Optimizing hybrid images for an easy screening of the visual acuity

The development of a hybrid image (HI) is a method to create asingle illusive picture, merging two images with different content in terms of spatialfrequencies. Recently such a kind of optical illusion has also been used in theresearch area of optometry and psychology. Our study is based on the most famousHI, “Einstein-Marilyn face”, created in 2007 for the “New Scientist” magazine. Thisstudy aims to observe the role of the spatial frequencies in the interpretation of aHI in function of the visual acuity. The results show that a correct selection of thecut-off frequencies is fundamental to generating an optimal HI,i.e.,withanopticalillusion characterized by a non-ambiguous and stable interpretation. The design ofworking HIs can open the way for new kinds of tests in the field of optometry, inparticular for the screening of myopia.