DETERMINATION OF A REFRACTIVE ERROR OF AN EYE

Abstract

A method, a device, and a computer program for determining a refractive error of at least one eye of a user are disclosed, as well as a method for manufacturing a spectacle lens for the user. The method entails: displaying a periodic pattern on a screen, wherein a parameter of the periodic pattern includes at least one spatial frequency, wherein the parameter of the periodic pattern is varied; detecting a reaction of the user indicating that the user is able to perceive the periodic pattern; determining a point in time at which the user perceives the periodic pattern; and determining a value for the refractive error of the eye or eyes of the user from the periodic pattern at that point in time, wherein the value for the refractive error is determined from the at least one spatial frequency, determined at the point in time, of the periodic pattern.

Claims

1. A method for determining a refractive error of one or both eyes of a user, the method comprising: representing at least one periodic pattern on a visual display unit, wherein at least one parameter of the at least one periodic pattern represented on the visual display unit includes at least one spatial frequency, and wherein the spatial frequency is varied; capturing, with an input unit, a reaction of the user depending on the at least one periodic pattern represented on the visual display unit; establishing, with an evaluation unit, a point in time at which a recognizability of the at least one periodic pattern represented on the visual display unit by the user is evident from the reaction of the user; and determining, with the evaluation unit, a value for the refractive error of the one or both eyes of the user from the established point in time, wherein the value for the refractive error is determined from the at least one spatial frequency of the at least one periodic pattern defined at the established point in time, wherein the input unit is selected from a keyboard or a touch-sensitive visual display unit of a mobile communications device.

2. The method as claimed in claim 1, wherein the at least one spatial frequency of the at least one periodic pattern is increased or decreased.

3. The method as claimed in claim 1, wherein the at least one periodic pattern is formed by a superposition of at least one periodic function and at least one constant function.

4. The method as claimed in claim 3, wherein the at least one periodic function is selected from at least one sine function, at least one cosine function, or a superposition thereof.

5. The method as claimed in claim 3, wherein at least one increasing function or at least one decreasing function is additionally superposed on the at least one periodic function so that the at least one spatial frequency of the at least one periodic pattern increases or decreases in a direction.

6. The method as claimed in claim 5, wherein the direction assumes an angle in relation to an orientation of the visual display unit, and wherein the angle is 0° or a multiple of 90°.

7. The method as claimed in claim 1, wherein the at least one periodic pattern is initially represented in the first direction and subsequently represented in a second direction which has been varied in relation to the first direction.

8. The method as claimed in claim 7, wherein the respective spatial frequency of the at least one periodic pattern in the first direction and in the second direction is used to determine a spherocylindrical correction.

9. The method as claimed in claim 1, wherein the value of the refractive error of the one or both eyes of the user corresponds to a defocusing of the one or both eyes of the user, wherein the defocusing is determined as Defocus [D] in diopter D as per equation (2),
Defocus [D]=21.3/spatial frequency.Math.pupil diameter [m]  (2) wherein the spatial frequency which the user can only just recognize or just still recognize is specified as a dimensionless number, and wherein the respective eye of the user has the pupil diameter in m.

10. The method as claimed in claim 9, wherein the pupil diameter of the one or both eyes of the user is captured by measurement, wherein the pupil diameter of the one or both eyes of the user is ascertained by recording an image of the one or both eyes of the user with a camera, by applying image processing to the image and by determining a pupil distance between the camera and the one or both eyes of the user.

11. A computer program for determining a refractive error of one or both eyes of a user, the computer program being stored on a non-transitory storage medium and being configured to cause a computer to: represent at least one periodic pattern on a visual display unit, wherein at least one parameter of the at least one periodic pattern represented on the visual display unit includes at least one spatial frequency, and wherein the spatial frequency is varied; capture, with an input unit, a reaction of the user depending on the at least one periodic pattern represented on the visual display unit; establish, with an evaluation unit, a point in time at which a recognizability of the at least one periodic pattern represented on the visual display unit by the user is evident from the reaction of the user; and determine, with the evaluation unit, a value for the refractive error of the one or both eyes of the user from the established point in time, wherein the value for the refractive error is determined from the at least one spatial frequency of the at least one periodic pattern defined at the established point in time, wherein the input unit is selected from a keyboard or a touch-sensitive visual display unit of a mobile communications device.

12. A method for producing a spectacle lens, which is implemented by processing a lens blank or a spectacle lens semifinished product, wherein the lens blank or the spectacle lens semifinished product is processed based on refraction data and, optionally, centration data, wherein the refraction data and optionally the centration data contain instructions for compensating a refractive error of one or both eyes of the user, and wherein the production of the spectacle lens includes a determination of the refractive error of the one or both eyes of the user, the method comprising: representing at least one periodic pattern on a visual display unit, wherein at least one parameter of the at least one periodic pattern represented on the visual display unit includes at least one spatial frequency, and wherein the spatial frequency is varied; capturing, with an input unit, a reaction of the user depending on the at least one periodic pattern represented on the visual display unit; establishing, with an evaluation unit, a point in time at which a recognizability of the at least one periodic pattern represented on the visual display unit by the user is evident from the reaction of the user; and determining, with the evaluation unit, a value for the refractive error of the one or both eyes of the user from the established point in time, wherein the value for the refractive error is determined from the at least one spatial frequency of the at least one periodic pattern defined at the established point in time, wherein the input unit is selected from a keyboard or a touch-sensitive visual display unit of a mobile communications device.

13. An apparatus for determining a refractive error of one or both eyes of a user, the apparatus comprising: a visual display unit configured to represent at least one periodic pattern and a change in at least one parameter of the at least one periodic pattern, wherein the at least one parameter includes at least one spatial frequency of the at least one periodic pattern; an input unit configured to capture a reaction of the user depending on the at least one periodic pattern represented on the visual display unit; and an evaluation unit configured to establish a point in time at which a recognizability of the at least one periodic pattern represented on the visual display unit by the user is evident from the reaction of the user, wherein the evaluation unit is further configured to determine a value for the refractive error of the one or both eyes of the user from the established point in time, wherein the value for the refractive error of the respective eye of the user is determined from the at least one spatial frequency of the at least one pattern defined at the established point in time, and wherein the input unit is selected from a keyboard or a touch-sensitive visual display unit of a mobile communications device.

14. The apparatus as claimed in claim 13, further comprising: at least one camera configured to record an image of the one or both eyes of the user, wherein the evaluation unit is further configured to ascertain the pupil diameter of the one or both eyes of the user by applying image processing to the image of the one or both eyes of the user and to determine a pupil distance between the at least one camera and the one or both eyes of the user.

15. The apparatus as claimed in claim 13, wherein the input unit, by way of an operation of the input unit, is configured to generate a measurement signal which is transmitted to the evaluation unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0112] FIG. 1 shows a typical exemplary embodiment of an apparatus for determining a refractive error of an eye of a user; and

[0113] FIG. 2 shows a flowchart of the method according to the disclosure for determining the refractive error of the eye of the user.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0114] FIG. 1 schematically shows a typical exemplary embodiment of an apparatus 110 for determining a refractive error of an eye 112 of a user 114. In the illustration in accordance with FIG. 1 and in the following description—but without loss of generality—the proposed apparatus 110 is embodied as a mobile communications device 116 in the form of a smartphone 118. An embodiment of the apparatus 110 in the form of some other mobile communications device 116, in particular as a cellular phone (cellphone) or tablet, is likewise conceivable, however.

[0115] The apparatus 110 comprises a visual display unit 120, which, as is evident from FIG. 1, substantially adopts the shape of a rectangle. The visual display unit 120 is configured to represent a symbol 122. According to the disclosure the symbol 122 represents a pattern 124 which comprises a graphical structure—in particular in contrast to noise which remains without identifiable structure—which has at least one spatial period, within which the structure of the pattern 124 is represented repeatedly. The pattern is therefore also referred to as a periodic pattern.

[0116] Furthermore, the visual display unit 120 is configured to represent a change in a parameter of the symbol 122 represented on the visual display unit. On account of the electronic control of the visual display unit 120 on the smartphone 118, the selected parameter of the pattern 124 represented on the visual display unit can be varied easily and over a broad scope. In the periodic pattern 124 present here, the parameter can typically be linked to a property of a periodic function. In particular, a repetition frequency can be used in this case, with which the structure can be represented with such repetition that similar points or regions can form over the structure of the pattern 124 as a result of the repetition. In the illustration as per FIG. 1 periodic maxima 126 and minima 128 are identifiable as typical configurations of similar points or regions of the pattern 124. The periodic function used here is a sine function. However, other periodic functions are conceivable, for example a cosine function or a superposition of a cosine function on a sine function.

[0117] According to the disclosure, the parameter of the symbol represented on the visual display unit 120 comprises at least one spatial frequency of the periodic pattern 124, wherein the term spatial frequency a reciprocal of a spatial distance 130 between adjacently arranged similar points, in particular between adjacent maxima 126 or between adjacent minima 128, in a spatially periodic change of the pattern. In this case, the spatial frequency can be specified in units of 1/m or alternatively as dimensionless number in “units per degree” or “cycles per degree.” As illustrated schematically in FIG. 1, the intensity of the pattern 124 in a first direction 132 of the extent of the visual display unit 120 can follow the curve of the periodic function, in particular the sine function, in this case. Other ways of determining the spatial frequency from the pattern are conceivable however, for example from the spacing of points of equal intensity.

[0118] As FIG. 1 furthermore shows, the periodic pattern in this particularly typical embodiment comprises a two-dimensional superposition of the periodic function, in particular the sine function, which extends in the first direction 132 along the extent of the visual display unit 120 and a constant function which extends in a second direction 134 along the extent of the visual display unit 120, which is arranged perpendicular to the first direction 132 in this case. However, other angles between the first direction 132 and the second direction 134 are likewise possible. In this way, the pattern 124 on the visual display unit 120 can be present in the form of stripes 136 arranged next to one another in periodic fashion, which are also referred to as the “sinusoidal grating.” However, other types of patterns 124 are likewise possible. The user 114 consequently observes the sinusoidal grating on the visual display unit from a defined distance, the sinusoidal grating comprising the stripes 136 arranged next to one another in periodic fashion with a high contrast and a multiplicity of spatial frequencies. A value ranging from 25 cm to 1 m, particularly typically from 40 cm to 75 cm, in particular a value of 50 cm, can typically be chosen for the distance.

[0119] In the case of nearsightedness (myopia) of the user 114, the eye 112 is defocused and such a value can be set for the distance. The same is implemented in the case of young myopic users wearing spectacles. The apparent resolution is very high in the case of a pair of spectacles which corrects a refractive error present sufficiently well. However, if the spectacles are only partially correcting, the eye 112 of the user 114 is defocused and such a value can be set for the distance. In the case of a young, farsighted (hyperopic) user 114, no measurement can be implemented in this way since a high level of residual accommodation of the eye 112 of the young user 114 does not allow any evidence of defocusing. In this case, the pattern 124 can be represented at a distance of at least 4 m; in this case, the smartphone 118 can be used as an input unit.

[0120] As is furthermore recognizable from FIG. 1 the pattern 124 can be represented on the extent of the visual display unit 120 in such a way that the first direction 132 and the second direction 134 can each be arranged parallel to an orientation of the visual display unit 120 parallel to an edge 138 of the visual display unit 120, which substantially adopts the shape of a rectangle in the illustration as per FIG. 1. In this way the pattern 124 can be adapted to the extent of the visual display unit 120 present. However, other ways of representing the pattern 124 on the visual display unit 120 are also conceivable, for example at an angle of 45°±15° or an odd multiple thereof in relation to the orientation of the visual display unit 120.

[0121] As FIG. 1 furthermore illustrates, a further function can be superposed on the selected periodic function. In the illustration as per FIG. 1, a decreasing function has been superposed on the sine function in relation to the first direction 132 in such a way that the spatial frequency of the periodic pattern 124 reduces along the first direction 132. In this way the representation of the pattern 124 on the visual display unit 120 can already have a number of spatial frequencies, which are arranged in a decreasing sequence in the first direction 132 in this case.

[0122] The apparatus 110 furthermore comprises an input unit 140 which is configured to capture a reaction of the user 114 depending on the symbol 122 represented on the visual display unit 120. In particular, the reaction of the user 114 can be captured in monocular fashion during, typically successively for each of the two eyes 112 of the user 114, wherein the user 114 can in each case cover the other eye 112, which is not being used. In this case, it is typically first the right eye 112 and subsequently the left eye 112 of the user that can be used to capture their reaction. In this case, the user can be prompted to change the eye 112 for observing the symbol 122 on the visual display unit 120, typically by way of appropriate menu navigation on the smartphone 118.

[0123] To allow the user 114 to facilitate a desired response to a stimulus of the eye 112 of the user 114 as a consequence of the representation of the symbol 122 on the visual display unit 120, the smartphone 118 can have an input area 142 in the embodiment as per FIG. 1, the input area being represented on the touch-sensitive visual display unit 120 (touchscreen) of the smartphone 118. In this case, the input area 142 can adopt the form of a virtual keyboard 144. As an alternative or in addition thereto, the input area 142 can however have a different type of configuration, for example in the form of a button 146. However, as a further alternative, provision can also be made for the input unit 140 to be attached away from the visual display unit 120 of the apparatus 110. As an alternative or in addition thereto, the input unit 140 can furthermore be configured to record a speech input, by means of which the user 114 can transmit the input of their reaction to the apparatus 110.

[0124] Independently of the actual type of embodiment of the input unit 140 the user 114 can consequently operate the input unit 140, typically by manual impingement of the input unit 140, in particular by means of a finger 148 of user 114, in such a way that the input unit 140, as a consequence of the impingement of the input unit 140 by the user 114, generates a measurement signal which can be transmitted to an evaluation unit 150 of the device 110. In a typical embodiment the user 114 can now set the spatial frequency at which they can just still recognize a black-white contrast; this corresponds to a first zero of the sine function represented on the visual display unit 120. This can be implemented, in particular, by virtue of a high spatial frequency being represented at the outset and the latter then being incrementally reduced, or by virtue of a low spatial frequency being represented at the outset and the latter then being incrementally increased. In this case, the value for the spatial frequency can be specified independently of the user 114. As an alternative or in addition thereto, the user 114 can be provided with the option of themselves influencing the spatial frequency represented on the visual display unit 120, in particular by way of actuating the input unit 140. Moreover, information as to whether the user 114 observes the visual display unit 120 with or without a visual aid can also be captured, typically likewise by actuating the input unit 140.

[0125] As illustrated schematically in FIG. 1, the apparatus 110 can furthermore have a housing 152, which may comprise the evaluation unit 150. As an alternative or in addition thereto, the evaluation unit 150 may, however, also be attached outside of the housing 152, wherein a wired or wireless connection (not illustrated) may be provided between the input unit 140 and the evaluation unit 150. However, further types of the implementation are possible.

[0126] According to the disclosure, the evaluation unit 150 is configured to determine a point in time at which a recognizability of the symbol 122 represented on the visual display unit 120 by the user 114 is evident from the reaction of the user 114, which should be understood to mean that the user 114 can only just still or only just recognize the spatial frequency of the periodic pattern 124 presented on the visual display unit. To this end, the spatial frequency in the periodic pattern 124 can increase or decrease in time and/or in space, in particular in the first direction 132. At the same time, the user 114 is urged to specify by way of an operation of the input unit 140 that they can just still or only just recognize the spatial frequency of the periodic pattern 124 represented on the visual display unit. In order to receive the reaction of the user 114 in the desired manner where possible, a display part 154 of the visual display unit 120 or, as an alternative or in addition thereto, an acoustic output unit (not illustrated) can be used to inform the user 114 accordingly or to urge the desired reaction.

[0127] According to the disclosure, the evaluation unit 150 is furthermore configured to determine a value for the refractive error of the eye 112 of the user 114 from a specification of the point in time at which it is evident from the reaction of the user 114 that the user 114 can just still or only just recognize the spatial frequency of the periodic pattern 124 represented on the visual display unit. To this end, the measurement signal generated by the user 114 during step b) by operating the input unit 140 is transmitted to the evaluation unit 150 which is configured to establish the desired point in time therefrom. Furthermore, on account of the electronic control of the visual display unit 120 on the smartphone 118, the spatial frequency of the periodic pattern 124 represented on the visual display unit 120 is known and can consequently be used by the evaluation unit 150 for the desired evaluation. To this end, the evaluation unit 150 in a particularly typical embodiment can furthermore be configured to set the desired parameter of the symbol 122, in particular the spatial frequency of the periodic pattern 124, by controlling the visual display unit 120.

[0128] To determine the value for the refractive error of the eye 112 of the user 114 from the spatial frequency of the periodic pattern 124 defined at the point in time, the determination of the apparent resolution of the eye 112 of the user 114 illustrated above is resorted to according to the disclosure. In the embodiment of the present disclosure according to FIG. 1, it is possible to this end to proceed as described above. As per equation (2) specified above

Defocus [D]=21.3/spatial frequency.Math.pupil diameter [m]  (2)

[0129] the defocusing which corresponds in a first approximation to the spherical equivalent of the sought-after correction can be ascertained in diopter D.

[0130] As per equation (2), however, the defocusing is dependent on a pupil diameter 156 of a pupil 158 in the eye 112 of the user 114. An average diameter of the pupil 158 in daylight ranging from 2 to 3 mm can be used as an estimated value for the pupil diameter 156. Typically, however, the pupil diameter 156 can be captured by measurement. To this end, an image of an eye area 160 of the user 114 can be recorded, in particular while the user 114 observes the sinusoidal grating on the visual display unit 120 of the smartphone 118. As illustrated schematically in FIG. 1, a camera 162 can typically be used to this end, wherein the camera 162 can typically be a front camera 164 of the smartphone 118.

[0131] Consequently, the desired image of the eye area 160 of the user 114 can be recorded by means of the camera 162 at any desired location. Geometric data of the pupil 158, in particular a relative position and the diameter 156 of the pupil 158 in the eye 112 of the user 114, can be ascertained from the recorded image, in particular by means of image processing which can typically be carried out by the evaluation unit 150.

[0132] If the spatial frequency of the periodic pattern 124 represented on the visual display unit 120 is known and if the pupil diameter 156 is known, the defocusing of the eye 112 of the user 114 can therefore be ascertained in diopters D using equation (2), the defocusing, as specified above, corresponding in a first approximation to the spherical equivalent of the sought-after correction. In a further embodiment it is possible to additionally ascertain a distance, referred to as pupil distance 166, between the camera 162 and the eye 112 of the user 114. A distance measurement can be performed to determine the pupil distance 166, typically a distance measurement already available in the smartphone 118. As an alternative or in addition thereto, the pupil distance 166 can be determined by triangulation by way of a known number of pixels of the camera 162 when a known object or image content is detected by the camera 162.

[0133] As already mentioned, the spherical equivalent of the correction can be determined to a first approximation by ascertaining the apparent resolution. However, the apparent resolution can also be determined along at least two meridians, typically by virtue of the periodic pattern 124 as per FIG. 1 being represented on the visual display unit 120, initially along the first direction 132 and, following this, (not illustrated) along the second direction 134 which is typically arranged perpendicular to the first direction 132 on the visual display unit 120. In this way, the vertex power values for each of the two principal meridians, which are perpendicular to one another, can be ascertained successively for the spherocylindrical spectacle lens with astigmatic power. For further details in this respect reference is made to WO 2018/077690 A1.

[0134] FIG. 2 schematically shows a flowchart of a typical exemplary embodiment of a method 210 according to the disclosure for determining the refractive error of the eye 112 of the user 114.

[0135] In a representation step 212 there is to this end, as per step a), the representation of the periodic patter 124 on the visual display unit 120, wherein the one spatial frequency of the periodic pattern 124 represented on the visual display unit 120 is varied.

[0136] In a capture step 214 there is, as per step b), the capture of the reaction of the user 114 depending on the spatial frequency of the period pattern 124 represented on the visual display unit 120 in accordance with the representation step 212.

[0137] In an establishment step 216 there is, as per step c), the establishment of the point in time at which a recognizability of the symbol 122 represented on the visual display unit 120 by the user 114 is evident from the reaction of the user 114 in the capture step 214, such that the user 114 can just still or only just recognize the spatial frequency of the periodic pattern 124 represented on the visual display unit 120 as per the representation step 212.

[0138] In a determination step 218 there is, as per step d), the determination of a value 220 for the refractive error of the eye 112 of the user 114 from the spatial frequency of the period pattern 124 defined for representing the periodic pattern 124 on the visual display unit 120 in the representation step 212 at the point in time ascertained in the establishment step 216.

[0139] The foregoing description of the exemplary embodiments of the disclosure illustrates and describes the present invention. Additionally, the disclosure shows and describes only the exemplary embodiments but, as mentioned above, it is to be understood that the disclosure is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art.

[0140] The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of.” The terms “a” and “the” as used herein are understood to encompass the plural as well as the singular.

[0141] All publications, patents and patent applications cited in this specification are herein incorporated by reference, and for any and all purposes, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.

LIST OF REFERENCE SIGNS

[0142] 110 Apparatus [0143] 112 Eye [0144] 114 User [0145] 116 Mobile communications device [0146] 118 Smartphone [0147] 120 Visual display unit [0148] 122 Symbol [0149] 124 Pattern [0150] 126 Maximum [0151] 128 Minimum [0152] 130 Spatial distance [0153] 132 First direction [0154] 134 Second direction [0155] 136 Stripes [0156] 138 Edge [0157] 140 Input unit [0158] 142 Input area [0159] 144 Keyboard [0160] 146 Button [0161] 148 Finger [0162] 150 Evaluation unit [0163] 152 Housing [0164] 154 Display part [0165] 156 Pupil diameter [0166] 158 Pupil [0167] 160 Eye area [0168] 162 Camera [0169] 164 Front camera [0170] 166 Pupil distance [0171] 210 Method for determining a refractive error of an eye of a user [0172] 212 Representation step [0173] 214 Capture step [0174] 216 Establishment step [0175] 218 Determination step [0176] 220 Value of a refractive error of a user's eye