Classifications

• • 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
  • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive

Definitions

• the invention relates to a method for the manufacture of a pair of spectacle glasses for improving visual acuity in patients with keratoconus not corrected with contact lenses or corrected with hard or soft contact lenses.
• Keratoconus is an eye condition in which a part of the cornea which is partly in front of the pupil slowly becomes thinner and a cone-shaped deformation (conus) forms at the site of this thinner part.
• the eye condition starts in puberty and can be progressive until the age of 40. Keratoconus occurs in both eyes but is asymmetrical in gradation. Keratoconus is estimated to occur in one out of 1,500 persons.
• a keratoconus patient's first symptom is blurred and/or double vision with one eye. With normal refraction with spherical and cylindrical lenses, it is often not possible to correct the blur and the shadowy double images.
• the best way to correct the visual deficit in keratoconus is with hard contact lenses. Hard contact lenses generally give better correction in keratoconus than a pair of glasses.
• Hard contact lenses can be corneal, scleral or hybrid contact lenses.
• One of the symptoms of uncorrected optics with keratoconus is that when looking at optotypes on a letter chart, a typical orientation-specific shadow formation occurs at the inferior part. After correction with glasses or soft contact lenses, this shadow formation at the inferior part of the optotypes remains unchanged. After correction with a hard contact lens, the keratoconus patient has better vision; a smaller typical orientation-specific shadow formation now occurs at the top of the letters.
• the typical orientation-specific shadow formation on optotypes in the uncorrected keratoconus patient is caused by the fact that the wavefront is deflected more strongly at the location of the conus (see Figure 1).
• the shadow that occurs after correction with a hard contact lens at the superior part of the letters is caused by the light at the location of the conus travelling a shorter path in comparison with the path of the light in the rest of the pupil (see Figure 2).
• the path of a wavefront that passes the optical elements of the eye is measured with aberrometry.
• Zernike polynomials are mathematical representations that describe the errors of the wavefront.
• Tilt, coma, secondary astigmatism, trefoil and tetrafoil are polynomials that characteristically occur in patients with keratoconus.
• kits with higher order aberration contact lenses and methods of use is known from US8894208A.
• This kit of contact lenses comprises two or more contact lenses with a known higher order aberration for each given lens power.
• the higher order aberration may comprise spherical aberration, a coma aberration or a trefoil aberration.
• a specialist selects a fitting lens from the kit and applies the fitting lens to the eye of the patient and measures a residual higher order aberration of the lens- eye system. If the residual higher order aberration exceeds a predetermined magnitude, the specialist selects a second fitting lens from the kit, applies the second fitting lens to the eye of the patient and measures the residual higher order aberration of the lens-eye system. This is repeated until the fitting lens is found that yields the best results.
• a wavefront corrected lens is known that is obtained from measurements with an aberrometer.
• Zernike polynomials By making use of the Zernike polynomials, it is possible to apply the unique patient-related wavefront to the anterior of the lens using lathe-cut technology.
• a specialist selects a fitting lens from the fitting set or measures over the already fitted lens, with which the wavefront of the patient is established.
• the uncorrected higher order aberrations are added as optical correction to the already present basic power.
• the disadvantage of this system is that the patient has no control over the visual end result; it ignores the adaptation of the patient and the capacity for binocular summation.
• An objective of the invention is to provide a method for obtaining a pair of spectacle glasses for the improvement of visual acuity in patients with keratoconus not corrected with contact lenses or corrected with hard or soft contact lenses, whereby it is not necessary to use an aberrometer or adaptive optics.
• the method according to the invention is characterized in that it comprises the following steps:
• each fitting glass has a positive strength in increasing segment strength and the remaining part has a strength equal to zero and in patients in which keratoconus is not corrected or corrected with soft lenses of each fitting glass one segment has a negative strength In incremental segment strength and the remaining part has a strength equal to zero, which segment is located on the underside of the fitting glass,
• the most effective fitting glass from the set of fitting glasses for the eye with the least amount of keratoconus by applying different fitting glasses of the set of fitting glasses according to the normal rules of the subjective refraction one by one to that eye, while the patient looks with both eyes to a reference object, whereby the most effective fitting glass is the fitting glass for that eye regarding which the patient says that they can see best with it,
• the most effective fitting glass from the set of fitting glasses for the eye with the highest degree of keratoconus by applying different fitting glasses of the set of fitting lenses according to the normal rules of the subjective refraction one by one to that eye, while the patient looks with both eyes at the optotypes, and the most effective fitting lens determined earlier is applied in front of the eye with the least amount of keratoconus, whereby the most effective fitting lens is the fitting lens for the eye with the highest degree of keratoconus regarding which the patient states that they can see best with it,
• the axis of the segment can be determined
• spectacle glasses manufactured in a manner as described above achieve a greater improvement of vision than if the spectacle glasses have only spherical and cylindrical strengths.
• Corrections resulting from unilateral measurements with the aid of an aberrometer or adaptive optics take no consideration of adaptation and binocular summation with which the visual acuity is improved by combining information originating from the left and right eyes.
• determining the right spectacle glasses is not based on aberrometry, but on subjective refraction, bearing in mind adaptation and binocular summation.
• the amount of correction of higher order aberrations is subjectively determined and is not based on measurements made with an aberrometer, but on characteristic wavefront patterns in patients with keratoconus.
• the invention also relates to a pair of spectacle glasses manufactured by the method according to the invention.
• the invention relates to a set of fitting glasses for the improvement of visual acuity in patients with keratoconus corrected with corneal, hybrid or scleral contact lenses.
• the set of fitting glasses is characterized in that the set of fitting glasses comprises more than two fitting glasses whose segment has a negative strength and the remaining part has a value of zero, which segment is at the bottom of the fitting glass, with the strength of the segment of the pass glasses differing from one another. It has been found that the visual acuity of a keratoconus patient can be improved with a fitting glass with a suitable sector-specific power.
• a suitable fitting glass can be found for every patient or at least almost every patient. It is noted that a sector with a rounded point has to be understood as belonging to the sector shape referred to above, or a sector that is centred or inclined in order to compensate for the centring or inclination of the contact lens on the eye.
• a further embodiment of the set of fitting glasses according to the invention is characterized in that the sector extends over an angle between 10 and 180 degrees. Preferably, the sector extends over an angle between 60 and 120 degrees and it is even more preferable that the sector be a quadrant.
• Figure 1 shows a typical wavefront of the uncorrected vision of a patient with keratoconus
• Figure 2 shows a typical wavefront of a patient with keratoconus corrected with a hard contact lens
• Figure 3 shows an embodiment of a fitting glass of the set of fitting glasses according to the invention.
• Figure 1 shows a typical wavefront of the uncorrected optics of a patient with keratoconus.
• a part 5 of the cornea 1 of the eye that is located partly in front of the pupil 3 is thinner and forms a cone-shaped projection.
• the shaded part 7 in the inferior part of the pupil 3 of the keratoconus patient represents a more negative power.
• Figure 2 shows a typical wavefront of a patient with keratoconus corrected with a hard contact lens 9.
• the shaded part 10 in the inferior part of the pupil 3 of the keratoconus patient represents a more positive power.
• Figure 3 shows an embodiment of a fitting lens of the set of fitting lenses according to the invention.
• the fitting glass 1 1 has a quadrant 13 with a positive power and the remaining part 15 of the front optics is piano (ie strength equal to zero). This quadrant is located at the underside of the fitting glass.
• a number of such fitting glasses of which the powers of the quadrants differ from each other through increasing power form a set that is used to correct of aberrations resulting from correction with hard contact lenses in patients with keratoconus.
• the power of the quadrants of the fitting glasses of the set preferably form a series with a fixed ascending degree of difference.
• the set of fitting glasses is made of fitting glasses with a positive strength segment on the underside and a strength of zero for the rest of the front.
• the strength of the segment of the fitting glasses increases 0.25 diopters from 0.25 diopters to 6.00 diopters.
• the procedure is as follows. First, it is determined which of the patient's eyes has the lowest degree of keratoconus. Then, for that eye, according to the normal rules of subjective refraction, first, the spherical value is determined with which the patient can see best, then the most effective fitting glass - the one with which the patient can see best - is determined from the set of fitting glasses by applying different fitting glasses of that set of fitting glasses one by one to that eye while the patient looks with both eyes at optotypes. Thereafter, this is repeated for the other eye of the patient.
• a spectacle glass is manufactured for each eye with a strength equal to that of the spherical fitting glass which is best seen with that eye and which has a segment with a strength equal to the sum of the strength of the segment of the selected most effective fitting glass for that eye and the strength of the spherical fitting glass that is best seen with that eye.
• the invention may, for example, also relate to a method for the manufacture of a pair of spectacle glasses for improving visual acuity in patients with keratoconus corrected with soft contact lenses instead of hard contact lenses. In that case, the sectors of the fitting glasses must have a more negative power.

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• Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
• Physics & Mathematics (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Eyeglasses (AREA)

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Citations (4)

• 2016
  • 2016-01-15 NL NL2016105A patent/NL2016105B1/nl active
• 2017
  • 2017-01-14 WO PCT/NL2017/050019 patent/WO2017123092A1/en active Application Filing
  • 2017-01-14 EP EP17717250.9A patent/EP3403137A1/de active Pending

Patent Citations (4)

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