Gaze behaviour during multiple object tracking is dependent on binocular vision integrity.

INTRODUCTION: Despite the critical importance of binocular vision integrity in daily activities, there exists limited understanding of how alterations in binocular vision integrity impact gaze behaviour during dynamic, complex psychomotor skills. This study aimed to measure how alterations in binocular vision integrity, created by Bangerter filters (BF), affect gaze behaviour during multiple object tracking (MOT). METHODS: During the experiment, 22 volunteers completed the MOT task under three different visual conditions. The first condition involved natural binocular viewing, while the second and third conditions used 0.4 and 0.2 neutral density BF, respectively, resulting in monocular blur in the sensorially dominant eye. During the MOT task, participants were instructed to track three of eight balls for 10 s, and the speed was adjusted using a staircase procedure. Throughout the task, the following gaze parameters were recorded: fixation duration, saccade duration, amplitude and frequency as well as blink rate. RESULTS: During MOT execution, participants employed three gaze strategies regardless of viewing conditions: saccadic movements were predominant, followed by maintaining fixation on a central location throughout the trial and to a lesser extent, smooth pursuit eye movements. There was a significant effect of manipulating viewing conditions on the MOT scores (p = 0.046, η2 = 0.09). As the viewing conditions became more difficult, we observed a decrease in fixation duration (p = 0.004, η2 = 0.16) and blink rate (p < 0.001, η2 = 0.20) and an increase in saccadic amplitude (p < 0.001, η2 = 0.29). CONCLUSIONS: The results support the notion that perceptual-cognitive skills depend on the integrity of binocular vision, underscoring the sensitivity of gaze behaviours to any impairment of binocular function.

The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence.

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well-being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re-greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling due to additional vegetation increases precipitation but decreases local water yield and steady-state runoff. Therefore, in the drier regions/periods and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Recent analyses indicate that the latter regime dominates the global response of the terrestrial water cycle to re-greening. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation as well as for motivating and guiding ecological restoration.

Diurnal Variation in Accommodation, Binocular Vergence, and Pupil Size.

SIGNIFICANCE: Our results show significant diurnal variations in accommodative function and the magnitude of the phoria. Therefore, when comparing visual measures in clinical or laboratory settings, performing the visual examination at the same time of day (±1 hour) is encouraged. PURPOSE: The aim of this study was to evaluate the accommodation, binocular vergence, and pupil behavior on three different times during the day. METHODS: Twenty collegiate students (22.8 ± 2.1 years) participated in this study. Participants visited the laboratory on three different days at 2-hourly intervals (morning, 9:00 to 11:00 am ; afternoon, 2:00 to 4:00 pm ; evening, 7:00 to 9:00 pm ). The binocular vergence and accommodative function were measured using clinical optometric procedures, and the accommodative response and pupil function were evaluated in binocular conditions using the WAM-5500 autorefractometer. RESULTS: The accommodative amplitude for the right and left eyes showed statistically significant differences for the time interval ( P = .001 and P = .02, respectively), revealing higher accommodative amplitude in the morning and afternoon in comparison with the evening. Participants were more esophoric when assessed in the morning in comparison with the evening at far and near ( P = .02 and P = .01, respectively) and when assessed in the afternoon in comparison with the evening at far distance ( P = .02). The magnitude of accommodative response was higher in the morning, and it decreased throughout the day at 500 ( P < .001), 40 ( P = .05), and 20 cm ( P < .001). No statistically significant differences were obtained for any other variable. CONCLUSIONS: This study shows small diurnal variations in some accommodative and binocular vergence parameters, but no effects were observed for the pupil response. These outcomes are of special relevance for eye care specialists when performing repeated accommodative or binocular vergence measures. However, the diurnal variations were modest and may not influence a routine orthoptic examination.

Effect of manipulating the vergence/accommodation and image size mismatches of the ±2D flipper test on the frequency and precision of accommodative facility.

PURPOSE: The ±2.00 D accommodative facility test presents several limitations, including the lack of objective information and inherent characteristics such as vergence/accommodative conflict, change in apparent size of the image, subjective criteria for judging blur and motor reaction time. By using free-space viewing conditions and an open-field autorefractor to monitor the refractive state, we examined the impact of manipulating these factors on the qualitative and quantitative assessment of accommodative facility. METHODS: Twenty-five healthy young adults (24.5 ± 4.5 years) took part in this study. Participants performed three accommodative facility tests (adapted flipper, 4D free-space viewing and 2.5D free-space viewing) under both monocular and binocular conditions in random order. A binocular open-field autorefractor was used to assess the accommodative response continuously, and these data were used to characterise accommodative facility quantitatively and qualitatively. RESULTS: There were statistically significant differences between the three testing methods both quantitatively (p < 0.001) and qualitatively (p = 0.02). For the same accommodative demand, a lower number of cycles was obtained for the adapted flipper condition in comparison with the 4D free-space viewing test (corrected p-value < 0.001, Cohen's d = 0.78). However, this comparison did not reach statistical significance for qualitative measures of accommodative facility (corrected p-value = 0.82, Cohen's d 0.05). CONCLUSIONS: These data provide evidence that the qualitative assessment of accommodative facility is not influenced by the inherent limitations of the ±2.00 D flipper test. The use of qualitative outcomes by incorporating an open-field autorefractor allows examiners to increase the validity of the accommodative facility test in both clinical and research settings.

Comparative Analysis of Mammal Genomes Unveils Key Genomic Variability for Human Life Span.

The enormous mammal's lifespan variation is the result of each species' adaptations to their own biological trade-offs and ecological conditions. Comparative genomics have demonstrated that genomic factors underlying both, species lifespans and longevity of individuals, are in part shared across the tree of life. Here, we compared protein-coding regions across the mammalian phylogeny to detect individual amino acid (AA) changes shared by the most long-lived mammals and genes whose rates of protein evolution correlate with longevity. We discovered a total of 2,737 AA in 2,004 genes that distinguish long- and short-lived mammals, significantly more than expected by chance (P = 0.003). These genes belong to pathways involved in regulating lifespan, such as inflammatory response and hemostasis. Among them, a total 1,157 AA showed a significant association with maximum lifespan in a phylogenetic test. Interestingly, most of the detected AA positions do not vary in extant human populations (81.2%) or have allele frequencies below 1% (99.78%). Consequently, almost none of these putatively important variants could have been detected by genome-wide association studies. Additionally, we identified four more genes whose rate of protein evolution correlated with longevity in mammals. Crucially, SNPs located in the detected genes explain a larger fraction of human lifespan heritability than expected, successfully demonstrating for the first time that comparative genomics can be used to enhance interpretation of human genome-wide association studies. Finally, we show that the human longevity-associated proteins are significantly more stable than the orthologous proteins from short-lived mammals, strongly suggesting that general protein stability is linked to increased lifespan.

Relationship between dynamic visual acuity and multiple object tracking performance.

We assessed the association between measures of dynamic visual acuity and a multiple object tracking task in physically active young adults. Ninety-four young adults performed the dynamic visual acuity and multiple object tracking tasks. Dynamic visual acuity was measured for horizontal and random walk motion paths at four target speeds (5, 10, 20, and 30°/s). For the multiple object tracking task, participants had to track three out of eight balls for 10 s, and the object speed was adjusted by a staircase procedure. We found that multiple object tracking performance was associated with better identification of horizontally and randomly moving targets in the dynamic visual acuity test (p < .001, r = -.35 [-.52, -.16]; and p < .001, r = -.52 [-.65, -.35]; respectively). This effect was consistent across all target speeds (all p-values<0.05). However, static visual acuity did not correlate with any measure of dynamic visual acuity or multiple object tracking (p > 0.170 in all cases). This study provides novel insights into the association between the ability to identify horizontally and randomly moving targets and track multiple objects. Future studies are needed to determine the potential utility of dynamic visual acuity for talent identification and predicting sports performance in real-game situations.

Manipulating expectancies in optometry practice: Ocular accommodation and stereoacuity are sensitive to placebo and nocebo effects.

INTRODUCTION: There is scientific evidence that an individual's beliefs and/or expectations play a role in the behavioural and physiological response to a given treatment. This study aimed to assess whether the dynamics of the accommodative response and stereoacuity are sensitive to experimentally induced placebo and nocebo effects. METHODS: Nineteen healthy university students performed three experimental sessions (placebo, nocebo and control) in randomised order, with the dynamics of the accommodative response (magnitude and variability), stereoacuity and subjective measures being assessed in all sessions. For the experimental manipulation, participants ingested an inert capsule that was alleged to have positive (white capsule, placebo condition) or negative (yellow capsule, nocebo conditions) effects on the human physiology. In the control condition, participants did not ingest a capsule. RESULTS: The data revealed that the variability of accommodation was sensitive to experimentally induced placebo and nocebo effects, showing a more stable accommodative response for the placebo compared with the nocebo condition (corrected p-value = 0.04, Cohen's d = 0.60). In addition, better stereoacuity was found with the placebo, compared with the nocebo (corrected p-value = 0.01, Cohen's d = 0.69) and control (corrected p-value = 0.03, Cohen's d = 0.59) conditions. Successful experimental manipulation was confirmed by the analysis of subjective perceptions. CONCLUSIONS: These findings provide evidence that manipulating expectations about the efficacy of an inert treatment affect the dynamics of the accommodative response (variability of accommodation) and stereoacuity. The results have important applications in both clinical and research outcomes, where individuals´ beliefs/expectations could modulate the visual function.

Changes in accommodation and behavioural performance with a contact lens for myopia management: A comparison between a dual-focus and a single-vision soft contact lens.

INTRODUCTION: Dual-focus soft contact lenses for myopia management have demonstrated to be an effective strategy to reduce myopia progression. However, this optical design has been shown to alter visual quality and accommodative function. The aim of this study was to examine the accommodative and behavioural performance during the execution of a psychomotor vigilance task (PVT) while wearing dual-focus and single-vision soft contact lenses. METHODS: The steady-state accommodative response was recorded with the WAM-5500 binocular open-field autorefractor during the execution of a 10-min PVT at 50 cm either with the dual-focus (MiSight 1-day) or single-vision (Proclear 1-day) soft contact lenses, using a sample of 23 healthy young adults. Each experimental session was performed on two different days in a counterbalanced order. RESULTS: A greater lag of accommodation, variability of accommodation and reaction time was found while wearing dual-focus in comparison with single-vision soft contact lenses (mean differences during the 10-min PVT were 0.58 ± 0.81 D, p < 0.001; 0.31 ± 0.17 D, p < 0.001 and 15.22 ± 20.93 ms, p = 0.002, respectively). Also, a time-on-task effect was found for the variability of accommodation and reaction time (p = 0.001 and p < 0.001, respectively), observing higher values over time. However, the lag of accommodation did not change significantly as a function of time-on-task (p = 0.33). CONCLUSION: Dual-focus soft contact lens wear influences the steady-state accommodative response and behavioural performance during the execution of a visual vigilance task in the short-term. Eye care practitioners should be aware of these effects when prescribing these lenses for myopia management, and provide specific recommendations according to the individual visual needs.

Effects of the COVID-19 lockdowns on the management of coral restoration projects.

Coral restoration initiatives are gaining significant momentum in a global effort to enhance the recovery of degraded coral reefs. However, the implementation and upkeep of coral nurseries are particularly demanding, so that unforeseen breaks in maintenance operations might jeopardize well-established projects. In the last 2 years, the COVID-19 pandemic has resulted in a temporary yet prolonged abandonment of several coral gardening infrastructures worldwide, including remote localities. Here we provide a first assessment of the potential impacts of monitoring and maintenance breakdown in a suite of coral restoration projects (based on floating rope nurseries) in Colombia, Seychelles, and Maldives. Our study comprises nine nurseries from six locations, hosting a total of 3,554 fragments belonging to three coral genera, that were left unsupervised for a period spanning from 29 to 61 weeks. Floating nursery structures experienced various levels of damage, and total fragment survival spanned from 40 to 95% among projects, with Pocillopora showing the highest survival rate in all locations present. Overall, our study shows that, under certain conditions, abandoned coral nurseries can remain functional for several months without suffering critical failure from biofouling and hydrodynamism. Still, even where gardening infrastructures were only marginally affected, the unavoidable interruptions in data collection have slowed down ongoing project progress, diminishing previous investments and reducing future funding opportunities. These results highlight the need to increase the resilience and self-sufficiency of coral restoration projects, so that the next global lockdown will not further shrink the increasing efforts to prevent coral reefs from disappearing.

The short-term effects of wearing swimming goggles on corneal biomechanics.

PURPOSE: This study aimed to assess the impact of wearing swimming goggles (SG) on corneal biomechanics. METHODS: Corneal deformation response, central corneal thickness (CCT), intraocular pressure (IOP) and biomechanically corrected intraocular pressure (bIOP) were measured with the Corvis system (Oculus Optikgeräte GmbH, Wetzlar, Germany) in thirty-one healthy young adults while wearing a drilled SG. All measurements were obtained before, at 30 s, 2 min, 3.5 min and 5 min of wearing SG, just after SG removal and after 2 min of SG removal. RESULTS: The corneal biomechanics is sensitive to SG wear, observing lower corneal deformability during SG use. Specifically, wearing SG caused an increase in the time and length of the first applanation and radius curvature at the highest concavity, as well as a decrease and in the velocity of the first applanation and time and deformation amplitude of the second applanation (p < 0.001 in all cases). After SG removal, corneal biomechanical parameters showed a rebound-effect, obtaining a higher corneal deformability in comparison with baseline reading (p-corrected < 0.05 in all cases). Additionally, IOP and bIOP significantly increased while wearing SG (p < 0.001 in both cases), whereas CCT remained stable (p = 0.850). CONCLUSIONS: Wearing SG modifies the biomechanical properties of the cornea, with reduced corneal deformability during SG wear. The outcomes of this study should be taken into consideration when making clinical decisions in subjects at high risk of developing corneal ectasias or glaucoma, as well as in the post-surgical management of these ocular conditions.

A Collection of Designed Peptides to Target SARS-CoV-2 Spike RBD-ACE2 Interaction.

The angiotensin-converting enzyme 2 (ACE2) is the receptor used by SARS-CoV and SARS-CoV-2 coronaviruses to attach to cells via the receptor-binding domain (RBD) of their viral spike protein. Since the start of the COVID-19 pandemic, several structures of protein complexes involving ACE2 and RBD as well as monoclonal antibodies and nanobodies have become available. We have leveraged the structural data to design peptides to target the interaction between the RBD of SARS-CoV-2 and ACE2 and SARS-CoV and ACE2, as contrasting exemplar, as well as the dimerization surface of ACE2 monomers. The peptides were modelled using our original method: PiPreD that uses native elements of the interaction between the targeted protein and cognate partner(s) that are subsequently included in the designed peptides. These peptides recapitulate stretches of residues present in the native interface plus novel and highly diverse conformations surrogating key interactions at the interface. To facilitate the access to this information we have created a freely available and dedicated web-based repository, PepI-Covid19 database, providing convenient access to this wealth of information to the scientific community with the view of maximizing its potential impact in the development of novel therapeutic and diagnostic agents.

The short-term effects of artificially-impaired binocular vision on driving performance.

Appropriate visual function is paramount to ensuring adequate driving performance and road safety. Here, we examined the influence of sudden artificially-impaired binocular vision on driving performance using a car simulator. Twenty-four young drivers (mean age 22.42 ± 3.19 years) drove under three different visual conditions (natural driving, monocular blur, and monocular occlusion) through three different traffic environments with low, medium, and high levels of complexity (highway, rural, and city, respectively). We assessed their driving performance, perceived level of task complexity, and subjectively-experienced road safety. Furthermore, as a manipulation check, we also evaluated the drivers' cardiac vagal responses, as a well-known index of task complexity. The sudden deterioration of binocular vision caused unsafe driving behaviours (distance out of the road and maximum breaking intensity) in the most complex traffic environments. Specific self-regulatory strategies (i.e. increased cardiac vagal responses) and subjective responses corroborated these results. Practitioner summary: This study provides evidence that the sudden deterioration of binocular vision has a detrimental effect on simulated driving performance. Our analysis of cardiovascular functioning shows that drivers adopt self-regulatory strategies when their binocular vision functioning is compromised. Abbreviations: VA: visual acuity; BV: binocular vision; HRV: heart rate variability; NASA: TLX: NASA-Task Load Index; SSS: Stanford Sleepiness scale; RMSSD: root mean square of successive difference; HF: high-frequency.

Effects of caffeine intake on the biomechanical properties of the cornea: a placebo-controlled, double-blind, crossover pilot study in low caffeine consumers.

PURPOSE: To assess the short-term effects of caffeine intake on the biomechanical properties of the cornea, as well as its possible association with the intraocular pressure (IOP), as measured by corneal visualization Scheimpflug technology (CorVis ST) in healthy subjects. METHODS: Twenty-two low caffeine consumers ingested either a caffeine (4 mg/Kg) or placebo capsule in two separate sessions. IOP and corneal biomechanics parameters, including time, velocity, length, and deformation amplitude at the first applanation (A1T, A1V, A1L, and A1D, respectively); time, velocity, length, and deformation amplitude at the second applanation (A2T, A2V, A2L, and A2D, respectively); time at the highest concavity (HCT), radius curvature at the highest concavity (HCR), deformation amplitude at the highest concavity (HCDA), and peak distance (PD), were measured with the Corvis ST before and after 30 min, 60 min, and 90 min of caffeine/placebo intake. RESULTS: Caffeine intake reduced the corneal deformability, inducing significant changes in A1T, A2V, A2T, HCDA, HCT, and PD (all p values < 0.05). Non-corrected and biomechanically corrected IOP values were higher after caffeine intake (p = 0.001 and 0.033, respectively). Also, the changes in IOP after caffeine intake were positively associated with A1T (r = 0.790 to 0.962), and negatively associated with A2T (r = - 0.230 to - 0.722) and PD (r = - 0.506 to - 0.644). CONCLUSIONS: Caffeine intake reduces the corneal deformability, with these changes being partially associated with the IOP rise. These findings evidence that exogenous factors such as caffeine intake should be taken into consideration when making clinical decisions that are based on the biomechanical properties of the cornea.

Short-term effects of caffeine intake on anterior chamber angle and intraocular pressure in low caffeine consumers.

BACKGROUND: Acute caffeine consumption causes a transient increase in IOP; however, the mechanisms underlying this phenomenon remain unknown. This study aims to determine the structural changes in cornea and anterior chamber associated with caffeine ingestion. METHODS: Seventeen healthy low caffeine consumers ingested a capsule of caffeine (~ 4 mg/kg) or placebo (300 mg of corn-starch) in a counterbalanced manner. We measured IOP by rebound tonometry and the anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA) and central corneal thickness (CCT) with the Pentacam rotating Scheimpflug camera. Subjective feelings of arousal were also obtained. All the dependent variables were obtained before and 30, 60 and 90 min after caffeine/placebo intake. RESULTS: Caffeine intake caused an acute IOP rise (p = 0.005, η2 = 0.403) and a narrowing ACA (p = 0.028, η2 = 0.266). However, our data did not reveal any effect on CCT, ACD and ACV after caffeine ingestion (p = 0.798, p = 0.346, p = 0.175, respectively). Participants reported greater levels of activation after ingesting caffeine in comparison to placebo (p = 0.037, η2 = 0.245). CONCLUSION: The IOP rise associated with caffeine intake may be caused by an ACA reduction, which may add resistance to the outflow of aqueous humour. The current results may be of special relevance for subjects at high risk for glaucoma onset or progression and may help to understand the mechanisms underlying caffeine-induced ocular hypertension.

Accommodative response in children with attention deficit hyperactivity disorder (ADHD): the influence of accommodation stimulus and medication.

BACKGROUND: There are claims that ocular accommodation differs in children with attention deficit hyperactivity disorder (ADHD) compared to typically developing children. We examined whether the accommodation response in ADHD children is influenced by changing the stimulus to accommodation in an attempt modify the level of attentional engagement or by medication for the condition. METHODS: We measured the accommodative response and pupil diameter using a binocular, open-field autorefractor in non-medicated and medicated children with ADHD (n = 22, mean age = 10.1 ± 2.4 years; n = 19; mean age = 11.0 ± 3.8 years; respectively) and in an age-matched control group (n = 22; mean age = 10.6 ± 1.9 years) while participants were asked to maintain focus on (i) a high-contrast Maltese cross, (ii) a frame of a cartoon movie (picture) and (iii) a cartoon movie chosen by the participant. Each stimulus was viewed for 180 s from a distance of 25 cm, and the order of presentation was randomised. RESULTS: Greater lags of accommodation were present in the non-medicated ADHD in comparison to controls (p = 0.023, lags of 1.10 ± 0.56 D and 0.72 ± 0.57 D, respectively). No statistically significant difference in the mean accommodative lag was observed between medicated ADHD children (lag of 1.00 ± 0.44D) and controls (p = 0.104) or between medicated and non-medicated children with ADHD (p = 0.504). The visual stimulus did not influence the lag of accommodation (p = 0.491), and there were no significant group-by-stimulus interactions (p = 0.935). The variability of accommodation differed depending on the visual stimulus, with higher variability for the picture condition compared to the cartoon-movie (p < 0.001) and the Maltese cross (p = 0.006). In addition, the variability yielded statistically significant difference for the main effect of time-on-task (p = 0.027), exhibiting a higher variability over time. However, no group differences in accommodation variability were observed (p = 0.935). CONCLUSIONS: Children with ADHD have a reduced accommodative response, which is not influenced by the stimulus to accommodation. There is no marked effect of medication for ADHD on accommodation accuracy.

Children with Attention-deficit/Hyperactivity Disorder Show an Altered Eye Movement Pattern during Reading.

SIGNIFICANCE: Attention-deficit/hyperactivity disorder (ADHD) is characterized by oculomotor abnormalities. However, the eye movement pattern of children with ADHD during reading has yet to be fully determined. This investigation provides novel insights into the altered eye movement pattern during oral reading of nonmedicated children with pure ADHD in comparison with age-matched controls. PURPOSE: The purpose of this study was to objectively compare the eye movement pattern during oral reading in a group of nonmedicated children with pure ADHD and an age-matched control group. METHODS: Forty-one children, 21 children with pure ADHD (9.3 ± 2.2 years, 15 boys) and 20 control children (9.3 ± 2.5 years, 10 boys), orally read a standardized text according to their age while the eye movement pattern was objectively recorded using the Visagraph Eye Movement recording system. RESULTS: The Bayesian statistical analyses revealed that children with ADHD exhibited a significantly higher number of fixations (Bayes factor 10 [BF10] = 3.39), regressions (BF10 = 9.97), saccades in return sweeps (BF10 = 4.63), and anomalies of fixations and regressions (BF10 = 3.66) compared with controls. In addition, children with ADHD significantly showed longer reading times (BF10 = 31.29), as well as lower reading rate (BF10 = 156.74) and grade-level equivalent (BF10 = 168.24) in comparison with controls. CONCLUSIONS: Our data showed that the nonmedicated children with pure ADHD have an altered eye movement pattern during oral reading when compared with controls, which cannot be attributable to any comorbid condition. The present outcomes may help to understand the link between ADHD and reading performance and design the most pertinent strategies to enhance the reading skills of this population.

Effects of a blue-blocking screen filter on accommodative accuracy and visual discomfort.

INTRODUCTION: The prescription of blue-blocking (B-B) filters for the management of visual symptoms and signs associated with the use of electronic devices is routinely performed by eye care specialists. However, the utility of B-B filters is a matter of debate and discussion by the scientific community due to the lack of evidence supporting their use. Here, we aimed to determine the effects of using B-B filters on the dynamics of the accommodative response and pupil size and perceived levels of visual discomfort, while performing a 30-min reading task at a close distance in subjects who routinely use electronic devices. METHODS: Nineteen healthy young adults (22.0 ± 2.7 years) read two 30-min passages on a computer screen placed at 50 cm, either while using a commercially available B-B filter or without any filter on two different days. The magnitude and variability of both the accommodative response and pupil size were dynamically measured for 60 s using the WAM-5500 open field autorefractometer at 4-5, 9-10, 14-15, 19-20, 24-25, and 29-30 min into the trial. The perceived levels of visual discomfort were also obtained. RESULTS: The lag and variability of accommodation were insensitive to the blue light level (p = 0.34 and 0.62, respectively). There was a time-on-task effect for the variability of accommodation, showing greater instability over time regardless of the blue light level. The use of the B-B filter was associated with improved reading speed (p = 0.02), with an increase of 16.5 words per minute. However, it was not associated with any significant change in pupil dynamics or the perceived levels of visual discomfort (p> 0.05 in both cases). CONCLUSIONS: Our data showed that the use of a B-B filter had no effect on accommodative dynamics or visual symptomatology. Based on these findings, there is no support for the prescription of B-B filters to attenuate the visual symptoms and signs associated with the use of electronic devices in healthy young adults.

Accommodative dynamics and attention: the influence of manipulating attentional capacity on accommodative lag and variability.

PURPOSE: There is evidence that attention can modulate ocular dynamics, but its effects on accommodative dynamics have yet to be fully determined. We investigated the effects of manipulating the capacity to focus on task-relevant stimuli, using two levels of dual-tasking (arithmetic task) and auditory feedback, on the accommodative dynamics at three different target distances (500, 40 and 20 cm). METHODS: The magnitude and variability of the accommodative response were objectively measured in 20 healthy young adults using the Grand Seiko WAM-5500 autorefractor. In randomised order, participants fixated on a Maltese cross while 1) performing an arithmetic task with two levels of complexity (low and high mental load); 2) being provided with two levels of auditory feedback (low and high feedback); and 3) without performing any mental task or receiving feedback (control). Accommodative and pupil dynamics were monitored for 90 seconds during each of the 15 trials (5 experimental conditions x 3 target distances). RESULTS: The lag of accommodation was sensitive to the attentional state (p = 0.001), where a lower lag of accommodation was observed for the high feedback condition compared to the control (corrected p-value = 0.009). The imposition of mental load while fixating on a distant target led to a greater accommodative response (corrected p-value = 0.010), but no effects were found for the near targets. There was a main effect of the experimental manipulation on the accommodative variability (p < 0.001), with the use of auditory feedback improving the accuracy of the accommodative system. CONCLUSIONS: Our data show that accommodative dynamics is affected by varying the capacity to focus on task-relevant stimuli, observing an improvement in accommodative stability and response with auditory feedback. These results highlight an association between attention and ocular dynamics and provide new insight into the control of accommodation.

Dynamics of the accommodative response under artificially-induced aniseikonia.

Aniseikonia has demonstrated to deteriorate the binocular function, however its impact on the accommodative response remains unknown. The present study aimed to analyze the effects of artificially-induced aniseikonia, using afocal magnifiers, on the dynamics of the accommodative response. The magnitude and variability of the accommodative response were objectively measured in 20 young healthy subjects by a binocular open-field autorefractometer. Participants observed a static stimulus for 90 s, under seven degrees of aniseikonia (0%, 1%, 3%, 5%, 8%, 10% and 12%), and at three distances (500 cm, 40 cm and 20 cm). Complementarily, near stereoacuity, and perceived levels of fatigue and visual discomfort were assessed. The degree of induced aniseikonia was associated with the magnitude of the accommodative response (p < 0.001, ηp2 = 0.329), obtaining a statistically significant reduced accommodative lag for the induced aniseikonia conditions of 8%, 10% and 12% in comparison to the control condition at 40 cm (p-corrected = 0.019, <0.001 and 0.013, respectively) and at 20 cm (p-corrected < 0.001, <0.001 and 0.003, respectively). However, the degree of induced aniseikonia did not reveal any effect on the variability of accommodation (p > 0.05). We also found a decline in near stereoacuity and an increment of visual symptomatology when inducing aniseikonia (p < 0.05). Our data evidenced that greater degrees of induced aniseikonia cause a heightened accommodative response. These preliminary findings may be of relevance for patients undergoing cataract or refractive surgery procedures in which aniseikonia can be induced.

Influence of holding weights of different magnitudes on intraocular pressure and anterior eye biometrics.

PURPOSE: This study is aimed at determining the impact of holding weight corresponding to the 10% and 20% of participants' body weight during 5-min on intraocular pressure (IOP) and anterior eye biometrics. METHODS: Eighteen healthy young adults grabbed two jugs with comfort-grip handles, which were filled with water in order to achieve the desirable load (10% and 20% of participants' body weight). A rebound tonometer and Oculus Pentacam were used to assess IOP and anterior segment biometrics, respectively, at baseline, after 0.5, 2, 3.5, and 5 min of holding weights, as well as after 0.5 and 2 min of recovery in each experimental condition (control, 10%, and 20%). RESULTS: There was a significant effect of the load used on IOP (p = 0.016, ƞp2 = 0.215) and anterior chamber angle (p = 0.018, ƞp2 = 0.211), with the load corresponding to 20% of participants' body weight promoting a significant IOP rise (corrected p value = 0.035, d = 0.67), and anterior chamber angle reduction (corrected p value = 0.029, d = 0.69) in comparison with the control condition. No effects of holding weight were observed for anterior chamber depth and central corneal thickness (p > 0.348). CONCLUSIONS: Our data evidence that holding weight during 5 min increases IOP and narrows the anterior chamber angle, being these effects significant when using a load corresponding to 20% of body weight. Based on the current outcomes, lifting or carrying heavy loads may be discouraged for glaucoma patients or individuals at high risk for glaucoma onset, although future studies should explore the clinical relevance of our findings.