The Bernell Aperture Rule™ Trainer Kit is a standard tool used in VT programs to improve various visual skills, including low fusional and accommodative reserves, poor stereopsis, fixation disparity, suppression, and tight accommodation-conversion relationship. It is perfect for individuals experiencing asthenopia and visually related learning problems. The trainer features progressive fixed demand and does not require polarized or colored lenses, making it easy to use. With a range of 30PD Base-Out to 17.5PD Base-In.