Although the effect of vertex distance on optical correction is well known, it is rarely taken into account in practice, except in cases of very strong corrections. When ophthalmic lenses were offered only in 0.25 D increments, this had little influence on most corrections.
But today, with refraction determined in 0.01 D increments* and the lenses associated with them, knowledge and measurement of vertex distance becomes particularly important. This article reviews the optical effects of vertex distance, shows how eye-to-phoropter distance can vary and discusses how vertex distance can now be taken into account for an accurate calculation of corrective lens power.
Article from the magazine "Point de vue"