Disclosed is an apparatus for measuring subjective ocular refraction including a display device configured to display a least one optotype and a refractive optical system arranged between an eye of a viewer and the display device, the refractive optical system having an optical power that can be varied according to a determined minimum step. The display device further includes a unit for varying optical power designed to generate a variation in the spherical and/or cylindrical optical power, such that the display device and the refractive optical system form a first image of the optotype with a first total optical power and, respectively, a second image of the optotype with a second total optical power, the variation in optical power between the first total optical power and the second total optical power being less than the determined minimum step.
