High accommodative lag (more than 0.75D) and accommodative variability with near work are both linked to visual fatigue and, possibly, even myopia. Because soft contact lenses may affect a patient’s accommodative function, researchers recently explored this association and found a larger accommodative lag, approximately 1D, and more fluctuations with soft contact lenses.
The team recorded dynamic accommodative response during 30-second intervals at five different distances (50cm, 40cm, 33cm, 25cm and 20cm) in 21 patients with a mean refractive error of -0.79±1.39D who wore soft contact lenses or spectacles on two different days. They conducted a second identical intervention to assess inter-session and inter-method repeatability.
They obtained larger lags of accommodation and a higher variability of accommodation at near distances with the use of soft contact lenses compared with spectacles. In fact, study participants wearing spectacles showed lags of accommodation less than 0.75D for all five viewing distances—the threshold for clinical relevance.
Accommodative variability has a close association with visual fatigue and myopia, and clinicians should note soft contact lenses can induce more variability during near tasks than spectacles, the researchers wrote in the study. Interestingly, the team found lower, although still significant, accommodative variability at the 40cm distance for both correction methods, which is the habitual distance for near tasks and near-task testing during ocular exams. “Visual functioning may be adapted to the habitually used distance in real life,” they speculate in the study.
These findings may have important research and clinical implications, as it could direct future experimental designs and guide clinical decision-making for corrective choices, the study authors concluded.
|Jiménez R, Redondo B, Davies LN, et al. Effects of optical correction method on the magnitude and variability of accommodative response: a test-retest study. Optom Vis Sci. July 22, 2019. [Epub ahead of print].|