Predicting the low vision reading add

Before evaluating a low vision patient with various optical aids, one should know the strength of the first lens (add) to be tried. The basic concept behind predicting this add is presented. The three most common methods of predicting the add are explained, and it is shown that all of these methods are variations of the basic concept. An analysis of the results of the three methods is given. An addendum discussing acuity notations and some common misunderstandings that occur is also included.