Holographic multivergence target for subjective measurement of the astigmatic error of the human eye.

In subjective refraction the spherical and cylindrical errors of the human eye are measured. Recently, we reported a technique by which the spherical error can be measured in one step using a hologram [K. V. Avudainayagam and C. S. Avudainayagam, Opt. Lett.28, 123 (2003)]. We have now developed a holographic target consisting of sunburst patterns to measure the astigmatic error of the human eye as well. Apart from being simple, quick, and low cost, holography offers the advantage of being an open field refraction system that is devoid of the problem of proximal accommodation. We describe the holographic target, its working principles, the measurement procedure, and the initial results obtained.