Method for determining a filter for an ophthalmic lens and ophthalmic lens comprising such a filter

Abstract

Disclosed is a method for determining a filter for an ophthalmic lens to be placed in front of the eye of the wearer, the filter being able to improve or maintain the visual comfort and/or the visual performances of the wearer. The determination method includes: a step of measuring a variable representative of sensitivity of the eye or both eyes of the wearer to a characteristic light flow, and a step of determining at least one optical characteristic of the filter according to the representative variable measured.

1 . A method for determining a filter for an ophthalmic lens intended to be placed in front of the eye of a wearer, said filter being able to improve or to maintain the visual comfort and/or visual performance of said wearer, the method comprising:
 a step of measuring a quantity representative of a sensitivity of an eye or of both eyes of the wearer to a characteristic light flux, and a step of determining at least one optical characteristic of said filter depending on the measured representative quantity.   
     
     
         2 . The method as claimed in  claim 1 , wherein said quantity representative of the sensitivity of the eye of the wearer to said characteristic light flux corresponds to a sensitivity to glare of said wearer. 
     
     
         3 . The method as claimed in  claim 1 , wherein said quantity representative of the sensitivity of the eye of the wearer to said characteristic light flux is chosen from at least one of the following quantities:
 an objective physiological measurand of the wearer,   an objective physical measurand of the wearer,   a subjective measurand related to the perception or to the expression of the wearer.   
     
     
         4 . The method as claimed in  claim 1 , wherein said quantity representative of the sensitivity of the eye of the wearer to the characteristic light flux is chosen from at least one of the following quantities:
 the intraocular scattering coefficient of the eye of the wearer,   the density of the macular pigment of the eye of the wearer,   the expressed or measured maximum variation in visual comfort and/or visual performance.   
     
     
         5 . The method as claimed in  claim 1 , wherein said step of measuring the quantity representative of the sensitivity of the eye of the wearer to the characteristic light flux comprises:
 a step of subjecting the wearer to said characteristic light flux, and   a step of characterizing said characteristic light flux,   the measurement of said representative quantity being carried out on the wearer subjected to said characteristic light flux.   
     
     
         6 . The method as claimed in  claim 1 , wherein said step of measuring the quantity representative of the sensitivity of the eye of the wearer to the characteristic light flux comprises:
 a step of subjecting the wearer to a questionnaire allowing the sensitivity of the wearer to said characteristic light flux to be assessed,   a step of collecting the responses of the wearer to said questionnaire,   the measurement of said representative quantity being carried out on the basis of said responses of the wearer to the questionnaire.   
     
     
         7 . The method as claimed in  claim 5 , wherein the step of characterizing said characteristic light flux consists in measuring at least one of the following quantities:
 the spatial distribution of said characteristic light flux,   the angular distribution of said characteristic light flux,   the spectrum of said characteristic light flux,   the intensity of said characteristic light flux.   
     
     
         8 . The method as claimed in  claim 1 , wherein said at least one determined optical characteristic of the filter consists of:
 the absorption coefficient of said filter,   the spectral response of said filter,   the spatial distribution of these characteristics over said ophthalmic lens.   
     
     
         9 . The determining method as claimed in  claim 1 , furthermore including a step of evaluating the impact of said characteristic light flux on the visual performance of the wearer, in which step at least one of the following measurements is carried out on the wearer:
 visual acuity,   contrast sensitivity,   visual field,   color perception,   distance perception,   eyelid movement,   pupil diameter,   visual discomfort on a discomfort scale, and   recovery time post-glare.   
     
     
         10 . The method as claimed in  claim 9 , wherein the measurement of said quantity representative of the sensitivity of the eye of the wearer to said characteristic light flux is carried out by means of a test filter placed in front of the eye of the wearer, the absorption coefficient and/or the spectral response of which is made to vary. 
     
     
         11 . The determining method as claimed in  claim 4 , wherein the quantity representative of the sensitivity to the characteristic light flux of the eye of the wearer is determined depending on the intraocular scattering coefficient measured at various wavelengths and wherein the absorption coefficient and/or the spectral response of the filter is adjusted depending on said intraocular scattering coefficient. 
     
     
         12 . The method as claimed in  claim 1 , wherein the selective attenuation of the filter is proportional to the quantity representative of the sensitivity to the characteristic light flux of the eye of the wearer. 
     
     
         13 . The method as claimed in  claim 1 , wherein said optical characteristic of the filter is also determined depending on an indicator of the light flux and/or visual need to which the wearer will be subject in his activities. 
     
     
         14 . The determining method as claimed in  claim 4 , wherein the quantity representative of the sensitivity of the eye of the wearer to the characteristic light flux is determined depending on the density and/or distribution of the macular pigment. 
     
     
         15 . The method as claimed in  claim 14 , wherein, in the determining step, the spectral response of the filter is determined as being in accordance with the absorption curve of the macular pigment as a function of wavelength. 
     
     
         16 . The method as claimed in  claim 14 , wherein, in the step of determining the filter, the spectral response of the filter is determined so that the system formed by the filter and the eye of the wearer has a spectral transmittance close to the spectral transmittance of a reference eye. 
     
     
         17 . The method as claimed in  claim 1 , wherein, in said determining step, the absorption coefficient of the filter and/or the spectral response of the filter is determined, so that, when the wearer is subjected to a predetermined light flux, the retinal illuminance E ret  received by the eye of the wearer is lower, at at least one wavelength, than a retinal illuminance threshold beyond which the visual comfort and/or the visual performance of said wearer is/are degraded. 
     
     
         18 . The method as claimed in  claim 4 , wherein, the quantity representative of the sensitivity to the flux of the eye of said wearer including the density of the macular pigment, the following rules are applied to determine the filter depending on the result of the measurement of the density of the macular pigment:
 if the density of the macular pigment is lower than 0.2: the spectral response of the filter is in accordance with the curve of the absorption of the macular pigment as a function of wavelength, said filter having at a wavelength of 460 nanometers a maximum absorption coefficient equal to 40%,   if the density d of the macular pigment is higher than 0.2: the spectral response of the filter is in accordance with the absorption curve f(λ) of the macular pigment as a function of wavelength λ, the absorption coefficient A(λ) of said filter at the wavelength X being such that: A(λ)=(1−d)*f(λ).   
     
     
         19 . The method as claimed in  claim 4 , wherein the quantity representative of the sensitivity to the flux of the eye of the wearer is the retinal illuminance E ret (λ) as a function of wavelength and wherein the method includes a step of determining the comfortable retinal illuminance E Comfort (λ) of said wearer as a function of wavelength and, when said retinal illuminance E ret  is higher than said comfortable retinal illuminance E Comfort  at at least a plurality of wavelengths, the filter is determined by its spectral response F(λ) which is then equal to the product of a predetermined constant α and the ratio of the comfortable retinal illuminance E Comfort (λ) to the retinal illuminance E ret (λ) of said wearer without filter, i.e. F(λ)=α×(E Comfort (λ)/E ret (λ)). 
     
     
         20 . A filter for an ophthalmic lens intended to be placed in front of the eye of a wearer, said filter being determined by virtue of the method as claimed in  claim 1 , so as to improve or to maintain the visual comfort and/or visual performance of said wearer. 
     
     
         21 . The filter as claimed in  claim 20 , said filter being an electrochromic or photochromic active filter. 
     
     
         22 . The filter as claimed in  claim 20 , said filter being a passive filter chosen from a set of predetermined filters, so that the determined optical characteristic of the filter is close to the same optical characteristic of the chosen predetermined filter. 
     
     
         23 . An ophthalmic lens intended to be placed in front of the eye of a wearer and including a filter as claimed in  claim 20 .