FR2762774A1 - METHOD FOR EVALUATING THE VISION OF AN INDIVIDUAL, AND CORRESPONDING CALIBRATION STANDARD - Google Patents

Abstract

The invention concerns a method for testing a person's sight, by displaying symbols on a screen (15), comprising a configuration phase, including a step of calibrating said screen (15) during which at least certain screen (15) control parameters are adjusted such that a shape (16) displayed on said screen coincides at least partly with the shape of a standard element (11) applied on said screen (15) surface. The invention also concerns the calibrating standard (11) designed to be applied on a screen (15) surface, so as to a cause a shape displayed (16) on said screen (15) to coincide with the shape thereof.

Description

Method for evaluating the vision of an individual, and corresponding calibration standard.

 The field of the invention is that of the evaluation of the vision, or visual acuity, of an individual. More specifically, the invention relates to an evaluation method based on the use of a display screen and computer means.

 Most often, currently, visual acuity tests are based on fixed and imprecise means, which can lead to a false evaluation.

 Thus, tests of visual acuity from afar are generally carried out on boards printed in black on white, placed at a predetermined distance. The best known scale is that of Monnoyer. On these plates are placed letters that must be read. There are several groups of letters on the same board, each of which has a particular dimension, corresponding to a degree of the vision scale (this scale being calculated for a distance of 5 meters).

 This ancient technique has many drawbacks. First of all, the number of letters is small, especially in the case of large letters. The test is therefore often skewed, because the patient remembers the letters. This is common during a session: the test is wrong for the second eye, the patient remembering what he has just read. More generally, we were able to verify that certain patients remember the letters from one session to the next.

 In addition, on this kind of plates, the contrast, that is to say the difference in light intensity between the color of the letter and that of the background, is very strong (and even maximized), which is not that very rarely happens in everyday life. It is therefore not possible to detect problems associated with the lower contrasts, conventionally encountered.

 In close-up acuity tests, the Parinaud scale is used in particular. The problems encountered are similar to those specified above. There is moreover a difficulty related to the text, the syntax and the general semantics of the text being able to pose a problem of understanding to certain people, in particular for a young public, without there being any visual problem whatsoever.

 We have tried to overcome these various drawbacks by using a display on a video screen or the like (projection of slides for example). These techniques increase the display possibilities. However, they remain frozen and are not scalable. The practitioner is not free to choose different aspects, and in particular the scale values.

 Furthermore, and mainly, these techniques are very expensive, because they require the acquisition of complete specialized equipment, adapted to the tests planned.

 Finally, these known techniques are specifically dedicated to the evaluation of far vision.

 The invention particularly aims to overcome these various drawbacks of the prior techniques.

 More specifically, a first objective of the invention is to provide a method of evaluating vision, which makes it possible to carry out very numerous tests, for the evaluation of far vision and / or near vision.

 Another objective of the invention is to provide such a method, which offers great freedom to the practitioner, in the manner of presenting and conducting his tests.

 Yet another objective of the invention is to provide such a method, which is easily adaptable to any practitioner, and to any patient.

 The invention also aims to provide such a method, which is inexpensive to implement. In particular, an objective of the invention is to provide such a method, not requiring the purchase of computer means and specific display screens.

 Another objective of the invention is to provide such a method, which is simple to use, and has suitable ergonomics, in particular for far vision tests.

 These objectives, as well as others which will appear subsequently, are achieved according to the invention using a method for evaluating the vision of an individual, of the type ensuring the display of symbols on a screen. , comprising a configuration phase, comprising a step of calibrating said screen during which at least some of the adjustment parameters of said screen are adjusted so that a shape displayed on said screen coincides at least in part with the shape of a standard element applied to the surface of said screen.

 Thus, it is not necessary to have a device, and in particular a screen, specific to the application. The method of the invention is easily adaptable to any type of current screen (whatever its standard and format). The practitioner therefore does not need to be equipped with specific equipment. He can use the microcomputer which he uses, for example, for his administrative applications.

 The invention is based on a completely new and inventive approach to the problem of the precision and accuracy of the scales used on the screen. Instead of imposing a predetermined and fixed material, it offers a particularly simple method allowing the use of any type of screen.

 The means used are particularly simple and inexpensive. It is indeed sufficient for a standard element and a display of a corresponding shape to adjust, with the adjustment elements equipping the screen.

Preferably, this process comprises the following steps:
- display on said screen of at least one marker allowing the
positioning and / or centering of said standard element;
- Application of said standard element on said screen, using said marks;
- display on said screen of a shape reproducing the shape of said element
standard;
- adjusting said screen so that said displayed shape and said shape
of the standard element coincide.

 According to an advantageous embodiment, said standard element has an opening in its central part and marks made near said opening, said marks being provided to coincide with said displayed marks, when said standard element is well positioned and / or centered.

 It is therefore particularly easy to position the standard element.

 Said standard element may have any shape. I1 can in particular have an essentially rectangular external shape.

 Preferably, said adjustment of the screen is carried out pixel by pixel.

 Furthermore, said configuration phase also advantageously includes a step of defining and / or choosing scale values and / or operating parameters.

 The practitioner can thus adapt the configuration of the process to his needs and / or habits.

 The method of the invention can be used both for the evaluation of far vision and of near vision.

Thus, it can include a far vision evaluation phase ensuring the visualization of at least one of the types of symbols belonging to the group comprising letters, numbers, "E" having undergone rotation and / or symmetry , forms, according to at least one of the provisions belonging to the group comprising:
- a single symbol;
- a line of symbols;
- at least two lines of symbols.

In this case, it advantageously comprises a step of adjusting at least one of the characteristics belonging to the group comprising:
- the type of symbols;
the arrangement on said screen;
- the position of said symbols;
- the number of said symbols;
- the color of said symbols;
color inversion;
- the contrast;
- the scale of said symbols;
- no variation in the size of said symbols.

 This gives great flexibility and the possibility of adapting the tests as required.

 Preferably, the method of the invention implements a computer pointing device operating remotely, the movement and / or validation commands transmitted by said pointing device allowing the control of said far vision evaluation phase, based on information displayed in a predetermined area of said screen, in a form readable from a long distance.

 Indeed, it is desirable that the practitioner is close to his patient, and no computer. This is not possible with current systems, which assume the use of the keyboard and, above all, the reading of information displayed on the screen with an unreadable size at several meters.

The method can also include a near vision evaluation phase, ensuring the viewing of texts with a step of adjusting at least one of the characteristics belonging to the group comprising:
- the spacing between letters;
- the spacing between the words;
- the spacing between the lines;
- the length of the text;
- the complexity of the text;
- the choice of texts;
- the color of the text and / or the background of the screen;
- the contrast;
- the scale;
- no variation in the size of the characters;
- the font.

 Again, these different settings make it possible to obtain a good exhaustiveness of the evaluation.

 The invention also relates, as such, to a standard for calibrating a screen in an individual's vision evaluation system, intended to be applied to the surface of said screen, so that brings in coincidence with its own form a form displayed on said screen.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given by way of simple illustrative and nonlimiting example, and of the appended drawings, among which:
- Figure 1 illustrates the principle of the screen calibration according to the invention;
- Figure 2 shows the proper positioning of the gaze relative to
the screen, during the calibration of figure 1
- Figure 3 illustrates the principle of remote operation, in the phase
from far vision assessment.

The process of the invention can advantageously be in the form of 3 independent modules each implementing one of the following phases:
- configuration phase;
- far vision assessment phase;
- near vision assessment phase.

 Each of these phases implements a software element that precisely controls the display of information on a display screen. The configuration phase is essential and essential, since it allows the process of the invention to be adapted to any type of screen. On the other hand, the practitioner can, according to his needs and specialties, use only one or the other of the evaluation phases.

 As already indicated, the invention differs in particular from the prior art in that it is easily and directly adaptable to any type of screen available on the market. By way of nonlimiting examples, the invention can be used with screens whose diagonal is 14, 15, 17, 19 or 21 inches, whatever the resolution (640 x 480, 800 x 600, 1024 x 768, ....). Whatever screen is used, the scale will always be true to reality.

 The configuration phase therefore allows the practitioner to adapt the process to the screen available to him.

 This configuration phase essentially provides for a step of calibrating the screen, illustrated in FIG. 1. For this, it has a standard 11, appearing in the example described in the form of a square with a side of 10 cm. , having an opening 12, in its center. Markers 13 have been placed near this opening.

 On the one hand, marks 14 are displayed on the screen which make it possible to center the standard 11 on the screen 15, making the marks 13 of the standard coincide with 14 of the screen. Furthermore, a square 16 is displayed on the screen 15, the dimensions of which are adjustable. The practitioner must therefore bring the adjustable square 16 to coincide with the external contour of the standard square 11.

 This adjustment is made pixel by pixel. When the two squares coincide, the method determines the ratio between the number of pixels and the number of centimeters. Objective information is then available, making it possible to visualize all the information coming to scale.

 It should be noted that during the adjustment, the trajectory of the gaze is important, as is illustrated by FIG. 2.

 Indeed, the physical structure of the screen, which includes a protective glass 21 and a phosphor grid, can translate a significant offset. In addition, the screens are not flat, but slightly concave. As a result, there may be an error in the pixel to centimeter ratio.

 To limit the error, it is imperative that the gaze is as much as possible in alignment with the horizontal axis of the screen, or in other words, perpendicular to the line tangent to the surface of the screen and passing through the center of it (trajectory 23).

 In the case of an offset trajectory 24, the exact alignment of the variable rectangle displayed on the screen and of the standard cannot be carried out. In addition, there will be an increase in the error of the pixel / centimeter ratio.

 Furthermore, the configuration phase can provide a step for choosing the values of the scales that the practitioner wishes to use. He may in particular fill in a table indicating a dimension, in centimeters, for a given scale value. He can also carry out these operations for the near scale, specifying the equivalent on the Parinaud scale.

The evaluation phase from afar can take over the basic functions of any vision test in particular. n can also understand the following aspects:
- choice among 4 types of objects: "E", letters, numbers, shapes;
- 3 types of layout: a single letter, a display on a line, a
multi-line display;
- changing the color of the object and the background color;
- contrast adjustment (according to a scale determined during the
configuration).

 Regarding the display of letters, it is desirable that the objects is the same proportion in height and in width, that is to say that they are inscribed in a square, the edges of which are tangent to the 'object.

 For this reason, a certain number of letters of the alphabet are preferentially removed. These are letters that are too wide, or not enough (for example the M and the I).

 The invention also provides an advantageous mode of remote control from which process, in distance evaluation. Indeed, it should be remembered that the evaluation of far vision is tested 5 meters from the screen. It is of course desirable for the practitioner to be at the side of his patient. n must therefore be able to act on the process without having to act on the keyboard. Otherwise, it should move constantly.

 To solve this problem, the use of a computer mouse is planned, according to a new approach, illustrated in FIG. 3.

In addition, the screen is split into 2 parts:
- a part including what the patient must decipher, call window of
job;
- a section reserved for viewing the parameters. This part is
present for example in the form of a vertical ruler 31 placed at
left of the working window.

 You cannot use the classic mouse cursor, which is too small to be used at a distance of 5 meters. The commands issued by mouse 32 have therefore been completely reconfigured. The movements 33 of the mouse allow the selection of an element in a menu 34. A movement from left to right or from top to bottom lowers the selection on the element located under that currently selected.

Conversely, a movement from right to left or from bottom to top results in the selection of the element placed above.

 The sensitivity of the displacement is a function of the number of pixels that the mouse must travel to change the selected element 34.

 The mouse buttons are used in two ways.

 When you have to validate an order or trigger an action, a double click on item 34 is enough. If a submenu is provided, indicated by the presence of triangles 36, to the left and to the right of the item's label, pressing the right button 37 gives the parameter the following value in the list of choices, and l pressing the left button 35 gives the previous value. A double click on the left button 35 brings up a submenu 38 containing the list of choices. Its navigation mode is identical to that of the main menu. To confirm the choice, click again.

 Advantageously, an item of the "permanent" menu 39 is provided with 2 states (active state and inactive state). If the choice is "active" the main menu 31 remains permanently displayed. If it is not active, this main menu disappears after a predetermined period of non-activity of the mouse (for example: 5 seconds). the slightest movement of the mouse has the effect of making this main menu visible again 31.

 The near assessment phase incorporates all of the characteristics present in the far vision assessment phase. It can also provide for the determination of typographical characteristics improving the reading of documents for a patient.

 The presentation of this close evaluation phase is however slightly different from that of the far evaluation. Indeed, the practitioner has 3 modes of manipulation of his interface.

 The first mode allows it to have access to the most complete visual interface.

What distinguishes this mode is essentially the presentation of the text in the form of a list, as found on classic brochures. The practitioner therefore has extracts from texts, the size of which decreases according to the values of the chosen scale. This scale is expressed in tenths and / or in Parinaud equivalent.

 The second mode partially takes over the previous interface. The practitioner always has the possibility of visually modifying a certain number of parameters. On the other hand, the list of extracts from texts of different sizes has disappeared, to make way for text of uniform size. It is possible to modify this size using a keyboard shortcut, or by going back to the first mode. This second mode is useful for testing a reader on several sentences. The texts conventionally slide from the bottom to the top, to reveal the lines not visible at a given time. It can in particular be used to test the fatigue resistance of the reader.

 In the third mode, the text area occupies the entire width of the screen.

 The practitioner also has the choice of the difficulty of the text. We can for example define 3 levels of difficulty. This makes it possible, for example, to avoid proposing to a child a text that is too difficult, that he has difficulty reading although his vision is good, and conversely, to present to another person a text that is too easy, that she guesses. more than she actually reads it.

 Different settings can be provided in addition to those already presented in the far evaluation phase, and in particular the choice of fonts, the presentation of the text, the distance between words, between characters, and / or between lines.

 Thus, the value of spacing between words is calculated as a percentage of the width of the character "space", so if you want twice a standard width between two words you will indicate 200%.

 The width between characters follows the same principle, with the difference that the character used is the character "L". n indeed represents the average width. This choice of a fixed multiplier coefficient is linked to the fact that it would be very unpleasant to have irregular spaces between the characters. This would be the case if one calculated the space according to the width of the preceding character, width - character being variable.

 When the practitioner changes one of these parameters, the transformation on the displayed text is immediate.

Claims (11)

1. A method for evaluating the vision of an individual, of the type ensuring the display of symbols on a screen (15), characterized in that it comprises a configuration phase, comprising a step of calibrating said screen (15 ) during which at least some of the adjustment parameters of said screen (15) are adjusted so that a shape displayed (16) on said screen (15) coincides at least in part with the shape of a standard element (11) applied on the surface of said screen (15). 2. Method according to claim 1, characterized in that it comprises the following steps:  - Display on said screen (15) of at least one marker (14) allowing the  positioning and / or centering of said standard element (11);  - Application of said standard element (11) on said screen (15), using said  marks (14);  - display on said screen (15) of a shape (16) similar to the shape of said  standard element (11);  - adjusting said screen (15) so that said displayed shape (16) and  said shape of the standard element (11) coincide. 3. Method according to claim 2, characterized in that said standard element (11) has an opening (12) in its central part and marks (13) made near said opening (12), said marks (13) being provided to coincide with said reference marks (14) displayed, when said standard element (11) is correctly positioned and / or centered. 4. Method according to any one of claims 1 to 3, characterized in that said standard element (11) has an essentially rectangular external shape. 5. Method according to any one of claims 1 to 4, characterized in that said adjustment of the screen is carried out pixel by pixel.  6. Method according to any one of claims 1 to 5, characterized in that said configuration phase also includes a step of defining and / or choosing scale values and / or operating parameters. 7. Method according to any one of claims 1 to 6, characterized in that it comprises a phase of evaluation of far vision ensuring the visualization of at least one of the types of symbols belonging to the group comprising letters, figures, "E" having undergone rotation and / or symmetry, shapes, according to at least one of the provisions belonging to the group comprising:  - a single symbol;  - a line of symbols;  - at least two lines of symbols. 8. Method according to claim 7, characterized in that it comprises a step of adjusting at least one of the characteristics belonging to the group comprising:  - the type of symbols;  - the arrangement on said screen;  - the position of said symbols;  - the number of said symbols;  - the color of said symbols;  - inversion of colors;  - the contrast;  - the scale of said symbols;  - no variation in the size of said symbols. 9. Method according to any one of claims 7 and 8, characterized in that it implements a computer pointing device (32) operating remotely, and in that the displacement and / or validation commands transmitted by said pointing device (32) allow the control of said far vision evaluation phase, as a function of information displayed in a predetermined area of said screen, in a form that can be read from a long distance. 10. Method according to any one of claims 1 to 9, characterized in that it comprises a phase of evaluation of near vision, ensuring the viewing of texts with a step of adjustments of at least one of the characteristics belonging to the group comprising:  - the spacing between letters;  - the spacing between words;  - the spacing between the lines;  - the length of the text;  - the complexity of the text;  - the choice of texts;  - the color of the text and / or the background of the screen;  - the contrast;  the scale;  - no variation in the size of the characters;  - the font. 11. Standard (11) for calibrating a screen in an individual's vision evaluation system, characterized in that it is intended to be applied to the surface of said screen (15), so that a shape (16) displayed on said screen is brought into coincidence with its own shape.