DEVICE AND METHOD FOR OPTICALLY MEASURING THE TRANSMISSION AND DIFFUSION OF OCULAR MEDIA

• US 20110157551A1
• Filed: 09/08/2009
• Published: 06/30/2011
• Est. Priority Date: 09/08/2008
• Status: Active Grant

• Current Assignee: Centre National De La Recherche Scientifique, Ecole Nationale Superieure De Techniques Avancees, Ecole polytechnique
• Original Assignee: Centre National De La Recherche Scientifique, Ecole Nationale Superieure De Techniques Avancees, Ecole polytechnique
• Inventors: Aptel, Florent, Deloison, Florent, Peyrot, Donald, Plamann, Kartsen, Crotti, Caroline
• Granted Patent: US 8,398,237 B2
• Time in Patent Office: Days
• US Class Current: 351/206
• CPC Class Codes: A61B 3/103 for determining refraction, e.g. refractometers, skiascopes
• CPC Class Codes: G01N 21/4785 Standardising light scatter apparatus; Standards therefor
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G01N 21/59 Transmissivity G01N21/25 takes precedence

Abstract

An optical device for measuring the transmission and diffusion of a tissue of the front segment of an eye, includes: a light source; an optical collimation system for directing the collimated light beam towards a tissue of the front segment of an eye to be characterized; an optical mire placed on the optical path between the optical collimation system and the tissue; an optical imaging system capable of receiving a light beam transmitted by the mire and the tissue and capable of forming an image of the mire on an image detector; and an image processing system capable of calculating a modulation transfer function for the tissue from an image of the mire through the ocular medium. The optical mire includes a set of alternately light and dark angular sectors radially distributed from a central point. Different image processing methods for extracting a function representing the transmission and diffusion characteristics of the tissue are described.

Claims

1. An optical device for measuring the transmission and diffusion of a tissue (7) of the front segment of an eye, said device comprising:

at least one light source (1) capable of emitting a light beam,

an optical collimation system (2, 4) capable of directing the collimated light beam towards a tissue (7) of the front segment of an eye to be characterized,

an optical mire (6) placed on the optical path between the optical collimation system (4) and the tissue (7) of the front segment,

an optical imaging system (9) capable of receiving a light beam transmitted by the mire (6) and by the front segment tissue (7) and capable of forming an image of the mire (6) on an image detector (10), and

an image processing system (11) capable of calculating a modulation transfer function for the tissue (7) from an image (22) of the mire through the tissue (7),

characterized in that;

said optical mire (6) comprises a set of alternately light (13.1, 13.2 . . . ) and dark (14.1, 14.2 . . . ) angular sectors (13, 14) radially distributed from a central point (O).

2. A device according to claim 1, characterized in that the optical mire (6) comprises a set of 2.N angular sectors (13.1, 14.1, 13.2, 14.2, . . . , 13.N, 14.N) having the same angular opening α

=180°

/N.

3. A device according to claim 1, characterized in that it comprises a spatial filter between the source and the optical collimation system.

4. A device according to claim 1, characterized in that the light source (1) is capable of emitting a light beam comprising a plurality of wavelengths and in that the device comprises a wavelength filtering means and is capable of measuring the transmission and diffusion of a tissue (7) of the front segment of an eye as a function of the wavelength.

5. A device according to claim 1, characterized in that it comprises a sample carrier capable of receiving a tissue of the front segment of an eye, from the following ones:

cornea, cornea graft, crystalline lens, sclera, aqueous humor, vitreous body.

6. A device according to claim 1, characterized in that it comprises a comparator capable of comparing the modulation transfer function for a tissue (7) of the front segment of an eye to a set of reference curves.

11. A device according to claim 2, characterized in that it comprises a spatial filter between the source and the optical collimation system.

12. A device according to claim 2, characterized in that the light source (1) is capable of emitting a light beam comprising a plurality of wavelengths and in that the device comprises a wavelength filtering means and is capable of measuring the transmission and diffusion of a tissue (7) of the front segment of an eye as a function of the wavelength.

13. A device according to claim 2, characterized in that it comprises a sample carrier capable of receiving a tissue of the front segment of an eye, from the following ones:

cornea, cornea graft, crystalline lens, sclera, aqueous humor, vitreous body.

14. A device according to claim 2, characterized in that it comprises a comparator capable of comparing the modulation transfer function for a tissue (7) of the front segment of an eye to a set of reference curves.

15. A device according to claim 3, characterized in that the light source (1) is capable of emitting a light beam comprising a plurality of wavelengths and in that the device comprises a wavelength filtering means and is capable of measuring the transmission and diffusion of a tissue (7) of the front segment of an eye as a function of the wavelength.

16. A device according to claim 3, characterized in that it comprises a sample carrier capable of receiving a tissue of the front segment of an eye, from the following ones:

cornea, cornea graft, crystalline lens, sclera, aqueous humor, vitreous body.

17. A device according to claim 3, characterized in that it comprises a comparator capable of comparing the modulation transfer function for a tissue (7) of the front segment of an eye to a set of reference curves.

18. A device according to claim 4, characterized in that it comprises a sample carrier capable of receiving a tissue of the front segment of an eye, from the following ones:

cornea, cornea graft, crystalline lens, sclera, aqueous humor, vitreous body.

19. A device according to claim 4, characterized in that it comprises a comparator capable of comparing the modulation transfer function for a tissue (7) of the front segment of an eye to a set of reference curves.

7. A method for measuring the transmission and diffusion of a tissue (7) of the front segment of an eye, comprising the following steps:

emitting a light beam from a light source,

collimating the light beam using an optical system (2, 4),

transmitting the collimated beam through an optical mire (6),

transmitting the optical beam spatially modulated by the mire through the tissue (7) of the front segment of an eye to be measured,

forming and acquiring an image of the mire (6) through the tissue (7) of the front segment of an eye, and

characterized in that it comprises a step of;

processing the image (22) of a mire comprising a set of alternately light (13.1, 13.2 . . . ) and dark (14.1, 14.2 . . . ) angular sectors (13, 14) radially distributed from a central point (O), comprising a Fourier transform operation to derive therefrom the modulus of the modulation transfer function for the tissue (7) of the front segment of an eye as a function of the spatial modulation frequencies of the mire.

8. A measuring method according to claim 7, characterized in that the step of image processing comprises the steps of:

two-dimensionally Fourier transforming the image (22) of the mire to derive therefrom a spectrum measurement of the image of the tissue (7) of the front segment of an eye as a function of a continuous or discrete set of spatial modulation frequencies of the mire (6),

normalizing this spectrum with respect to the spectrum of an image (21) of the mire obtained without the tissue (7) to obtain a curve of the modulus of the modulation transfer function (MTF) of the tissue (7) of the front segment of an eye.

9. A measuring method according to claim 7, characterized in that the step of image processing comprises the following steps:

analysing the image of the mire according to a series of rings of centre 0′ and

radius r (0<

r<

R_MAX),

determining the modulation rate of each ring by adjusting a sinusoidal function, and

calculating the modulus of the modulation transfer function as a function of the spatial frequencies corresponding to each of said rings,

normalizing with respect to a MTF curve without sample.

10. A measuring method according to claim 7, characterized in that the step of image processing comprises the following steps:

analysing the image of the mire according to a series of rings of centre 0′ and

radius r (0<

r<

R_MAX),

projecting the intensity of each ring in a matrix of polar coordinates (r, θ

),

converting the axe r into a spatial frequency ν

, to obtain a matrix in coordinates (ν

, θ

),

applying a one-dimensional Fourier transform for each row,

determining the column vector corresponding to the fundamental harmonic ω

₀ of modulation of the mire,

calculating the modulus of the modulation transfer function (MTF) based on values of the column vector at the frequency ω

₀, as a function of the spatial modulation frequencies ν

corresponding to each of said rings,

normalizing the modulus of the modulation transfer function with respect to a measurement without sample.