Role of Mandelbaum-like effect in the differentiation of hyperopes and myopes using a hologram.

Recently, we tested the vision of spectacle corrected subjects using a special hologram (http://dx.doi.org/10.1364/BOE.3.001173). A subject viewing through this hologram sees the images of various numbers at different distances from the eye. Each of these images subtends an angle of 50' at the eye. Each image corresponds to a different amount of divergence or convergence at the eye. The limit of convergence (positive blur) with which a subject can recognize the numbers was measured. Hyperopes could recognize numbers with 0.9 D more of positive blur in comparison with myopes. This difference was not obtained with a standard test chart under white light illumination using positive lenses to provide the blur. The observed difference with the hologram is then attributed to the multivergence nature of the target in the hologram and/or the monochromaticity of the illumination used. Using a hologram of a logMAR chart at a single distance of infinity we have now found that the observed difference is induced by the multivergence target and is due to an effect that is similar to the Mandelbaum effect. We present the details of this experiment and compare the results obtained with our earlier experiment.