Because new IOL designs that target presbyopia correction are optimized for different reading distances or lifestyles, it is interesting to study their visual performance when combined binocularly. We compare the binocular through focus (BTF) visual acuity (VA) provided by different combinations of IOLs measured using an adaptive optics vision simulator (AOVS).
Different bifocal diffractive IOL designs with add powers at the IOL plane between +4D and +2.75D were evaluated in this study. We used a binocular AOVS to measure high contrast VA as a function of object vergence with SLOAN letters. Five subjects were tested with a 3.5 mm aperture in white light for the following conditions: 1) bilateral induction of the phase profile corresponding to the same IOL designs and 2) combinations of multifocals with add power ranging from +4D to +2.75D.
The bilateral induction of the +4D-bifocal design had a secondary peak in the BTF curve between -2.5D and -3D. VA for intermediate distance (i.e. -1.5D) was 0.30±0.14 LogMAR. The +2.75D-bifocal design had its near focal point at -2D, while the VA for intermediate distance was 0.08±0.12 LogMAR. The combination of these two designs provided with a VA of approximately 0.1 LogMAR between -1.5 and -3D (Figure).
We compared BTF VA curves measured for bilateral and mix-and-match combinations of different designs. The bilateral induction of the diffractive bifocal designs resulted in near and far VA of approximately 0.0 LogMAR. Mix and matching these 2 designs provides similar near and far performance while at the same time providing intermediate vision. These results indicate that the binocular combination of existing IOLs may be used to address individual patients’ visual needs.