How do lighting levels and contrast affect vision with multifocal contact lenses?

Paper title: Visual Performance of Centre-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm

Authors: Hannah R Gregory (1), Augustine N Nti (1), James S Wolffsohn (2), David A Berntsen (1), Eric R Ritchey (1)

1. The Ocular Surface Institute, University of Houston College of Optometry, Houston, Texas
2. Optometry and Vision Science Research Group, Department of Life and Health Sciences, Aston University, Birmingham, UK

Date: Mar 2021

Reference: Gregory HR, Nti AN, Wolffsohn JS, Berntsen DA, Ritchey ER. Visual Performance of Centre-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm. Optom Vis Sci. 2021 Mar 1;98(3):272-279.

[Link to open access paper]

This study measured the visual performance for non-presbyopes of two multifocal lens designs commonly used for myopia control, in varying lighting and contrast conditions.

Young adults aged between 21 and 29 years with myopia between -0.75D and -6.00D were fit binocularly with Biofinity spherical lens, Biofinity multifocal with +2.50D Add power, and NaturalVue multifocal. After lens fit, over-refraction was performed and 29 of 50 eyes wearing the Biofinity multifocal required over-refraction, with a mean of  −0.37 ± 0.13 diopter sphere. Only one eye wearing the NaturalVue Multifocal required an over-refraction of power −0.50 diopter sphere to optimize distance visual acuity.

The performance of each lens type for distance and near was measured using logMAR acuities for high and low contrast targets under different lighting conditions of bright light, dim light and dim light with a glare source.

• For high and low contrast distance vision, brighter light conditions gave better vision than dim light, with all lens types giving a mean logMAR acuity of -0.1 logMAR or better (around 6/5 or 20/17) for distance and near.
• When the light was dimmer, multifocals gave a 1-line reduction in acuities for high contrast targets and a 2-line reduction for low contrast.
• When a glare source was introduced in dim light, vision for high contrast targets remained similar, but a reduction of 0.5 logMAR acuity with all lenses (around 5 lines) was seen for low contrast targets observed with the glare source.
• Reading rate was reduced with both multifocals compared to single vision, by around 4-8% compared to single vision. This was observed regardless of print size.
• There were no significant differences between the two multifocal designs in any of the tests.

The multifocal lenses gave similar vision levels in high contrast vision and normal, bright light conditions to the single vision lens, despite being different designs.  However, they both performed less well under low contrast and dimmer light conditions for visual acuities, and les well for reading speed under high contrast, normal lighting conditions.

These two multifocal contact lenses have been found to reduce low contrast and lower lighting visual acuities compared to single vision, and to reduce reading speed slightly. This study included young adult myopes - any different impact on children is not known.

Over-refraction of these multifocal lens designs to optimize distance visual acuity is important, especially for the Biofinity multifocal which needed -0.25 to -0.50 additional power for best acuity. This was less of an issue for the NaturalVue multifocal. This finding is in line with the BLINK study which found children needed an average of -0.62D over-refraction for best corrected visual acuity in the Biofinity centre-distance +2.50 Add multifocal.¹

Eye care practitioners should to remember that measuring the high contrast visual acuities of multifocal lenses in normal, bright conditions is not necessarily predictive of the lens behaviour in other conditions.

Further research is needed on the reading speed and acuity impact of multifocal designs when used for myopia control in children, particularly in lower lighting conditions. Children wearing these lenses may not have the same visual demands for lower lighting or glare situations (eg. driving) and their ability to observe a reduction in visual quality, compared to adults, is also not known.

Title: Visual Performance of Centre-distance Multifocal Contact Lenses Fit Using a Myopia Control Paradigm

Authors: Hannah R.Gregory, Augustine N.Nti, James S.Wolffsohn, David A.Berntsen, Eric R.Ritchey

[Link to open access paper]