Astigmatic decomposition: an alternative subjective refraction test employing conventional instrumentation.

The Humphrey Vision Analyser introduced the refractive technique of astigmatic decomposition with the aid of Alvarez continuously variable sphere-cylinder lenses. The adaptation of astigmatic decomposition to conventional trial lens systems and a Stokes' lens is described. Refractive errors measured by this technique and by crossed cylinder are compared in 33 optometric patients (one eye each) to assess the relative validity of the method, which compares well with data published on the Humphrey Vision Analyser. Astigmatic decomposition can be considered as an alternative subjective refraction test to more conventional methods.