Devices and methods for determining tear film condition - Patents.com

Abstract

The present invention provides a device for determining the condition of an eye's tear film, the device comprising: at least one light source arranged to form a pattern of source points for projecting a plurality of light rays onto a corneal surface; a lens-camera system arranged to receive each of the plurality of reflected light rays reflected on the corneal surface, thereby forming a pattern of image points; and a computing unit arranged to determine the condition of the eye's tear film based on the image points and / or to determine data representative of the condition of the eye's tear film based on the image points and provide the data representative of the condition of the eye's tear film to a user. [Selected Figure] Figure 1

Description

[Technical field]

[0001] The present invention relates to a device for determining the condition of an eye's tear film.The present invention further relates to a method for determining the condition of an eye's tear film. [Background technology]

[0002] The corneal surface of the eye is normally covered with a tear film, i.e. a layer of tear fluid on the corneal surface. This tear film is also known as the tear film or tear film layer. Due to evaporation of the tears, the tear film gradually thins while the eyelids remain open after blinking. After some time the tear film also breaks down, but usually a person blinks before the tear film breaks down. Movement of the eyelids over the corneal surface restores the tear film.

[0003] In the prior art, several devices have been proposed to monitor the condition of the tear film, in particular to determine the break up time (TBUT), the period between an eye blink and the subsequent break up of the tear film providing information about the quality of the tear film formed during the eye blink.

[0004] Patent Document 1 discloses a device configured to non-invasively measure the state of a tear film formed on a corneal surface. The device of Patent Document 1 includes an optical projection system that projects a ring-shaped pattern including a plurality of concentric rings onto the corneal surface. An imaging device, for example a CCD camera, is provided to receive a reflected image of the projected light from the corneal surface. An operation unit calculates a degree of distortion of the reflected image based on a density value distribution of the image captured by the imaging device. Based on the calculated degree of distortion, the operation unit can quantify the state of the tear film.

[0005] The device in Patent Document 1 provides a device that can non-invasively measure the state of the tear film formed on the corneal surface and can quantitatively measure the state of the tear film without using a reflected image from the retina, but the results of this device are still limited.

[0006] It is therefore an object of the present invention to provide a device and / or method for determining the tear film status, or at least to provide an alternative device and / or method, respectively, which can provide improved results with regard to determining the tear film status. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 1844702 Summary of the Invention [Means for solving the problem]

[0008] The present invention relates to a device for determining the condition of an eye's tear film, comprising: at least one light source configured to form a pattern of source points for projecting a plurality of light beams onto the corneal surface; a lens-camera system adapted to receive each of the plurality of reflected light beams reflected from the corneal surface thereby forming a pattern of image points; a computing unit arranged to determine a tear film condition of the eye based on the image point and / or to determine data representative of the tear film condition of the eye based on the image point and to provide the data representative of the tear film condition of the eye to a user; The present invention provides a device including:

[0009] The device of the present invention provides a pattern of source points for projecting a plurality of light beams onto the corneal surface, and a pattern of image points formed by the respective plurality of reflected light beams reflected on the corneal surface.

[0010] It has been found that image points may provide a better basis for identifying the state of the tear film of the eye, since they may provide more useful distortion information than, for example, the ring pattern proposed in EP 1844702. For example, the points have a more accurate local definition. Local deformations in all directions may be recognized, whereas a ring-shaped pattern can only be used to detect radial deformations. Furthermore, with a ring-shaped pattern it may be more difficult to distinguish between local and global distortions of the projected pattern.

[0011] As a result of the use of a pattern of image spots, the determination of the tear film condition can be based on only a small number of images, ie less than five images. Preferably, the determination is based on one image.

[0012] The computing unit may be arranged to determine the state of the tear film of the eye based on the image point. The computing unit may, for example, be arranged to calculate a value representative of a current state of the tear film at a location or region within the eye and to indicate whether this value exceeds one or more threshold values.

[0013] A computing unit may also be arranged to determine data representative of the tear film status of the eye based on the image points and to provide the data representative of the tear film status of the eye to a user, e.g. an operator of the device, a physician or any other person interested in this data. This data representative of the tear film status enables the user to determine, preferably directly, the tear film status of the eye.

[0014] Because the device of the present invention allows a user to obtain or determine the state of the tear film of the eye, or at least data representative of the state of the tear film of the eye, this information may also be used to diagnose ocular surface diseases, such as dry eye syndrome. Furthermore, because the state of the tear film may be determined using only a small number of images and therefore within a short time interval, the device of the present invention may also be used to monitor the development of the tear film over time. For example, the breakup time of the tear film may be determined.

[0015] It should be noted that in one embodiment, each source point may have its own light source, e.g., an LED may be provided for each source point. In this embodiment, the device would have multiple light sources. Alternatively, all source points of a subgroup of source points may be linked to a single light source, e.g., a light source whose light is distributed to multiple optical fibers whose end points form the source points emitting light rays towards the corneal surface.

[0016] In one embodiment, the computing unit is arranged to determine the state of the tear film of the eye based on comparing the source points and the image points and / or comparing the pattern of source points and the pattern of image points. The comparison of the source points and the image points or the comparison of their patterns may be used to determine the state of the tear film. A uniform and consistent tear film of sufficient thickness has a mirror-like reflection. As a result, the image points and the source points have similar shapes and / or dimensions. When the tear film state deteriorates, for example in the case of a non-uniform tear film or a relatively thin tear film, the image points and / or their patterns formed from the reflected light rays become more distorted.

[0017] In one embodiment, the computing unit is configured to determine, for each of a plurality of image points, a value representative of a local distortion of the respective image point, and the value representative of the local distortion of the respective image point can be used to determine the state of the tear film of the eye.

[0018] Local distortion is defined herein as the degree to which an individual source point is imperfectly reflected and received as an image point due to local causes. This imperfect reflection is usually caused by the local condition of the tear film, i.e., independently of the tear film condition at other locations. Because the imperfect reflection is caused by the local condition of the tear film, different image points will usually have different shapes and intensities of reflection, even if the tear film conditions associated with these image points are approximately the same.

[0019] The value representing the local distortion of each image point, also referred to in this specification as the local distortion coefficient, provides a value representing the local state of the tear film since only locally induced imperfect reflections are taken into account.

[0020] In one embodiment, the computing unit may, for example, defining regions around a central position of each image point, the defined regions being non-overlapping and preferably contiguous; analyzing the shape of each image point within its own defined area; quantifying, for each image point, a value representative of the local distortion of the respective image point based on the analyzed shape; It may be provided to establish a value representative of the local distortion by:

[0021] This quantification could be, for example, 0 for in-focus points and 1 for locally distorted points, but a more distributed scale could also be used, for example a range of 1 to 5 or a range of 1 to 10, to quantify the local distortion of individual image points into a local distortion coefficient.

[0022] The distribution of defined regions and the associated local distortion coefficients may be displayed on a map, for example by using a color code / scale to indicate the amount of local distortion within a region.

[0023] In one embodiment, the computing unit is arranged to determine a pattern of grid lines, the intersections of which are formed by the positions of the determined image points, and the distortions in the pattern of grid lines may determine the state of the tear film of the eye or data representative thereof. To determine this pattern of grid lines, the computing unit may first calculate the positions of the image points, for example by calculating a centre point of each image point of the pattern of image points. These centre points may be connected to each other by connecting lines to form the grid lines.

[0024] The pattern of source points may be selected, for example, such that most of the grid lines are parallel or perpendicular to one another, such that when the pattern of grid lines exhibits a large number of straight, parallel or perpendicular grid lines, it may be concluded that the tear film condition is relatively good, and when the pattern of grid lines exhibits a large number of non-straight, non-parallel or non-perpendicular grid lines, it may be concluded that the tear film condition is relatively poor.

[0025] The pattern of grid lines may be presented to the user to allow the user to identify the condition of the tear film of the eye based on the data.

[0026] In another embodiment, the computing unit may be arranged to determine the tear film condition of the eye based on the grid line representation by analysing the straightness of the grid lines and their parallelism or perpendicularity to each other.

[0027] In one embodiment, the device includes a display device arranged to display the state of the tear film of the eye and / or data representative of the state of the tear film of the eye. The display device may be a computer screen, but may also be a printer. Advantageously, relevant data, such as graphical information, may be presented to the user. The display device may for example be arranged to display a pattern of grid lines representative of the state of the tear film of the eye.

[0028] In one embodiment, the computation unit includes a memory unit provided with pattern information based on a pattern of source points, the computation unit being arranged to establish, for each of the plurality of reflected light rays, a one-to-one correspondence between source points and image points based on the pattern information; The computing unit is further provided to determine a tear film condition of the eye based on a comparison of the image point and the source point.

[0029] The resulting data of the comparison of source points and image points may be stored, for example in a database, and compared with previously acquired data of the same eye or with reference data, for example acquired from other eyes of the same person or from other people. Data may also be used over longer periods of time to determine the effectiveness of treatment of an ocular surface disorder, such as dry eye syndrome.

[0030] In an embodiment, the computing unit is arranged to determine a tear film condition of the eye based on an individual comparison of an image point of the pattern of image points with a corresponding source point of the pattern of source points.

[0031] The computing unit is arranged to establish, for each of the plurality of reflected light beams, a one-to-one correspondence between the source points and the image points based on the pattern information of the pattern of source points. This enables the computing unit to perform a one-to-one comparison between the source points and the image points and to determine, for each of the image points, a quantitative assessment of the tear film condition at the location on the corneal surface corresponding to the respective image point. In particular, it will be apparent that the use of the pattern of source points and image points provides the possibility of performing suitable individual comparisons between the source points and the corresponding image points.

[0032] After each comparison of the source points with the corresponding image points, the results of the individual comparisons may be grouped to provide a single qualitative value for one or more areas of the ocular surface or a single qualitative value representative of the tear film condition across the corneal surface of each eye.

[0033] The results of the comparison, i.e., the state of the tear film, may be presented, for example, in a map. The map may present values ​​associated with individual source and image points, or values ​​associated with selected groups of source and image points. The map may be shown, for example, on a computer display or printed on paper.

[0034] In one embodiment, the computational unit is arranged to identify values ​​representing global distortions of image points, the values ​​representing the global distortions of each image point representing the effects of global causes which affect a large number, all possible image points in approximately the same way, and the computational unit is arranged to, if necessary, use the values ​​representing the global distortions of the image points to correct or compensate individual image points for the effects of the global causes.

[0035] Global distortion is defined herein as the degree to which a perfect pattern of source points is imperfectly reflected and received as a pattern of image points due to global causes, such as caused by movement of the device relative to the tear film. Because the imperfect reflection is caused by global causes, changes in the shape and / or intensity of the reflection will typically be approximately the same for all image points.

[0036] Global distortion of the image points arises from global causes, typically the movement of the device relative to the tear film during the period of projecting multiple light rays onto the corneal surface and receiving the respective multiple reflected light rays reflected on the corneal surface. If the global distortion effect is not taken into account during the processing of the image data, especially during the comparison of the individual source points with the corresponding image points, the effect caused by the global distortion can have a negative effect on the assessment of the tear film condition.

[0037] Thus, a computation unit may be arranged to correct individual image points for the effects of the movement: the computation unit may first check whether there is a large global distortion in the pattern of image points and may be able to correct / compensate the pattern of image points only if it is determined that a large global distortion occurs.

[0038] In an alternative embodiment, the device may be configured to determine that the pattern of image points is not suitable for identifying the condition of the tear film of the eye when the value representing the global distortion exceeds a predetermined threshold.

[0039] The global distortion of an image point is typically identified by looking for the same distortion for a significant number of image points, preferably for all image points. By quantifying these corresponding distortions, a value representative of the global distortion can be established. This value representative of the global distortion, also referred to herein as the global distortion factor or stability quality factor, can be used to correct and / or compensate individual image points.

[0040] In one embodiment, the pattern information includes an identifier for each source point, which may be used to identify a one-to-one correspondence between source points and image points.

[0041] In one embodiment, the at least one light source includes a light source that projects light rays of different colors such that the pattern of source points includes at least two different colors. By using different colors in the pattern of source points, the effort with which a one-to-one correspondence between source points and image points can be established can be significantly reduced and / or the reliability with which a one-to-one correspondence between source points and image points can be established can be significantly increased. In order to obtain a proper evaluation and comparison of the source points and image points, it is very important that the matching of the source points and image points is performed accurately.

[0042] The present invention further provides a method for determining a tear film condition of an eye, the method comprising: - projecting, using at least one light source, a plurality of light rays from a pattern of source points onto the corneal surface; receiving, with a lens-camera system, each of a plurality of reflected light beams reflected from the corneal surface, thereby forming a pattern of image points; - determining, using a computing unit, a tear film state of the eye based on the image point, and / or determining, using a computing unit, data representative of the tear film state of the eye based on the image point and providing the data representative of the tear film state of the eye to a user. Includes.

[0043] In one embodiment, determining the condition of the tear film of the eye comprises comparing source points to image points and / or comparing a pattern of source points to a pattern of image points.

[0044] In one embodiment, the step of determining the state of the tear film of the eye includes a step of determining, for each of a plurality of image points, a value representative of a local distortion of the respective image point, wherein the value representative of the local distortion of the respective image point can be used to determine the state of the tear film of the eye.

[0045] In one embodiment, the step of identifying a value representative of the local distortion comprises: defining regions around a central position of each image point, the defined regions being non-overlapping and preferably contiguous; analyzing the shape of each image point within its own defined area; quantification of local distortion coefficient values ​​for each image point based on the analyzed shape; Includes.

[0046] In one embodiment, the method includes identifying a pattern of grid lines, where intersections of the grid lines are formed by the locations of the identified image points, and where distortions in the pattern of grid lines represent a condition of the tear film of the eye.

[0047] In one embodiment, the method includes displaying the condition of the tear film of the eye and / or data representative of the condition of the tear film of the eye using a display device.

[0048] In one embodiment, the method includes creating a map indicative of the local distortion of each image point or group of image points.

[0049] In one embodiment, the method comprises: - providing pattern information based on a pattern of source points; - establishing a one-to-one correspondence between each of the source points and a respective image point based on the pattern information; - comparing image points with source points to identify the condition of the tear film of the eye; Includes.

[0050] In one embodiment, the comparing step includes determining a tear film condition of the eye based on an individual comparison of an image point of the pattern of image points with a corresponding source point of the pattern of source points.

[0051] In one embodiment, the method comprises: identifying values ​​representative of global distortion of image points, each value representing the effect of global causes affecting a large number of, approximately the same, all possible image points; correcting or compensating individual image points for the effects of global causes using values ​​representative of the global distortion of the image points; and / or determining that the pattern of image points is not suitable for identifying a state of the tear film of the eye when the value representative of the global distortion exceeds a predetermined threshold. Includes.

[0052] Embodiments of the device according to the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0053] [Figure 1] FIG. 1 illustrates an embodiment of a device according to the invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating a panel containing a multi-color source point pattern that can be applied in a topographer according to the present invention. [Diagram 3] FIG. 3 is a schematic diagram illustrating an image point pattern obtained using a stimulator including seven panels as shown in FIG. 2. [Figure 4] FIG. 2 is a schematic diagram showing three source points and associated image points; [Diagram 5] FIG. 2 is a schematic diagram showing three source points and associated image points; [Figure 6]FIG. 2 shows a mosaic of defined regions, each region associated with an image point. [Figure 7] This is a map showing the state of the tear film in each region of the eye. [Figure 8] FIG. 2 is a diagram showing an example of a grid line display representing the state of the tear film of the eye. [Figure 9] FIG. 2 is a diagram showing an example of a grid line display representing the state of the tear film of the eye. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] An embodiment of a device according to the invention is shown diagrammatically in Figure 1. The device is adapted to determine the condition of the tear film of the eye.

[0055] The device is based on the corneal topographer shown and described in WO 2012 / 067508, the contents of which are incorporated herein by reference in their entirety.

[0056] The embodiment of Figure 1 illustrates diagrammatically a polychromatic stimulator 100 arranged to project multiple light beams onto the corneal surface 110. The stimulator 100 may have, for example, a conical or hemispherical shaped surface 120 on which multiple source points are arranged to project multiple light beams onto the corneal surface 110. In one embodiment, the source points may be provided by mounting LEDs 130 of different colors on the surface 120. Alternatively, the source points may be formed by the end of an optical fiber arranged to emit light beams towards the corneal surface 110.

[0057] As shown diagrammatically, an incident light ray I emitted by a source point (Sp) 130.1 (with coordinates (Xs, Ys, Zs)) intersects with the corneal surface 110 (at a corneal intersection point C (with coordinates (Xc, Yc, Zc)) resulting in a reflected light ray R directed towards a lens 150 of a lens-camera system for recording the corneal reflection. The reflected light ray R is then received by a camera plane 170 of the lens-camera system resulting in an image point (Ip) with coordinates (Xi, Yi, Zi). As can be seen from FIG. 1, the opening of the cone 120 (or hemisphere) faces the corneal surface 110 of the eye to be measured. The illustrated device further includes a calculation unit 180, e.g. a computer, or a microprocessor, for processing the captured image and constructing a mathematical representation of the tear film condition based on the captured image. The calculation unit 180 includes a memory unit for storing relevant data such as the pattern information of the source points. A display device 181, such as a computer screen or a printer, may be provided for displaying the relevant data.

[0058] In one embodiment, the multi-color stimulator includes multiple segments, which may be the same or different. As an example of such an embodiment, the source points of the stimulator are attached to multiple boards, such as PCBs. In such a setup, multiple PCB panels may be assembled to form an approximately conical shape. By way of example, such a stimulator may be constructed using at least three panels. Below, a more detailed example is shown, including seven PCB panels. FIG. 2 shows a schematic plan view of such a panel 200, where symbols 0, +, and ● are used to indicate the positions of the source points of different colors. In the illustrated example, 96 source points (e.g. LEDs) are provided on the panel. Seven such panels may be assembled, where each PCB panel may have an identical arrangement of source points, i.e. color LEDs, to form an approximately conical stimulator. In one embodiment, the arrangement of the source points on the panels is such that a substantially rectangular grid pattern is formed by reflection on a spherical surface. In FIG. 3, an image pattern 300 resulting when seven panels according to FIG. 2 are used is shown diagrammatically. The image points are derived from a generally rectangular grid pattern, as indicated by the dotted line 310. To distinguish a particular panel from other panels (assuming the panels are identical), the orientation of the rectangular grid pattern may be used. Such orientation may then be used to help establish the unique identity of the image points. The orientation of the grid pattern may, for example, be derived from an evaluation of the positions of a subset of the image points. As can be seen from the source point pattern in FIG. 2, to achieve such a rectangular grid pattern as an image point pattern, the source points may be arranged along a curve, for example the curve 210 as shown in FIG. 2.

[0059] To establish a one-to-one correspondence between source points and image points, the device applies color pattern information based on the multi-color pattern of the source points. Such information may, for example, describe a portion of the color pattern, for example, as an array of multiple matrices. As an example, an n×m matrix (e.g., 2×2 or 3×3) may be used to describe the color pattern of an n×m source point. By matching the color pattern of the matrix to the pattern of the image point, a correspondence between the image point and the source point may be established.

[0060] As described above, the device of the present invention includes at least one light source arranged to form a pattern of source points for projecting a plurality of light beams onto the corneal surface of the eye to be examined, and a lens-camera system arranged to receive respective ones of the plurality of reflected light beams reflected on the corneal surface, thereby forming a pattern of image points.

[0061] After the computation unit 180 receives the pattern of image points, for each of the multiple reflected rays, the computation unit 180 establishes a one-to-one correspondence between source points and image points based on the pattern information stored in the memory unit.

[0062] The computing unit 180 may then determine the state of the tear film of the eye based on a comparison of the image points with the source points. The comparison is based on an individual comparison of an image point of the pattern of image points with a corresponding source point of the pattern of source points. This approach is based on the insight that the reflectivity of the corneal surface at a location on the corneal surface depends on the state of the tear film on the corneal surface at that location. In particular, a value representative of the local distortion of the image points relative to the source points is a reliable measure for determining the state of the tear film.

[0063] Local distortion is the degree to which an individual source point is imperfectly reflected and received as an image point. This imperfect reflection is typically caused by the local condition of the tear film, i.e., independent of the tear film condition at other locations. Because the imperfect reflection is caused by the local condition of the tear film, different image points will usually have different shapes and intensities of reflection, even if the tear film conditions at the different image point locations are approximately the same. It should be noted that local distortion in the reflection of a single source point may result in a change in shape or size. Also, a single source point may be distorted such that the image point splits into multiple spots.

[0064] The source points are small spots of light resulting from multiple light rays projected onto the corneal surface. These source points have, for example, a circular shape with a relatively small diameter. Depending on the reflectivity of the corneal surface at the location where the image point is projected onto the corneal surface, the reflection will be more specular when the tear film conditions are relatively good and more locally distorted when the tear film conditions are relatively poor.

[0065] However, another effect may also affect the reflection of light rays on the corneal surface. This effect is called global distortion. Global distortion is defined herein as the degree to which a perfect pattern of source points is imperfectly reflected and received as a pattern of image points. The imperfect reflection of this perfect pattern is caused by global causes, such as the movement of the device relative to the corneal surface. Because the imperfect reflection is caused by global causes, the effect on the change in shape and intensity of the reflection will typically be approximately the same for different image points in the pattern of image points.

[0066] In order to accurately use the source and image points to identify the state of the tear film of the eye, the effect of the global distortion, if any, must be corrected or compensated for. The calculation unit 180 may first check whether the global distortion coefficient exceeds a certain threshold, and may only correct / compensate when the global distortion exceeds this threshold. It may also be determined that when the global distortion coefficient exceeds a certain threshold, the pattern of image points is not suitable for identifying the state of the tear film due to the global distortion.

[0067] FIG. 4 shows three source points SP1, SP2, SP3 and three image points IP1, IP2, IP3 as an example. Please note that due to local distortion, the first image point IP1 includes multiple (four) image spots. The calculation unit 180 has already established a one-to-one correspondence between the source points SP1, SP2, SP3 and the corresponding image points IP1, IP2 and IP3, respectively. Please note that the first and second source points SP1, SP2 and the first and second image points IP1, IP2 are located relatively closer to each other compared to the positions of the third source point SP3 and the third image point IP3. This is indicated by the dashed separation line in FIG. 4.

[0068] In FIG. 4, source and image points are depicted superimposed. By evaluating the pattern of source points SP1, SP2, SP3 and the associated pattern of image points IP1, IP2, IP3, it can be seen that all image points contain corresponding distortions caused by the movement of the device relative to the corneal surface during the projection of the light beam and the reception of the reflected light beam. This movement is indicated by the arrow M. Since these corresponding distortions in the pattern of image points are caused by global causes, it is desirable to correct / compensate for these distortions so that they are not used as an indicator of the tear film condition. This compensation can be performed by identifying a global distortion coefficient, i.e. the corresponding distortion at almost all image points, and using this global distortion coefficient to compensate for the distortion of the entire pattern of image points.

[0069] 5 shows the three source points SP1, SP2, SP3 and the three image points IP1, IP2, IP3 after such compensation. It should be noted that the compensation may be performed in any other suitable manner and does not necessarily result in a change in the shape of the respective image points IP1, IP2, IP3.

[0070] Here, it can be seen that the first and second image points IP1, IP2 exhibit relatively locally distorted shapes compared to the corresponding source points SP1, SP2, respectively. In contrast, the shape of the third image point IP3 changes only slightly relative to the third source point SP3. It can be concluded that the location on the corneal surface associated with the third image point IP3 provides a relatively good mirror-like reflection indicative of a good tear film condition, while the locations on the corneal surface of the first and second image points IP1, IP2 provide a poor reflection with a relatively high local distortion indicative of a poor tear film condition.

[0071] In order to provide useful feedback regarding the local distortion of each of the image points, the computational unit 180 is configured to identify, for each of the multiple image points, a value representative of the local distortion of the respective image point, which value representative of the local distortion of the respective image point can be used to indicate / identify the state of the tear film of the eye.

[0072] In one embodiment, the following steps are taken to establish a value representing the local distortion of each image point.

[0073] As a first step, the computation unit 180 defines, for each image point, a region around the center position of that image point, the defined regions being non-overlapping and contiguous. An example of a mosaic of such regions is shown in FIG.

[0074] In a next step, the shape of each image point within its own defined area can be examined by the calculation unit 180, and then, based on the analyzed shape, a local distortion coefficient can be quantified for each image point, i.e. a value representing the local distortion of each image point.

[0075] Quantification of the local distortion within each region may be performed using any suitable scoring system. For example, image points may be classified into two categories: those without local distortion and those with local distortion. Regions without local distortion may be indicated, for example, by a "0" and regions with local distortion may be indicated by a "1". The scoring system may include multiple scales, such as no distortion, low distortion, medium distortion, high distortion, and very high distortion, indicated, for example, on a scale from "1" to "5". Any other scoring system may be applied.

[0076] The smudge coefficients of individual image points for an area of ​​the eye may be combined into a composite local distortion coefficient to represent the tear film condition. For example, for each panel of the stimulator (one panel is shown in FIG. 2), a composite local distortion coefficient may be specified that is used to represent the tear film condition for each area of ​​the corneal surface. It is also possible that a single local distortion coefficient may be specified for the entire corneal surface of the eye.

[0077] Fig. 7 shows a map in which the distribution of the defined regions of Fig. 6 is shown, each of the regions being filled according to a greyscale. The brightness of the greyscale indicates the local distortion coefficient of the image point associated with this region. For example, darker grey indicates a region with a low local distortion coefficient, i.e. a relatively good tear film condition, and lighter grey indicates a region with a high local distortion coefficient, i.e. a relatively poor tear film condition.

[0078] The map of Figure 7 provides the device operator with appropriate feedback regarding the condition of the tear film in the eye. This map can be displayed on a computer monitor or printed.

[0079] The data of the map, or more generally the individual and / or combined local distortion coefficients, may be stored in a database, for example in a memory unit, for future reference. The data may be used, for example, to monitor the condition of the tear film over time, for example to identify the time between eye blinking and tear film breakup. However, the data may also be used over a longer period of time, for example to identify the effectiveness of treatment of an ocular surface disorder, such as dry eye syndrome.

[0080] 9 and 10 show another type of representation of the state of the tear film of a human eye. This representation can be displayed, for example, by the display unit 181. This representation is based on grid lines drawn between the centers of the image points. If the source points were perfectly reflected, the grid lines would be straight lines running parallel or perpendicular to each other. Non-straightness of the grid lines, or non-parallel or non-perpendicular grid lines, indicates that the corresponding image points are distorted.

[0081] In one embodiment, the display device is arranged to display data representative of the state of the tear film of the eye as a pattern of grid lines, the intersections of the grid lines being formed by the positions of the identified image points, and distortions in the pattern of grid lines can identify the state of the tear film of the eye.

[0082] 9 shows a gridline representation in which the gridlines are relatively straight and parallel or perpendicular, indicating relatively good tear film condition.

[0083] 10 shows a gridline representation in which the gridlines are less straight and less parallel or perpendicular, indicating a relatively poor tear film condition.

[0084] Thus, the representations shown in Figures 9 and 10 based on a comparison of the pattern of source points and the pattern of image points provide the user with data representative of the condition of the tear film of the eye and enable the user to identify the condition of the tear film of the eye based on the data.

[0085] In another embodiment, the computing unit may be arranged to determine the tear film condition of the eye based on the grid line representation by analysing the straightness of the grid lines and their parallelism or perpendicularity to each other.

[0086] Where necessary, detailed embodiments of the present invention are disclosed herein, but it should be understood that the disclosed embodiments are merely exemplary of the present invention, and that the present invention may be embodied in various forms. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching those skilled in the art to employ the present invention in a variety of virtually any suitable detailed structure. Moreover, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the present invention.

[0087] The terms "a" or "an," as used herein, are defined as one or more. The term multiple, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and / or having, as used herein, are defined as comprising (i.e., open language not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

[0088] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0089] A single processor or other unit may fulfill the functions of several items recited in the claims.

Claims

1. 1. A device for determining the condition of an eye's tear film, comprising: at least one light source arranged to form a pattern of source points for projecting a plurality of light beams onto the corneal surface; a lens-camera system positioned to receive each of the plurality of reflected light beams reflected off the corneal surface, thereby forming a pattern of image points; a computing unit arranged to determine the state of the tear film of the eye based on the image points and / or to determine data representative of the state of the tear film of the eye based on the image points and to provide the data representative of the state of the tear film of the eye to a user; Including, the computing unit is arranged to determine, for each of a plurality of image points, a value representative of a local distortion of the respective image point, the value representative of the local distortion of the respective image point being capable of being used to determine the state of a tear film of the eye. the computing unit is arranged to determine a value representative of a global distortion of image points, the value representative of the global distortion of each image point being representative of the effect of global causes affecting a large number, all possible image points, in substantially the same way; the device is configured to determine that the pattern of image points is not suitable for identifying the state of a tear film of the eye when the value representative of the global distortion exceeds a predefined threshold. device.

2. The device of claim 1 , wherein the computing unit is arranged to determine the state of the tear film of the eye based on comparing the source points with the image points and / or comparing a pattern of the source points with a pattern of the image points.

3. The computing unit includes: defining regions around a central position of each image point, said defined regions being non-overlapping and contiguous; analyzing the shape of each image point within its own defined area; quantifying, for each image point, a value representative of said local distortion of said respective image point based on said analyzed shape; 3. A device according to claim 1, arranged to establish a value representative of the local distortion for each image point by:

4. 4. The device according to claim 1, wherein the computing unit is arranged to identify a pattern of grid lines, intersections of the grid lines being formed by the positions of the identified image points, and wherein distortions in the pattern of grid lines allow the state of, or data representative thereof, of the tear film of the eye to be identified.

5. A device according to any one of claims 1 to 4, wherein the device comprises a display device arranged to display the condition of the tear film of the eye and / or the data representative of the condition of the tear film of the eye.

6. the computing unit includes a memory unit provided with pattern information based on the pattern of source points, the computing unit being arranged to establish, for each of the plurality of reflected light rays, a one-to-one correspondence between source points and image points based on the pattern information, the computing unit being further arranged to determine the condition of the tear film of the eye based on a comparison of the image points and the source points. A device according to any one of claims 1 to 5.

7. The device of claim 6 , wherein the computing unit is arranged to determine the state of a tear film of the eye based on individual comparisons of image points of the pattern of image points with corresponding source points of the pattern of source points.

8. The device of any one of claims 1 to 7, wherein the at least one light source comprises a light source projecting light rays of different colours such that the pattern of source points comprises at least two different colours.

9. 1. A method for determining tear film status in an eye, comprising: - projecting, using at least one light source, a plurality of light rays from a pattern of source points onto the corneal surface; - receiving, with a lens-camera system, each of a plurality of reflected light beams reflected on the corneal surface, thereby forming a pattern of image points; - determining, using a computing unit, the state of the tear film of the eye based on the image points and / or determining, using a computing unit, data representative of the state of the tear film of the eye based on the image points and providing the data representative of the state of the tear film of the eye to a user. Including, determining the state of the tear film of the eye and / or determining data representative of the state of the tear film of the eye based on the image points and providing the data representative of the state of the tear film of the eye to a user comprises determining, for each of a plurality of image points, a value representative of a local distortion of the respective image point, the value representative of the local distortion of the respective image point being usable to determine the state of the tear film of the eye; The method comprises: identifying values ​​representative of global distortion of image points, said values ​​representative of global distortion for each image point representing the effects of a large number of global causes affecting all possible image points in approximately the same way; correcting or compensating individual image points for the effect of the global causes using values ​​representative of the global distortion of the image points; and / or determining that the pattern of image points is not suitable for identifying the state of the tear film of the eye when the value representative of the global distortion exceeds a predetermined threshold. A method comprising:

10. 10. The method of claim 9, wherein identifying the condition of the tear film of the eye comprises comparing the source points to the image points and / or comparing a pattern of the source points to a pattern of the image points.

11. The step of identifying a value representative of the local distortion comprises: defining regions around a central position of each image point, said defined regions being non-overlapping and contiguous; analyzing the shape of each image point within its own defined area; quantifying values ​​of local distortion coefficients for each image point based on the analyzed shape; The method of claim 9 or 10, comprising:

12. 12. The method according to claim 9, further comprising identifying a pattern of grid lines, intersections of the grid lines being formed by the positions of the identified image points, and distortions in the pattern of grid lines being indicative of the state of a tear film of the eye.

13. The method according to any one of claims 9 to 12, wherein the method comprises displaying the condition of the tear film of the eye and / or the data representative of the condition of the tear film of the eye using a display device.

14. A method according to any one of claims 9 to 13, wherein the method comprises the step of creating a map indicative of the local distortion of each image point or group of image points.

15. The method comprises: - providing pattern information based on the pattern of source points; - establishing a one-to-one correspondence between each of said source points and a respective image point based on said pattern information; - comparing said image points with said source points to identify said condition of the tear film of said eye; The method according to any one of claims 9 to 14, comprising:

16. 16. The method of claim 15, wherein the comparing step comprises identifying the condition of a tear film of the eye based on individual comparisons of image points of the pattern of image points with corresponding source points of the pattern of source points.

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