Patent Description:
Ophthalmologists observe eyes and their parts in order to check their health status, to diagnose any diseases and, if necessary, to choose treatments.

Ophthalmologists perceive color images of the eyes and their parts, and often base their diagnoses on the colors of the eye parts.

Anyway, the perception of colors by ophthalmologists is influenced by objective and subjective factors. The quality of a diagnosis on an eye strongly depends on the apparatus that was used for observing the eye and its parts as well as on the skill of the ophthalmologist who made the diagnosis.

From document <CIT> are known methods, systems and computer readable storage devices for determining a color score for at least a portion of a biological tissue by obtaining a digital image of the biological tissue, receiving a selection of a portion of the image as an evaluation area, determining for each of a plurality of pixels within the evaluation area, a plurality of color components that are based on a Cartesian color space, determining, from the color components, a hue value in a polar coordinate based color space, determining a color value based on the hue value for each of the plurality of pixels, and assigning a color score to the evaluation area based on an average of the color values of the plurality of pixels.

However, as already mentioned above, also the solution according to <CIT> is device-dependent (there is one color in the image that is correct, i.e. the color used for balancing, but no guaranties are provided regarding the other colors of the image, i.e. the color dynamic of the image).

Therefore, it would be desirable to provide ophthalmologists with methods and apparatuses that assist them in the objective evaluation of the colors of eye parts, in particular of the iridocorneal regions of eyes as it is difficult to observe such regions well.

The basic idea behind the present invention provides for selecting at least one sub-image within a detected image corresponding to a region of interest, computing at least one statistic parameter of the selected sub-image, and determining an indicator based on the computed statistic parameter.

One or more of such indicators may be provided to the ophthalmologist as examination result or results.

It is important that the detection of color images is preceded by calibrating a pair of at least one color image detector device and at least one color illuminator device. Calibration may be carried out only once (for example when the medical apparatus used for image detection is manufactured) or repeatedly (for example once a year).

The color images are detected in a device-dependent color space (being a RGB color space) and then transformed in a device-independent and perceptually-uniform color space (being the CIE LAB color space).

A first important idea behind the present invention provides for computing a computed color (for example an average color) of the sub-image, computing a distance between the computed color and a comparison color (for example a "reference red" color), and providing the distance as an examination result.

A second important idea behind the present invention provides for detecting a plurality (at least two) of color images of an iridocorneal region of an eye at different times (for example every <NUM>-<NUM>) and comparing them. Before, such detections, fluorescein is administered to the person under examination.

A third important idea behind the present invention is to use a predetermined grading scale (for example Scheie's angle pigmentation scale) for determining the indicator.

The present invention is defined by the appended claims that have to be considered an integral part of the present description.

A first aspect of the present invention corresponds to a method of creating and processing a color image of an iridocorneal region of an eye.

A second aspect of the present invention, which is not part of the claimed subject-matter, corresponds to an apparatus for creating and processing a color image of an iridocorneal region of an eye.

Processing of color images of iridocorneal regions of eyes may be carried out for example in the medical apparatus that detects the images, in a computer connected to the medical apparatus that detects the images, in a computer non-connected to the medical apparatus that detects the images. In the last case, images may be stored for example in a memory device to be read by or connected to the computer.

A third aspect of the present invention, which is not part of the claimed subject-matter, corresponds to a computer program product for processing color images of iridocorneal regions of eyes. Such computer program products may be downloaded from a communication network and/or stored on a computer-readable medium and/or stored in a processor-readable medium of a processing unit.

The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the present invention and, together with the detailed description, explain these embodiments. In the drawings:.

The following detailed description of exemplary embodiments refers to the accompanying drawings.

The following detailed description does not limit the present invention. Instead, the scope of the present invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

In <FIG>, an eye is labeled <NUM> and its iridocorneal annular zone <NUM>; considering <FIG>, as known, the iridocorneal annular zone <NUM> is substantially delimited on the left side by the iris, on the right side by an annular portion of the cornea, and on the intermediate side by the trabecular meshwork and adjacent tissues <NUM>.

An apparatus according to the present invention, such as the one shown in <FIG>, is designed for observing of at least a portion of an iridocorneal annular zone of an eye, detecting one or more color images of the region, processing the images and providing one or more examination results. Preferred embodiments of such apparatus allow observation of the whole annular zone, i.e. the annular portion has an amplitude of <NUM>° as in <FIG>. Alternative embodiments of such apparatus may allow observation for example of one portion having amplitude of e.g. <NUM>° or <NUM>° or <NUM>°, or of a set of separate portions having amplitude of e.g. <NUM>° or <NUM>° or <NUM>°.

The status of the tissues in the iridocorneal zone of the eye is relevant but not limited to the diagnosis of for example primary open-angle glaucoma, angle-closure glaucoma, normal tension glaucoma, low tension glaucoma, secondary glaucoma, primary congenital glaucoma, inflammatory glaucoma, lens-related glaucoma, traumatic glaucoma, iridocorneal endothelial (ICE) syndrome, glaucoma in phacomatoses, iridocorneal dysgenesis, ghost cell glaucoma, glaucoma in cavernous sinus fistula, glaucoma in intraocular tumors, glaucoma in ciliochoroidal detachment, Glaucoma in epithelial ingrowth, glaucoma in iridoschisis, and, in general, ocular hypertension, trabecular meshwork damages, neovascularization of the iridocorneal structures, anomalies of the ciliary body, iris damages and pathogenic strains.

The <NUM>° portion of the iridocorneal zone of <FIG> is divided in a number of adjacent sub-portions <NUM>; in particular, by way of example, it is divided in eight sub-portions <NUM> having the same amplitude of <NUM>°. It is to be noted that according to alternative embodiments, the number of sub-portions may be different, for example from e.g. four to e.g. thirty-six.

The observation and detection portion of the apparatus of <FIG> is described in detail in international patent application published as <CIT> (see its Fig. <NUM>).

Alternative observation and detection arrangements that may be used for implementing the present invention are shown and described in detail in international patent application published as <CIT>.

It is to be noted that the present invention may be implemented through observation and detection arrangements different from those shown and described in <CIT>.

Natural light that is rather diffused (i.e. coming from different directions) and rather weak does not allow a good observation of the iridocorneal annular zone of an eye. Therefore, according to the present invention, artificial light is much preferably used.

The apparatus of <FIG> (largely corresponding to Fig. <NUM> of document <CIT>) is suitable for observation of the whole iridocorneal annular zone of an eye and comprises: a stationary illumination assembly consisting of one illumination electric (in particular electronic) device <NUM>, a stationary image capturing assembly consisting of one image capturing electric (in particular electronic) device <NUM>, and a stationary front optical assembly <NUM>; the illumination device <NUM> has a light emitter <NUM>; the image capturing device <NUM> has a light sensor <NUM> consisting of a matrix of light detectors.

According to alternative embodiments of the present invention, the apparatus may comprise a plurality of illumination devices and/or a distinct plurality of image capturing devices (see e.g. <FIG> of document <CIT>). The light sensors of the image capturing devices may be separate sensors or portions of a single large light sensor.

The image capturing assembly of <FIG> is used for detecting color images of iridocorneal regions of eyes. The image capturing device <NUM> of the assembly comprises of a bi-dimensional array of pixels. The color images are in a color space defined by three color dimensions thus a color of each pixel of the array is associated to three color components,.

In the embodiment of <FIG>, the illumination device <NUM> is successively associated to a distinct and different illumination optical path that goes to a corresponding sub-portion (see e.g. elements <NUM> in <FIG>) of the iridocorneal annular zone of an eye.

In the embodiment of <FIG>, the image capturing device <NUM> is successively associated to a distinct and different imaging optical path that comes from a corresponding sub-portion (see e.g. elements <NUM> in <FIG>) of the iridocorneal annular zone of an eye.

In the embodiment of <FIG>, the front optical assembly <NUM> has a front surface <NUM> designed to be located close, i.e. at a short distance, to the front surface of an eye <NUM>, a rear surface <NUM> designed to be located far, i.e. at a long distance, from the front surface of an eye <NUM>; a viscous optical coupling agent, for example an ophthalmic gel, is applied on the front surface of the optical assembly and/or to the outside surface of the cornea before applying the optical assembly to the eye. According to a good practice, the above-mentioned "short distance" between the front surface of the assembly and the front surface of the eye should be the range <NUM>-<NUM>, preferably in the range <NUM>-<NUM>; shorter distances and longer distances have preferably to be avoided; in particular contact between the assembly and the eye has preferably to be avoided. The above-mentioned "long distance" depends on the length of front optical assembly and is preferably in the range <NUM>-<NUM>, more preferably in the range <NUM>-<NUM>.

In the embodiment of <FIG>, the assembly <NUM> comprises a central portion <NUM> located between the front surface <NUM> and the rear surface <NUM> and a lateral portion <NUM> located around the central portion <NUM> and surrounding it completely (i.e. it is <NUM>° wide). According to this embodiment, the central portion <NUM> is a solid transparent prism having the shape of truncated octagonal pyramid; the front surface <NUM> is concave (corresponding to the convex outside surface of the cornea); according to this embodiment, the lateral portion <NUM> consists of a single-piece reflecting element <NUM> adjacent to the lateral surface of prism so that it has eight reflecting surfaces facing the central portion <NUM>.

The equipment of <FIG> comprises also a rear optical assembly <NUM> and one stationary beam splitter <NUM>.

The rear optical assembly <NUM> has two functions distinct from each other: rotating the illumination light beam coming from the illumination device <NUM> and going to the eye <NUM> and rotating the imaging light beam coming from the eye <NUM> and going to the image capturing device <NUM>. Both these rotations are around the symmetry axis X of the front optical assembly <NUM>.

The rear optical assembly is rotary in the sense that some of its components are arranged to rotate, in particular to carry out a rotation motion (R in <FIG>) around the symmetry axis X of the front optical assembly. According to this embodiment there is a central mirror <NUM> and a lateral mirror <NUM>; both mirrors <NUM> and <NUM> rotate around the symmetry axis X of the front optical assembly <NUM> step-by-step by e.g. <NUM>° and correspondingly e.g. eight images are successively created on the sensor <NUM>; properly, the illumination light beam and the imaging light beam are rotated around the symmetry axis X of the front optical assembly <NUM> in their way between the eye <NUM> and the central mirror <NUM> and, parallelly, between the reflecting element <NUM> and the lateral mirror <NUM>.

According to the embodiment of <FIG>, the assembly <NUM> and all its components (in particular, the central portion <NUM> and the lateral portion <NUM>) is stationary; this means that a panoramic image of a whole iridocorneal annular zone of an eye may be obtained without moving it.

The color images detected through the image capturing assembly of apparatus <NUM> are then processed.

In the embodiment of <FIG>, the images detected by the light sensor <NUM> are conceptually (see dashed line) transferred to an image processing system <NUM>; there are various transferring possibilities. It is to be noted that a preliminary (analog and/or digital) processing may be carried out inside the image capturing device <NUM>.

According to alternative embodiments of the present invention, images detected by a plurality of light sensors are conceptually transferred to an image processing system either contemporaneously (for example parallel connection) or sequentially (for example bus connection).

According to the embodiment of <FIG>, the image processing system <NUM> is inside the apparatus <NUM>. System <NUM> comprises for example a processing unit <NUM> (for example a microprocessor connected to some memory), an input device <NUM> (for example a keyboard and/or a mouse) and output device <NUM> (for example a screen and/or a printer and/or a CD/DVD burner), connected together. There is a connection between image capturing device <NUM> and image processing system <NUM> that is internal to apparatus <NUM>.

According to the embodiment of <FIG>, the image processing system <NUM> is outside the apparatus <NUM>. System <NUM> may be for example a PC and comprises for example a processing unit <NUM> (for example a microprocessor connected to some memory), an input device <NUM> (for example a keyboard and/or a mouse and/or a reception device) and output device <NUM> (for example a screen and/or a printer and/or a CD/DVD burner), connected together. There is a connection between image capturing device <NUM> and image processing system <NUM>. Such connection may be a simple connection embodied by e.g. an electric cable or a complex connection embodied by e.g. an Internet connection (see element <NUM> in <FIG>). In order to transfer color images externally, apparatus <NUM> comprises a transmission device (see element <NUM> in <FIG>); the transmission device is internally directly connected to image capturing device <NUM>. On the other side, system <NUM> comprises a reception device (see element <NUM> in <FIG>).

According to the embodiment of <FIG>, the image processing system <NUM> is outside the apparatus <NUM>. System <NUM> may be for example a PC and comprises for example a processing unit <NUM> (for example a microprocessor connected to some memory), an input device <NUM> (for example a keyboard and/or a mouse and/or a CD/DVD reader) and output device <NUM> (for example a screen and/or a printer and/or a CD/DVD burner), connected together. According to this embodiment, images are transferred through a memory device, for example a CD/DVD (see element <NUM> in <FIG>). In order to transfer color images externally, apparatus <NUM> comprises a CD/DVD burner (see element <NUM> in <FIG>); the CD/DVD burner is internally directly connected to image capturing device <NUM>. On the other side, system <NUM> comprises a CD/DVD reader (see element <NUM> in <FIG>).

In general, the method according to the present invention comprises the preliminary step of:.

Preferably and typically, the whole imaging chain (i.e. illumination, acquisition and display of images) is calibrated in four successive steps:.

Calibration may be carried out only once (for example when the medical apparatus used for image detection is manufactured) or repeatedly (for example once a year).

There are many color spaces. The most widespread are the RGB color space and the CMY color space. Other color spaces were defined for example by CIE [Commission Internationale de l'Eclairage]: the CIE XYZ color space, the CIE LAB color space and the CIE LUV color space.

It is simple and effective to detect images in a device-dependent color space, such as RGB, through an ordinary image detector device (available on the market), and to select sub-images still in a device-dependent color space.

Then it is preferable to transform the sub-image in the device-dependent color space to a sub-image in a device-independent and preferably perceptually-uniform color space, in particular a CIE LAB color space.

In some cases, the region of interest, or "ROI", may correspond to an entire image. In other cases, a single image may comprise more than one region of interest.

The selection of the region of interest may be completely manual or completely automatic or manual but guided by an automatic procedure.

It is to be noted that the same region of interest may provide a first set of (one or more) indicators and a second set of (one or more) examination results. The number of examination results may be different from the number of indicators; in fact, one examination result may be based on some indicators.

It is to be noted that an examination result may be a number and/or a "class"/"grade".

It is to be noted that an examination result may also be an image, for example a (black- and-white or color) processed image, or a graph, for example a linear or circular graph showing a plurality of indicators.

It is to be noted that the method according to the present invention may provide a plurality of examination results.

Many method embodiments lie within the broad definition of the method according to the present invention as set out above.

According to a first category of methods:.

A comparison color may be predetermined and, for example, may derive from an examination trial on a plurality of persons.

According to a specific embodiment in this first category, the comparison color is a "reference red" color. The distance may be considered an indicator of the quantity of blood in the tissue.

If for example image processing is carried out in the RGB color space and if for example the comparison color is a "reference red" color, the computation of the average color and of the distance between the comparison color and the average color may take into account even only one color component (i.e. "red") of all the pixels of the sub-image.

If for example image processing is carried out in the CIE LAB or CIE LUV color space and if for example the comparison color is a "reference red" color, computation of the average color and of the distance between the comparison color and the average color takes into account two color components (i.e. A and B or U and V) or three color components of all the pixels of the sub-image.

According to a sub-category of the first category of methods, a plurality (at least two) of color images of an iridocorneal region of an eye at different times is detected, a plurality (at least two) of sub-images are selected (corresponding to the same or substantially the same sub-region), and a plurality (at least two) of average colors are computed and compared between each other.

The time period between successive detections may be for example in the range from <NUM> to <NUM>.

Such method may be used for checking the flow of aqueous humor through the trabecular meshwork. In this case, fluorescein is administered to the person under examination before such detections. In the case of gonioscopy, fluorescein appears to be green. Therefore, the level of green of the trabecular meshwork corresponds to the quantity of aqueous humor flowing in the trabecular meshwork. Furthermore, the variation of the level of green of the trabecular meshwork may be considered an indicator of the flow of aqueous humor through the trabecular meshwork.

If for example image processing is carried out in the RGB color space and if for example the comparison color is a "reference green" color, computation of the average color and of the difference or distance between the comparison color and the average color may take into account even only one color component (i.e. "green") of all the pixels of the sub-image.

If for example image processing is carried out in the CIE LAB or CIE LUV color space and if for example the comparison color is a "reference green" color, computation of the average color and of the difference or distance between the comparison color and the average color takes into account two color components (i.e. A and B or U and V) or three color components of all the pixels of the sub-image.

In general, according to this sub-category of the first category, the method comprises at least the examination steps of:.

The method may also comprise the examination step of:.

Fluorescein may be administered to the person under examination exactly at the time of detecting the first color image or shortly before.

The first computed color (for example an average color) may be used as a reference color for the person under examination.

A plurality of color image detections and color distance computations may be carried out.

According to a second category of methods, in step D, the indicator is determined based on a predetermined grading scale. In this case, the examination result is a "grade" or "class" in the predetermined grading scale.

The grading scale may be a "qualitative" grading scale while the statistic parameter/parameters used for determining the indicator is/are "quantitative" parameters.

The grading scale may be a known grading scale such as for example Scheie's angle pigmentation scale. This scale is used for visual comparison by ophthalmologists.

The grading scale may be a new grading scale derived from a known grading scale such as for example Scheie's angle pigmentation scale. For example, it turned to be advantageous to use a grading scale wherein: new grade I corresponds to the combination of Scheie's grades <NUM> and I, new grade II corresponds to Scheie's grades II, new grade III corresponds to the combination of Scheie's grades III and IV.

Classification according to the Scheie's angle pigmentation scale or a modified Scheie's angle pigmentation scale may advantageously be carried out through a statistical classifier (e.g. decision tree, random forest, neural network, support vector machine, etc.); for example, the statistical classifier may be based on a set of statistic parameters, in particular an average value and a kurtosis index value.

More in general, classification may be carried out through a deterministic or statistical classifier based on a set of statistics and/or deterministic (i.e. measured) parameters.

According to a first set of embodiments in the second category of methods,.

According to an embodiment of the first set, the CIE LAB space is used; the average value of the A component is tested, if avg(A)<=<NUM> then the examination result is new grade I else the kurtosis index value of the L component is checked, if kurt(L)<=<NUM> then the examination result is new grade II else the examination result is new grade III.

According to a second set of embodiments in the second category of methods,.

In this case, the method may comprise the further a preliminary step of training the neural network classifier only once or repeatedly or continuously.

Especially according to the second category of methods, it may be advantageous that:.

In this case, in step E the plurality of indicators and/or a linear or circular graph showing the plurality of indicators may be provided as examination result. In addition to the indicators and/or graph, a plurality of images may be provided.

An apparatus according to the present invention may comprise means specifically adapted to carry out the method as set out above.

An apparatus according to the present invention may comprise means specifically adapted to carry out the examination at least the steps B, C, D of the method as set out above. Such means correspond for example to systems <NUM>, <NUM>, <NUM> and <NUM> respectively in <FIG>, <FIG>, in particular units <NUM>, <NUM> and <NUM>.

Some of the means for carrying out the method are typically software means; indeed, one aspect of the present invention is a "computer program product".

Such product may be downloadable from a communication network, such as for example the Internet.

Such product may be stored on a computer-readable medium, such as for example a CD or DVD.

Claim 1:
Method of creating and processing a color image of an iridocorneal region (<NUM>) of an eye (<NUM>) comprising the examination steps of:
A) detecting at least one color image of an iridocorneal region (<NUM>) of an eye (<NUM>) through a detector device (<NUM>) consisting of a bi-dimensional array of pixels, wherein the at least one color image is in a color space defined by three color dimensions thus a color of each pixel of said bi-dimensional array is associated to three color components, wherein the detector device (<NUM>) and a color illuminator device (<NUM>) are preliminary calibrated as a pair,
B) selecting at least one sub-image within said detected image corresponding to a region of interest,
C) computing at least one statistic parameter of said selected sub-image, wherein the statistic parameter is selected from the group comprising an average value of a color component, a variance value of a color component, a minimum value of a color component and a maximum value of a color component, a skewness value of a color component, a kurtosis index value of a color component, a distribution of a color component, a distribution gradient of a color component,
D) determining an indicator based on said at least one statistic parameter,
E) providing said indicator as an examination result;
wherein step A provides a color image in a device-dependent color space being RGB, and
wherein before step C, there is a step F of transforming the sub-image in the device-dependent color space to a sub-image in a device-independent and perceptually-uniform color space being CIE LAB,
wherein at least steps B, C, D, E and F are carried out by a computer program.