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.

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.

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.

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.

The intraocular pressure lowering-effect of low-intensity aerobic exercise is greater in fitter individuals: a cluster analysis.

This study aimed to determine the influence of physical fitness level and sex on intraocular pressure (IOP) during the low-intensity aerobic exercise. Forty-four participants (twenty-two men) cycled 30 minutes at low intensity (10% of the maximal power). Maximal power was determined by asking participants to perform maximal sprints of 6 seconds against 3-4 different resistances separated by 3 minutes of rest. The IOP was measured on 9 occasions (1) prior to the warm-up, (2) after the warm-up, (3-7) every 6 minutes during the low-intensity cycling task, and (8-9) 5 and 10 minutes after the cycling task. Low-intensity aerobic exercise had a lowering effect on IOP, being the beneficial effect more accentuated and prolonged in the High-fit group (IOP reduction compared to baseline lasted 30 minutes) than in the Low-fit group (IOP was only reduced at 6 minutes of exercise compared to baseline). Participants´ sex had no effect on the IOP behaviour at any time point (p = 0.453). These findings indicate that individuals who need to reduce IOP levels (i.e., glaucoma patients or those at risk) should increase or maintain a high fitness level to benefit more from the IOP lowering effect during low-intensity aerobic exercises.

Intraocular pressure responses to walking with surgical and FFP2/N95 face masks in primary open-angle glaucoma patients.

PURPOSE: The use of face mask is globally recommended as a preventive measure against COVID-19. However, the intraocular pressure (IOP) changes caused by face masks remain unknown. The objective of this study was to assess the impact of wearing surgical and FFP2/N95 face masks during a 400-m walking protocol on IOP in primary open-angle glaucoma (POAG) patients. METHODS: Thirteen subjects diagnosed of POAG (21 eyes) were enrolled in this study. IOP was measured at baseline, during the 400-m walking protocol and after 5 min of passive recovery while POAG patients wore a surgical mask, FFP2/N95 mask and no mask in randomized order. From the 21 POAG eyes, we analyzed the IOP changes caused by physical exercise with two face masks and without wearing any face mask. RESULTS: At rest (baseline and recovery measurements), the use of the different face masks did not affect IOP levels (mean differences ranging from 0.1 to 0.6 mmHg). During physical activity, wearing an FFP2/N95 mask caused a small (mean differences ranging from 1 to 2 mmHg), but statistically significant, IOP rise in comparison to both the surgical mask and control conditions (Cohen's d = 0.63 and 0.83, respectively). CONCLUSION: Face masks must be used to minimize the risk of SARS-CoV-2 transmission, and POAG patients can safely use FFP2/N95 and surgical masks at rest. However, due to the IOP rise observed while walking with the FFP2/N95 mask, when possible, POAG patients should prioritized the use of surgical masks during physical activity.

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.

Intraocular pressure increases during dynamic resistance training exercises according to the exercise phase in healthy young adults.

PURPOSE: To determine the intraocular pressure (IOP) changes caused by the execution of lower body and upper body resistance training exercises leading to muscular failure depending on the exercise phase (concentric vs. eccentric). We also assessed the influence of the exercise type (back squat vs. biceps curl) and level of effort on the IOP response. METHODS: Nineteen physically active young adults performed four sets (2 exercise type × 2 exercise phase) of 10 repetitions leading to muscular failure while adopting a normal breathing pattern. IOP was measured by rebound tonometry at baseline, after each of the ten repetitions, and after 1 min of recovery. RESULTS: There was a main effect of the exercise phase (p < 0.001, η2 = 0.56), observing greater IOP values in the eccentric condition of the back squat and concentric condition of the biceps curl. Also, greater IOP values were obtained for the back squat in comparison with the biceps curl (p < 0.001, η2 = 0.61), and IOP progressively increases with the level of accumulated effort (p < 0.001, η2 = 0.88; Pearson r = 0.97-0.98). CONCLUSIONS: IOP fluctuates during the different phases of the repetition in dynamic resistance training exercises, being greater IOP values observed during the more physically demanding phases of the exercise (eccentric phase of the back squat and concentric phase of the biceps curl). A heightened IOP response is positively associated with muscle size (back squat > biceps curl) and with the level of effort (number of accumulated repetitions). Based on these findings, highly demanding dynamic resistance training should be avoided when maintaining stable IOP levels is desirable.

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.

Effects of Blood Flow Restriction at Different Intensities on IOP and Ocular Perfusion Pressure.

SIGNIFICANCE: The use of blood flow restriction allows obtaining beneficial physical adaptions when combined with low-intensity exercise or even when used alone. We found that using blood flow restriction may be a potential strategy to avoid IOP and ocular perfusion pressure fluctuations provoked by strength and endurance training. PURPOSE: The purpose of this study was to assess the influence of bilateral blood flow restriction in the upper and lower body at two different intensities on IOP and ocular perfusion pressure, as well as the possible sex differences. METHODS: Twenty-eight physically active university students (14 men and 14 women) took part in the study, and blood flow restriction was bilaterally applied with two pressures in the legs and arms. There were five experimental conditions (control, legs-high, legs-low, arms-high, and arms-low). IOP was measured by rebound tonometry before, during (every 4 seconds), and immediately after blood flow restriction. Ocular perfusion pressure was measured before and after blood flow restriction. RESULTS: We found that only the arms-high condition promoted a statistically significant IOP rise when compared with the rest of the experimental conditions (all Bayes factors10, >100; effect sizes, 1.18, 1.06, 1.35, and 1.73 for the control, arms-low, legs-high, and legs-low conditions, respectively). For ocular perfusion pressure, there was strong evidence for the null hypothesis regarding the type of blood flow restriction (Bayes factor10, 0.012); however, men showed an ocular perfusion pressure reduction after blood flow restriction in the arms-high condition (Bayes factor10, 203.24; effect size, 1.41). CONCLUSIONS: This study presents preliminary evidence regarding the safety of blood flow restriction in terms of ocular health. Blood flow restriction may be considered as an alternative training strategy to reduce abrupt fluctuations in IOP and ocular perfusion pressure because its use permits a considerable reduction of exercise intensity.

Intraocular Pressure Responses to Four Different Isometric Exercises in Men and Women.

SIGNIFICANCE: The performance of resistance exercise has evidenced to induce abrupt intraocular pressure (IOP) changes, which has been linked to the onset and progression of glaucoma. We found that four different isometric resistance exercises lead to an instantaneous and progressive IOP elevation, with these changes being independent of the type of exercise. PURPOSE: The impact of physical exercise on IOP has demonstrated to be dependent on exercise type and intesity, as well as individuals' characteristics. In this study, we aimed to explore the influence of the load, exercise type, and participant's sex on the IOP behavior during a 2-minute isometric effort. METHODS: Twenty-eight physically active collegiate students performed 2 minutes of isometric exercise in the military press, biceps curl, leg extension, and calf raise exercises against two different loads (high load and low load). Intraocular pressure was measured by rebound tonometry before, during (semicontinuos assessment [24 measurements]), and after 10 seconds of recovery in each of the eight (four exercises × two loads) conditions. RESULTS: We found a statistically significant effect of load (P < .001, np = 0.906), with greater IOP values when performing the isometric exercises against heavier loads. There was a positive IOP rise during the execution of isometric exercise in the high-load condition, returning to baseline levels after 10 seconds of passive recovery. The exercise type and participant's sex did not reveal statistically significant differences (P = .33 and P = .56, respectively). CONCLUSIONS: Our data evidenced an instanteneous and progressive IOP rise during the execution of isometric exercise leading to muscular failure, regardless of the exercise type and participant's sex. After exercise, IOP rapidly retuned to baseline levels (within 10 seconds). The inclusion of glaucoma patients in future studies is guarranteed.

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.

Effects of caffeine consumption on intraocular pressure during low-intensity endurance exercise: A placebo-controlled, double-blind, balanced crossover study.

IMPORTANCE: Intraocular pressure (IOP) is sensitive to caffeine intake and physical exercise. However, the combined effect of caffeine intake and physical exercise on IOP levels remains unknown. BACKGROUND: We aimed to assess the effects of caffeine consumption before exercise on the IOP behaviour during low-intensity endurance exercise. DESIGN: A placebo-controlled, double-blind, balanced crossover study at the University of Granada. PARTICIPANTS: Eighteen physically active young adults (age = 23.3 ± 2.4 years) participated in this study. METHODS: Participants performed 30 minutes of cycling at 10% of maximal power production after 30 minutes of ingesting a capsule of caffeine (~4 mg/kg) and placebo in two different days and following a double-blind procedure. MAIN OUTCOME MEASURE: IOP was measured at baseline (before caffeine/placebo ingestion), after 5 minutes of warm-up, during cycling (6, 12, 18, 24 and 30 minutes) and recovery (5 and 10 minutes) by rebound tonometry. RESULTS: There was a significant effect of caffeine consumption (P < .001, η2 = 0.50), showing that the ingestion of caffeine before exercise counteracted the IOP-lowering response to low-intensity endurance exercise. Greater IOP values at 12, 18, 24 and 30 minutes (corrected P-values<.05, ds = 0.90-1.08) of cycling were observed for the caffeine in comparison to the placebo condition. CONCLUSIONS AND RELEVANCE: The ingestion of caffeine (~4 mg/kg) 30 minutes before performing low-intensity endurance exercise counteracts the IOP-lowering effect of low-intensity exercise. These results highlight that the ingestion of a considerable amount of caffeine before exercise should be discouraged for individuals who would benefit from the IOP reduction associated with low-intensity exercise (ie, glaucoma patients or those at risk).