clearly, the incoming light must be focused on the retina. The better this process works, the sharper our vision - and we are then able to distinguish objects from each other with greater precision. Visual [...] media such as cornea, lens or vitreous humour with the retina can lead to reduced visual acuity, for instance, if the media do not focus the incoming light on the retina, but instead focus it in front of [...] acuity is not only necessary for fitting glasses or contact lenses, but it also provides the basis for optimum selection and individual adjustment of magnifying vision aids. Determining visual acuity In