Off the Cuff: DEWS II

This study evaluated the continuous circadian intraocular pressure (IOP) fluctuation using a contact lens sensor during normal daily activities, as well as the relationship between IOP fluctuation and disease progression in primary angle closure glaucoma (PACG) eyes.

Circadian IOP fluctuations were recorded by Sensimed Triggerfish sensors in 25 PACG eyes. The sensor output signals were transformed using B-spline smoothing and described by functional data analysis. Glaucoma progression was documented with serial changes in mean deviation (MD) and visual field index (VFI) in Humphrey automated perimetry and retinal nerve fiber layer (RNFL) thickness.

Statistically significant differences were found from 2200 to 2300 and from 0700 to 0800 in gradients of the IOP fluctuation curve, as well as from 2300 to 2400 and 0800 to 0900 in curvatures of the IOP fluctuation curves, between the progressive MD and stable MD groups. Significant gradient differences were also found from 1500 to 1600 and 0600 to 0800 between the progressive VFI and stable VFI groups, and from 2400 to 0100 and 0200 to 0300 between the progressive RNFL and stable RNFL groups.

Significant differences in circadian IOP fluctuation between progressive and stable PACG eyes were identified. Researchers concluded that large IOP fluctuations may be associated with disease progression in PACG eyes.

Investigators assessed visual performance of single-vision and multifocal soft contact lenses. At baseline, 44 myopic participants (ages 18 to 35) were fitted bilaterally with a control lens (AirOptix Aqua). At four follow-up visits, a total of 16 study lenses (five single-vision, 11 multifocal lenses) were fitted contralaterally. After one hour of lens wear, participants rated (scale 1 to 10): vision clarity (distance, intermediate and near), magnitude of ghosting at distance, comfort during head movement and overall comfort. Distance high-contrast visual acuity (HCVA), central refraction and higher-order aberrations, and contact lens centration were measured.

For single-vision lenses, vision ratings were not significantly different from controls. The control outperformed Acuvue Oasys, Clariti Monthly and AirOptix Night and Day in HCVA. Most refraction and higher-order aberration measures were not different between lenses. The Night and Day lens showed the greatest differences compared to the control, i.e., C[4, 0] was more positive at distance (Δ=0.019μm) and near (Δ=0.028μm). For multifocal lenses, the majority of vision ratings (84%) were better with the control, including HCVA. Proclear Multifocal lenses showed greatest differences for M, C[3, -1] and C[4, 0] at distance and near, and were inferiorly de-centered.

Design differences between single-vision lenses had a small impact on visual performance. Investigators determined that lenses featuring multifocality decreased visual performance, in particular when power variations across the optic zone were large and/or the lens was significantly de-centered.

Researchers reveal that humans identify four “unique hues”—blue, green, yellow and red—that do not appear to contain mixtures of other colors. Unique yellow (UY) is particularly interesting because it is stable across large populations: Participants reliably set a monochromatic light to a stereotypical wavelength. Individual variability in the ratio of L- and M-cones in the retina, and effects of aging impact unique green (UG) settings [1,2], but cannot predict the relatively small inter-individual differences in UY [2,3]. The stability of UY may arise because it is set by the environment rather than retinal physiology. Support for this idea comes from studies of long-term, artificial chromatic adaptation [4,5], but there is no evidence for this process in natural settings.

In a recent study, researchers measured 67 participants in York (England) in the winter and summer and found a significant seasonal change in UY settings. In comparison, Rayleigh color matches that would not be expected to exhibit environmentally driven changes were found to be constant. The seasonal shift in UY settings is consistent with a model that reweights L- and M-cone inputs into a perceptual opponent color channel after a small, seasonally driven change in mean L:M cone activity.