Each subject was measured in two different sessions. Session 1 involved measuring TFVA, and the eye's wave aberrations under natural conditions (i.e., natural pupil and free accommodation) for a series of accommodative demands (0 to 4.5 D), while targets were viewed through the multifocal patterns MP1, MP2 and MP3, and a single vision (SV) control condition. Session 2 involved performing TFVA measurements under cycloplegia (1% tropicamide ophthalmic solution, USP Alcon Laboratories, Inc. Fort Worth, TX, USA; two drops before the experiment and repeated every hour) and 5 mm fixed artificial pupil, through MP1, MP2, MP3, and SV. Measurements under natural accommodation allow to assess quality of vision under natural pupil dynamics, and accounting for the effect of accommodation, also including the effects of the natural aberrations of the eye, as well as the coupling of those with the multifocal patterns both at far and near. Measurements under paralyzed accommodation and a fixed pupil diameter, allow direct comparisons of lens performance across individuals, and account for the effect of the coupling of the design and the aberrations of the eye, excluding the effect of accommodation.
Visual stimuli (E letter for VA measurements and Maltese cross for accommodation and focus adjustment) were illuminated with monochromatic light (555 nm) and viewed monocularly (the contralateral eye was covered with a patch). Subjects were aligned to the system and adjusted the best focus at distance (starting with positive defocus) using a keypad to change the power of the tunable lens. The zero-defocus was obtained from the average of at least 5 focus settings repetitions, for each pattern, for both natural accommodation and paralyzed accommodation, and it varied by less than 0.50 D across conditions. The duration of Session 1 was 3.5 hours, with frequent breaks. The duration of Session 2 was approximately 1.5 hours. All measurements were performed monocularly in a darkened room. Before starting the measurements, subjects were instructed on the nature of the experiment and trained with several practice trials.