs
【摘要】 Present a new computer-adapted color vision test (NCACVT) and explain its reliability and value in practical application. METHODS: Farnsworth-Munsell 100 Hue test (FM100HT) and Holmgren tests had been modified and adapted to computer application. Classic method of Ishihara pseudoisochromatic plate test (IPPT) was assumed to be a convenient screening tool for color blindness; therefore the subjects were classified as color defective group (Group I) and control group (Group II) according to the Ishihara test results. Group I consisted of color defective 13 subjects (12M, 1F) aged between 19-29 (median 21) years old and Group II consisted of non defected control group of 13 subjects (8M, 5F) aged between 19-28 (median 22) years old. In order to investigate color sensitivity in both of groups, all subjects were tested with both FM100HT and NCACVT. The findings from the classical IPPT, FM100HT, and NCACVT methods were statistically compared. The error scores of NCACVT and FM100HT in two groups were analyzed by using Mann-Whitney U Test. RESULTS: The differences in error scores were statistically significant respectively (U = 169, P <0.05; U =153 P <0.05). The cut-off point for diagnosing color vision deficiency according to NCACVT was found 23 by using receiver operating characteristic curve (ROC). According to cut-off error score of 23, NCACVT was found 100% sensitive and 100% specific in screening color vision deficiency. CONCLUSION: These features make this test a dependable, original ophthalmic practical screening test according to Harper& Reeves.
【关键词】 color vision; computer-adapted test for color vision; FM 100 Hue test; holmgren test
INTRODUCTION
Parallel to the contemporary technological advancements, computers have been used more and more effectively in medical research. Utilization of computers for different fields had not been cost-effective before, but nowadays, many computer programs can be easily obtained at minimal costs and can be used in each and every level of scientific studies.
There are two important tools for computerized color processing: the monitor and the video-graphics card. Improvement in the optical quality of computer-generated monitor color images has been one of many important developments in computer technology.
Trichromatic monitors have replaced the monochromatic ones. Color image resolution has reached to 24 bit. Mathematically speaking, this means that it is possible to generate 224 (16 777 216) different color hues in a computer monitor. Even, some of these different Red/Green and Blue triplets can generate similar hue. But in spite of this it is an enormous range, enabling us to do experimental research on color discrimination and sensitivity[1].
The most common testing method utilizes Ishihara's IPPT for the classification of congenital color vision defects[2, 3]. This test consists of polychromatic cardboard plates. These plates are printed matter and inevitably lose their isochromatic features. In addition, different editions of these booklets may differ in color consistency. Another fact is that it is impossible to standardize the lighting conditions and testing time for each subject[2].
The Holmgren Test is another method for color vision testing[4]. The subject is given three pieces of colored yarn, and asked to sort out strands of identical colors from a bunch. Nevertheless, tactile sensation as well as color vision is involved in this test. Therefore, the confounding effect of textures instead of colors, in discrimination, should be eliminated. In addition, pieces of yarn may fade by time, and colors may become paler.
The FM100HT is a sensitive and accurate test for color discrimination. It identifies the zones of color confusion in congenital or acquired color vision defects. In this test, there are 85-colored pastel caps arranged in a numerical order according to a color sequence which is quite obvious for a normal subject [5, 6]. When studied with this test, the subject is given these colored caps and asked to align correctly. The results of the test are recorded on a circular graph showing the errors made by the subject as deviations from the circular pattern. The greater the error score, the farther it is plotted from the center of the circle. Color deficient persons make characteristic errors in arranging the caps. Acquired color vision defects often impair hue discrimination. Confusion is predominantly seen between yellow and blue colors. In the other hand congenital color defects confusion are seen between red and green colors.
These colored caps have colored cardboard in their centers and are apt to get paler in time. Test time varies considerably between subjects and it is not possible to standardize. It is also important that this test requires quite a lot of training for the tester and many mistakes can be made by manually calculating the total error scores. A major disadvantage of this test is the laborious and time-consuming calculation needed to score the results and plot them on a chart for interpretation. On the other hand, computerized color vision test methods have many advantages as it was mentioned before[6, 7].
We have created computer emulations of the FM100HT using a commonly available personal computer. The presenting NCACVT program, written in Borland Builder 5 in C++ language, performs the calculation and reports both the individual color cap error scores and the total error scores. Our color monitor was calibrated to a standard display of colors using a special computer program without using an external hardware. Standardization of color displayed from the monitor was made by qualitatively. By means of this NCACVT we overcame the difficulties, such as color fading, background illumination, response-time, and eliminated senses other than vision. We are able to store the results for further studies.
We propose that, this original test for subject's color discrimination ability is practical, cost-effective, sensitive, specific, reproducible, and reliable.
MATERIAL AND METHODS
Ishihara's test was modified as a mass-screening test into a series of slides, and projections were used to screen color-deficient persons among the medical students[8, 9]. Presence or absence of color vision deficiency was assessed with classic Ishihara test and further evaluated with FM100HT. A subject who failed in both tests without any organic eye disease, which mainly affects on red and green color discrimination, was considered to have congenital color vision deficiency (CCVD). Thirteen students (12 M, 1 F) with CCVD aged from 19 to 29 years (median 21) established Group I; and 13 students (8 M, 5 F) with normal color vision formed Group II aged from 19 to 28 years (median 22). All subjects had a complete eye examination at the university ophthalmology clinic and had best corrected visual acuities of 20/20. They were required to wear their untended glasses during testing when necessary. These subjects were tested with, IPPT, FM100HT, NACVT.
Application of IPPT This test consists of a series of numbered color plates. The plates are made of dots of the primary colors printed on a background mosaic of similar dots in a confusing variety of secondary colors. The primary dots are arranged in numerical patterns that cannot be recognized by patients with deficient color perception.
Subjects were tested in the same room with adequate daylight. Plates were shown to them in a vertical orientation, from a distance of 1 meter. Responses were noted down on a pre-designed form[2. 3, 9].
Application of FM100HT Boxes containing the colored caps were put on a table with black background, illuminated by a fluorescent day light lamp (Philips TLE 22 W 54 diurnal Circular) from a 40 cm distance. Subjects were asked to arrange the hues in any order that they think is correct. They were allowed to take their time in arranging the colored caps. Error scores were calculated and were plotted on a specially designed circular graph[6].
Introduction of NCACVT Brightness, saturation and hue were the main characteristics of colors. Intensity or brightness was represented as quanta per unit time from a unit area of radiating emitter. Depth of color was saturation, and hue was created by the wavelength of light. Different monitors and video - graphics cards may lead to substantially different colors. In this study, a special computer program was used for the standardization of the monitor colors (wiziWYG program from PRAXI soft Inc) before every single test stage[1]. Afterwards, our NCACVT was run. We had a subjective standardization process during application of NCACVT that we have used software. When we consider that this new computer program will be used in daily practice of clinicians in the out-patient settings or at the place where quick and reliable assessment of color vision deficient as term applies normal trichromatic vision subjects must prepare and makes standardization on a standard monitor with a standard VGA card on it with practical monitor standardization software. Where we have been used WIZIWYG; Proxisoft? This software was written by using Borland Builder 5 in C++ language compatible with Microsoft Windows operating system. The desktop configuration consisted of a P III processor, standard 24-bit video-graphics card on it and a monitor with 85 Hz. horizontal frequencies and resolution of 800x600 pixels. The first image of the program is in a circular order of 30 round shapes, each having a different color (see Figure 1A). These colored circles are numbered on the screen and are separated by equal distance in a circular fashion. These 30 different color hues were created using HLS color naming space with a programming algorithm derived from RGB system of Microsoft so as to have constant saturation and brightness but differing hue components. The hue component presents the changed parameters of each color. This avoids the possibility of color blinds to discriminate colors by saturation and/or brightness.
Application of the NCACVT All subjects were well informed by the tester about the test procedure. There is an introductory mini-test at the beginning of the principal testing program. This introductory phase there were 7 different color caps were showed, which are recognizable for both in normal and the color blinds. The subjects compared the sample test color with the circle colors by moving the mouse anticlockwise for matching until subject reaches the corresponding color cap and clicks on the mouse (Figure 1A). After this mini-test illustration the principal test was started. The colored circles are numbered on the screen and are separated by equal distance in a circular fashion. The principal colors representing red, green and blue (RGB) are numbered as 1, 11, and 21 respectively and they are shown with bold arrows. Numbers 6, 16 and 26 are the colors created by mixing two of the principal colors of the RGB system and they are shown with light arrows. In other words, these are the cyan-magenta-yellow (CMYK) systems principal colors. There are 4 more intermediate hues in between these marked ones (Figure 1B). This presentation allows an even distribution of colors having close wavelengths in different quadrants. Consecutive presentations of the comparing test colors are also random and successive colors have distant wavelengths. Thirty colors are presented one after another and the subject moves the comparing test color anticlockwise until subject reaches the corresponding color cap and clicks on the mouse (Figure 1C). If the subject has color vision deficiency, subject may choose more than one colored circles which disappeared from view and saved (Figure 1D). Every click was saved as the score of each response and the "error score" for that subject is calculated by computer program at the end of the test (Table 1).
儿童白内障I期植入折叠式人工晶状体
正常成年家猫不同明适应条件下闪光视网膜电图的变化