METHOD TO ESTABLISH THE SIZE OF THE DIFFERENT AREAS OF A PROGRESSIVE LENS

Abstract

Method to establish the size of the zones of near A.sub.c, far A.sub.L and intermediate A.sub.i vision of a progressive lens by generating, thanks to virtual reality, a gaze map of the user while following a stimulus in at least two planes at two different distances. Once the gaze maps have been made in those two planes or more, the area of each zone is calculated from the maximum horizontal and vertical amplitudes and the points of maximum frequency. In this way, the lens is adapted to the way a user looks.

Claims

1. A method to establish the size of zones of near A.sub.C, far A.sub.L and intermediate A.sub.I vision of a progressive lens, wherein the method comprises the following steps: a. generating a gaze map through the use of virtual reality in a near plane and a distant plane; b. calculating a maximum horizontal amplitude of each map in degrees, Δa.sub.L, Δa.sub.C; c. calculating a maximum vertical amplitude of each map in degrees Δb.sub.L, Δb.sub.C; d. determining the size of the far vision area A.sub.L in mm.sup.2 from an average of the maximum horizontal and vertical amplitude in the far plane (Δab.sub.L) following a linear relationship whose result for Δab.sub.L values between 10° and 80° is obtained according to the following relationship:
A.sub.L=i×Δab.sub.L+j, wherein i has values between 1.0 mm.sup.2/° and 1.4 mm.sup.2/° and j has values between 120 mm.sup.2 and 160 mm.sup.2; e. determining the size of the near vision area (A.sub.C) in mm.sup.2 from the average of the maximum amplitude in horizontal and vertical in the near plane (Δab.sub.C.sup.) following a linear relationship whose result for values of Λab.sub.C between 10° and 80° is obtained according to the following relationship:
A.sub.C=k×Δab.sub.C+l, wherein k has values between 0.15 mm.sup.2/° and 0.25 mm.sup.2/° and wherein 1 has values between 20 mm.sup.2 and 30 mm.sup.2; f. determining the size of the intermediate vision area A.sub.1 in mm2 from the angle formed by the points of maximum frequency in each plane, PM.sub.L and PM.sub.C with the origin of coordinates βPM.sub.LC following a linear relation whose result for βPM.sub.LC values between 0° and 18° is obtained according to the following relationship:
A.sub.1=m×βPM.sub.LC+n wherein m has values between 0.5 mm.sup.2/° and 1.5 mm.sup.2/° and n has values between 15 mm.sup.2 and 30 mm.sup.2, and wherein steps b-f are performed by a processor.

2. The method according to claim 1, wherein i has a value of 1.2 mm.sup.2/° and j has a value of 140 mm.sup.2.

3. The method according to claim 1, wherein k has a value of 0.02 mm.sup.2/° and 1 has a value of 25 mm.sup.2.

4. The method according to claim 1, wherein m has a value of 1.0 mm.sup.2/° and n has a value of 23 mm.sup.2.

5. A method for manufacturing a progressive lens, the method comprising delimiting the size of the areas of the near A.sub.C, far A.sub.L and intermediate A.sub.I vision zones, wherein said size is calculated according to of the the method of claim 1.

6. A computer program product comprising program code which, when loaded into a processor, causes said program code to execute the method of claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] In order to help a better understanding of the features of the invention and to complement this description, the following figures are attached as an integral part thereof, the nature of which is illustrative and not limiting.

[0033] FIG. 1: schematic representation of the zones of a progressive lens.

[0034] FIG. 2: graphical representation of the areas of a progressive lens calculated from the astigmatism and addition values (diamonds: far vision zone; circles: intermediate vision zone; squares: near vision zone; gray: zones 4 and 5 without clear vision). The cross shows the location of the fitting cross point. The dot shows the location of the NRP.

[0035] FIG. 3: diagram of the test where the position of the user is seen with respect to the coordinate system, and the two planes with the stimulus path, in dashed line. D.sub.R is the gaze point of rest.

[0036] FIG. 4: graphic representation of the vertical and horizontal amplitudes Δa and Δb of a gaze dynamics map. The different intensities of gray show the values of frequency of use.

[0037] FIG. 5: diagram of the relative position of the frequency maps and the points (PM.sub.L y PM.sub.C) of maximum frequency in far and near projected on the plane of the lens, as well as the angle (βPM.sub.LC) formed by these two points with respect to the coordinates origin.

DETAILED DESCRIPTION

[0038] For each user, the following sequence of steps is followed: [0039] 1 Protocol to ensure the correct fit of a virtual reality glasses to the users head (adjustment of fastening straps, correct position of the glasses in front of the eyes, etc). [0040] 2. Transfer of the patient to the virtual space where the test will be performed. It is a relaxed and distraction-free environment. [0041] 3. Preparation of the patient to ensure a natural position of the back and neck. [0042] 4. The patient is asked to look at infinity and the tilt of the head relative to the ground is recorded as their Resting Position and the patient's gaze direction relative to the ground as the Direction of Rest (D.sub.R). [0043] 5. A Cartesian coordinate system is defined with the origin (0,0,0) at the midpoint of the vector joining the users pupils. The xy plane is defined parallel to the ground and the z axis perpendicular to the ground. A vector is defined that has the origin of the coordinate system as its origin and has the direction of rest (D.sub.R) as its direction. It is defined that the xz plane contains this vector [0044] 6. The Far Zone is defined as the portion of the plane parallel to yz with a value of x corresponding to the far distance for which the Far Area (A.sub.L) of the progressive lens is to be adjusted (for example, 5 meters or more for a multipurpose progressive lens) and having a horizontal size of at least 100° and a vertical size of at least 80°. These angles are measured from the origin of coordinates (0 m, 0 m, 0 m). [0045] 7. The Near Zone is defined as the portion of the plane parallel to yz with a value of x corresponding to the near distance for which the Near Area (A.sub.C) of the progressive lens is to be adjusted (for example, 0.4 meters for a multipurpose progressive lens) and having a horizontal size of at least 100° and a vertical size of at least 80°. These angles are measured from the origin of coordinates (0 m, 0 m, 0 m). [0046] 8. A stimulus appears on the Far Zone of the virtual space located at the point of intersection between this zone and the resting gaze vector D.sub.R. The stimulus can be a flying object such as a bird, an insect, a drone, etc. [0047] 9. The stimulus moves over the Far Zone following a predetermined path with a homogeneous time distribution in all its portions. The linear velocity of the stimulus will be set between 0.2 m/s and 0.6 m/s, preferably 0.4 m/s. The virtual reality device records eye and head movements as the patient follows the stimulus with his/her gaze. [0048] 10. At the end of the path established over the Far Zone, the stimulus moves to the Near Zone and makes a path analogous to that of the Far Zone, covering the same opening angle and at an equivalent angular speed. The virtual reality device records eye and head movements. [0049] 11. End of test and registration. [0050] 12. The device calculates and shows the gaze dynamics map in each plane to the patient.

[0051] With the recording of head and eye movements in each plane (FIG. 3), a map of frequency of use of the lens plane can be calculated when the stimulus is in the far plane and another map when it is in the near plane.

[0052] Consequently, two gaze dynamics or frequency of use maps will be generated, one for each distance. The following parameters will be extracted from each of these maps (FIGS. 4 and 5): [0053] Δa.sub.L: maximum horizontal amplitude of the far map in degrees (FIG. 4). [0054] Δb.sub.L: maximum vertical amplitude of the far map in degrees (FIG. 4). [0055] Δab.sub.L: average value in degrees of the maximum horizontal amplitude Δa.sub.L and maximum vertical amplitude Δb.sub.L of the far map. [0056] Δa.sub.C: maximum horizontal amplitude of the near map in degrees (FIG. 4). [0057] Δb.sub.C: maximum vertical amplitude of the near map in degrees (FIG. 4). [0058] Δab.sub.C: average value in degrees of the maximum horizontal amplitude Δa.sub.C and maximum vertical amplitude Δb.sub.C of the near map. [0059] PM.sub.L: point of maximum frequency of use of the lens plane when the stimulus is in the far plane. If there is more than one point with the same maximum frequency value, a point having as horizontal coordinate the average of the horizontal coordinates of the maximum points found, and as vertical coordinate the average of the vertical coordinates of the maximum points found (FIG. 5). [0060] PM.sub.C: point of maximum frequency of use of the lens plane when the stimulus is in the near plane. In the event that there is more than one point with the same value of maximum frequency, a point having as horizontal coordinate the average of the horizontal coordinates of the maximum points found, and as vertical coordinate the average of the vertical coordinates of the maximum points found (FIG. 5). [0061] βPM.sub.LC: angle formed by PM.sub.L y PM.sub.C points with the origin of coordinates (FIG. 5).

[0062] Thus, a total of 9 parameters are obtained for each user.

[0063] The areas of a progressive lens are defined as: [0064] A.sub.I (intermediate vision area or “intermediate vision clear zone”): area in mm2 in the intermediate zone where the value of astigmatism is less than 0.50, and the value of the mean power is greater than +0.25 D of the far target power value and the average power value is less than 85% of the target value of the addition.

[0065] The size of the intermediate vision area (A.sub.I) in mm2 of the progressive lens will be determined from the angle formed by the PM.sub.L and PM.sub.C points with the origin of coordinates (βPM.sub.LC), expressed in degrees (°), following a linear relationship for βPM.sub.LC values between 0° and 18° according to the following relationship:

A.sub.I=m×βPM.sub.LC+n

wherein m has values between 0.5 mm.sup.2/° and 1.5 mm.sup.2/°, preferably 1.0 mm.sup.2/° and n has values between 15 mm.sup.2 and 30 mm.sup.2, preferably 23 mm.sup.2.

[0066] A.sub.L (far vision area or “far vision clear zone”): area in mm.sup.2 in the far zone where the astigmatism value is less than 0.50 D and the mean power value is less than +0.25 D of the target far power value. In the upper part, the area limits 8 mm above the pupil position (known as the fitting cross or segment). The lower part limits 4 mm below the pupil at the point known as PRP.

[0067] The size of the far vision area (A.sub.L) in mm2 of the progressive lens will be determined from the average of the maximum horizontal and vertical amplitude of the gaze dynamics map in the far plane (Δab.sub.L), expressed in degrees (°), following a linear relationship for Δab.sub.L values between 10° and 80° according to the following relationship:

A.sub.L=i×Δab.sub.L+j

[0068] Wherein i values are between 1.0 mm.sup.2/° and 1.4 mm.sup.2/°, preferably 1.2 mm.sup.2/° and j values are between 120 mm.sup.2 and 160 mm.sup.2, preferably 140 mm.sup.2.

[0069] A.sub.C (near vision area or “near vision clear zone”): area in mm.sup.2 in the near zone where the astigmatism value is less than 0.50 D and the mean power value is greater than 85% of the target value of addition. At the bottom, the area limits 2 mm below the near reference point (known as the Near Reference Point or NRP).

[0070] The size of the near vision area (A.sub.C) in mm.sup.2 of the progressive lens will be determined from the average of the maximum horizontal and vertical amplitude of the gaze dynamics map in the near plane (Δab.sub.C), expressed in degrees (°), following a linear relationship for Δab.sub.c values between 10° and 80° according to the following relationship:

A.sub.C=k×Δab.sub.C+l

wherein k values are between 0.15 mm.sup.2/° and 0.25 mm.sup.2/°, preferably 0.20 mm.sup.2/° and where l values are between 20 mm.sup.2 and 30 mm.sup.2, preferably 25 mm.sup.2.

[0071] By virtue of the method of the invention it is possible to design a lens whose areas are specially adapted to the dynamics of the users gaze.

[0072] In view of this description and figures, the person skilled in the art will be able to understand that the invention has been described according to some preferred embodiments thereof, but that multiple variations can be introduced in said preferred embodiments, without exceeding the object of the invention as claimed.