Retinal Straylight Measurements for Assessing Wear-Related Changes in Monthly Soft Contact Lenses

Visual quality in the human eye depends on the integrity of ocular structures. Soft contact lenses interact directly with these structures and can also serve as an external source of straylight. The purpose of this study was to quantify changes in optical quality among habitual wearers of monthly disposable silicone hydrogel soft contact lenses (SCLs) by comparing retinal straylight with new versus month-old lenses. Retinal straylight was measured using a C-Quant straylight meter in 33 young adults (22.0 ± 1.4 years) wearing either comfilcon A (n = 17) or lotrafilcon B (n = 16) lenses. Measurements were first performed with month-old SCLs that had been worn for ≤4 h that day; after lens replacement and a 15 min adaptation period, measurements were repeated with new SCLs. The mean decimal logarithm of the straylight parameter, log(s), was significantly higher with month-old SCLs (0.97 ± 0.17) than with new SCLs (0.86 ± 0.15; paired t-test, p < 0.001), yielding an average increase of Δlog(s) = 0.11 ± 0.08. No significant difference was found between materials. Thirty-six percent of participants reported end-of-cycle visual discomfort. These findings indicate that monthly SCLs at the end of the replacement period can measurably increase retinal straylight.