Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/14—Eye parts, e.g. lenses, corneal implants; Implanting instruments specially adapted therefor; Artificial eyes
  • A61F2/16—Intraocular lenses
  • A61F2/1613—Intraocular lenses having special lens configurations, e.g. multipart lenses; having particular optical properties, e.g. pseudo-accommodative lenses, lenses having aberration corrections, diffractive lenses, lenses for variably absorbing electromagnetic radiation, lenses having variable focus
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/14—Eye parts, e.g. lenses, corneal implants; Implanting instruments specially adapted therefor; Artificial eyes
  • A61F2/16—Intraocular lenses
  • A61F2/1613—Intraocular lenses having special lens configurations, e.g. multipart lenses; having particular optical properties, e.g. pseudo-accommodative lenses, lenses having aberration corrections, diffractive lenses, lenses for variably absorbing electromagnetic radiation, lenses having variable focus
  • A61F2/1648—Multipart lenses
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/14—Eye parts, e.g. lenses, corneal implants; Implanting instruments specially adapted therefor; Artificial eyes
  • A61F2/16—Intraocular lenses
  • A61F2/1613—Intraocular lenses having special lens configurations, e.g. multipart lenses; having particular optical properties, e.g. pseudo-accommodative lenses, lenses having aberration corrections, diffractive lenses, lenses for variably absorbing electromagnetic radiation, lenses having variable focus
  • A61F2/1648—Multipart lenses
  • A61F2/1651—Multipart lenses comprising a telescope
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/08—Auxiliary lenses; Arrangements for varying focal length

Definitions

• the present invention relates to retinal image enlargement systems, used for optical correction of macular degeneration.
• Age-related macular degeneration is a condition of the macula, which spans the retina at the back of the eye. This degeneration corresponds to a loss of the activity of the rods of the retina located in the macula and causes the wearer to lose a large part of his visual acuity.
• near vision the affected person loses the ability to read; in far vision, walking becomes a difficult activity.
• US-A-4,666,446 proposes an intraocular implant for patients suffering from macular degeneration, intended to replace the lens.
• the implant has a first diverging part and a second converging part, superimposed or concentric in the figures.
• the converging part provides the patient with vision which is substantially identical to that which he had before replacing the lens with the implant, in other words vision without enlargement.
• the diverging part when combined with a lens outside the eye, forms a telescopic system and provides an enlarged image of a given object.
• US-A-4,932,971 proposes a solution for the treatment of patients with macular degeneration, who already have a bag implant.
• This document describes a lens provided with extensions, which are fixed on the peripheral part of a bag implant.
• the lens of this document is thus capable of being fixed in situ on a bag implant, previously implanted, without involving removing the bag implant or having haptics other than those of the existing implant.
• 21358PC 2 US-B-6 197 057 also proposes a system for correcting macular degeneration.
• This system uses an intraocular implant, which is placed in the eye in front of the lens or in front of a bag implant replacing the lens.
• the intraocular implant has a central zone of strong negative power and a peripheral zone without refractive effect on the light passing through it.
• the system provides normal vision in the absence of a lens outside the eye; in the presence of an external lens of high positive power, the system provides an enlarged image.
• the correction principle is therefore similar to that described in US-A-4,666,446.
• the intraocular implant has the shape of a prism and the system has the effect of redirecting the rays entering the eye to a part of the retina other than the macula, which is not affected by macular degeneration.
• WO-A-93 01765 and US-A-5,030,231 describe other systems for enlarging retinal images. These documents do not provide any indication of the size of the image task outside the system axis.
• US-A-5,532,770 describes a method and a device for evaluating the vision of a subject through an intraocular implant. It is mentioned that one can consider different positions of the implant in the eye. However, it is not suggested in this document that the different positions are different positions of the same implant, nor that one can take account of the modifications of the position of the implant in the same subject. On the contrary, this document mentions different implants, or different positions of the implant. It is advantageous to have as large a field of vision as possible in a retinal image enlargement system. In particular, the field of vision should allow easy reading. Another newly identified problem of prior art systems is that of sensitivity to set-up errors.
• the various components of the telescopic system - lens external to the eye and implant - have a high power.
• An offset or an angular shift (tilt) of the elements of the telescopic system can considerably reduce the field of vision and the characteristics of the system. This is all the more problematic since the implantation cannot guarantee a high positioning precision: independently of the implantation precision, the tissues evolve after the operation and can cause displacement of the implant.
• the system is intended for visually impaired patients with macular degeneration; these patients have often lost their fixing capacity, due to the loss of central vision, and generally use their peripheral vision without it being possible to guarantee that their eccentric gaze direction is stable. The patient's age can also make it difficult to take measurements for precise positioning of the outer lens.
• a retinal image enlargement system comprising: - an intraocular implant having a peripheral part and a central part of negative power, - a lens of positive power intended to be placed outside of the eye, the lens and the implant being adapted to produce in the fundus of the eye of a standard user an enlarged image of an object, in which, for a pupil of 1.5 mm in diameter, all point object in a field reading object produces in the back of the eye an image spot with a size between 20 to 50 ⁇ m, for a wavelength of the visible spectrum.
• any point object in a reading object field produced in the background of the 'eye an image spot with a size between 20 to 50 microns, for a wavelength of the visible spectrum.
• This condition can also be imposed for a variation in a range of ⁇ 5 °, or even in a range of ⁇ 10 °.
• any point object in a reading object field produces in the background of the eye an image spot of a size between 20 and 50 ⁇ m, for a wavelength of the visible spectrum.
• the lens has diffractive properties, for example obtained by modifying the profile of one of the surfaces of the lens.
• diffractive properties for example obtained by modifying the profile of one of the surfaces of the lens.
• any point object in a reading object field produces in the back of the eye an image spot with a size between 5 and 80 ⁇ m, for three wavelengths distributed in the visible spectrum.
• the three wavelengths distributed in the visible spectrum can be respectively chosen in the ranges from 400 to 500 nm, from 500 to 600 n and from 600 to 800 nm.
• the system may also have one or more of the following characteristics: - the lens is a Fresnel lens; 21358PC 4 - the central part of the implant is spherical; - The front face of the lens is a conical whose conicity is between 0 and -1, preferably between -0.2 and -0.6; - the system has a magnification of between 2 and 4; - the system has in the conditions of use a distance between the lens and the implant greater than or equal to 19 mm; - the reading object field is located at a distance of 25 cm from the lens and covers an angle of 10 °; - the reading object field is defined by an opening angle at the level of the retina of ⁇ 24 °.
• the invention also proposes, in another embodiment, a method for determining by optimization of a retinal image enlargement system, comprising
• the modification step is also carried out so that in the presence of a variation in the angular position of the lens with respect to the chosen wearing conditions, within a range of ⁇ 2 °, any point object in a field reading object produces in the back of the eye an image spot with a size between 20 to 50 ⁇ m, for a wavelength of the visible spectrum.
• This constraint can also be imposed for a variation of the angular position of the lens within a range of ⁇ 5 °, or even within a range of ⁇ 10 °. It is also possible that the modification step is carried out so that in the presence of an offset of the lens within a range of ⁇ 0.5 mm with respect to the chosen wearing conditions, any punctual object in an object field of reading produces in the back of the eye an image spot with a size between 20 to 50 ⁇ m, for a wavelength of the visible spectrum. This constraint can also be imposed for an offset of the lens in a range of ⁇ 1 mm, or even ⁇ 2 mm. It can also be imposed that the modification step comprises the application of diffractive properties to the lens.
• the modification step can be carried out so that in the presence of a variation in the angular position of the lens with respect to the chosen wearing conditions, within a range of ⁇ 5 °, any point object in a reading object field produces in the back of the eye an image spot with a size between 5 to 80 ⁇ m, for three wavelengths distributed in the visible spectrum.
• the modification step is carried out so that in the presence of a decentering of the lens within a range of ⁇ 1 mm relative to the chosen wearing conditions, any point object in a field object of reading produces in the back of the eye an image spot with a size between 5 to 80 ⁇ m, for three wavelengths distributed in the visible spectrum.
• the object field can be defined in the process as located at a distance of 25 cm from the lens and covering an angle of 10 °, or even be defined by an opening angle at the level of the retina of ⁇ 24 °.
• FIG 1 a diagram in view from above in section of an eye-lens optical system with an implant according to the invention
• - Figure 2 a schematic view in vertical section on a larger scale of the eye-lens system
• - Figure 3 a graph of the distance of the object field in reading as a function of the eye-eye distance in a system according to the invention and according to the state of the art
• - Figure 4 a graph of the size of the image spot in the object field of a system according to the invention compared to the image spot of a system according to the prior art
• - Figure 5 a graph corresponding to that of Figure 4, with an offset of the vene of 1 mm
• - Figure 6 a diagram in view from above in section of an eye-lens optical system with an implant according to the invention
• FIG. 1 shows a diagram of an eye-lens optical system according to the invention.
• the lens outside the eye is simply described hereinafter as “lens” or “vene”; similarly, the intraocular implant is simply designated by the word “implant” in the following description.
• the lens and the implant cause a magnification of the image projected on the back of the eye, like a telescope.
• the lens-implant assembly is therefore described in the following as a "telescopic system", even if it is not strictly speaking a telescope.
• 21358PC 6 There is shown in the figure an axis 2 corresponding to the primary direction of viewing. The axis 2 passes through the center of rotation 30 of the eye 4.
• the eye is shown diagrammatically; we recognize the cornea 6, the pupil 8, the retina 10, the lens or the bag implant 12 as well as an intraocular implant 14 according to the invention.
• the model proposed in Accommodation-dependent model of the human eye with aspherics, R. Navarro, J. Santamaria and J. Bescos, Vol. 2, No 8 / August 1985, Opt. Soc. Am. A. by replacing, if necessary, the lens with a bag implant.
• the figure also shows the lens 16 outside the eye.
• the lens is mounted in a spectacle frame, opposite the eye.
• the axis 2 cuts, the front face 18 of the lens, at a point which is generally situated 4 mm above the geometric center of the front face, when the vene is used both in far vision and in vision of close and for standard positioning of the frame.
• the vene is used only in near vision and it is advantageous that the axis 2 intersects the front face 18 directly on its geometric center.
• point O be the point of intersection of the rear face and axis 2.
• the tangent to the rear face 20 of the lens at point O forms with a vertical axis passing through the point O an angle called the pantoscopic angle.
• the tangent to the rear face of the lens at point O forms with an axis orthogonal to axis 2 an angle called a curve.
• the values of the distance between the point O and the center of rotation of the eye, the pantoscopic angle and the curve are called "bearing conditions".
• the choice of wearing conditions and of an eye model allows a complete modeling of the effects of an external lens and of an implant according to the invention.
• the vene is used only in near vision and it is advantageous that the pantoscopic angle and the curve are zero.
• the lens can be replaced by a bag implant and the characteristics of the bag implant can be taken into account. It is simpler to have an implant behind the pupil, as shown in Figure 1, when the lens is or has been replaced by a bag implant.
• a bag implant has a thickness of the order of a millimeter, which is less than the thickness of a natural lens, which is of the order of 4 millimeters.
• the intraocular implant 14 has a central zone 22 having a negative power and a peripheral zone 24.
• the central zone typically has a diameter of between 1.5 and 2 mm.
• the peripheral zone can have zero optical power.
• FIG. 1 schematically shows the focused rays 26 passing through the lens 16, the opening of the pupil 8 and the central area 22 of the implant. These rays participate in the formation on the retina of an enlarged image.
• FIG. 1 schematically shows the focused rays 26 passing through the lens 16, the opening of the pupil 8 and the central area 22 of the implant. These rays participate in the formation on the retina of an enlarged image.
• the invention proposes to define the characteristics of the intraocular implant 14 and the lens 16 by taking into account possible variations in the position of the lens relative to the nominal position of the lens in the system. It is based on the observation that patients with macular degeneration no longer have acuity in central vision and generally only have a weak residual acuity - less than 2/10 e - thanks to their peripheral vision. It is therefore not necessary that the image spot produced by the implant in the eye, in the presence of the external lens, be punctual.
• an acceptable degradation of the optical quality of the system at the center of the object field makes it possible to improve the optical quality of the system at the periphery of the object field, or to accept variations in the position of the lens with respect to its nominal position.
• the invention is based on the observation that in the type of telescopic system considered, the field of vision is very quickly limited by the optical quality of the system if the lens and the intraocular implant are not jointly and conectly optimized, what US-A-4 666 446, US-A-4 932 971 and US-B-6 197 057 do not offer. US-A-4 957 506 seeks very important optical quality, so that the system remains limited. in the field of vision.
• FIG. 2 shows a schematic view in vertical section on a larger scale of the eye-lens system.
• FIG. 2 shows the axis 2 of the main direction of gaze, the eye 4 with a schematic representation of the implant 14, a schematic representation of the lens 16, as well as the object field 32.
• d the distance between the front face of the implant and the rear face of the lens and d the distance between the object and the front face of the lens.
• Tolerances of the telescopic system are improved with respect to lens positioning defects. It is therefore advantageous that the wearing conditions considered use a distance between the lens and the center of rotation of the eye of the order of 33 mm, or even a distance between the lens and the eye of the order of 18 mm.
• a distance between the lens and the eye is considered to be greater than or equal to 15 mm under the conditions of use of the system; this corresponds to a lens-implant distance greater than or equal to 19.43 mm; a 19 mm lower terminal is suitable.
• This distance value is conventional for patients with low vision.
• the choice of the angle ⁇ is representative of a usual reading field ensuring comfort in reading; in fact, this value corresponds to a range of approximately 8 cm on the sheet which allows you to see a few words on the sheet, that is to say the part of the text on which the reader is concentrated at a given moment.
• Another solution consists in using a field defined at the level of the retina by an opening angle of ⁇ 24 °.
• the reasoning and the criteria remain valid.
• the image spot on all wavelengths can have a size greater than the size of the image spot for a given wavelength.
• the image spot in purple has a size similar to the image spot in red; however, the position of these image spots on the retina may be slightly offset, so that the image spot in purple and in red has a size greater than the respective sizes of image spots in purple and in red.
• the reasoning and the criteria therefore apply for any wavelength of the visible spectrum - but not necessarily for the image spot grouping together all the wavelengths of the visible spectrum.
• the telescopic system produces an image spot on the back of the eye.
• the image spot is defined as being twice the mean square deviation of the position of the light rays on the retina, for a beam of rays coming from a given object point covering a pupil of given size.
• Other means of defining the image spot provide equivalent results and the use of this ray tracing program is not an obligation.
• the position of the implant in front of the pupil does not change the definition of the image spot.
• the image spot has a size greater than or equal to 20 ⁇ m.
• This value reflects the fact that it is not necessary, due to the poor visual acuity of patients with macular degeneration, that the image spot be punctual.
• a separation power of 5 minutes of arc corresponding to an acuity of 2/10 e gives an image spot of 24 ⁇ m on the retina; it is therefore not necessary, given the visual acuity of the patients, for the image spot to have a size much smaller than this value, since the final resolution will be given by the retina.
• the image spot has a size less than or equal to 50 ⁇ m. This higher value is chosen for patient comfort.
• This image spot dimension prevents the patient from perceiving a deterioration in acuity. It is not necessary to measure the image spot for all of the possible positions of an object in the object field. For a system of revolution, it suffices to choose three or four points on a radius (semi-meridian); this solution remains valid for an aspherical system like that given in example below. It is advantageous that the image spot always remains in this range of values, even in the event of the lens 16 shifting from its nominal position on the axis 2, in a range of at least ⁇ 0.5 mm. It is also advantageous that the image spot always remains within this range of values, even in the event of an angular offset of the lens 16 relative to its position.
• the optical characteristics of the telescopic system are as follows. As explained above, the lens has positive power. A power greater than or equal to 15 diopters is advantageous for ensuring that the telescopic system has a magnification between 2 and 4. At least one of the faces of the lens can be aspherical.
• the implant has a central part with a strongly negative power; this power is typically less than -20 diopters, or even less than -60 diopters.
• magnification of the telescopic system between 2 and 4.
• a magnification of the telescopic system between 2 and 4 - preferably close to 3 - for a object field in a range of ⁇ 10 ° is suitable for patients little affected by macular degeneration.
• the system is simple to use and discreet. It ensures good reading comfort with a conect reading speed.
• the central part of the implant typically has one or more of the following characteristics: - a diameter between 1.5 and 2 mm; the lower value is sufficient for the contrast in the presence of the external lens to be greater than 0.25 for a pupil of 3 mm; the upper value of the diameter range ensures that, in the absence of the external lens, the patient retains a usable peripheral vision; - an absolute power value greater than or equal to 20 diopters; this value is chosen, taking into account the distances in the lens-eye system and the characteristics of the lens, to ensure the required magnification of the telescopic system; - spherical surfaces; the absence of aspherical surfaces in the central part of the implant facilitates the manufacture of the implant; This is possible because the optical performance of the system sought is not very important and adapted to the poor visual acuity of the patients.
• - a thickness in the center greater than or equal to 0.1 mm; this minimum value ensures the solidity of the implant; - a thickness at the edge less than or equal to 0.5 mm and a total optical diameter of 5 to 6 mm; this maximum value of thickness allows a careful implantation of the implant, while the value of the optical diameter ensures that the implant does not limit the entry of rays into the eye.
• the peripheral part of the implant extends around the central area. The total diameter of the implant is chosen so as to allow it to be positioned in the patient's eye, in front of the lens or of a bag implant replacing the lens, or even in front of the pupil, as explained above.
• the implant 21358PC 11 has an external optical diameter of 5 to 6 mm, with, if necessary, the haptics necessary to keep it in position in the patient's eye.
• the rear face of the central part of the implant is advantageously concave with a radius of between 3 and 5 mm, preferably a radius of 3.85 mm; This ensures that the telescopic system will be less sensitive to an offset or an angular offset of the implant for a magnification 3 of the telescopic system.
• the central thickness of the implant and the radius of the front face of the central part of the implant can advantageously be chosen (but this is not an obligation) depending on the possible residual ametropia of the patient.
• a radius of 4.40 mm and a thickness of 0.1 mm can be chosen for the implant.
• the peripheral part of the implant has no optical effect and the ametropia of the patient is corrected by the bag implant.
• the radius of the front surface of the implant can also be adapted to correct the effects of a patient's residual ametropia on the optimal reading distance of the system.
• a choice of radii between 3.8 and 5.5 mm makes it possible to correct the effects of a residual ametropia of the patient between -5 and +5 diopters, for a hydrophilic acrylic implant with an index of 1.460.
• the peripheral part of the implant is not aspherical, to facilitate the manufacture of the implant. This can be obtained by direct machining techniques or molding or others known per se for the manufacture of intraocular implants.
• the lens external to the eye may have the following characteristics.
• the lens has a power greater than or equal to 15 diopters; this value is adapted, taking into account the distance between the lens and the eye and taking into account the position of the reading object field, to ensure a magnification between 2 and 4.
• the lens has a thickness in the center less than 15 mm.
• K in the range [-1; 0] corresponding to an ellipse whose shape varies between a sphere and a parabola, and preferably in the range [-0.6; -0.2], for example K ⁇ -0.42 as proposed below.
• NMAX is the degree of aspherization and the coefficients K, are the coefficients of aspherization of higher order.
• the external lens can be tinted using filters commonly used in low vision vision to limit the glare effects commonly seen in people with AMD, but it is not a requirement.
• An example of a system according to the invention has the following characteristics.
• the magnification of the system is 3, for an implant corresponding to the model of the eye proposed above.
• the distance is 22.43 mm, which corresponds to an eye distance of 18 mm, and the distance d 2 is 25 cm.
• the object field is defined by an angle ⁇ of ⁇ 10 °.
• the lens is made of index 1.665 and has a thickness in the center of 9.5 mm.
• the rear face is concave spherical with a radius of 250 mm.
• the front face has a radius of curvature at the center R oSC of 25.28 mm and a coefficient of aspherization K of -0.42. With these characteristics, the lens has a power at the center of 24 diopters.
• the intraocular implant is of the kind shown in Figure 1 and is held behind the pupil and in front of a bag implant by haptics. It is spherical biconcave.
• the central part of the rear face has a radius of 3.85 mm.
• the radius of the front face and the thickness of the central part of the implant are given in the table below, according to the conection of ametropia which the peripheral part of the implant causes.
• FIG. 3 is a diagram of the reading distance in mm, as a function of the eye-eye distance in mm, in a system according to the invention and in a system according to the state of the art represented by US-A-4 957 506.
• the system of the example is provided for a nominal eye-eye distance of 18 mm; for this eye-to-eye distance, the reading field is located at a distance d 2 of 25 cm from the front face.
• FIG. 3 shows the necessary variations in the distance d 2 for the system to retain the same optical properties, as a function of the variations in the eye-eye distance.
• the figure shows that the reading distance of the system according to the invention remains between 18 and 43 cm (deviation from -7 cm to +18 cm), when the eye-eye distance varies between 14 and 21 mm (deviation from -4 mm to + 3mm).
• the graph in FIG. 3 shows the values calculated for a system according to US-A-4,957,506; the graph shows that this prior art system is much more sensitive to the position of the vene before the eye.
• Figures 4 to 6 are diagrams showing the characteristics of the proposed example, compared to the prior art described in US-A-4,957,506, in the table in column 5.
• Figure 4 gives the size of the image spot in the object field, as a function of the angle ⁇ in degrees. Specifically, for each angle value plotted on the abscissa axis, we considered a point in the object field and we plotted the size of the image spot, in ⁇ m. The figure shows in dark lines the values obtained in the system of the invention and in unbroken lines the values of the state of the art. It can be seen that the image spot has a size of between 20 and 40 ⁇ m for all the points of the object field in the system of the invention.
• the size of the image spot in the center is zero.
• the image spot size exceeds 40 ⁇ m for an angle value of around 5 ° and exceeds 100 ⁇ m for an angle value of around 7.5 °.
• the prior art system is too efficient compared to the acuity of the wearer; when one deviates from the axis, the performance of the system decreases rapidly and the reading field is therefore narrow.
• the invention by accepting a degradation in optical performance on the axis, ensures a wider field of vision.
• Figures 5 and 6 illustrate the effect of a lens positioning defect, relative to the nominal position.
• Figure 5 is similar to Figure 4, but the lens is offset from the axis by a distance of 1 mm.
• the figure shows that the size of the image spot of the system of the invention remains between 20 and 50 ⁇ m over the whole of the object field.
• the prior art system has an image spot size which greatly exceeds 70 ⁇ m on either side of the optical axis.
• the decentering of the lens does not cause loss of optical performance in the field of vision in reading; conversely, in the prior art system, an offset of 1 mm causes a reduction of more than a third of the amplitude of the field of vision.
• Figure 6 is similar to Figure 4, but the lens is rotated relative to the axis, by an angle of 5 °.
• the figure shows that the size of the image spot of the system of the invention remains between 20 and 50 ⁇ m over the whole of the object field.
• the prior art system has an image spot size which exceeds 100 ⁇ m on the object field, on either side of the optical axis.
• a rotation of the lens in the system of the invention does not cause loss of optical performance in the field of vision in reading; conversely, in the prior art system, a 5 ° rotation of the lens causes a reduction of almost a quarter of the amplitude of the field of vision.
• a retinal magnification system which is not very sensitive to variations in the position of the external lens, relative to the nominal position.
• An example of a system according to the invention has been given as well as ranges of values of the various characteristics of the system.
• Other embodiments of the invention can be obtained by optimizing the surfaces of the lens and the implant. Optimization can be carried out in a manner known per se, using software such as that marketed under the brand Code V by the company ORA (Optical Research Associates).
• - we choose a standard eye model, or, for a custom definition, we determine the characteristics of the wearer's eye; - the conditions for wearing the lens are chosen, either for a standard wearer or tailor-made for a given wearer; - a back face of the implant and lens is chosen, for example with the values proposed above; - Consider a thickness and a starting front face for the lens and for the implant, to ensure on the axis a reasonable image spot, the magnification and a reading distance dl desired; - constraints are set on the system, corresponding to the magnification and the reading distance dl desired; - constraints are fixed, corresponding to image spot sizes for several points distributed in the object field; - The shape and thickness of the front faces of the lens and the implant are varied to get closer to the targets.
• FIG. 7 shows a view similar to that of FIG. 1, for another embodiment of the invention.
• the system of Figure 7 differs from that of Figure 1 in that the lens or vene 40 is a Fresnel lens.
• the front face 42 of the lens therefore has the conventional form of a Fresnel lens, with concentric zones.
• the solution of FIG. 7 makes it possible to limit the thickness of the lens: compared with the example proposed above of a lens having a thickness at the center of 9.5 mm, the solution of FIG. 7 makes it possible to provide a same power at the center of 24 diopters, with a thickness of about 2 mm.
• the same material and the same aspherization of the front face are kept.
• the radii of the Fresnel lens can be determined in a manner known per se; we can for example consider the following values: - thickness at the center of the Fresnel lens: 2 mm - jump value: 1 mm.
• the material of the lens of FIG. 1 has an index of 1.665 and an Abbe number of 31.
• the size of the image spot is between 20 and 50 ⁇ m , as explained above.
• the size of the image spot for a point in object space can reach 300 ⁇ m, in particular at the edge of the field.
• a material with an index 1.502 and an Abbe number of 58 can be used in place of this material, such as the material sold under the mark CR39 by the company PPG Industries, Pittsburgh, USA.
• the property of an image spot is kept between 20 and 50 ⁇ m for a wavelength; however, the size of the image spot for a point in object space, over all the wavelengths of the visible spectrum, then becomes less than 150 ⁇ m, which significantly reduces the discomfort linked to the chromatism of the system.
• the lens has diffractive properties.
• the lens then has surface and / or index variations close to the transmitted wavelengths. 21358PC 17
• ⁇ 546 nm.
• ⁇ 546 nm.
• Such diffractive properties make it possible to limit the chromatism of the system.
• These diffractive properties advantageously have a symmetry of revolution, like the rest of the magnification system. The system as a whole then presents a symmetry of revolution, which avoids favoring part of the field of vision.
• This element can be applied or provided on the front face or on the rear face of the lens of FIG. 1, or also on the rear face of the lens of FIG. 7.
• An example is given below in a configuration similar to that of FIG. 1.
• the lens consists of a material with an index of 1.665 and an Abbe number of 31, as in the example in FIG. 1.
• the rear face 20 is concave spherical radius 150 mm.
• the thickness in the center is 9.5 mm
• the implant is spherical biconcave, with a rear face with a radius of 3.85 mm; the radius of the front face and the thickness at the center of the implant depend on the corrected ametropia. For zero ametropia, we consider for example a front face of radius 4,986 mm and a thickness in the center of 0.1 mm.
• the system has, for any wavelength in the visible range, a focal spot size of less than 50 ⁇ m for any point object in the reading object field.
• a focal spot size of less than 50 ⁇ m for any point object in the reading object field.
• the focal spot of a point object in the object reading field for three wavelengths thus chosen a size of 20 to 50 ⁇ m is obtained.
• the size of the focal spot obtained for three wavelengths is calculated, as proposed above, using the mean square deviation. Therefore, the value of the focal spot for three wavelengths is not a simple function of the three values of focal spot for the three wavelengths considered.
• FIG. 8 shows a graph similar to that of FIG.
• FIG. 4 shows a graph similar to that of FIG.
• FIG. 9 shows the example of an offset of the lens by 1 mm.
• We 21358PC 19 notes on the graph that the size of the focal spot remains between 5 and 80 ⁇ m, for each of the wavelengths considered as for light at these three wavelengths.
• FIG. 10 shows a graph similar to that of FIG. 6, giving the sizes of the focal spots for the wavelengths ⁇ ⁇ ⁇ 2 and ⁇ 3 , for these three wavelengths as well as the size of the focal spot in the prior art system described in US-A-4,957,506.
• Figure 10 shows the example of an angular offset of the lens by 5 °. As in the example in FIG. 9, it can be seen on the graph that the size of the focal spot remains between 5 and 80 ⁇ m, for each of the wavelengths considered as for light at these three wavelengths.
• Figure 11 is a graph similar to that of Figure 8; the size of the focal spot calculated for the three wavelengths ⁇ ls ⁇ 2 and ⁇ 3 is plotted on the graph in the system having diffractive properties given by way of example. The size of the focal spot calculated for these three wavelengths in the system of document US Pat. No. 4,957,506 is also shown in solid lines on the graph. The comparison of FIG. 8 and of FIG.
• the diffractive properties of the lens can be determined by optimization, according to the principles set out above. We can first optimize the lens and the implant, without particular diffractive properties to obtain a system close to the desired solution, then optimize the system again by integrating the diffractive properties. In doing so, the properties of the lens initially obtained will be significantly modified. Alternatively, the lens can be optimized by integrating the diffractive properties from the start.
• the invention is not limited to the preferred examples given above. We could use other wearing conditions than those proposed by way of example; we could also use another model for the eye. It is also possible to use other optimization methods than those proposed.

Landscapes

• Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
• General Health & Medical Sciences (AREA)
• Vascular Medicine (AREA)
• Animal Behavior & Ethology (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Transplantation (AREA)
• Cardiology (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Prostheses (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=34355473

Family Applications (1)

Country Status (7)

Families Citing this family (11)

Family Cites Families (16)

• 2003
  • 2003-10-14 FR FR0312009A patent/FR2860706B1/fr not_active Expired - Fee Related
• 2004
  • 2004-10-12 AU AU2004281565A patent/AU2004281565B2/en not_active Ceased
  • 2004-10-12 JP JP2006534785A patent/JP2007508088A/ja not_active Ceased
  • 2004-10-12 WO PCT/FR2004/002581 patent/WO2005037145A1/fr active Application Filing
  • 2004-10-12 EP EP04817214A patent/EP1677707A1/de not_active Withdrawn
  • 2004-10-12 CA CA002542615A patent/CA2542615A1/en not_active Abandoned
• 2006
  • 2006-04-13 US US11/404,491 patent/US20060247766A1/en not_active Abandoned
• 2010
  • 2010-08-05 JP JP2010176215A patent/JP4902895B2/ja not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events