Optical instrument for measuring the density of macular pigment in the eye and associated method. The instrument comprises: - a light source (500), - several lenses L1, L2, L3 located between the light source and the eye to study, - a diaphragm D1 conjugate to the eye pupil plane to allow control of the entrance position of the light in the eye, - a photodetector (520), - a mirror M that directs the light exiting the eye to the photodetector (520), - a diaphragm D2 conjugated to the pupil plane of the eye, which determines the output path of the light from the fundus of the eye, - at least one lens L4 between D2 diaphragm and the photodetector (520), and the light source (500) comprises a central part (501) and a peripheral part (502), the light source (500) being modulated at four different frequencies corresponding to green light in the central part, green light in the peripheral part, blue light in the central part and blue light in the peripheral part, projecting the light source (500) on the fundus of the eye, so that the central part (501) of the light source (500) is projected onto the macula of the eye, and the response signal from the fundus of the eye is received at the photodetector (520).
