A new test of visual acuity using a holographic phase grating and a laser

A new visual acuity testing device is able to determine a specific visual acuity of the retina even in the presence of opacities of the ocular media, such as a cataract. This is achieved by forming two spatially coherent, quasimonochromatic point sources near the nodal point of the eye. The two spherical waves that emanate from the point sources interact to produce a pattern of stripes on the retina. The intensity of the pattern is easily varied. More importantly, the pattern can be projected over different-sized retinal areas corresponding to visual fields of 0.5 to 15 degrees in diameter. The device may be useful for vision research and preoperative assessments of visual potential.