WO2019110858A1

WO2019110858A1 - Method, system and computer program for measuring the posterior vertex diopter power of an astigmatism lens

Info

Publication number: WO2019110858A1
Application number: PCT/ES2018/070774
Authority: WO
Inventors: Vicente Micó Serrano
Original assignee: Universitat De València
Priority date: 2017-12-04
Filing date: 2018-12-04
Publication date: 2019-06-13
Also published as: ES2715510A1

Abstract

The method comprises: a) placing an astigmatism lens in a lensmeter comprising a Stokes' lens; b) focusing the image of the test target on the reticle simultaneously for the two perpendicular meridians, carried out by means of a single movement of the test target and using the Stokes' lens; and c) measuring the posterior vertex diopter power from the size of the single movement of the test, the relative angle θ through which each of the lenses of the Stokes' lens has been rotated, and the global angular position of the Stokes' lens. The invention also relates to a system using the method of the invention and to a computer program adapted to automatically calculate the measurement of the method of the invention.

Description

DESCRIPTION

Method, system and computer program to measure the posterior vertex diopter power of an astigmatic lens

Sector of the technique

The present invention relates generally, in a first aspect, to a method for measuring the posterior vertex diopter power of an astigmatic lens, comprising the use of a front-opener, and in particular to a method comprising the use of a modified front-o-meter. that incorporates a Stokes lens, and that allows the measurement to be done more quickly, simply and free of ambiguities.

A second aspect of the present invention concerns a system adapted to implement the method of the first aspect of the invention.

In a third aspect, the present invention concerns a computer program adapted to automatically calculate the measurement of the posterior vertex diopter power of the astigmatic lens of the method of the first aspect of the invention.

State of the prior art

The frontofocometer is an instrument that is essential in ophthalmic optics because it allows to measure the diopter power of the lenses, and thus control the prescriptions. Its basic function is to determine the posterior vertex power of a lens to determine the equivalent number of diopters. There are numerous books and manuals that describe both the components that comprise it and its scheme and operation.

By way of illustration, Figure 1 shows the diagram of a manual frontofocómetro, which consists essentially of a bulb B that emits light that is condensed by one or several Fv, Fo lenses that finally ends up being focused on a T test of the frontofocometer , which in general is in the shape of a cross is usually composed of two pairs of 3 lines in perpendicular directions and a succession of points with circular geometry. After the T test, a system of collimating lens C sends the image of the test to infinity or, in other words, provides a beam of parallel or collimated illumination. Said collimated beam leaves the frontofocometer to a small open space where the lens to be measured will be placed and, subsequently, falls back on an OB objective that focuses the light on a R-grid. Said reticle serves, essentially, to reference and orient the directions of the test and to measure prismatic effects by decentering. Finally, a OC ocular lens system sends the image back to infinity, leaving the collimated beam by the eyepiece of the device. When the observer (emmetropic or compensated ametropic) looks through said OC eyepiece, he observes a beam of light that comes from infinity, so the image of that beam is formed on his retina. Said beam carries information of the test in cross T and of the reticle R, reason why both objects appear neatly focused in the retina of the observer. Additionally, there is a parallel system E, Eg, D, P that allows to introduce in the plane of the reticle R a small circular field with the scale of measurement that, in the previous conditions, will mark 0 diopters since there is no measuring lens.

The lens (s) L to be measured is positioned (n) / fixed (n) in the open space between the collimator system C and the OB lens: they rest on the support shell that is just to the right of collimator C and are fixed with the help of a pressure system (kind of articulated arm between C and OB). When the introduced lens L is spherical (there is no astigmatism), the entire T test is equally unfocused in all directions (Figure 2a) and can be refocused by acting on the frontofocometer power wheel. Said power wheel (not illustrated) displaces the position of the T test so that the beam is no longer collimated at the output of system C but collimates after passing through the lens L. Thus, the entire OB + R eye system + OC continues to act the same and provide a collimated beam to infinity that the observer sees sharply focused on his retina. But this is because the axial position of the T test has been changed. This change in position is calibrated to diopters so that the spherical power of the L lens can be read on the circular dial when looking through the eyepiece of the frontofocometer.

However, when the lens L to be measured is astigmatic (it has astigmatism), the image of the T test is differently defocused depending on the power of each meridian. An astigmatic lens is characterized by having two maximal powers in two directions or perpendicular meridians. The measurement of the power of the lens L is done by focusing on each meridian separately and noting the powers with which these consecutive approaches are made (Figure 2b-c). Subsequently, the annotated powers are managed to obtain the sphero-cylindrical notation of the dioptric power (S, Ocb) with a series of associated problems that will be described below.

A method for measuring the posterior vertex diopter power of an astigmatic lens is therefore known, comprising the characteristics of the preamble of claim 1 of the present invention, that is to say: a) arranging an astigmatic lens on a support shell of a frontofocometer, between a collimator and an objective thereof; b) illuminating and displacing a test of the front-electrode to collimate a beam of light, containing an image of said test, on said objective, after going through said collimator and said astigmatic lens, and focusing on a reticule of the frontofocometer at least a portion of said image corresponding to at least one meridian of two perpendicular meridians in which the astigmatic lens has two respective maximum powers; and c) measuring the posterior vertex diopter power of the astigmatic lens from at least the magnitude of said test displacement.

As indicated above, in such known method or standard procedure, step b) comprises carrying out two displacements of the test, one for each of the two mentioned meridians, and step c) comprises making two measurements of the diopter power, one by displacement of the test. The fact of having to carry out the aforementioned two displacements and two measurements means that the time necessary to make the total measurement of the lens, that is to say for the two meridians, is considerably high.

The aforementioned standard procedure is described in more detail below.

As explained above, essentially and for the case of astigmatic lenses, the frontofocometer provides the measurement of the frontal powers corresponding to the two main meridians of the lens. In this way, the focus of the test is achieved in two main directions where the test image appears sharp but distorted (in fact what is observed corresponds to the two focal points of the astigmatic beam refracted by the lens).

Once the lens is placed on the support coch of the frontofocometer and to obtain both main powers, it is necessary to carry out a double process in which it moves (variation of the vergence of the incident light) and its orientation is varied (cross-axis rotation) optical). This is achieved, respectively, by turning the spherical focusing wheel of the front-opener and rotating the knob that turns the test until it reaches one of the two positions of maximum sharpness, that is, until one of the two main focal points is focused. Note that you can never have both focuses focused at once, never if the lens is astigmatic.

If we consider, for example, the most generalized test consisting of a cross with three lines per segment and a circle formed by points, when its orientation and position are correct, the image of each of these points will be a line whose size will vary depending on the astigmatism of the lens. In this case, we will be focusing on one of the two focal points, which should be perfectly centered in the reticle so that the reading is correct (reading without induced prismatic effect). At that time, the dioptric scale will mark the frontal power of the posterior vertex of one of the main meridians.

After obtaining one of the readings, in order to focus the other focus it is enough to rotate the spherical power focusing wheel to modify the position / vergence of the test without changing its orientation. In this way, the lines perpendicular to the previous ones are clearly observed, noting again the power value indicated in the dioptric scale.

From both readings noted, the astigmatism is given by the difference between the two measured frontal powers. Now, to obtain the optical formula of the power of the problem lens, it is necessary to consider that when a vertical line is clearly observed, it constitutes the focal image of the horizontal meridian. Therefore, it can be said that the observation of a focused focal allows to know the power of the meridian perpendicular to the orientation of said focal. In an example applied to an astigmatic power lens (- 0.25, -1, 00x0 °) the principal meridians are oriented in the directions 0 ° -180 ° and 90 ^or - 270 °. However, when you are viewing the horizontal line of the test clearly, you are measuring the frontal power of the vertical meridian (-1.25D) of the astigmatic lens, and vice versa (-0.25D).

From both readings, the optical formula of the lens, in its direct regular sphero-cylindrical notation, is obtained in the following way: i) it is taken as sphere (S) the most positive reading of both, ii) the value of the cylinder (C) is obtained as the difference in module between both powers with a negative sign, and iii) the axis of the cylinder (b) is the meridian where the value of the power that has been taken as sphere has been written down. In the previous example, the main powers are -0,25D @ 0 ° and -1, 25D @ 90 °, where @ means "in the meridian of", so the value of the sphere turns out to be S = -0, 25D. As defined, the cylinder value turns out to be C = - | -0,25-1, 25 | = -1 D and the cylinder axis is b = 0 ^or . Finally, the total sphero-cylindrical notation is recorded in the form (S, Ocb) = (-0.25, -1, 00x0 °). This notation is known as the direct sphero-cylindrical formula since the value of the cylinder is defined as a negative lens value. In addition, the transposed sphero-cylindrical notation can be defined from the following values: (S + C, -Oc (b + 90 °)) resulting in the previous example in (-1, 25D, + 1x90 °).

Another way to record the results is from the bicilíndrica notation in which the main powers are specified as pure cylindrical lenses. Bearing in mind that when a few lines of the test are clearly focused, the power is at 90 ° of them, the previous lens can be specified as the sum of two cylinders of main powers equal to (Oicbi) = (-0,25x90 ° ) and (0 _2c b ₂ ) = (-1, 25x0 °). In this way, the procedure continues the following steps: i) take as S the most positive reading of both, ii) the value C is obtained as the difference in module between both powers with a negative sign, and iii) the axis of the cylinder (b) is the countershaft of the value of the axis that has been written down as the value of S (or value of the axis in which it has been written down as a value of S plus 90 °). In this way, the measure of (S, Ocb) = (-0.25, -1, 00x0 °) is obtained again. These two pure cylindrical lenses can then be easily combined to obtain the above-cited sphero-cylindrical notation.

This procedure is used daily in most optics for such important aspects as, for example: i) measurement of the power that a client wears in his glasses, ii) verification that the astigmatic lenses that have been ordered from the factory corresponds to the refraction for which it has been requested and there is no error, and iii) properly position and mark said lens in the frontofocometer as a previous step to mount it in glasses to deliver to a client.

In addition to the aforementioned disadvantage relative to the high time associated with the standard measurement method, it also suffers from other drawbacks. In particular, there are ambiguities in the annotation process of dioptric power. Since there are different ways to specify the measured power (direct sphero-cylindrical notation, bi-cylindrical, power per meridian, etc.), there are different ways to record the results to obtain the final notation of the lens power that has been measured. In addition, the measurement process itself is confusing if all the variables that come into play are not taken into account (powers in meridians perpendicular to the sharp lines of the test, axes and countershafts of cylindrical lenses, etc.). This leads to an increase in the probability of error in the annotation of the results and, therefore, to the failure in the measurement of the lens. This error is crucial in a refraction process since the glasses delivered to the client do not correspond to the refraction obtained in the cabinet. Unfortunately, this usually happens relatively frequently in day-to-day optics where there are usually errors in the annotation of the axis rather than in the power readings. As an example, in the previous example it would be typical for the measured power of the lens to be (-0.25, -1, 00x90 °) instead of (-0.25, -1, 00x0 °). And the only way to solve it is by asking the factory for another lens for this time, to measure it and position it / mark it well in order to mount it well in glasses.

It appears, therefore, necessary to offer an alternative to the state of the art that covers the gaps found therein, by providing a method to measure the posterior vertex diopter power of an astigmatic lens that in particular does not suffer from the disadvantages of described above as the standard measurement procedure, and that considerably improves its performance, both in terms of speed and simplicity as well as the probability of errors in the measurement. Explanation of the invention

For this purpose, the present invention concerns, in a first aspect, a method for measuring the posterior vertex diopter power of an astigmatic lens, comprising: a) arranging an astigmatic lens on a support shell of a front-opener, between a collimator and an objective thereof; b) illuminating and displacing a test of the frontofocometer to collimate a beam of light, containing an image of said test, on said objective, after passing said collimator and said astigmatic lens, and focusing on a lattice of the frontofocometer at least a portion of said image corresponding to at least one meridian of two perpendicular meridians in which the astigmatic lens has two respective maximum powers; and c) measuring the posterior vertex diopter power of the astigmatic lens from at least the magnitude of said test displacement.

Unlike the methods of the state of the art, the method proposed by the first aspect of the present invention comprises, in a characteristic manner, providing, as a front-opener, a modified frontofocometer incorporating a Stokes lens with a rotation axis that is aligned with the optical axis of the frontofocometer and which is common both for a relative turn, opposite sign, of each of the lenses that make up the Stokes lens and for a global rotation of the entire Stokes lens.

Likewise, according to the method proposed by the first aspect of the invention: step b) comprises focusing on the reticle the image of the test simultaneously for both of said two perpendicular meridians, by means of a single displacement of the test and acting on the Stokes lens for performing said global rotation and / or relative rotation, so that it adopts a certain global angular position and certain relative angular positions, for each lens of the Stokes lens; and step c) comprises obtaining the measurement of the posterior vertex diopter power of the astigmatic lens simultaneously for both of the two perpendicular meridians from the magnitude of said single displacement of the test, of the relative angle Q that has been rotated each of the lenses that make up the Stokes lens, and the overall angular position of the Stokes lens.

The method proposed by the first aspect of the invention fulfills the three objectives indicated above, that is, the simplicity and speed in obtaining the measurement and, above all, that of eliminating errors insofar as they can occur with the standard method. Them and thanks to being able to focus simultaneously on the reticle both directions of the test, seeing clearly the test lines of both main meridians of the astigmatic lens under measurement.

The inclusion in the frontofocometer of an element capable of measuring astigmatism without altering the spherical power is key to the method of the present invention. This element is known as Stokes lenses and, in general (for the first implementation, explained below), is based on two ordinary cylindrical lenses, of equal power but opposite sign, and which can be turned in counter-direction. In this way, when both axes of the lenses are aligned, the Stokes lens does not introduce refractive power because the negative cylinder is compensated with the positive. However, as the cylindrical lenses are rotated in opposite directions, resulting astigmatism is generated in a certain direction and equal to 45 ° of the initial starting position of the axes of the lenses. The generated astigmatism reaches its maximum value when both lenses have been turned 45 ° one with respect to the other, case that is to have axes of the positive and negative cylinders at 90 ° or crossed one with respect to the other. That is why, often, this type of lens is also known as the crossed cylinder lens of Jackson, although this name is reserved for fixed power lenses while in a Stokes lens the power is variable.

In addition, another of the advantages that has a Stokes lens (and by inclusion a cross-cylinder type lens of Jackson) is that they have a null spherical component and, therefore, does not affect the measure of spherical power given by the wheel of vergence that has the frontofocómetro.

By way of explanation, it should be noted that, essentially, the spherical component (M) of an astigmatic lens is defined as M = S + C / 2 and a Stokes lens has a null component M because the values of S and C are self-adapting to provide M = 0D (not a pure cylindrical lens where M will always be different from 0 since, although a pure cylinder does not have a value of S, it does have a value of C). This fact is very important because it allows to measure independently the astigmatism and the spherical component: one by means of the Stokes lens and the other by means of the spherical power wheel of the front-opener. Therefore, both main meridians of the test can be clearly focused by reducing the measurement time, now we only have to measure once and not two as before (one for each meridian), and we also eliminate the possibility of making the errors associated with the method of standard measurement because the process of annotation of values is unambiguous. It should be noted that the present invention is applicable to the most generalized test consisting of a cross with three lines per segment and a circle formed by points, as well as any other valid for the measurement of astigmatism and which includes, therefore, elements of image distinguishable for both main meridians of the astigmatic lens.

According to an exemplary embodiment, the method proposed by the first aspect of the invention comprises providing said modified frontofocometer with the Stokes lens disposed between the astigmatic lens and the objective.

Alternatively, the method proposed by the first aspect of the invention comprises arranging the Stokes lens in another location, provided that the conditions set out below are met.

The Stokes lens can be placed anywhere in the frontofocometer scheme because it does not introduce spherical power that misaligns the measurement with the power wheel of the frontofocometer. Now, two things have to be taken into account. On the one hand, the ease of insertion of the Stokes lens. In this sense, the easiest thing is to introduce it in the free open path that the frontofocometer provides. And on the other hand, it is necessary to respect the distance between the collimator lens and the supporting shell of the lens to be measured. That is, the lens to be measured must be supported on the support shell because that is where the posterior vertex focal is measured (if the lens to be measured moves axially, the reading changes and no later vertex power is being measured) .

In order to design a frontofocometer from scratch, you can place the Stokes lens where you want, either behind the collimator lens (in the vicinity of the frontofocometer test), or between the collimator lens and the lens to be measured (it is a matter calibrate it properly), either between the lens to be measured and the objective, or between the objective and the eyepiece. Each position has its peculiarities and an adequate calibration should be carried out. Of course, where it is easier to locate the Stokes lens is in the open area because there the beams are collimated.

And thinking of a system of coupling of the Stokes lens to a conventional manual frontofocometer, it is necessary to respect the distance between the collimator lens and the support shell. Otherwise, it could be placed in any of the aforementioned sites except between the collimator lens and the support shell. However, the most appropriate site remains in the open space where the beam is collimated.

According to a preferred embodiment of the method proposed by the first aspect of the invention, step c) comprises obtaining the measurement of the posterior vertex diopter power of the astigmatic lens in Fourier polar notation, in the form of [M , Jxp], where: M (as defined above, as M = S + C / 2) corresponds to the value of a power scale of the frontofocometer that is a function of the magnitude of the single displacement of the test and corresponds to the spherical equivalent of the astigmatic lens, J = C sin (20) is the value of the crossed cylinder of Jackson that is obtained from the values of cylindrical power C of the Stokes lens and of the relative angle Q that is rotated each one, and b + 45 ° is the global angular position, or global orientation, of the Stokes lens that allows to generate pure astigmatic component in the form of a variable Jackson crossover with the main meridians of the astigmatic lens in b and b + 90.

According to an example of embodiment, the method proposed by the first aspect of the invention comprises performing a conversion, preferably automatic, of the measurement of the posterior vertex diopter power of the obtained astigmatic lens, from said polar Fourier notation to a spherical-cylindrical notation, direct or transposed.

The method proposed by the first aspect of the invention comprises performing said conversion for a direct sphero-cylindrical notation expressed in the form of (S, Ocb), where S = M + J, C = -2J, and b = b.

The mentioned method of conversion between the values of the realized measurement (magnitude of the only displacement of the test, angle Q and global angular position of the Stokes lens) in polar Fourier notation to the standard sphero-cylindrical notation, is also relevant to the time to meet the three objectives indicated above, ie the simplicity and speed in obtaining the measure and, above all, to eliminate errors to the extent that they can be produced with the standard method.

According to an example of embodiment, the method proposed by the first aspect of the invention also comprises automatically detecting, by means of position sensors, the magnitude of the single displacement of the test (for example, indirectly through the detection of the position of the test). the spherical focusing wheel of the frontofocometer), the relative angular positions of the Stokes lens lenses and the overall angular position of the Stokes lens.

Advantageously, the method proposed by the first aspect of the invention comprises obtaining the measurement of the posterior vertex diopter power of the astigmatic lens by calculating it automatically by processing the values obtained by means of the automatic detection indicated in the previous paragraph or by processing some values supplied by the a user to a computing device responsible for carrying out the aforementioned automatic calculation. The expressions or equations indicated above, which define S, C and b for direct spherical-cylindrical notation, are implemented, in the case that the conversion of notations is automatic, by means of an algorithm included in a software application installed in a device. external computation or included in the modified front-opener itself, which is executed taking as input the values of [M, Jxp] either entered by hand by a user (through corresponding input means associated with the computing device), or obtained directly by the computer device itself, having automatically calculated this or another computing device in communication with it.

Although for an example of embodiment of the method proposed by the first aspect of the invention is a user who through an eyepiece of the frontofocómetro determines when the test image is focused on the reticle, alternatively, for another example of embodiment, the The method of the first aspect of the invention comprises automatically determining when the test image is focused on the reticle, capturing superimposed images of the reticle and the test by means of image acquisition (including one or more image sensors, associated optical elements, and components and associated electrical and electronic circuitry) and processing them by means of image recognition software.

According to an example of embodiment, the method proposed by the first aspect of the invention comprises automatically and in a controlled manner the displacement of the test and the relative and global turns of the Stokes lens, until reaching positions for which it is obtained said determination that the test image is focused on the reticle, either such determination made, preferably, automatically (through the aforementioned image recognition) or carried out by a user looking through the eyepiece of the frontofocometer .

For a first implementation, the Stokes lens is formed by two cylindrical lenses of equal power in module but of opposite sign, while for a second implementation the Stokes lens is formed by two equal sphero-cylindrical lenses with zero spherical equivalent (no introduces spherical component) of opposite values of sphere and cylinder. In both cases, the spherical equivalent of the combination of both lenses (either cylindrical or sphero-cylindrical) in the Stokes lens is zero.

For an example of embodiment of the method proposed by the first aspect of the invention, it comprises properly positioning and marking, prior to beveling and goggle assembly, an astigmatic lens manufactured with the dioptric power measured in step c), Aligning it previously to the marking with the global orientation of the Stokes lens determined when making the measurement.

The aforementioned positioning / marking of an astigmatic lens in the appropriate orientation to compensate for a certain refractive error of a patient in glasses, follows a process inverse to the measurement of the frontal dioptric power. Once the sphero-cylindrical refraction is known, an inverse notation conversion is made to the one explained above, that is to say Fourier polar notation and the pertinent values are obtained (magnitude of the single displacement of the test, angle Q and global angular position of the Stokes), which are introduced in the modified frontofocometer, that is, they are applied to the displacement of the test and to the Stokes lens.

Subsequently, the astigmatic lens is inserted to position it in its place enabled of the frontofocometer (support shell) and the astigmatic lens is rotated, without touching any control of the frontofocometer, until the test image is seen clearly. The rotation is around the optical axis and what is being done is to position the main meridians of the astigmatic lens according to the desired orientation. In this way, when the entire test appears clearly on the observer's retina (or in an image acquired by means of image acquisition), that is, when the image of the test has been focused on the reticle simultaneously for both of the two meridians perpendicular, the astigmatic lens will have been correctly positioned, that is, it will have been determined that it is in a suitable position for the marking. The astigmatic lens is then marked with the usual system of the frontofocometer and is worn with beveling and assembly in glasses.

The positioning process provides the same advantages as the measurement process, ie: i) it saves time since you do not have to check both meridians (everything appears sharp at the same time) and, more importantly, ii) reduces the error of the positioning associated with conventional methods, since there is no possibility of being wrong with inverse readings in the main meridians.

Although in the present document, said positioning and marking process has been described as dependent on the measurement method of the first aspect of the present invention, it could alternatively be the object of independent protection.

A second aspect of the present invention concerns a system for measuring the posterior vertex diopter power of an astigmatic lens, comprising a modified frontofocometer incorporating a Stokes lens with a rotation axis that is aligned with the optical axis of the frontofocometer and which is common both for a relative turn, opposite in sign, of each of the lenses that make up the Stokes lens and for a global turn of the whole Stokes lens, and which is configured to implement the method of the first aspect of the present invention.

For an example of embodiment, the system of the second aspect of the present invention comprises at least one processor configured to process values of magnitude of the single displacement of the test, of the relative angular positions of the lens of the Stokes lens and of the position overall angle of the Stokes lens, to automatically calculate the measurement of the posterior vertex diopter power of the astigmatic lens to implement step c) of the method of the first aspect of the present invention to implement the embodiments described above and referred to said automatic calculation.

According to another embodiment, the system of the second aspect of the present invention comprises at least one processor configured to process, according to a conversion algorithm, the values obtained in polar Fourier notation for the measurement of the posterior vertex diopter power of the astigmatic lens, to automatically convert them into values of a sphero-cylindrical notation, thus implementing the embodiments of the method of the first aspect of the present invention described above and referred to said automatic notation conversion.

According to another embodiment, the system of the second aspect of the present invention is configured to implement the embodiments of the method of the first aspect of the present invention described above and referred to automatic positional detections and automatic calculation of the measurement of the posterior vertex diopter power of the astigmatic lens from said positional detections. For this purpose, the system comprises:

- position sensors configured and arranged to detect the position of said test, and therefore the magnitude of its displacement, the relative angular positions of the Stokes lens lenses and the overall angular position of the Stokes lens; Y

- an electronic control system operatively connected to said position sensors to receive output signals thereof which are indicative of the position detections made, and which includes at least one processor configured to process data contained in said output signals to automatically calculate the measurement of the posterior vertex diopter power of the astigmatic lens.

For yet another embodiment of the system proposed by the second aspect of the present invention, it is configured to implement the embodiments of the method of the first aspect of the present invention described above and referred to the automatic determination of when the test image is focused on the reticle, for which system comprises a system for acquiring and recognizing images which in turn comprises means for acquiring images (including one or more image sensors, associated optical elements, and components and associated electrical and electronic circuitry) that are configured and arranged to acquire superimposed images of the reticle and the test, and an image recognition software to process the acquired images to automatically determine when the test image is focused on the reticle.

Additionally, for another example of embodiment, the system of the second aspect of the present invention is configured to implement the embodiments of the method of the first aspect of the present invention described above and referred to the automatic and controlled realization of the displacement of the test and the relative and global turns of the Stokes lens, for which the system comprises actuating means kinematically connected (directly or indirectly through supports or mounts thereof) to the test, to the lens lenses of Stokes and to the Stokes lens, and which are operatively connected to said electronic control system to receive corresponding control commands generated by it, and in response to them carry out, automatically and controlled, the displacement of the test and the turns relative and global of the Stokes lens.

As for the modified frontofocometer, the present invention contemplates that this is manufactured with the modification described above, that is with the incorporation of the Stokes lens, whether manual, semi-automatic or automatic, or provide an accessory that incorporates the lens of Stokes and that is directly coupled to the existing frontofocómetros.

A kit including such an accessory and the elements necessary to implement the method of the first aspect of the present invention is proposed by a further aspect of the present invention.

The present invention also concerns, in a third aspect, a computer program including program code instructions that when executed in a processor implements step c) of the method of the first aspect of the invention by automatically calculating the power measurement posterior vertex of the astigmatic lens.

According to an embodiment, the computer program according to the third aspect of the present invention includes program code instructions that when executed in a processor carry out the automatic conversion of the power measurement posterior vertex diopter of the obtained astigmatic lens, from the Fourier polar notation to a sphero-cylindrical notation, implementing those embodiments of the method of the first aspect of the invention explained above and referred to such automatic conversion of notations.

For another embodiment, the computer program according to the third aspect of the present invention includes program code instructions that when executed in a processor automatically carry out the inverse conversion of notations, from the spherical notation to the cylindrical to the Fourier polar notation, of the measurement of the posterior vertex diopter power of the astigmatic lens to be positioned and marked, of the embodiment of the method of the first aspect of the invention explained above and referred to the positioning and marking of a lens astigmatic

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages and features will be more fully understood from the following detailed description of exemplary embodiments with reference to the accompanying drawings, which should be taken by way of illustration and not limitation, in which:

Figure 1 shows the diagram of a manual front-opener, used for the application of the standard measurement procedure, as described above with reference to said figure in the section of prior art;

Figure 2 shows the defocusing of the T test for: (a) spherical lens, and (b) - (c) astigmatic lenses applying the standard measurement procedure;

Figure 3 shows a simplified diagram of a modified manual front-opener to be used by the method of the first aspect of the invention and forming part of the system proposed by the second aspect of the invention, for an example of embodiment;

Figure 4 shows a series of schematic views of the Stokes lens of the frontofocometer of Figure 3, for different relative angular positions of the two lenses LS + and LS- that make it, and different global angular positions of the Stokes lens. In particular, a double example of the use of the Stokes LS lens is illustrated. By rows: (a) - (b) - (c) and (d) - (e) - (f) are for the particular case of generation of pure astigmatic power at 0 ° / 90 ° and for the generic case of b / (b + 90 °), respectively. By columns: (a) and (d) represent the initial step with the axes of the pure cylinders aligned, (b) and (e) for an arbitrary rotation of Q ⁰ , and (c) and (f) for the maximum rotation of 45 °.

Figure 5 shows a graph relating to a calibration performed with a Stokes lens constructed by the present inventor from two pure cylinders, and incorporated into a frontofocó manual meter, thus obtaining the modified front electrode according to the present invention, used to carry out an experimental validation of the method and system of the present invention.

Figure 6 shows a series of illustrations corresponding to images obtained by the standard measurement method (left and center columns) and the method proposed by the first aspect of the invention (right column), for the measurement of different astigmatic lenses.

Detailed description of ones

of realization

In Figure 3 a possible scheme of frontofocómetro modified according to the present invention is illustrated, where the elements of the same have been reduced to the indispensable ones. From left to right it is illustrated: the light source F (in the form of a bulb or LED), a condensing lens C, the cross-T test, a system of lenses colimagers Le, the astigmatic lens to measure L supported on the shell of support of the frontofocómetro, the lens of Stokes LS, the objective OB of the eyepiece, the reticle R and the ocular OC.

For the illustrated embodiment, the Stokes LS lens is composed of two cylindrical lenses of equal value and opposite sign. Said lenses have been identified in Figure 3 as LS + and LS- to designate, respectively, the positive and negative cylindrical lenses.

That is to say that for the example of embodiment illustrated in Figure 3, the first implementation indicated in a previous section has been chosen, for which the Stokes lens is formed by two cylindrical lenses of equal power in module but of opposite sign.

Said first implementation means that a pure positive cylinder with an arbitrary axis is being coupled at 45 ° (note that the axis is irrelevant but to understand the example it is better to fix a value) with a pure negative cylinder of the same power in module with axis in 45 °, that is: (Cx45 °) + (-Cx45 °). In this situation, the resulting power is zero (both cylinder and sphere) and therefore not act on the astigmatic lens to be measured. But the Stokes lens allows to rotate equally but in the opposite direction both pure cylindrical lenses until reaching the orthogonality situation after having rotated ± 45 ° both lenses, a situation that is described by (Cx90 °) + (-Cx0 °). At that time, the lens resulting from the sum of both cylinders can be written as a cross cylinder of Jackson of power J = C and axis a 0 ^or that in Fourier polar notation is written as [Cx0 °] while in spherical notation Cylindrical is formulated as (C, -2CxO °). Note that if the rotation had been + 45 °, the notations [-Cx0 °] or (C, -2Cx90 °) would have been reached. This means that the lens Stokes generated to vary from 0 to 45 ° ^or orientations pure astigmatism cylinders generates a varying potential to a maximum value of | 2C | in module with some Main meridians of 0-90 °. This Stokes lens would be perfect to compensate for the astigmatism of an L lens that generates the blur shown in Figure 2.

For any other orientation of the main meridians of the astigmatic lens L to be measured, the Stokes LS lens can be rotated globally from 0 to 180 ° (no more needed) to generate the astigmatic power aligned with said meridians and to obtain the image of the T test focused simultaneously in all directions.

Likewise, if the astigmatic lens L in addition to astigmatism has a spherical component, this component is compensated with the own spherical power wheel of the frontofocometer to be able to have the entire test focused simultaneously. The spherical power read from the circular dial of the frontofocometer is not properly a spherical power but a spherical equivalent of the L lens. This is because, according to the present invention, the measurement is being made in the Fourier polar notation of the dioptric power.

Therefore, the total readings obtained for an L lens, which in sphero-cylindrical notation is represented as (S, Ocb), are, as indicated in a previous section: [M, Jxp] where M is read directly of the power scale of the frontofocometer and it turns out to be M = S + C / 2, J which is the value of the crossed cylinder of Jackson that is obtained from the cylindrical power values C of the Stokes lens and of the relative angle Q that both lenses have been rotated, and p that is the overall orientation of the Stokes lens.

Following the description of the scheme illustrated in Figure 3, in this both lenses LS +, LS- are held by a mount (not shown) that allows the lenses to rotate at the same angle but in the opposite direction. In addition, the frame can globally rotate the entire Stokes LS lens to cover the entire angular range of astigmatism orientations. In this way, we start from a position in which the axes of the lenses LS +, LS- are aligned and, therefore, there is no resultant astigmatic component. This situation is represented in Figure 4a in which it has been chosen for simplicity that the overall angle of the Stokes LS lens is 45 °. Note that this situation (axes of the matching LS + and LS-lenses) would be the one chosen for the measurement of the dioptric power in spherical lenses since the measurement would correspond to the reading originated by the power wheel of the frontofocometer when no astigmatic component was induced ( case of Figure 2a).

However, for the case in which the lens L is an astigmatic lens with main meridians at 0 ^o and 90 °, with the position of Figure 4a of the cylindrical lenses LS +, LS- of the Stokes LS lens does not compensate the astigmatic component, so that the T test will be defocused in one of its main meridians (cases of Figs 2b-c) being able to alternate between them acting on the spherical power wheel. Now, if the Q angle is varied between the axes of the cylindrical lenses LS +, LS- of the Stokes LS lens (Q belonging to the angular range of ± 45 ° of the global angle of 45 °), a pure astigmatic power is generated in the shape of a crossed cylinder of Jackson of power "C sin (20)" and "-C sin (20)" in the meridians horizontal (0 ^o ) and vertical (90 °). This situation corresponds to Figure 4b in which, as an example, pure cylindrical lenses have been rotated ± 20 °. That pure astigmatic power (in the form of a crossed cylinder of Jackson) will be maximum when the angle of turn Q is equal to + 45 ° (or -45 °), in which case the horizontal and vertical powers are + C (or -C) and - C (or + C), respectively. This situation corresponds to the diagram of Figure 4c. Note that, independently of the angle Q, the main meridians of the pure astigmatic power always leave ± 45 ° from the global orientation of the Stokes LS lens (in this particular case, horizontal and vertical meridians). In this particular case, these powers generate a pure astigmatic component in the form of a Jackson cross cylinder of power [Cx0 °] (or [-CxO ⁰ ]) that is part of the Fourier polar notation of the dioptric power.

For any other global orientation (Figs 4d-e-f), the maximum powers of ± C are obtained in other principal meridians located at ± 45 ° of the global orientation or angle "b + 45 °". Therefore, when we want to measure the power of an astigmatic lens whose main meridians are at an arbitrary value of "b" and "b + 90 °", respectively, we must start from an overall position of the Stokes lens " b + 45 ° "or" b-45 ° "so that the astigmatic power is generated precisely in" b "and" b + 90 ° ".

The following values are those that must be adjusted experimentally to determine the power of the L lens that is intended to be measured:

1. The value of the overall angular position of the Stokes LS lens (or angle called "b + 45 °") that allows to generate pure astigmatic component in the form of a variable cross cylinder of Jackson with the main meridians in "b" and " b + 90 °. "

2. The value of the angle that the pure cylindrical lenses must rotate in the opposite direction (or angle Q) to generate the astigmatic component of power J = C sin (20) which is equal but changed in sign to the cylinder of the astigmatic lens L.

3. The value of the spherical equivalent component (M) provided by the spherical diopter power wheel of the frontofocometer.

With these three experimentally adjusted values we have all the necessary information to determine the astigmatic power according to the Fourier polar notation [M, Jxb] of the L lens proposed by the present invention, without margin of error in the handling and annotation of the results because an image of the T test of the frontofocó etro completely clear in all its orientations.

Alternatively, for the second implementation of the Stokes lens described in a previous section, this is done with two identical sphero-cylindrical lenses but with opposite values of sphere and cylinder. This means that if a lens has a notation (C, -2Cxa °), the other lens must have (-C, 2Cxa °) being arbitrary and equal the global position of ("b + 45 °" or "b-45 ° "). All of the above for the case of pure cylindrical lenses, also serves for the case of these sphero-cylindrical lenses with zero spherical equivalent.

To validate experimentally as a laboratory demonstrator the method proposed by the present invention, the present inventor has constructed a Stokes lens by taking a Risley prism support existing in an ancient phoropter and replacing the prisms by two cylindrical lenses of ± 1.50D of power, and have introduced the Stokes lens thus constructed in a manual front-opener to modify it in accordance with the present invention. Figure 5 shows a graph relating to a calibration, performed with the manual front-scope meter itself, in which the technique proposed by the method of the first aspect of the present invention has been implemented, of generated powers (ordinate axis) as the lenses cylindrical rotating (abscissa axis). First of all, to say that the angle of rotation is not in degrees but in prismatic diopters (D) since the dial of the Risley prism support is in said units; therefore, I had to perform a step from D to angle (°) in order to know which angle corresponds to the readings given by the scale of D. Note that in the proposed invention, in general the reading dial is find in degrees facilitating the measurement procedure. It can be seen in Figure 5 how the cylindrical component is generated from a position 0 equivalent to both cylinders with the axes aligned (position around 10D) to reach its maximum value of -3D at 45 ° of rotation of each lens (position around 0D). In addition to the generated cylinder, the lens also generates a value of S so that the total M is always zero (M = 0D).

In the calibration of Figure 5 it can be seen how the components C and S fit perfectly to the expected values (theoretical values) and both components are generated in the proportion S = -C / 2 making the total value of M always zero .

In addition to the opposite rotation of both cylindrical lenses, the Risley prism support allows both lenses to rotate the same amount globally. This fact is vital either to be able to align the Stokes lens with the main meridians of the lens to be measured (measurement process of the lens) or to fix a given orientation and align the lens with this orientation (process of marking and assembly of the lens). the lens in glasses). In this way, whatever the astigmatic component of the lens (value and orientation) can be compensated with the Stokes lens while the spherical component of said lens is adjusted with the spherical power wheel of the frontofocómetro itself. This is based on a measurement procedure, proposed by the present invention, which includes a double process in which the spherical power wheel of the frontofocómetro is rotated while the orientation of the Stokes lens is varied to position on The main meridians of the lens. Afterwards, you only have to retouch the angle between the cylinders to get a clear image of the test where all your lines are focused at the same time.

With the modified front endoscope with the Stokes lens constructed by the present inventors, the measurement of an astigmatic lens as described above has been carried out in an example, that is to say a lens of (-0.25, -1.00x0 °) in notation spheron-cylindrical, and the obtained measurement result has been validated, which has offered values of M = -0.75D, J = + 0.50DY b = 0 ^or , which are expressed in Fourier polar notation as [-0.75, + 0.50x0 °], which have been converted to sphero-cylindrical notation through the expressions indicated above in this document.

In addition to the above-explained experiment, the present inventor has performed tests with different astigmatic, positive and negative lenses, measured with the standard method and with the method proposed by the first aspect of the present invention. The tests have been performed up to a power of | 3 | D of astigmatism (in module) that corresponds to the maximum power of the Stokes lens generated; however, this range can be extended to much higher powers without having to account for other cylinders and a finer pitch of the dial in the Stokes lens. In addition, tests have been done in different orientations and with different lighting sources (the manual frontofocómetros have two types of illuminations: white light and green filter).

In Figure 6 and as a mosaic, illustrations of some (not all, the most representative) of the measurements made are included. These are representative schemes of some measures taken. In the first two columns have been included illustrations corresponding to the images from the standard method where you can see, separately, clear both directions or meridians of the frontofocometer test along with the power readings (circular dial in each image) of both measurements . These powers are annotated separately (white text at the top of the illustrations) to obtain the spheroidal-cylindrical notation of the posterior vertex diopter power of the measured lens (bold text at the bottom of both illustrations). On the other hand, the column on the right includes an illustration corresponding to the image obtained from the method proposed by the present invention, in which it can be seen how the test of the frontofocó meter appears clear in all its directions simultaneously. Noting the spherical power values M given by the dial adjustment wheel of the frontofocómetro (circular dial of the illustrations) and the values given by the Stokes lens in power and orientation, we obtain the Fourier polar notation [M, ύcb ] (included in white at the top of the illustrations) from which the spherical-cylindrical notation is derived and which coincides exactly with that obtained by the classical method.

A person skilled in the art could introduce changes and modifications to the described embodiments without departing from the scope of the invention as defined in the appended claims.

Claims

A method for measuring the posterior apex diopter power of an astigmatic lens, comprising: a) disposing an astigmatic lens on a support shell of a front-opener, between a collimator and a lens thereof; b) illuminating and displacing a test of the frontofocometer to collimate a beam of light, containing an image of said test, on said objective, after passing said collimator and said astigmatic lens, and focusing on a lattice of the frontofocometer at least a portion of said image corresponding to at least one meridian of two perpendicular meridians in which the astigmatic lens has two respective maximum powers; and c) measuring the posterior apex diopter power of the astigmatic lens from at least the magnitude of said test displacement; characterized in that it comprises providing, as said frontofocometer, a modified frontofocometer that incorporates a Stokes lens with a rotation axis that is aligned with the optical axis of the frontofocometer and that is common both for a relative turn, opposite in sign, of each of the lenses that make up the Stokes lens as for a global rotation of the entire Stokes lens, and because: said step b) comprises focusing on said network the image of the test simultaneously for both of said two perpendicular meridians, by a single displacement of the testing and acting on said Stokes lens to perform said overall rotation and / or said relative rotation, so that it adopts a given overall angular position and certain relative angular positions, for each lens of the Stokes lens, and said step c) comprises obtain the measurement of the posterior vertex diopter power of the astigmatic lens simultaneously for both of said two merid perpendicular from the magnitude of said single displacement of the test, from the relative angle Q that has been rotated each of the lenses that make up the Stokes lens, and from the overall angular position of the Stokes lens.

2. Method according to claim 1, characterized in that it comprises providing said modified frontofocometer with the Stokes lens disposed between said astigmatic lens and said objective.

3. Method according to claim 1 or 2, characterized in that step c) comprises obtaining the measurement of the posterior vertex diopter power of the astigmatic lens in Fourier polar notation, in the form of [M, cb], where:

M corresponds to the value of a power scale of the frontofocometer that is a function of the magnitude of the single displacement of the test and corresponds to the spherical equivalent of the astigmatic lens,

J = C sin (20), is the value of the crossed cylinder of Jackson that is obtained from the values of cylindrical power C of the Stokes lens and of the relative angle Q, and b + 45 ° is the global angular position, or global orientation, of the Stokes lens that allows to generate pure astigmatic component in the form of a variable Jackson crossover with the main meridians of the astigmatic lens in b and b + 90.

Method according to claim 3, characterized in that it comprises carrying out a conversion of the measurement of the posterior vertex diopter power of the obtained astigmatic lens, from said polar Fourier notation to a sphero-cylindrical notation, direct or transposed.

5. Method according to claim 4, characterized in that it comprises performing said conversion for a direct sphero-cylindrical notation expressed in the form of (S, Ocb), where S = M + J, C = -2J, and b = b .

6. Method according to any one of the preceding claims, characterized in that it comprises automatically detecting, by means of position sensors, said magnitude of the single displacement of the test, said relative angular positions of the lens of the Stokes lens and said angular position. of the Stokes lens.

7. Method according to any one of the preceding claims, characterized in that it comprises performing step c) of obtaining the measurement of the posterior vertex diopter power of the astigmatic lens by calculating it automatically.

8. Method according to claim 7 when dependent on the 6, characterized in that it comprises carrying out said automatic calculation by processing the values obtained by said automatic detection.

9. Method according to claim 6, 7 or 8, characterized in that it comprises automatically determining when the test image is focused on the reticle, capturing superimposed images of the reticle and the test by means of image acquisition and processing them by means of a image recognition software.

10. Method according to claim 9, characterized in that it comprises performing automatically and in a controlled manner said test displacement and said relative and global turns of the Stokes lens, until reaching positions for which said automatic determination is obtained. the test image is focused on the reticle.

1. Method according to claim 4 or 5, or any of claims 6 to 10 when depending on the 4 or 5, characterized in that it comprises carrying out said conversion automatically.

12. Method according to any one of the preceding claims, characterized in that it comprises performing, by means of said modified frontofocometer, a positioning and marking process of an astigmatic lens manufactured from the measurement obtained in step c).

13. Method according to claim 12 when it depends on the 4 or 5, characterized in that said positioning and marking process comprises:

- perform an inverse conversion of notations, from the sphero-cylindrical notation to the polar Fourier notation;

- obtain, from the polar Fourier notation, the values of the magnitude of the single displacement of the test, of the relative angle Q and of the overall angular position of the Stokes lens, and apply the displacements associated with the obtained values, both to the displacement of the test as to the turns, relative and global, of the Stokes lens;

- insert the astigmatic lens into the support shell of the modified front-opener, rotate it until focusing on the reticle the test image simultaneously for both of the two perpendicular meridians, and then determine that it is in a suitable position for the labeling; Y

- mark the astigmatic lens when it is in that position suitable for marking.

14. System for measuring the posterior vertex diopter power of an astigmatic lens, characterized in that it comprises a modified frontofocometer that incorporates a Stokes lens with a rotation axis that is aligned with the optical axis of the frontofocometer and is common for both relative rotation, opposite in sign, of each of the lenses that make up the Stokes lens as for a global rotation of the entire Stokes lens, and which is configured to implement the method according to any one of claims 1 to 13.

15. System according to claim 14, characterized in that it comprises at least one processor configured to process values of magnitude of the single displacement of the test, of the relative angular positions of the lenses of the Stokes lens and of the overall angular position. of the Stokes lens, to automatically calculate the measurement of the posterior vertex diopter power of the astigmatic lens to implement step c) of the method according to claim 7 or 8.

16. System according to claim 14 or 15, characterized in that it is configured to implement the method according to claim 1, for which it comprises at least one processor configured to process, according to a conversion algorithm, the values obtained in notation Fourier polar for the measurement of the posterior vertex diopter power of the astigmatic lens, to automatically convert them into values of a sphero-cylindrical notation.

17. System according to any one of claims 14 to 16, characterized in that it is configured to implement the method according to claim 8, for which it comprises:

18. System according to claim 17, characterized in that it is configured to implement the method according to claim 10, for which it also comprises an image acquisition and recognition system comprising an image acquisition means configured and arranged to acquire superimposed images of the reticle and the test, and an image recognition software to process the acquired images to automatically determine when the test image is focused on the reticle.

19. System according to claim 18, characterized in that it is configured to implement the method according to claim 10, for which it comprises drive means connected kinematically to the test, to the lenses of the Stokes lens and to the Stokes lens. , and which are operatively connected to said electronic control system to receive corresponding control commands generated by it, and in response to them carry out, automatically and controlled, said test displacement and said relative and global turns of the Stokes lens.

20.- Computer program, including program code instructions that when executed in a processor implement step c) of the method according to claim 7 or 8, automatically calculating the measurement of the posterior vertex diopter power of the astigmatic lens .

21. Computer program according to claim 20, which includes program code instructions that when executed in a processor carry out the automatic conversion of the measure of the posterior vertex diopter power of the obtained astigmatic lens, from the Fourier polar notation to a sphero-cylindrical notation, implementing the method of claim 11.

22. Computer program according to claim 20 or 21, which includes program code instructions that when executed in a processor automatically perform the inverse conversion of notations, from the spherical-cylindrical notation to the notation. Fourier polar, of the measurement of the posterior vertex diopter power of the astigmatic lens to position and mark, of the method of claim 13.