1. An ophthalmic device for measuring objectively the blurring of optical images projected on the retina of the human eye, including: a) a target consisting of at least one rectangle, b) an optical projection system for imaging said target on the retina of the human eye, c) an optical image acquisition system for conveying the retinal image of said target back onto the image plane of a photo-electronic imaging device, d) a photo-electronic imaging device for transforming the retinal image of said target to an electronic signal which represents the image, e) a computer for processing the electronic image in order to obtain a measurement of the blurring of the retinal image of said target.