Dual Focus Contacts May Alter Contrast Sensitivity, Perceived Visual Quality

Dual focus contacts for myopia control offer comparable distance vision to single vision contact lenses, but may result in increased aberrations, decreased contrast sensitivity, and worsened visual quality as reported by wearers, according to a study published in Contact Lens and Anterior Eye.

Researchers enrolled 20 individuals with myopia (mean age, 23.0 years; 60% women; spherical equivalent [SE], −3.26 diopters [D]) in the prospective, randomized study to compare visual performance and image quality between single vision contact lenses and dual focus contacts for myopia control. Study participants underwent random assignment to one of the lenses for 1 week before crossing over to the other lens for another week following a 2-day washout period. The team assessed high- and low-contrast visual acuity, contrast sensitivity, ocular higher-order aberrations (HOAs), and Strehl ratio. Study participants reported perceived visual quality using the Quality of Vision (QoV) questionnaire for both contact lenses at 1-week follow up.

Distance visual acuity was comparable between the dual focus contacts and the single vision contact lenses in both high (P =.414) and low contrast conditions (P =.431, but there was a significant reduction in low-contrast near visual acuity with the dual focus contacts compared with the single vision lenses (P =.011), the report shows.  

Contrast sensitivity differences between the 2 lenses was associated with lighting conditions and spatial frequencies (F=128.81, P <.001). Wavefront aberrations of the dual focus contacts showed an increase in total HOAs, trefoil, and spherical aberrations for 3 and 6 mm pupil sizes compared with the single vision lenses. The Strehl ratio while wearing the myopia control contact lenses was significantly reduced compared with the single vision lenses at a 6.0 mm pupil diameter (P <.001). Higher overall scores (P =.026) and reports of more frequent symptoms (P =.019) with the QoV assessment indicated poorer visual performance with the dual focus contacts.

“The results of this study showed significant differences in [contrast sensitivity], higher-
order aberrations, and QoV questionnaire scores between [defocus incorporated soft contact] lenses and single vision [contact lenses], despite similar distance visual acuity between various [contact lens] designs,” according to the researchers. “The higher scores of the QoV questionnaire with [defocus-incorporated soft contact] lenses compared to single-vision [contact lenses] may be related to decreased [contrast sensitivity] at medium or high spatial frequencies and increased higher-order aberrations.”

Study limitations include a failure to consider contact lens wear history and monocular measurements of visual performance.