Optical detection techniques are at present mainly based on an array of silicon detectors or charge coupled devices (CCDs). CCDs output a signal proportional to light intensity that is converted into digital numbers and fed into a computer for further processing. While this solution offers the possibility of high precision computation and is thus well suited for signal restitution (compression of images, filtering, etc.) and measurement techniques, it is usually not satisfactory when perceptive tasks are required in real- time and embedded in a microsystem, like for example in the case of optical motion detection of a ball in a pointing device like a trackball. Photonic microsystems based on the assembly of optical elements and an analog VLSI circuit as the optical detector and processing unit, hereafter called 'artificial retina,' provide a new way to develop innovative sensors when real-time processing, low-cost, low-power and portability are required. Combining the processing capabilities of optical components, and not only their imaging properties, with the massively parallel, collective and non-linear processing of a large number of signals on the artificial retina has lead to successful industrial photonic microsystems. The present paper discusses the use of artificial retinas in photonic microsystems. The resulting properties and the constraints on the optical front-end design, as well as on the assembly of the microsystem, are illustrated through some industrial realizations.