The Visual Impact of Uncorrected Astigmatism in Eyes Fitted with Dual Focus Myopia Control Lenses

To quantify the impact of uncorrected astigmatism in myopic eyes fitted with dual focus (DF) myopia control contact lenses.

The right eyes of 10 young adult myopes were corrected with standard single vision (SV, Proclear 1 day, CooperVision, Inc.) and DF (MiSight 1 day, CooperVision, Inc.) contact lenses. SV and DF contact lens powers were determined from SV over-refractions and any ocular astigmatism was corrected using cylindrical trial lenses. Visual acuity and subjective vision were measured through added cylindrical trial lenses (0.00DC, 0.75DC, 1.25DC, 1.75DC and 2.25DC) with spherical equivalent adjustments. With the 2.25D astigmatic lenses, spherical trial lenses were also used to focus the front edge, centre and back edge of the interval of Sturm. Data were analysed using linear mixed-effects regression models.

High illumination visual acuity was similar for both lens types (zero astigmatism model-estimated intercept: -0.25 logMAR for SV; -0.24 logMAR for DF), and visual acuity decreased linearly with increasing astigmatism, similarly with both SV (0.27 logMAR/D) and DF (0.23 logMAR/D) lenses. Under low room illumination and in the absence of astigmatism, SV acuity was slightly superior to DF (mean logMAR -0.03 and +0.06 for SV and DF, respectively) and the rate of visual acuity decline with increasing astigmatism was less for DF (0.21 logMAR/D) than for SV lenses (0.26 logMAR/D; p = 0.04). Subjective quality of vision ratings were higher for SV lenses compared to DF lenses (model-estimated intercept: 93 vs. 86). Quality of vision ratings decreased linearly with increasing astigmatism at nearly identical rates for both lens types (~19 rating units/D). LogMAR acuity and subjective ratings were similar when the edges or the centre of the interval of Sturm were focused.

Uncorrected astigmatism had an almost identical impact on visual acuity and vision quality in eyes fitted with DF myopia control and SV contact lenses.