Dual-Focus Contact Lenses May Reduce Accommodative Response at Near Focus

Dual-focus soft contact lenses may have lower initial near-work induced transient myopia (NITM) and a lower magnitude of accommodation during execution of near tasks than single vision contact lenses, according to a study published in Clinical Experimental Optometry. 

Researchers conducted a study of 24 patients with myopia (mean age: 20.5±2.0 years, mean refractive error: -2.89±1.53 D). They evaluated all participants a total of 4 times and randomly fit each patient with both dual-focus and single vision daily disposable contact lenses. The investigators also administered the Stanford Sleepiness Scale (SSS) on the third and fourth visits to ensure consistent levels of alertness throughout the course of the study. 

All patients remained in total darkness for a 3 minute period to control for possible transient accommodative after effects prior to initiating the investigation. Researchers then measured accommodative response by having participants fixate on a maltese cross 5 m away for a period of 10 seconds. Immediately after, they instructed participants to fixate on a near target placed 20 cm away on a smartphone for a period of 5 minutes. They quickly removed the near target at the conclusion of the 5 minute period and once again had patients focus on the distant target 5 m away for 3 minutes.

Investigators found that although participant alertness levels were comparable with both lenses (P =.802), they noticed greater levels of blurring and eye fatigue in the dual-focus design compared with the single vision lenses (P <.001 and P =.036, respectively). A repeated measures ANOVA test revealed a greater magnitude of accommodation in the single vision lenses compared with the dual-focus(F_1,23=16.33, P <.001, η²_p=0.41), but no statistically significant difference in NITM magnitude by lens design (F_1,23=0.85, P =.37, n²_p=0.041).

“These findings may provide relevant information for better understanding the acute effects of wearing dual-focus soft contact lenses for myopia control on the accommodative function, as well as its possible role on the development and progression of myopia,” according to the researchers. 

Study limitations include a small sample size and failure to include participants from a wider pool of age ranges. 

Reference

Jiménez R, Redondo B, Galán T, Machado P, Molina R, Vera J. Impact of dual-focus soft contact lens wear on near work-induced transient myopia. Clin Exp Optom. Published online January 24, 2022. doi:10.1080/08164622.2022.2029684