The invention relates to an optical instrument for measuring the density of macular pigment in the eye, and to an associated method. The instrument comprises: a light source (500)； multiple lenses (L1, L2, L3) situated between the light source and the eye to be studied； a diaphragm (D1) conjugate in the plane of the pupil of the eye to be studied, for allowing control of the position at which light enters the eye； a photodetector (520)； a mirror (M1) that directs the light leaving the eye towards the photodetector (520)； a diaphragm (D2) conjugate in the plane of the pupil of the eye, which determines the exit path of the light from the fundus of the eye； and at least one lens (L4) between the diaphragm (D2) and the photodetector 520). The light source (500) comprises a central part (501) and a peripheral part (502) and is modulated in 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, the light source (500) projecting onto the fundus of the eye such that the central part (501) of the light source (500) remains projected on the macula of the eye, and such that the response signal from the fundus of the eye is received in the photodetector (520).Instrumento óptico para la medida de la densidad del pigmento macular en el ojo y método asociado. El instrumento comprende: - una fuente de luz (500), - varias lentes L1, L2, L3 situadas entre la fuente de luz y el ojo a estudiar, - un diafragma D1 conjugado en el plano de la pupila del ojo a estudiar para permitir el control de la posición de entrada de la luz en el ojo, - un fotodetector (520), - un espejo M1 que dirige la luz de salida del ojo hacia el fotodetector (520), - un diafragma D2 conjugado en el plano de la pupila del ojo, que determina el camino de salida de la luz proveniente del fondo de ojo, - al menos una lente L4 entre el diafragma D2 y el fotodetector (520), y la fuente de lu
