This chapter will show the optical models of ametropia and presyopia by backward method (BM). The design activity of ophthalmic lens involves relatively simple, often elementary geometric optics. In general, ophthalmic lens design is given by tracing the light from the object to the image plane, i.e., the retina. And this can be called the forward method (AM). By BM, the position of the object and image is interchanged, i.e., retina plays the role as object. Using BM gives an alternative way to know how the eye works as a lens, and the retina now acts as the object tells more information for the correction of ametropia and presbyopia for its curve shape and the location. Applying this BM geometric analysis, we can see the correction of ametropia by correction lens, i.e., spectacle, is to fulfill the needs to put the object at the conjugate places of retina formed by the myopic and hyperopic eye. For verification, the optical simulation by Zemax is applied to simulate the image forming processing, i.e., the conjugation between the retinal and it counter parts. Similarly, this geometric analysis can be applied to analyze the progressive addition lenses (PALs) by the revised BM.
Part of the book: Eyesight and Imaging