Age-related deficits in attentional control of perceptual rivalry

AbstractSome aspects of attentional processing are known to decline with normal aging. To understand how age affects the attentional control of perceptual stability, we investigated age-related changes in voluntarily controlled perceptual rivalry. Durations of the dominant percept, produced by an ambiguous Rubin vase-faces figure, were measured in conditions that required passive viewing and attentional control: holding and switching the dominant percept. During passive viewing, mean dominance duration in the older group was significantly longer (63%) than the dominance duration found in the young group. This age-related deficit could be due to a decline in the apparent strength of the alternating percepts as a result of higher contrast gain of visual cortical activity and a reduction in the amount of attentional resources allocated to the ambiguous stimulus in older people compared to young adults. In comparison to passive viewing, holding the dominant percept did not significantly alter the dominance durations in the older group, while the dominance durations in the young group were increased (∼100%). The dominance durations for both age groups in switch conditions were reduced compared to their passive viewing durations (∼40%). The inability of older people to voluntarily prolong the duration of the dominant percept suggests that they may have abnormal attentional mechanisms, which are inefficient at enhancing the effective strength of the dominant percept. Results suggest that older adults have difficulty holding attended visual objects in focus, a problem that could affect their ability to carry out everyday tasks

The role of peripheral ocular length and peripheral corneal radius of curvature in determining refractive error

PURPOSE: The purpose of this study was to extend the knowledge of peripheral biometric component and its relationship to refractive status in healthy individuals by determining the correlation between peripheral ocular length to peripheral corneal radius ratio and the refractive error. METHODS: This prospective study was conducted on thirty-three healthy adult participants. Refractive error was assessed objectively and subjectively and recorded as the mean spherical equivalent. Central and peripheral ocular lengths at 30° were assessed using partial coherence interferometry under dilation with 1% tropicamide. Central and peripheral corneal radius of curvature was assessed using Scheimpflug topography. Peripheral ocular lengths at 30° were paired with peripheral corneal curvatures at the incident points of the IOLMaster beam (3.8 mm away from corneal apex) superiorly, inferiorly, temporally and nasally to calculate the peripheral ocular length-peripheral corneal radius ratio. Descriptive statistics were used to describe the distribution and spread of the data. Pearson’s correlation analysis was used to present the association between biometric and refractive variables. RESULTS: Refractive error was negatively correlated with the axial length-central corneal radius ratio (r = −0.91; p < 0.001) and with 30° peripheral ocular length-peripheral corneal radius ratio in all four meridians (r ≤ −0.76; p < 0.001). The strength of the correlation was considerably lower when only axial length or peripheral ocular lengths were used. CONCLUSION: Using the ratios of peripheral ocular length-peripheral corneal radius to predict refractive error is more effective than using peripheral corneal radius or peripheral ocular length alone

Myopia Outcome Study of Atropine in Children (MOSAIC): an investigator-led, double-masked, placebo-controlled, randomised clinical trial protocol

Background: The Myopia Outcome Study of Atropine in Children (MOSAIC) aims to explore the efficacy, safety, acceptability and mechanisms of action of 0.01% unpreserved atropine for myopia control in a European population. Methods: MOSAIC is an investigator-led, double-masked, placebo-controlled, randomised clinical trial (RCT) investigating the efficacy, safety and mechanisms of action of 0.01% atropine for managing progression of myopia. During Phase 1 of the trial, 250 children aged 6-16 years with progressive myopia instil eye drops once nightly in both eyes from randomisation to month 24. From month 24 to 36 participants are re-randomised in Phase 2 of the trial, into continued 0.01% atropine, and washout, at 1:1 ratio for those participants initially randomised to the intervention arm (n=167), during which any potential rebound effects on cessation of treatment will be monitored. All participants initially assigned to the placebo (n=83) crossover to the intervention arm of the study for Phase 2, and from month 24 to 36, instil 0.01% atropine eye drops in both eyes once nightly. Further treatment and monitoring beyond 36 months is planned (Phase 3) and will be designed dependent on the outcomes of Phase 1. Results: The primary outcome measure is cycloplegic spherical equivalent refractive error progression at 24 months. Secondary outcome measures include axial length change as well as the rebound, safety and acceptability profile of 0.01% atropine. Additional analyses will include the mechanisms of action of 0.01% atropine for myopia control. Conclusions: The generalisability of results from previous clinical trials investigating atropine for myopia control is limited by the predominantly Asian ethnicity of previous study populations. MOSAIC is the first RCT to explore the efficacy, safety and mechanisms of action of unpreserved 0.01% atropine in a predominantly White population