An apparatus for use in determining a neurochromatic lens prescription. The apparatus includes an opening operable for use in a patient observing a visual target and a trial lens slot operable for use in inserting a trial lens into the patients line of sight and the opening. The apparatus further includes a channel operable for sliding the trial lens into a centered position within the opening and a trial lens retainer operable for holding one or more trial lenses resulting in visual function improvement. The channel is coupled to the trial lens slot and the channel is operable for sliding the trial lens horizontally into the opening. The trial lens retainer is operable to retain the one or more trial lenses within the patients line of sight.
