Figure 3. Optical configuration used to measure optical aberrations of the eye. An infrared source [1] with 200 µW is focused towards the eye through spherical lenses [6] and [16]. A filament light source [5] is used to illuminate a light diffuser, which is attached to a reticule containing a balloon picture [4] (this is simply a psychological advantage that calls the patient's attention during accommodation). This accommodation system shall be tested during the second phase of this project, in which measurements will be made on human eyes. The image formed by lens [3] and beam splitter [2] is located at a far point from the patient in order to induce the accommodation of the crystalline. Approximately 1% of the incident light scattered at the back of the eye (retina) is reflected back to the beam splitter [7], goes through spherical lenses [8] and [9], a stop [10] located at the focal point of lenses [9] and [11] for elimination of undesired reflections at the cornea [17] and finally hits the Hartmann-Shack (HS) sensor [12]. A charge coupling device (CCD) [13] is placed on the focal plane of the HS micro-lenses, and attached to a "frame-grabber" [14] installed in an IBM compatible computer, where the HS images are processed [15] and the optical aberration is calculated.