Patent Description:
This invention relates to an incterometer and a method for evaluation of total serum bilirubin concentration in a subject using an incterometer.

Severe neonatal jaundice or "hyperbilirubinemia" (serum bilirubin equal to or greater than <NUM>/dL) affects ~<NUM> million newborns annually and places them at risk for permanent brain injury or death. It is critical to monitor newborns for elevated bilirubin so that therapeutic intervention can occur before serum levels become high. The "gold standard" for measurement of bilirubin is serum measurements from blood. These require a heel puncture or venapuncture to obtain a blood sample which is painful to infants and distressing to caregivers.

An early icterometer, the 'Gosset' icterometer, provided a non-invasive device having stripes of graded yellow color shades painted or adhered on a transparent plastic with gaps between them [<NPL> and <NPL>AM. In the areas of the transparent gaps the plastic device is pressed against the skin, such as the nose, of an infant to temporarily blanch the skin and reveal the underlying subcutaneous tissue color. Matching of the yellow color stripes to subcutaneous tissue color, and reference to an associated chart of bilirubin ranges that corresponded to each color provided an estimate of the level of bilirubin. Although the device was economical, its adoption for detection of jaundice was short lived due to difficulties in use. In particular, interpretation of color-matching between skin and color stripes was sensitive to the lighting environment and users reported unreliable results due to poor lighting [ <NPL>]. In addition, the device was not easy to clean since the colors were attached or painted on exposed surfaces, and, although not invasive, the device did require physical contact with the infant.

Improved devices that provide accuracy and are not invasive use spectrophotometric methods for jaundice assessment [<NPL>]. However, such devices are expensive and require a power source. This presents a barrier to implementation when jaundiced babies are evaluated where such equipment is typically not available such as in downstream healthcare settings such as primary healthcare clinics or the home, and where resources are scarce such as in developing countries.

A recent improved device includes an icterometer similar to the Gosset icterometer but with holes punched through the colored areas providing a clear window through which blanched skin is viewed. This provides an easier comparison of the colored areas to the blanched skin color. The device is low cost and noninvasive. If used under proper lighting the device provides high diagnostic accuracy for neonatal jaundice screening [<NPL>]. However, the device is still prone to user error as it requires judgement on the part of the user in determining the proper lighting. In addition, the device construction includes punching a hole through the colored areas which are on paper overlayed on, rather than embedded within, a plastic substrate. This constitutes a potential contamination site which limits re-using the device or cleaning it before use.

Therefore, a bilirubin measurement device for improved jaundice screening is still needed. Improvements sought include devices that are economical, cleanable, and easy to use. The present disclosure is directed to solving these and other problems.

The invention can be summarised by the appended set of claims.

In general, the inventions described herein relate to devices for measurement of bilirubin. The devices are economical and robust, do not require external power and are simple to use. Testing for bilirubin is also non-invasive to the subject, not requiring heel puncture or venapuncture.

A first implementation of the disclosure is an icterometer. The icterometer includes a plate including a surface comprising: a stepwise gradient of yellow colors; a series of windows in the surface, each window in the series bordered by one of the colors, and each window including a transparent portion in the plate; and a lighting indicator configured to indicate the quality of lighting. Optionally, the icterometer further comprises a corresponding color indicium for each color in the color gradient on the surface or on a transparent external surface overlapping the color gradients. Optionally, the lighting indicator is a metameric pair of colored areas on the surface. Optionally, the metameric pair displays metamerism under natural daylight or natural daylight simulators. For example, the metameric pair displays metamerism under D50 or a D65 lighting.

Optionally, the plate is waterproof and inert to cleaning solutions applied to an external surface. Optionally, an external surface of the plate is coated with an antimicrobial coating. Optionally, the plate includes acrylic, polycarbonate, a silica-based glass, or combinations thereof. Optionally, the surface comprising a stepwise gradient of colors is encased in an interior of the plate.

Optionally, the stepwise gradient of colors comprises at least <NUM> and not more than <NUM> colors. Optionally, the colors correspond to the colors of subcutaneous tissue of a subject having a total serum bilirubin between about <NUM> and <NUM>/dL. Optionally, the plate is configured as an elongated flat object having a length between about <NUM> and <NUM>, a width between about <NUM> and <NUM>, and a thickness of between about <NUM> and <NUM>.

Optionally, the plate of the icterometer includes: a back plate including, a lip protruding from a surface of the back plate at an outer edge of the back plate, and a series of transparent protrusions in a center area and protruding in the same direction as the lip; a middle layer including the color gradient, the lighting indicator, and a series of through holes, each through hole bordering each one of the transparent protrusions and defining one of the windows, and wherein a first surface of the lip borders an edge of the middle layer; a cover plate comprising a transparent material for viewing of the color gradient and the lighting indicator, and for viewing through the plate at positions corresponding to the transparent protrusions on the back plate; and wherein a second surface of the lip is coupled to a surface of the cover plate and provides a water proof seal. Optionally, the second surface of the lip comprises an adhesive layer. Optionally, the middle layer comprises a web material and the color gradient and lighting indicator are printed, coated or otherwise attached to the web material.

A second implementation of the disclosure is an icterometer including: a plate including a surface comprising, a stepwise gradient of colors; a series of windows in the surface, each window in the series bordered by one of the colors, and each window including a transparent portion in the plate; and wherein the plate is waterproof and inert to cleaning solutions applied to an external surface. Optionally, an external surface of the plate is coated with an antimicrobial coating. Optionally, the plate includes acrylic, polycarbonate, a silica-based glass, or combinations thereof. Optionally, the surface including a stepwise gradient of colors is encased in an interior of the plate. Optionally, the plate is configured as an elongated flat object having a length between about <NUM> and <NUM>, a width between about <NUM> and <NUM>, and a thickness of between about <NUM> and <NUM>.

Optionally, according to the second implementation, the plate comprises: a back plate including, a lip protruding from a surface of the back plate at an outer edge of the back plate, and a series of transparent protrusions in a center area and protruding in the same direction as the lip; a middle layer including the color gradient, and a series of through holes, each through hole bordering each one of the transparent protrusions and defining one of the windows, and wherein a first surface of the lip borders an edge of the middle layer; a cover plate comprising a transparent material for viewing of the color gradient, and for viewing through the plate at positions corresponding to the transparent protrusions on the back plate; and wherein a second surface of the lip is coupled to a surface of the cover plate and provides a water proof seal. Optionally, the second surface of the lip comprises an adhesive layer. Optionally, the middle layer comprises a web material and the color gradient is printed, coated or otherwise attached to the web material.

A third implementation of the disclosure is an icterometer kit. The kit includes an icterometer according to the first or second implementation. Optionally, the sleeve includes step-wise instruction for operation of the icterometer. Optionally, the sleeve includes a table listing color indicia and a corresponding total serum bilirubin concentration.

A fourth implementation of the disclosure is a method for evaluating total serum bilirubin concentration in a subject including: (a) determining a test location having natural or simulated natural lighting using the lighting indicator of the icterometer according to the first implementation; (b) placing the subject in the test location; (c) pressing a window of the icterometer according to the first implementation against the subject's skin to blanch the skin and reveal a subcutaneous tissue color through the window; (d) comparing the subcutaneous tissue color viewed through the window to the color bordering the window; (e) repeating steps (c) and (d) using one or more additional windows of the icterometer; (f) selecting a color that most closely matches the subcutaneous tissue color of the subject; and (g) determining a bilirubin level from tabulated values of color and corresponding bilirubin concentration. Optionally, the icterometer includes at least a first window and a second window; the subcutaneous tissue color corresponds to a color between a first color indicated through the first window and a second color indicated through the second window; and the corresponding bilirubin level is a selected value between the bilirubin level associated with the color viewed through the first window and the second window.

A fifth implementation of the disclosure is a method for evaluation of total serum bilirubin concentration in a subject comprising: (a) identifying a test location having natural or simulated natural lighting; (b) placing the subject in the test location; (c) pressing a window of the icterometer according to the second implementation against the subject's skin to blanch the skin and reveal a subcutaneous tissue color through the window; (d) comparing the subcutaneous tissue color viewed through the window to the color bordering the window; (e) repeating steps (c) and (d) using one or more additional windows of the icterometer; (f) selecting a color that most closely matches the subcutaneous tissue color of the subject; and (g) determining a bilirubin level from tabulated values of color and corresponding bilirubin concentration. Optionally, the icterometer includes at least a first window and a second window; the subcutaneous tissue color corresponds to a color between a first color indicated through the first window and a second color indicated through the second window; and the corresponding bilirubin level is a selected value between the bilirubin level associated with the color viewed through the first window and the second window.

The above summary is not intended to represent each implementation or every aspect of the present disclosure. Additional features and benefits of the present disclosure are apparent from the detailed description and figures set forth below.

The disclosure will be better understood from the following description of exemplary embodiments together with reference to the accompanying drawings.

While the present disclosure is susceptible to various modifications and alternative forms, specific implementations and embodiments thereof have been shown by way of example in the drawings and will herein be described in detail.

The present inventions can be embodied in many different forms. Representative embodiments are shown in the drawings and will herein be described in detail. The present disclosure is an example or illustration of the principles of the present disclosure and is not intended to limit the broad aspects of the disclosure to the embodiments illustrated. To that extent, elements, and limitations that are disclosed, for example, in the Abstract, Summary, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference, or otherwise. For purposes of the present detailed description, unless specifically disclaimed, the singular includes the plural and vice versa; and the word "including" means "including without limitation. " Moreover, words of approximation, such as "about," "almost," "substantially," "approximately," and the like, can be used herein to mean "at," "near," or "nearly at," or "within <NUM>-<NUM>% of," or "within acceptable manufacturing tolerances," or any logical combination thereof, for example.

<FIG> depicts an icterometer <NUM>, according to some implementations of the description. The icterometer includes a plate <NUM> including a surface <NUM>. The surface has a step wise gradient of colors <NUM>, each color is shown in <FIG> bounded by dashed lines <NUM> for clarity. As use herein "stepwise" indicates the area in each square indicated by the bounding dashed lines is one color. The plate also includes a series of windows <NUM>, each window in the series is bordered by one of the colors <NUM>. The window is a transparent portion in the plate, allowing visible light to transmit through the plate. The plate also includes a lighting indicator <NUM> to indicate the quality of the lighting.

In some implementations, the plate further includes a color indicium <NUM>. For example, and without limitation, the indicium can be numbers <NUM> through <NUM> shown in <FIG>. Any other indicia can be used, such as any alphanumeric value, alphanumericals, words, pictograms, etc. In some implementations, each color <NUM> is assigned a unique indicium. The color indicia <NUM> can be formed on the surface <NUM> or any other surface of the plate <NUM>. The color indicia <NUM> can be formed by any means such as printing, etching, or engraving. In some implementations, the color indicia <NUM> is positioned on plate <NUM> so that when it is viewed, it is superimposed on the color <NUM> that the color indicia <NUM> is associated with. For example, in some implementations, the color indicia <NUM> is on the surface <NUM>, while in other implementations the color indicia <NUM> can be on a transparent cover above surface <NUM> of plate <NUM>.

The lighting indicator <NUM> can be any lighting indicator. In some implementations, the lighting indicator <NUM> is a metameric pair of colored areas on the plate <NUM>. For example, the colored areas can be on the surface <NUM>. The pair of colors are selected to be a metameric pair. That is, the metameric pair appear to be the same color, i.e. displaying "metamerism" under specific lighting conditions. For example, in some implementations, the metameric pair displays metamerism under natural daylight or natural daylight simulators, such as D50 or D65 lighting. Lighting designated D65, or illuminant D65 is a standard artificial daylight illuminant defined by the international commission on Illumination (CIE). Lighting designated D50, or illuminant D50 has a slightly different spectrum.

In some implementations, the icterometer <NUM> is waterproof and inert to a cleaning solution applied to external surfaces of the plate. As used herein, "inert" refers to the cleaning solution not negatively impacting the use of the icterometer <NUM>. For example, the cleaning solution does not etch, scratch, discolor, and or degrade the structural integrity of the plate <NUM>. As used herein, the cleaning solution can be any solution can be any solution or pure liquid that removes extraneous materials that may adhere to the icterometer <NUM>. For example, extraneous materials can include dirt, grease, bacteria, cells, biological fluids and the like. In some implementations, the cleaning solution includes a disinfectant, bleach, alcohol (e.g., ethanol, isopropanol), a bacteriostat, a detergent, boiling water or combinations of these. In some implementations, the device is inert to boiling water. In some implementations, the device is inert to steam treatment or autoclave conditions. In some implementations, the device is inert to UV light or similar irradiation.

The icterometer <NUM> can, according to some implementations, be treated with an antimicrobial coating. For example, external surfaces of plate <NUM> can be treated with an antimicrobial coating. Without limitation, and by way of example, these can include one or more of graphene materials, polycationic hydrogels, silver nanoparticles, polymer brushes, dendrimers, and copper.

The plate <NUM> can be made using one or more materials. For example, in some implementations, structural materials such as acrylic, polycarbonate and silica-based glass can be used. In particular, optically transparent materials are used to view the colors <NUM> from the top side of the icterometer <NUM> (as viewed in <FIG>) and to form the windows <NUM>. In some implementations, opaque materials can be used, such as along the edges of plate <NUM>, where they do not obscure viewing of colors <NUM> and windows <NUM>. Opaque materials can include, for example, plastics, rubbers, and metals.

Although <FIG> depicts <NUM> colors <NUM> and <NUM> color indicia <NUM>, this is not to be construed as limiting. For example, in some implementations the step wise gradient of colors can be at <NUM> and not more than <NUM> colors. Similarly, the optional color indicia can be between <NUM> and <NUM>, inclusive.

In some implementations, each color <NUM> is the color associated with the color of subcutaneous tissue. For example, when skin is blanched by compressing it with the device, flow of blood is limited or stopped temporarily, and the underlying color of the fat pad is revealed. This fat pad is where the bilirubin accumulates and can be seen. In some implementations, the colors <NUM> correspond to the colors of subcutaneous tissue for a subject having total serum bilirubin between about <NUM> and <NUM>/dL.

Although, more colors than <NUM> can be used in some implementations, this can complicate usage of the icterometer <NUM> because each color step, or difference between adjacent colors would diminish and be harder for the user to distinguish. In addition, the difference between serum bilirubin levels with more than <NUM> subdivisions is not critical for screening subjects according to some implementations of this description. Similarly, although in some implementations two colors can be used, this provides limited nuance with respect to bilirubin levels. As used here, bilirubin levels and bilirubin concentrations are used interchangeably.

In some implementations, the plate <NUM> is configured as a disk, a square or any n-sided object having a diameter greater than its width. In some implementations, the plate <NUM> is configured as an elongated flat object (e.g., a ruler) having a length between about <NUM> and <NUM>, a width between about <NUM> and <NUM>, and a thickness of between about <NUM> and <NUM>. In some implementations, the plate <NUM> can include gripping areas near and along edges of the plate, i.e., in areas not obscuring the view of colors <NUM>. For example, although not depicted in <FIG>, in some implementations, the plate <NUM> can be dog-bone shaped such that ends <NUM> and <NUM> are wider than the area having colors <NUM>. In some implementations, the plate <NUM> is flat, and in other implementations the plate <NUM> is curved, such as concave or convex.

In some implementations, the surface <NUM> which includes the step wise gradient of colors <NUM> is encased in the plate <NUM>. As used herein, "encased" refers to the surface being surrounded by and protected (e.g., from water and biological fluids) by being an internal surface of the plate <NUM>. In some implementations, the surface <NUM> is an internal surface upon which the colors <NUM> are printed or painted upon, and this surface is overlaid with material covering the surface. In some implementations, the surface <NUM> is a surface on a thin film placed on an internal surface of the plate, and the thin film is overlaid with material covering the thin film. For example, the thin film can be a continuous film such as a plastic or thin metal or the thin film can be a web such as paper.

The icterometer <NUM> can be made by any method. Without limitation, and by way of example, manufacturing means can include extrusion, casting, molding, additive manufacturing (e.g., 3D printing), subtractive manufacturing (e.g., CNC machining, laser etching), drilling, laser cutting, and combinations of these.

<FIG> depicts a blown-up view of an icterometer <NUM>, according to some implementations. In this implementation, a plate <NUM> includes a back plate <NUM>, a middle layer <NUM>, and a cover plate <NUM>.

The back plate <NUM> includes a lip <NUM> protruding from a surface <NUM> of the back plate <NUM>, at outer edge <NUM>. The back plate <NUM> also includes a series of transparent protrusions <NUM> in a center area <NUM>. The protrusions <NUM> protrude away from surface <NUM>, and in the same direction as the lip <NUM>. In some implementations, the protrusions <NUM> protrude and equal amount or less than the lip <NUM>.

The middle layer <NUM> includes a color gradient <NUM>, and a series of through holes <NUM>. In some implementations, the middle layer <NUM> also includes a lighting indicator <NUM>. Each of the through holes <NUM> border a corresponding protrusion <NUM>. For example, when assembled, the edges <NUM> of through hole <NUM>, surround the edges <NUM> of transparent protrusion <NUM>. The protrusions <NUM> are transparent through surface <NUM> and define the perimeter of windows through plate <NUM>. A first surface <NUM> of lip <NUM> borders the edge <NUM> of the middle layer <NUM>.

The cover plate <NUM> includes a transparent material, for example at least in areas covering color gradient <NUM> and lighting indicator <NUM>. Accordingly, the cover plate provides a view of the color gradient <NUM> and lighting indicator <NUM>. The cover plate <NUM> also provides viewing through the plate <NUM> at positions corresponding to the protrusions <NUM>.

A second surface <NUM> of lip <NUM> contacts a surface <NUM> of the cover plate <NUM> providing a waterproof seal. In some implementations the surface <NUM> and surface <NUM> are flat. In some implementations the surface <NUM> and <NUM> are curved. In some implementations, the surface <NUM> includes a groove and the surface <NUM> includes a corresponding lip or protrusion that mates with the groove. In some implementations, the surface <NUM> includes a groove and the surface <NUM> includes a corresponding lip or protrusion. In some implementations, the surfaces <NUM> and <NUM> are in direct contact. In some implementations, the surface <NUM> are not indirect contact, for example, wherein a gasket or an adhesive layer couples the surfaces. In some implementations, the surface <NUM> is coupled to the surface <NUM> by fusion welding or ultrasonic welding.

In some implementations, the middle layer <NUM> is a thin film such as a plastic film or metal foil. In some implementations, the middle layer is a web material such as paper. The color gradient <NUM> can be painted, printed or etched on a surface <NUM> of the middle layer <NUM>. The lighting indictor <NUM> can be painted, coated, printed or etched on surface <NUM>. The color gradient <NUM> and lighting indicator <NUM> can also be provided as an adhesive patch adhered to surface <NUM>.

A viewing direction is indicated by dashed arrow <NUM>. The user can view the surface <NUM> and step gradient of colors <NUM>, lighting indicator <NUM> through cover plate <NUM>. The user can also view through cover plate <NUM> and protrusions <NUM> through plate <NUM>.

In some implementations, an icterometer described herein comprises an optically variable security element. For example, the icterometer described herein comprises an optically variable security element at an end of the icterometer distal from the end comprising the lighting indicator. Optically-variable elements display different optical effects, such as depth, motion, or chromatic effects, under different observation or illumination conditions. In some implementations, the optically variable element is a logo.

In some implementations, the icterometer comprises an optically variable security element on surface <NUM> or <NUM> at an end of the icterometer distal from the end comprising the lighting indicator <NUM>. In some implementations, the middle layer <NUM> contains an optically variable security element on surface <NUM>, or opposite surface, at an end of the icterometer distal from the end comprising the lighting indicator <NUM>.

In some implementations, an icterometer descried herein comprises an expiry or recommended replacement element. For example, the icterometer described herein comprises an expiry date at an end distal from the end comprising the lighting indicator and on the opposite surface of the security element. The expiry date can be printed, painted, or etched.

In some implementations, the icterometer comprises an expiry date on surface <NUM> or <NUM> at end of the icterometer distal from the end comprising the lighting indicator <NUM> and on the opposite surface of the security element. In some implementations, the middle later <NUM> contains an expiry date painted, printed, or etched on surface <NUM>, or opposite surface, at an end of the icterometer distal from the end comprising the lighting indicator <NUM>.

According to some implementations of the description is a kit including an icterometer, such as icterometer <NUM> or <NUM>, and a sleeve for holding the icterometer. <FIG> depicts a kit <NUM> having a sleeve <NUM> dimensioned for holding an icterometer <NUM> (or <NUM>), according to some implementations. In some implementations, the kit <NUM> includes a hinge <NUM> in the sleeve <NUM>. <FIG> depicts the sleeve <NUM> where the hinge <NUM> is indicated by a dashed line and is configured as a fold in the sleeve <NUM>. The hinge <NUM> hingedly connects a first portions <NUM>, and second portion <NUM> of the sleeve <NUM>.

In some implementations, the first portion <NUM> and second portion <NUM> of the sleeve <NUM> comprise means for attaching a surface of the first portion <NUM> with a surface of the second portion <NUM>. In some implementation, the means for attaching a surface of the first portion <NUM> with a surface of the second portion <NUM> includes a magnetic fastening assembly having a first and second magnetic elements. One of the first portion <NUM> and second portion <NUM> comprises the first magnetic element and the other of the first portion <NUM> and second portion <NUM> comprises the first magnetic element.

In some implementations, the sleeve <NUM> includes stepwise instructions <NUM> for operation of the icterometer. For example, instructions <NUM> can be printed on portion <NUM>. In some implementations, the instructions can include cleaning instructions. In some implementations, the kit further includes cleaning agents, such as disinfectant wipes, in the sleeve or attached to the sleeve. In some implementations, the icterometer includes a table <NUM> listing colors or a color indicia and corresponding total serum bilirubin concentration. For example, the table <NUM> can be printed on portion <NUM>. The table can list a "score" (corresponding to color indicia or fractions thereof) and the corresponding total serum bilirubin as shown in Table <NUM>.

<FIG> is a flow diagram <NUM> showing the steps for evaluating the total serum bilirubin concentration in a subject according to some implementations. The steps can be modified according to the icterometer being used. For example, in a first step <NUM>, a test location is determined. The test location should be selected for appropriate lighting. For example, an appropriate location can include a place with daylight or natural daylight simulators. In some implementations, this can be done by selecting a location, such as a location next to a window during daylight hours, or a location having D50 or D65 illuminators. According to the invention, the icterometer includes a lighting indicator and the location can be confirmed to be appropriate by using the lighting indicator <NUM> (<FIG>), or <NUM> (<FIG>). Once the test location <NUM> is determined, the subject is placed <NUM> in the test location for subsequent testing.

Testing includes pressing a window, such as one window <NUM> (<FIG>) against the subject's skin <NUM>. Any exposed skin of the subject can be used. In some implementations, the nose is used. In other implementations, a knee is used. In other implementations, the sole of a foot can be used. The amount of pressure applied is enough to blanch the skin and thereby reveal the color of subcutaneous tissue. Testing also includes comparing the subcutaneous tissue color viewed through the window <NUM> to the color bordering the window <NUM> (e.g., color gradients <NUM> of <FIG>). Optionally, the steps <NUM> and <NUM> are repeated in step <NUM>. The repeated step <NUM> can be more than once, for example this can be repeated for each color in step wise color gradient <NUM>.

The repeat step <NUM> is done enough times for the user to select <NUM> a color <NUM> that most closely matches the subcutaneous tissue color of the subject. In implementations where the icterometer includes a color indicium <NUM> (<FIG>), the color indicia are noted. The color <NUM> or color indicia <NUM> is compared <NUM> to tabulated values of corresponding bilirubin levels, thereby determining the bilirubin level for the subject.

Although the devices described herein are icterometer, for example icterometer <NUM> (<FIG>), other uses for the device are contemplated. The device can be used for any application where the tissue color needs to be determined. For example, the devices can be used for colorimetric assessment of skin color for skin grafting. As another example, the device can be used for the evaluation of anemia. The devices can also be used to determine a surface color. For example, in these implementations, the device is not pressed against the subject to reveal the subcutaneous tissue color, but simply placed against a surface such as the subject's skin or other surfaces. For example, the devices can be used for matching tooth enamel color to a series of shades use for dental prosthetics. For such applications, different gradient of colors that what is used for the icterometer <NUM> can be used. The device can even be used for surface color matching for inanimate objects, such as wall color.

Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variants thereof, are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. Furthermore, terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. The scope of the invention is defined by the following claims.

The embodiments will be more readily understood by reference to the following examples, which are included merely for purposes of illustration of certain aspects and embodiments of the present disclosure and should not be construed as limiting.

An exemplary icterometer includes the following components as shown by <FIG>:.

The three components (i, ii, and iii) above are layered together, with the paper in the middle layer. These are permanently fixed. The fixing points should be the outer edges of the ruler where the two plates meet. There should be no attachment in the hole areas. A sleeve for holding the icterometer is cut, printed and assembled. The ruler is placed in the sleeve.

Claim 1:
An icterometer (<NUM>; <NUM>) comprising:
a plate (<NUM>; <NUM>) including a surface (<NUM>) comprising, a stepwise gradient of colors (<NUM>); and
a series of windows (<NUM>) in the surface (<NUM>), each window (<NUM>) in the series bordered by one of the colors (<NUM>), and each window (<NUM>) including a transparent portion in the plate (<NUM>; <NUM>);
characterized in that
the icterometer (<NUM>; <NUM>) comprises a lighting indicator (<NUM>; <NUM>) configured to indicate the quality of lighting, and optionally
the plate (<NUM>; <NUM>) is waterproof and inert to cleaning solutions applied to an external surface.