Parinaud ‘s Syndrome

While an object is moving toward the eye, convergence eye movements permit stereopsis and prevent diplopia by moving the eyes in opposite horizontal directions, this maintains the image of an object to fall onto the fovea of each eye. Fixation of a near object induces not only convergence but also accommodation of the lenses and constriction of the pupils, these three responses constitute the near reflex . Convergence is stimulated by two major stimuli : retinal blur and retinal disparity. Retinal blur is the loss of image sharpness, while retinal disparity is falling of images of a single object onto a non-corresponding parts of the retina of the two eyes. Retinal blur elicits accommodative convergence and retinal disparity elicits fusional convergence, both stimuli combine to produce appropriate convergence eye movements.