Multifocal contacts benefit young adults, those with presbyopia
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Multifocal contact lenses improved visual performance in young adults and those with presbyopia, despite small but consistent degradation, according to a study published in PLoS One.
“The present study reveals that center-near lenses do not degrade high contrast
visual acuity significantly while maintaining far vision in young adults and produce some
visual benefit at near in presbyopes,” Shrilekha Vedhakrishnan, a predoctoral researcher at the Institute of Optics in Madrid, and colleagues wrote. “Factors such as visual degradation at far, visual benefit at near and visual constancy (uniformity of vision across distances) should be considered in the management of myopia and presbyopia with [multifocal contact lenses (MCLs)] and to gain insights on the mechanism of operation of these lenses.”
Vedhakrishnan and colleagues divided 15 study participants of European ancestry into two groups: The first group included 10 young adults (average age, 26.9 years; average spherical equivalent, –2.2 D) and the second included five patients with presbyopia (average age, 53 years; 0.25 D). Researchers assessed through focus visual acuity (TFVA) with center-near MCLs of three additions (low, medium and high) across both groups and studied whether visual performance was affected by accommodation, age and pupil diameter (in cyclopleged patients). A group without MCLs (NoLens) was included as a control.
Researchers found that MCLs produced consistent benefits at near distances for young participants with paralyzed accommodation (1.025 logMAR) and in patients with presbyopia with both paralyzed and natural accommodation (1.071 logMAR, on average), as well as “a small but consistent degradation” (0.925 logMAR, on average across eyes and condition) at far distances.
In addition, researchers found that TFVA in young adults in the NoLens control group and all MCLs showed statistically significant differences between natural and paralyzed accommodation (P < 0.01), but there were no significant differences in patients with presbyopia using MCLs. Increasing pupil diameter with the high-add MCL (0.08 logMAR shift from 3- to 5-mm pupil size) also improved visual acuity in young adults, while MCLs reduced visual imbalance, according to the study.
Overall, results showed that visual acuity was better among young adults compared with patients with presbyopia for all conditions (MCLs and NoLens). However, despite MCLs producing small but consistent degradation at far in all conditions, young adults with paralyzed accommodation and patients with presbyopia in both paralyzed and natural accommodations experienced benefits at near.
“Our results show that MCLs produce a more uniform quality of vision across distances,” Vedhakrishnan and colleagues wrote. “We can speculate that a higher visual constancy is a preferred scenario than overall better (but also less uniform) vision, as achieved in young adults with natural vision, and this may explain the high degree of acceptance of MCLs when prescribed to myopes.”
Perspective
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MCLs are used to manage myopia, based on the theories of peripheral retinal defocus and accommodative lag, by removing the signals that cause the eye to elongate.
It has been thought that center-distance designs are best for maintaining distance visual acuity (VA) and are the better choice for myopia control. This article describes that center-near MCLs can be another option that maintains distance VA.
The researchers discovered that center-near MCLs can degrade distance VA, with the higher add having a more significant degradation effect than a standard monofocal lens. They showed that young adults with accommodation (24- to 38-year-olds) overall had better VA than presbyopes with MCLs; the young adult’s distance and near VAs were maintained around 6/6. Pupil sizes showed a minimal effect on performance on either group, indicating preservation of good VA and functionality in center-near MCLs.
Accommodative lag is thought to be one of the theories of axial elongation in myopia. This report discusses how center-near MCLs allow a more accurate accommodative response, reducing accommodative lag. While additional research is required to investigate the efficacy differences of center-near vs. center-distance for myopia control, the presence of the near addition in MCLs will produce a sufficiently strong inhibitory signal to slow down myopia progression.
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