A new method of measuring lens refractive index
in solution and measuring lens power
in air and in solution is extended. Prompted by a clinical need, the new method using lens power
can be extended by applying it to prismatic power as well. This article provides a theoretical basis explaining why this can be done.
The prismatic power of a prism
is derived from first principles. Snell's Law
and geometrical optics provide the framework for demonstrating the validity of the resulting formula.
The sameness in formula derived using lens power
is shown, both from a paraxial and non-paraxial optics
perspective. The effect of varying lens material and amount of prism
The prismatic method described provides a useful alternative method of determining the refractive index
of any lens. In some cases, it may be the only method available. Practitioners should consider when each method will provide optimal results.