Dual Focus Contact Lens Reduces Hyperopic Defocus Without Altering Accommodation

Dual focus contact lens treatment does not affect accommodative behavior, but does reduce hyperopic defocus and increase myopic defocus in pediatric patients with myopia, according to a study published in Optometry and Vision Science.

Researchers enrolled 17 children with myopia (mean age, 16.61 years) who were previously treated with a dual focus contact lens and bilaterally fit them with the study lenses. The team used pyramidal aberrometry to measure wavefronts while participants viewed high contrast near stimuli at 3.98, 0.98, 0.48, 0.31, and 0.23 meters. After an adaptation period of 15 minutes, participants repeated the trial while wearing single vision contact lenses.

During single vision lens wear, the participants achieved an approximate focus in the pupil center during accommodation, but experienced up to 2.00 diopters (D) of hyperopic defocus in the pupil margins due to combined accommodative lag and negative spherical aberration. 

While wearing the dual focus contact lenses, the patients accommodated similarly to focus in the pupil center, but when viewing 3 of the 5 near targets (0.48, 0.31 and 0.23 m), the +2.00 D add within the study lens shifted the mean defocus from +0.75 D to -1.00 D, reducing the hyperopic defocus from 52% to 25%. Overall myopic defocus increased from 17% to 42%, the report shows.  

Several myopia control methods specify annular zone add powers, but will not help to determine myopia control efficacy, according to the researchers.

“Missing from these descriptions of the lenses themselves is a quantification of the myopic defocus dose delivered to the myopic child’s retina,” the study authors explain. “This distinction is important because the ability for a myopia control intervention to deliver myopic defocus depends on the eye’s optics as well as the lens’ treatment zone design.”

Study limitations include a short study duration and a failure to account for lens decentration in the dual focus contact lenses.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.