Meaning And Application of the Spherical Equivalent
Joseph I. Pascal · Clinical and Experimental Optometry · 1954
SummaryThe spherical equivalent is the spherical lens which places any astigmatic eye in a condition of meridional balance. That is, it changes the astigmatism into equally‐mixed astigmatism and produces retinal images made up of diffusion circles. It is often desirable to modify the full Rx as a first prescription, and the best modification is to reduce the cylinder and increase the sphere so that the partial Rx has the same spherical equivalent as the full Rx.