Molecular sensing of mechano- and ligand-dependent adhesion GPCR dissociation.

Adhesion G-protein-coupled receptors (aGPCRs) bear notable similarity to Notch proteins1, a class of surface receptors poised for mechano-proteolytic activation2-4, including an evolutionarily conserved mechanism of cleavage5-8. However, so far there is no unifying explanation for why aGPCRs are autoproteolytically processed. Here we introduce a genetically encoded sensor system to detect the dissociation events of aGPCR heterodimers into their constituent N-terminal and C-terminal fragments (NTFs and CTFs, respectively). An NTF release sensor (NRS) of the neural latrophilin-type aGPCR Cirl (ADGRL)9-11, from Drosophila melanogaster, is stimulated by mechanical force. Cirl-NRS activation indicates that receptor dissociation occurs in neurons and cortex glial cells. The release of NTFs from cortex glial cells requires trans-interaction between Cirl and its ligand, the Toll-like receptor Tollo (Toll-8)12, on neural progenitor cells, whereas expressing Cirl and Tollo in cis suppresses dissociation of the aGPCR. This interaction is necessary to control the size of the neuroblast pool in the central nervous system. We conclude that receptor autoproteolysis enables non-cell-autonomous activities of aGPCRs, and that the dissociation of aGPCRs is controlled by their ligand expression profile and by mechanical force. The NRS system will be helpful in elucidating the physiological roles and signal modulators of aGPCRs, which constitute a large untapped reservoir of drug targets for cardiovascular, immune, neuropsychiatric and neoplastic diseases13.

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.

Effects of Phenylcapsaicin on Intraocular and Ocular Perfusion Pressure During a 30-Min Cycling Task: A Placebo-Controlled, Triple-Blind, Balanced Crossover Study.

The main objective of this placebo-controlled, triple-blind, balanced crossover study was to assess the acute effects of phenylcapsaicin (PC) intake (2.5 mg) on intraocular pressure (IOP), ocular perfusion pressure (OPP), and heart rate (HR) during a 30-min cycling task performed at 15% of the individual maximal power. Twenty-two healthy young adults performed the cycling task 45 min after ingesting PC or placebo. IOP was measured with a rebound tonometer before exercise, during cycling (every 6 min), and after 5 and 10 min of recovery. OPP was assessed before and after exercise. HR was monitored throughout the cycling task. We found an acute increase of IOP levels related to PC consumption while cycling (mean difference = 1.91 ± 2.24 mmHg; p = .007, ηp2=.30), whereas no differences were observed for OPP levels between the PC and placebo conditions (mean difference = 1.33 ± 8.70 mmHg; p = .608). Mean HR values were higher after PC in comparison with placebo intake (mean difference = 3.11 ± 15.87 bpm, p = .019, ηp2=.24), whereas maximum HR did not differ between both experimental conditions (p = .199). These findings suggest that PC intake before exercise should be avoided when reducing IOP levels is desired (e.g., glaucoma patients or those at risk). Future studies should determine the effects of different ergogenic aids on IOP and OPP levels with other exercise configurations and in the long term.

Influence of the body positions adopted for resistance training on intraocular pressure: a comparison between the supine and seated positions.

OBJECTIVES: A variety of factors are known to mediate on the intraocular pressure (IOP) response to resistance training. However, the influence of the body position adopted during resistance training on IOP remain unknown. The objective of this study was to determine the IOP response to the bench press exercise at three levels of intensity when performed in supine and seated positions. METHODS: Twenty-three physically active healthy young adults (10 men and 13 women) performed 6 sets of 10 repetitions against the 10-RM (repetition maximum) load during the bench press exercise against three levels of intensity (high intensity: 10-RM load; medium intensity: 50% of the 10-RM load; and control: no external load) and while adopting two different body positions (supine and seated). A rebound tonometer was employed to measure IOP in baseline conditions (after 60 s in the corresponding body position), after each of the 10 repetitions, and after 10 s of recovery. RESULTS: The body position adopted during the execution of the bench press exercise significantly affected the changes in IOP (p < 0.001, ηp2 = 0.83), with the seated position providing lower increases in IOP levels compared to the supine position. There was an association between IOP and exercise intensity, with greater IOP values in the more physically demanding conditions (p < 0.001, ηp2 = 0.80). CONCLUSIONS: The use of seated positions, instead of supine positions, for the execution of resistance training should be prioritized for maintaining more stable IOP levels. This set of findings incorporates novel insights into the mediating factors on the IOP response to resistance training. In future studies, the inclusion of glaucoma patients would allow to assess the generalizability of these findings.

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.

Chronic Pharmacological Increase of Neuronal Activity Improves Sensory-Motor Dysfunction in Spinal Muscular Atrophy Mice.

Dysfunction of neuronal circuits is an important determinant of neurodegenerative diseases. Synaptic dysfunction, death, and intrinsic activity of neurons are thought to contribute to the demise of normal behavior in the disease state. However, the interplay between these major pathogenic events during disease progression is poorly understood. Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by a deficiency in the ubiquitously expressed protein SMN and is characterized by motor neuron death, skeletal muscle atrophy, as well as dysfunction and loss of both central and peripheral excitatory synapses. These disease hallmarks result in an overall reduction of neuronal activity in the spinal sensory-motor circuit. Here, we show that increasing neuronal activity by chronic treatment with the FDA-approved potassium channel blocker 4-aminopyridine (4-AP) improves motor behavior in both sexes of a severe mouse model of SMA. 4-AP restores neurotransmission and number of proprioceptive synapses and neuromuscular junctions (NMJs), while having no effects on motor neuron death. In addition, 4-AP treatment with pharmacological inhibition of p53-dependent motor neuron death results in additive effects, leading to full correction of sensory-motor circuit pathology and enhanced phenotypic benefit in SMA mice. Our in vivo study reveals that 4-AP-induced increase of neuronal activity restores synaptic connectivity and function in the sensory-motor circuit to improve the SMA motor phenotype.SIGNIFICANCE STATEMENT Spinal muscular atrophy (SMA) is a neurodegenerative disease, characterized by synaptic loss, motor neuron death, and reduced neuronal activity in spinal sensory-motor circuits. However, whether these are parallel or dependent events is unclear. We show here that long-term increase of neuronal activity by the FDA-approved drug 4-aminopyridine (4-AP) rescues the number and function of central and peripheral synapses in a SMA mouse model, resulting in an improvement of the sensory-motor circuit and motor behavior. Combinatorial treatment of pharmacological inhibition of p53, which is responsible for motor neuron death and 4-AP, results in additive beneficial effects on the sensory-motor circuit in SMA. Thus, neuronal activity restores synaptic connections and improves significantly the severe SMA phenotype.

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.

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.

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.

New Method for Obtaining a Bioactive Essence Extracted from Iberian Ham Fat Rich in MUFA and Antioxidants.

Iberian ham is one of the most representative Spanish products and presents an excellent nutritional and sensory quality. Iberian ham trimming fat is considered a by-product and to give a new use to this remaining part could represent a healthy and innovative option for obtaining sustainable foods. The purpose of this work was to obtain a new bioactive ingredient from Iberian ham trimming fat with the highest amount of antioxidants and monounsaturated fatty acids (MUFA), using a new non-invasive solvent-free method. To obtain the essence, two different extraction procedures were carried out. After fatty acid characterization, degree of acidity, peroxide index and a basic sensory analysis were performed. Antioxidant in vitro activity and total phenolic compounds (TPC) were also determined. This new ingredient showed a better sensory profile than raw ham fat, a lower degree of acidity, a higher content of MUFAs, and also showed a higher antioxidant capacity and an increase in phenolic compounds compared to the raw material. This bioactive essence could be used as a food, a cosmetic or a nutraceutical ingredient to prevent certain diseases related to oxidative stress and could also contribute to the maintenance of the circular economy.

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.