Patent ID: 7441896

Claim:
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* LD B +0.355* LD G −0.882* LD R +2.60* LD R′ where LD B , LD G , LD R and LD R′ 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.