US 7,441,896 B2 · Macular pigment measurements

Abstract

Apparatus for use in measuring the density and spatial distribution of macular pigment in an eye comprises a camera (4) for capturing a color image of an eye, at least one filter (36) for filtering light reaching the camera (preferably by filtering the light illuminating the eye). The filter (36) has a transmission spectrum with one peak in the region of light absorbed by the pigment and another peak in a region where no such absorption occurs. The filter increases the sensitivity of the camera to macular pigment while enabling the effect of other pigments to be reduced or eliminated. A method of measuring macular pigment involves obtaining a color image of an eye, the image having two color components each having a spectrum having a respective one of said peaks. Corresponding portions of the components are mathematically combined so as to provide a measurement of macular pigment density and the results of the combination are used to provide an output representative of the contribution of macular pigment to the image.

Claims15

Dependent claims

Apparatus for use in measuring the density and spatial distribution of macular pigment in an eye, the apparatus comprising a camera for capturing one or more colour images of the retina of an eye under examination, one or more filters for filtering the light reaching the camera so as to provide four retinal image components the spectra of which have peaks substantially at 460 nm (blue), 530 nm (green), 600 nm (red) and 680 nm (far red) respectively, the apparatus including an image processor for processing the image or images captured by the camera, wherein the image processor is operable to perform a linear mathematical combination of logarithms of the four components, with weighting, in order to eliminate contributions from non-uniform distributions of melanin, rod photo pigments and cone photo pigments over the retina, wherein the logarithms are combined to obtain the macular pigment density D at a given location in the image by the formula:

D=−0.525*LDB+0.355*LDG−0.882*LDR+2.60*LDR′
where LDB, LDG, LDR and LDR′ are the logarithms of the differences between the intensities at a given location and a peripheral location in the blue, green, red and far red component respectively.

A method of measuring macular pigment density and spatial distribution in an eye, the method comprising the steps of,

a) capturing a colour image of the retina of the eye, the image having a first and second colour component, the first colour component having a spectrum with a first peak of which is at a wavelength at which the absorption by macular pigment is at a maximum, the second component having a second peak at which substantially no such absorption occurs and a third colour component having a spectrum which has a third peak;
b) mathematically combining the image components at each region of the image, to remove at least some colour contributions not arising from the macular pigment and
c) providing an output representative of the contribution of the macular pigment to the image, wherein,
a further colour component of the retina is obtained, said further component having a peak at a different wavelength of light, and data on the further component is used in said mathematical combination to eliminate the effect of non uniform distribution of rod photopigment across the retina,
the peaks of the spectra of the components are substantially at 460 nm (blue), 530 nm (green) 600 nm red and 680 (far red) respectively, and
the logarithms are combined to obtain the macular pigment density, D, at a given location by the formula:
D=−0.525*LDB+0.355*LDG−0.882*LDR+2.60*LDR′
where LDB, LDG, LDR and LDR′ are the logarithms of the differences between the intensities at the given location and a peripheral location in the blue, green, red and far red component respectively.

5 more elements

Dependencies are inferred from the claim text.

Macular pigment measurements

Life of this patent

Macular pigment measurements

Life of this patent

Abstract

Claims15