Impact of Visual Cues on the Magnitude and Variability of the Accommodative Response in Children With Emmetropia and Uncorrected Hyperopia and Adults

Repeated measures analysis for steady-state evoked potentials

INTRODUCTION

Brain response to repetitive stimuli generates steady-state evoked potentials (ssEP) that vary depending on the experimental conditions. To analyze these responses, Fourier measurements extracted from ssEP data require statistical techniques to differentiate neural responses across various experimental conditions within the same participant(s). In this study, we introduce new statistical methods to compare multiple dependent clusters of discrete Fourier measurements corresponding to multiple experimental conditions.

METHODS

We present two statistics: 1) The first statistic is derived from repeated measures analysis of variance (ANOVA) for complex numbers, used to compare multiple dependent circular clusters of Fourier estimates under the assumption of equal variance across the clusters. 2) The second statistic is employed when either the assumption of circularity within the clusters or the assumption of equal variance across the clusters is violated. In this case, we derive the statistic from the rank-sum Friedman test to compare multiple related clusters of complex numbers.

RESULTS

We demonstrated the validity of the statistics using simulated and empirical ssEP data. Our methods offer robust statistical tools that maintain a constant Type-I error of 0.05 in all conditions, including equal or unequal variance-covariance matrix of the real and imaginary components of Fourier estimates across the circular and elliptical clusters, even in the presence of outliers in the dataset. Furthermore, our statistics demonstrate a lower Type-II error compared to repeated measures multivariate analysis of variance (rmMANOVA).

CONCLUSION

The statistical methods enable us to compare multiple dependent clusters of Fourier estimates corresponding to multiple experimental conditions within the same participant(s), whether or not the variance is equal across the circular or elliptical clusters, even with outliers in the dataset.

Accommodation microfluctuation in individuals with mTBI and the potential effect of chromatic filter on this parameter

Individuals with mild traumatic brain injury (mTBI) exhibit significant accommodative abnormalities. Accommodation microfluctuation (MFs) plays an important role in the accommodation steady-state control. This study was set to investigate the characteristics of the MFs in mTBI subjects and whether chromatic filter (CF) or neutral density filter (ND) would impact these parameters. 54 healthy and 30 mTBI young adults participated. Tonic accommodation (TA) was recorded in complete darkness after dark adaptation. The steady-state accommodation response (AR) for various stimulus distances was recorded at baseline (no filter; NF), with CF and ND. The low and high frequency component (LFC and HFC respectively) of MFs was analyzed. Subjects with mTBI exhibited significantly lower MFs, especially at higher stimulus levels. There was a strong negative correlation between the accommodation error (AE) and the LFC. Increased lag of accommodation (AE > 0 D) was associated with lower LFC and vice versa. Both filter conditions exerted a minimum impact on the MFs overall. A strong positive correlation between MFs and TA was revealed for both groups. Our study showed that mTBI significantly impaired the MFs of accommodation. The observed lower MFs power in mTBI appears to be subsequent to the higher lag of accommodation, suggesting an underlying deficit in the accommodative motor controller to generate sufficient response. The strong correlation between TA and MFs, as well as the lack of effect from different filters, further supports the theory that sensory blur detection does not play a significant role in MFs of accommodation.

Validation of the PowerRef 3 for Measuring Accommodation: Comparison With the Grand Seiko WAM-5500A Autorefractor

Purpose

This validation study examines the PowerRef 3 as a method for measuring accommodation objectively. We assess agreement with refractive measurements obtained simultaneously by the Grand Seiko WAM-5500A autorefractor.

Methods

Refractive measurements were recorded simultaneously using the PowerRef 3 and WAM-5500A in 32 noncyclopleged participants aged 15 to 46 years. Accommodative states were recorded for 10 seconds at six accommodative demands (5 diopters [D], 4 D, 3 D, 2.5 D, 2 D, and 0 D) while participants fixated a high-contrast Maltese cross. WAM-5500A measurements were converted to power in the vertical meridian for comparison with PowerRef 3 data. Dioptric difference values were computed, and agreement was assessed using Bland-Altman plots with 95% limits of agreement (LOA) and intraclass correlation coefficient analyses.

Results

The mean absolute dioptric differences measured 0.14 D or less across accommodative demands. Analyses showed an excellent intraclass correlation coefficient across the tested demands (0.93). Bland-Altman plots indicated a bias of -0.02 D with 95% LOA of -1.03 D to 0.99 D. The 95% LOA was smallest for the 3 D demand (-0.71 D to 0.64 D), and largest at 5 D demand (-1.51 D to 1.30 D).

Conclusions

The mean dioptric differences between the PowerRef 3 and WAM-5500A autorefractor were small and not clinically significant. While some variability in agreement was observed depending on the tested demand, the PowerRef 3 demonstrated good agreement with the WAM-5500A.

Translational Relevance

The PowerRef 3 may be used to obtain objective measures of accommodation both monocularly and binocularly and provides a more flexible method, especially in pediatric populations.

Refractive Error and Eye Health: An Umbrella Review of Meta-Analyses

Purpose: To explore the associations between refractive errors and multiple eye health outcomes. Methods: This is an umbrella review based on systematic reviews with meta-analyses. In our study, refractive errors included myopia, hyperopia, astigmatism, and anisometropia. We reconducted the meta-analyses whose primary data were available in sufficient detail by random effect model. Heterogeneity was assessed by I ². The main outcomes included myopic macular degeneration (MMD), retinal detachment (RD), cataract, open-angle glaucoma (OAG), strabismus, age-related macular degeneration (AMD), and diabetic retinopathy (DR). Results: Myopia was associated with increased risk of MMD (relative risk = 102.11, 95% CI 52.6-198.22), RD (3.45, 1.08-11.00), nuclear cataract (2.15, 1.53-3.03), posterior subcapsular (PSC) cataract (1.74, 1.41-2.15), OAG (1.95, 1.74-2.19), exotropia (5.23, 2.26-12.09), but decreased risk of DR (0.83, 0.66-1.04), and early AMD (0.80, 0.67-0.94). From mild-to-high myopia, the association strengthened for MMD, RD, nuclear cataract, PSC cataract, OAG, and DR. Hyperopia was associated with an increased risk of early AMD (1.09, 1.01-1.18) and esotropia (22.94, 10.20-51.62). Astigmatism and anisometropia were associated with increased risk of both exotropia and esotropia. Conclusions: Myopia, especially high myopia, demonstrated the highest risk for eye health outcomes, such as MMD, RD, OAG, nuclear and PSC cataracts, and exotropia. However, myopia was associated with a lower risk of early AMD and DR. Individuals with hyperopia are more likely to suffer early AMD and esotropia. Astigmatism and anisometropia predispose to strabismus. A lot of research studies on the mechanism of the associations are needed. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=239744; identifier: 239744.

Vergence, accommodation, and visual tracking in children and adolescents evaluated in a multidisciplinary concussion clinic

Many patients with concussion experience visual symptoms following injury that lead to a diagnosis of convergence insufficiency, accommodative insufficiency, or saccadic dysfunction. However, these diagnostic categories are based on aggregates of clinical tests developed from a non-concussed population and therefore may not accurately describe visual deficits in the concussed population. Thus, we sought to understand individual metrics of visual dysfunction in chronically symptomatic post-concussion patients. This retrospective cross-sectional study included patients examined at the multidisciplinary concussion clinic (MDCC) at Boston Children's Hospital over four years. Patients aged 5-21 years who had a complete assessment of eye alignment, vergence, accommodation, and visual tracking, and had visual acuity better than or equal to 20/30 in each eye were included. Patients with history of amblyopia, strabismus, or ocular pathology were excluded. Chart review yielded 116 patients who met inclusion criteria (median age 15 years, 64% female). The majority of patients (52%) experienced a single concussion and most were sports-related (50%). Clinical data show vergence, accommodation, or visual tracking deficits in 95% of patients. A receded near point of convergence (NPC, 70/116) and reduced accommodative amplitude (63/116) were the most common deficits. Both NPC and accommodative amplitude were significantly correlated with one another (r = -0.5) and with measures of visual tracking (r = -0.34). Patients with chronic post-concussion symptoms show deficits in individual metrics of vergence, accommodation and visual tracking. The high incidence of these deficits, specifically NPC and accommodative amplitude, highlights the need for a detailed sensorimotor evaluation to guide personalized treatment following concussion.