Claims:1. A device (100) for the identification of colour blindness, comprising:
a circular plate, said circular plate comprising:
a first plurality of hues (101), said first plurality of hues (101): being of yellow and green; ranging from 550 nm to 570 nm; being plotted as small circles in a numerical pattern in the foreground; and being configured to be unidentifiable by persons suffering from colour blindness, when grouped with other similar hues; and
a second plurality of hues (102), said second plurality of hues (102): being of green, yellow, orange, gray, and red; ranging from 470 nm to 600 nm; being plotted as small circles; and being configured to be seen by both persons with normal vision and those who suffer from colour blindness,
said device (100) being made of polyethylene terephthalate, with the printing parameters for the polyethylene terephthalate substrate being: 20 µm drop spacing, three layers of printing, 120° Centigrade sintering temperature for 30 minutes, and optimum resistivity of 5.25 µ-cm.
2. The device (100) for the identification of colour blindness as claimed in claim 1, wherein the diameter of the circular plate is 7.6 cm.
3. The device (100) for the identification of colour blindness as claimed in claim 1, wherein the circular plate subtends 10.8 degrees at a viewing distance of 40 cm.
4. The device (100) for the identification of colour blindness as claimed in claim 1, wherein the small circles are of varied chromaticity, with their diameters ranging from 0.1 cm to 0.4 cm.
5. The device (100) for the identification of colour blindness as claimed in claim 1, wherein the device is rectangular in shape.
6. The device (100) for the identification of colour blindness as claimed in claim 1, wherein the device (100) is printed with dimensions of 10.5 cm × 8.5 cm.
7. A kit for the identification of colour blindness, comprising:
the circular plate as claimed in claim 1, in which the first plurality of hues (101) is plotted as small circles to form the number 12, said circular plate being a demonstration plate;
six sets of screening plates, with each set of screening plates comprising three screening plates, with each screening plate comprising the first plurality of hues (101) that is plotted as small circles to form a randomized number, said randomized number being selected from: 16, 7, 5, 73, 10, 8, 26, and 42; and
classification plates that classify protan and deutan, said classification plates comprising the first plurality of hues (101) that is plotted as small circles to form the numbers ‘96’ and ‘35’, respectively. , Description:TITLE OF THE INVENTION: A DEVICE AND KIT FOR THE IDENTIFICATION OF COLOUR BLINDNESS
FIELD OF THE INVENTION
The present disclosure is generally related to the identification of colour blindness. Particularly, the present disclosure is related to a device for the identification of colour blindness. More particularly, the present disclosure is related to a device and kit for the identification of colour blindness.
BACKGROUND OF THE INVENTION
Colour vision deficiency (also known as colour blindness) is a defect in ‘colour perception’ of the eyes. This deficiency is more common in men compared to women; it is prevalent in as much as 8% of males and 0.4% of females globally. People with colour blindness can only see a limited range of colours, and are prone to making mistakes in colour identification.
The need for colour vision testing as a routine optometric/ophthalmologic examination is well-emphasized, as colour blindness has a profound impact on the choice of career/growth in the career for a person. Also, the Indian Judiciary Department has noticed increased legal cases of colour blindness and career rejections among the youth of the country.
The Ishihara pseudo isochromatic plate, a paper-based printed testing tool, is widely used to detect colour blindness by optometrists and ophthalmologists. However, this testing tool suffers from various drawbacks. First, it is expensive, and its print quality and paper durability get deteriorated over the course of use in vision screening camps, due to exposure to various atmospheric conditions. Second, the tool has also been reported to lose its print solidity earlier than the estimated time, with noticeable shifts in the colorimetric values. This affects the reliability of the testing, and has led to limited research data. Third, it is time-consuming for doctors or health care service providers. Fourth, it is not validated for the screening of colour blindness in children. Fifth, it cannot be used under different illuminations.
The disclosures in US2937567 and EP2873364B1 are related to the identification of colour blindness. However, the disclosed inventions cannot be used for the mass screening of colour blindness and are time-consuming. Further, the print material is paper-based, as a result of which it undergoes massive wear and tear, requiring frequent replacement. Moreover, since the set pattern is not randomized (i.e. the same order sets are used repeatedly), patients may be able to memorize the pattern, as a result of which the results are not reliable.
There is, therefore, a need in the art, for a more affordable, highly reliable, and extremely durable device and kit for the identification of colour blindness, which has the capacity to test mass population in a minimal time.
SUMMARY OF THE INVENTION
A device for the identification of colour blindness is disclosed. The device comprises a circular plate, said circular plate comprising: a first plurality of hues and a second plurality of hues.
Said first plurality of hues: is of yellow and green; ranges from 550 nm to 570 nm; and is plotted as small circles in a numerical pattern in the foreground. The first plurality of hues plotted as small circles in a numerical pattern is configured to be unidentifiable by persons suffering from colour blindness, when grouped with other similar hues.
Said second plurality of hues: is of green, yellow, orange, gray, and red; ranges from 470 nm to 600 nm; and is plotted as small circles. The second plurality of hues is configured to be seen by both persons with normal vision and those who suffer from colour blindness.
Said device is made of polyethylene terephthalate, with the printing parameters for the polyethylene terephthalate substrate being: 20 µm drop spacing, three layers of printing, 120° Centigrade sintering temperature for 30 minutes, and optimum resistivity of 5.25 µ-cm.
A kit for the identification of colour blindness is also disclosed.
The disclosed device: withstands wear and tear; is highly durable; does not undergo de-colourization; is configured for use in hospitals, eye screening camps, and schools; uses only four plates to quickly screen a person, thereby saving time; is simple to use; is calibrated for various illuminations and outdoor sunlight illumination; and is available both in hard copy as well as calibrated digital images. Further, the use of randomized set pattern makes it harder for persons to memorize the pattern.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 illustrates an embodiment of a device for the identification of colour blindness, in accordance with the present disclosure.
Figure 2 illustrates an embodiment of a device for the identification of colour blindness on polyethylene terephthalate material booklet, in accordance with the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the word "comprise" and “include” and variations such as "comprises", "comprising", “includes”, and “including” may imply the inclusion of an element or elements not specifically recited.
Throughout this specification, the disclosure of any range is to be construed as being inclusive of the lower limit of the range and the upper limit of the range.
As illustrated in Figure 1, a device (100) for the identification of colour blindness is disclosed. The construction of the device (100) is based upon the principle that the colour of a target (digit or letter) embedded in the background of another colour appears ‘falsely of the same colour’ to an individual suffering from colour blindness.
Selection of Wavelengths
In humans, the long and the middle wavelength cone pigments are arranged in a head-to-tail array in the X-chromosome, and the mutation, deletion or rearrangement (number) of the long and middle cone photo pigments results in colour blindness. Spectral tuning studies show that the amino acids present in exon 5 contribute primarily to the spectral tuning difference in the long and middle genes (= 7 nm).
Based on the spectral tuning and spectral shifts due to amino acid sequences, specific wavelengths for background and foreground are chosen. The long and the middle wavelength cone pigments have peak spectral sensitivities near 560 and 530 nm, respectively, with normal variations within 8 nm.
In an embodiment of the present disclosure, the foreground comprises hues of yellow and green ranging from 550 nm to 570 nm, and the background comprises hues of green, yellow, orange, gray, and red, selectively ranging from 470 nm to 600 nm.
550 nm to 570 nm means random wavelengths between 550 nm and 570 nm; for example, 554 nm, 555 nm, 563 nm, and 569 nm. Similarly, 470 nm to 600 nm means random wavelengths between 470 nm and 600 nm; for example 472 nm, 486 nm, 520 nm, 531 nm, and 588 nm. The random numerals are selected based on close resemblance with l, a, b values, and visual inspection by colour vision deficient people.
The colours are selected based on the red-green dichromatic lines of confusion for protans and deutans in the 1931 XYZ chromaticity diagram. Luminance noise is added to reduce luminous contrast clues in the figures. The XYZ values are transformed into the International Commission on Illumination (CIE) L*a*b* co-ordinates and validated to ensure that the co-ordinates fall within the colour gamut of the inks, and then the CIE L*a*b* values are transformed into CMYK values for printing. During the printing process, the consistency of the colour stimuli is provided by means of International Color Consortium colour management system, which may be inbuilt with the printer. The quality of the printed images is assessed using the CIE L*a*b* space with white reference: American National Standards Institute T ‘absolute white’ under ISO 12647-2 printing standard.
Construction of the Device
As illustrated in Figure 1, an embodiment of the device (100) comprises a circular plate of diameter 7.6 cm, said circular plate comprising: a first plurality of hues (101) plotted as small circles in a numerical pattern in the foreground, and a second plurality of hues (102) plotted as small circles. The first plurality of hues (101) plotted as small circles in a numerical pattern is configured to not be identified by persons suffering from colour blindness, when grouped with other similar hues. The second plurality of hues (102), on the other hand, is configured to be seen by both persons with normal vision and those who suffer from colour blindness. The circular plate subtends 10.8 degrees at a viewing distance of 40 cm. The small circles are of varied chromaticity and their diameters range from 0.1 cm to 0.4 cm.
In another embodiment of the present disclosure, the device (100) is rectangular in shape.
The diameter of the device (100) may vary, and depends on viewing angle, working distance, ergonomics, and visual tasks of the patients.
The shape of the first plurality of hues (101) and the second plurality of hues (102) may vary with the shape of the device (100).
The hues plotted as circles in a numerical pattern (101) cannot be seen by a person suffering from colour blindness, when grouped with other similar hues.
Visual clues are eliminated by deliberate variation of spot size in both pattern and background, which depend upon the detection of edges in the pattern. Similarly, the hue of individual spots is varied to overcome problems associated with differences in luminosity between figure and background.
The test is thus randomly anisoluminant and free of problems related to edge artefact. The device (100) is printed in a size that is easy to hold, with dimensions of 10.5 cm × 8.5 cm. Based on the percentage of errors made by the normal trichromat or the misreading of numerals, specific numerals (12, 16, 7, 5, 73, 10, 8, 26, and 42) are selected for the pattern in the PIPs (Pseudo Isochromatic Plates).
The dimensions of the device (100) are calculated based on how a patient (children and adults) can see the plate from an average near-reading working distance, which is 30 cm - 50 cm.
The number ‘12’ is constructed as a ‘demo’ plate, where the foreground and the background have a single hue. The other three plates are designed as screening plates. The plates that classify protan and deutan are available at the end of the six screening sets. These are used when an individual fails the screening plates.
Each screening set comprises a demonstration plate (number ‘12’), followed by three screening plates (the three screening plates could comprise any three numbers from 16, 7, 5, 73, 10, 8, 26, and 42). Set 1 is followed by set 2, set 3, set 4, set 5, and set 6. Each of the sets comprises randomized numbers, except for the demonstration plate, in which number ‘12’ is common in all the sets.
For example, set 1 might comprise 12, 5, 73, and 16. Likewise, set 2 might comprise 12, 26, 10, and 7. In all the sets, the numbers are either randomized or different, but not repeated in the same pattern.
The plates that classify protan and deutan are called classification plates. The numbers used are ‘96’ and ‘35’ (numerals for background pattern hues), respectively. In the classification plates, a person who has protonopia or strong protonomaly will be able to identify numbers on the ‘right’ side more clearly than the ones on the left, whereas, those who have deuteranopia or strong deuteranomaly will identify numbers on the ‘left’ clearly.
Material Used
The material used is a plastic polymer, such as polyethylene terephthalate. Due to the polar and amorphous molecular structural components, these polymers are lightweight and exhibit good resistance to impact, have a 55–75 MPa shatter, are durable (25 years in under 100% relative humidity conditions), and have a melting point that is greater than 250 degrees Celsius.
The optimum printing parameters for the polyethylene terephthalate substrate are: 20 µm drop spacing, three layers of printing, and 120° Centigrade sintering temperature for 30 minutes. The measured optimum resistivity is 5.25 µ-cm.

Printing Process
The chart is printed using dry electrophotography with pigment-based ink, using a digital printer with CMYK attributes. The consistency in wavelengths and CIE L*a*b* values of individual hues of the plates are analysed using a spectrophotometer (Photo research Spectrophotometer PR-670). The L*a*b* values of the respective hues are found to be consistent after printing with a colour difference (Delta E) of less than 1.2 for each hue in the L*a*b* colour space. The permanence of the images by this method is estimated to be up to 75 years before showing signs of degradation or discoloration.
In eye/vision screening camps, primary and tertiary eye care centers, children and adults can be screened for colour vision deficiency with the disclosed device (100). For each person, a particular set among the six sets can be shown, starting from the demonstration plate (number ‘12’). The demonstration plate helps the doctors identify whether: the person is co-operative and understands the instructions given to him/her, or if he/she is non-cooperative and/or unable to read numbers for various other reasons.
Once the demo plate is shown, it is followed by showing the screening plates, which can be read by a person with normal vision, but not by a person with colour blindness. Thus, the result will be four out of four for a normal person, whereas, for a person with colour blindness, it will be one out of four, as he/she would have read only the demo plate and not any of the screening plates in a particular set.
Once colour deficiency is identified, the type of colour-deficiency that the person has can be tested using the classification plates. The test can also be re-checked/re-confirmed with another set.
In camps, schools, when testing for colour deficiency, particularly, when children stand in a queue, it is advantageous to show a different set for each child (i.e. set 1 can be shown to child 1, set 2 to child 2, and so on. This prevents the children standing behind from memorizing and reciting the pattern.
Accordingly, the present disclosure also relates to a kit for the identification of colour blindness, comprising:
a demonstration plate, in which the first plurality of hues (101) is plotted as small circles to form the number 12;
six sets of screening plates, with each set of screening plates comprising three screening plates, with each screening plate comprising the first plurality of hues (101) that is plotted as small circles to form a randomized number, said randomized number being selected from: 16, 7, 5, 73, 10, 8, 26, and 42; and
classification plates that classify protan and deutan, said classification plates comprising the first plurality of hues (101) that is plotted as small circles to form the numbers ‘96’ and ‘35’, respectively.
The disclosed device (100) offers the following advantages: withstands wear and tear; is highly durable; does not undergo de-colourization; configured for use in hospitals, eye screening camps, and schools; uses only four plates to quickly screen a person, thereby saving time; simple to use; calibrated for various illuminations and outdoor sunlight illumination; and available both in hard copy as well as calibrated digital images. Further, the use of randomized set pattern makes it harder for persons to memorize the pattern.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations and improvements without deviating from the spirit and the scope of the disclosure may be made by a person skilled in the art. Such modifications, additions, alterations and improvements should be construed as being within the scope of this disclosure.

LIST OF REFERENCE NUMERALS
100 – Device for the Identification of Colour Blindness
101 – First Plurality of Hues Plotted as Small Circles in a Numerical Patter
102 – Second Plurality of Hues Plotted as Small Circles