The influence of high addition soft multifocal contact lenses on visual performance

Aim of the study
The purpose of this study was to investigate the influence of multifocal contact lenses with medium and high additions (ADD: +2.00 D and +4.00 D) on short-term visual functions in a young, healthy adult population. Additionally, the impact of central zone size (3 mm and 4.5 mm) on visual functions was analyzed.

Material and methods
Each subject (N = 24) was fitted with three different designs of soft contact lenses: (1) distance power plano with ADD +2.00 D (Relax, SwissLens) – ADD2, (2) distance power plano with ADD +4.00 D (Relax, SwissLens) – ADD4, (3) single vision spherical plano lenses (Orbis, SwissLens) – ADD0. In each pair of lenses, near and distance visual acuity (VA), the consensual response of accommodation (using the photorefraction method), accommodation facility and peripheral contrast sensitivity were measured.

Results
Mean distance VA decreased with lenses with a 3 mm central zone size compared to a 4.5 mm central zone size (p = 0.019) and with ADD2 power compared to ADD0 (p = 0.004) in both central zone size groups. There was no statistically significant effect of ADD power or central zone size on near VA. The size of the central zone influenced contrast sensitivity functions (the area under the log contrast sensitivity function was 5.8 vs. 6.7, for 3 mm and 4.5 mm central zone size, respectively, p < 0.001). The mean lag of accommodation increased with ADD (p = 0.003). The slope of the linear function of accommodation was lower for ADD2 and ADD4 lenses (p = 0.005) and this effect was observed for both central zone sizes.

Conclusions
Higher addition (ADD4) powers influenced short-term visual functions in a similar way to that of medium (ADD2) addition powers in tested multifocal lens. The decrease of distant VA and increase in accommodative lag were observed with higher and medium addition powers. Because the size of the central distance zone negatively influenced some visual functions, this parameter should be considered individually in the fitting of soft multifocal contact lenses for myopia control.