Effects of Limited Peripheral Vision on Shuttle Sprint Performance of Soccer Players

Impact of Peripheral Refractive Errors in Mobility Performance

Purpose

The purpose of this study was to investigate the functional effects of peripheral refractive errors on mobility performance through a stair negotiation task.

Methods

Twenty-one young, normal sighted subjects navigated through an obstacle with steps, wearing spectacles that altered only their peripheral refraction. Lenses were used to induce positive defocus (+2 diopters [D] and +4 D), negative defocus (-2 D and -4 D), or astigmatism (+1.75 D and -3.75 D, axis 45 degrees) in the periphery. Feet trajectories were analyzed, and several gait assessment parameters were obtained. Statistical tests were conducted to determine significant performance differences between the lenses. Peripheral refraction in each subject was measured using a scanning Hartmann-Shack wavefront sensor to assess the impact of intrinsic peripheral refraction on the experiment.

Results

Statistically significant differences in performance appeared when peripheral errors were superimposed. Crossing time with respect to plano lenses increased by 6.2%, 7.6%, 19.2%, and 29.6% for the -2 D, +2 D, -4 D, and +4 D lenses, respectively (P < 0.05 in the last 3 cases). Subjects exhibited slower walking speeds, increased step count, and adopted precautionary measures. High-power positive defocus lenses had the biggest impact on performance, and differences were observed in distance to steps between induced positive and negative defocus.

Conclusions

In this laboratory-based study without an adaptation period, peripheral refractive errors affected stair negotiation, causing cautious behavior in subjects. Performance differences among types of peripheral defocus may result from magnification effects and intrinsic peripheral refraction. These results highlight the importance of understanding the effects of induced peripheral errors by myopia control and intraocular lenses.

Performance of soccer players under acute physical fatigue: An approach based on cognitive, tactical and physical aspects

This study aimed to verify whether peripheral perception, tactical behaviour, and physical performance are influenced by acute physical fatigue in soccer players. The study included 24 trained soccer players (18.6 ± 1.5 years) from two Brazilian clubs. The TSAFT90 test was used to induce acute physical fatigue. The results showed that physical fatigue did not affect peripheral perception (p = 0.360). Regarding tactical behaviour, improved efficiency was observed for the principles of offensive coverage (p = 0.029), width and length with the ball (p = 0.044), and concentration (p = 0.008). On the other hand, a reduction was observed in the number of tactical actions of offensive coverage (p = 0.020) and recovery balance (p = 0.042). Also, improved accuracy in the principles of defensive balance (p = 0.009), recovery balance (p = 0.021) and defensive unity (p = 0.003) occurred under physical fatigue. A reduction in the physical performance outcomes total distance covered (p < 0.001), average speed (p < 0.001), sprints (p = 0.029), number of accelerations (p = 0.008) and decelerations (p = 0.008) were also detected. The internal (p < 0.01) and external (p < 0.01) workload was higher under physical fatigue. Overall, acute physical fatigue did not influence peripheral perception. However, physical performance was reduced under fatigue, the perceived effort increased, and tactical behaviours were affected by decreasing tactical actions performed near the ball, increasing errors in defensive movements in the lateral corridors and the last defensive line, and improving offensive tactical actions performance.

Reflexive Saccades Used for Objective and Automated Measurements of Contrast Sensitivity in Selected Areas of Visual Field

Purpose

This study proposes a novel approach for objective and automated peripheral contrast sensitivity (CS) testing using reflexive saccades. Here the CS was examined in various areas the of visual field (VF) using a live analysis of gaze data. For validation of the new test, we examined CS with an established procedure of identifying the orientation of a contrast stimulus.

Methods

To perform and validate the saccade-based testing, two separate measurement events were performed. In the first, participants were asked to execute a saccade toward a newly-appeared stimulus in their VF. After the saccade execution or stimulus expiry, reporting the target orientation was required in a four-alternatives forced choice (4AFC). Therefore the first measurement yields two outcomes (objective and subjective). In the second measurement, only the identification of the stimulus orientation was requested, while fixating a central mark. Stimulus contrast was controlled by an adaptive psychometric procedure in both measurements.

Results

The study found strong correlations (all r ≥ 0.79) of CS values for all three possible testing methods (saccade-based responding in saccadic measurements, keyboard-based responding in saccadic measurements, keyboard-based responding in non-saccadic measurements), showing the feasibility of employment of reflexive saccades in such testing. Second, this study shows a significant influence of eccentricity and direction of the stimulus on the CS function.

Conclusions

CS measured with reflexive saccades is comparable to other testing methods over several areas of the participant's VF. Hence, we propose it as a novel and objective testing procedure for CS measurements.

Translational Relevance

Assessment of CS using reflexive saccades extends the portfolio of suggested eye movement-based tests, allowing objective examination across the VF, which might be helpful especially in the early detection of various eye diseases.

Reduced Contrast Sensitivity Function in Central and Peripheral Vision by Disability Glare

Various glares can decrease visual performance and cause discomfort, thus increasing drivers' risk for traffic accidents in real life. The current study aimed to systematically investigate glare sensitivity in the central and peripheral visual fields by measuring contrast sensitivity function (CSF) under nonglare, steady glare, and transient glare conditions. Nine observers with normal visual acuity in the dominant eye were enrolled. The CSF in central and peripheral vision (the 5° upper left visual field) was measured in a mesopic environment while the stimulus was displayed under three conditions: nonglare, steady glare, and transient glare. An orientation identification task was used to obtain the CSF. After the experiment, the observers were asked to report their level of discomfort in the presence of the glare. The area under the log CSF (AULCSF) and cut-off spatial frequency served as indicators of visual performance. In agreement with previous studies, both steady and transient glare reduced the AULCSF and cut-off frequency. However, the AULCSF and cut-off frequency were reduced more for central vision than for nearly peripheral vision. In addition, the extent of the decreases in the AULCSF and cut-off frequency was greater for steady glare than for transient glare; in contrast, more discomfort was associated with transient glare than steady glare.

A novel Bayesian adaptive method for mapping the visual field

Measuring visual functions such as light and contrast sensitivity, visual acuity, reading speed, and crowding across retinal locations provides visual-field maps (VFMs) that are extremely valuable for detecting and managing eye diseases. Although mapping light sensitivity is a standard glaucoma test, the measurement is often noisy (Keltner et al., 2000). Mapping other visual functions is even more challenging. To improve the precision of light-sensitivity mapping and enable other VFM assessments, we developed a novel hybrid Bayesian adaptive testing framework, the qVFM method. The method combines a global module for preliminary assessment of the VFM's shape and a local module for assessing individual visual-field locations. This study validates the qVFM method in measuring light sensitivity across the visual field. In both simulation and psychophysics studies, we sampled 100 visual-field locations (60° × 60°) and compared the performance of qVFM with the qYN procedure (Lesmes et al., 2015) that measured light sensitivity at each location independently. In the simulations, a simulated observer was tested monocularly for 1,000 runs with 1,200 trials/run, to compare the accuracy and precision of the two methods. In the experiments, data were collected from 12 eyes (six left, six right) of six human subjects. Subjects were cued to report the presence or absence of a target stimulus, with the luminance and location of the target adaptively selected in each trial. Both simulations and a psychological experiment showed that the qVFM method can provide accurate, precise, and efficient mapping of light sensitivity. This method can be extended to map other visual functions, with potential clinical signals for monitoring vision loss, evaluating therapeutic interventions, and developing effective rehabilitation for low vision.

Static and dynamic visual acuity and refractive errors in elite football players

BACKGROUND

The aim of this study was to investigate static and dynamic visual acuity, refractive error, and the use of visual compensation of elite football players.

METHODS

From 2015 to 2017, 147 professional players from five teams were analysed. Screening consisted of a survey about the use of visual correction, and measurement refractive error, static visual acuity and dynamic visual acuity. Refractive error was assessed using an autorefractor. Distance static visual acuity was evaluated using a Snellen chart. Dynamic visual acuity was measured at five metres using the software COI-SV. All athletes were male with a mean age of 24.6 ± 4.1 years.

RESULTS

The mean refractive error of the athletes was -0.04 ± 0.83 D, and 16.4 per cent were myopic. Statistically significant differences were found for dynamic visual acuity (p = 0.033), based on the position occupied. Goalkeepers displayed the best dynamic visual acuity and forwards had the lowest values (0.82 ± 0.14 and 0.62 ± 0.17, respectively). The forwards presented with the highest prevalence of myopia and goalkeepers the lowest, at 22.5 per cent and 12.5 per cent, respectively. All goalkeepers who needed to use a correction for play used it, whereas only 16 per cent of the forwards who needed a correction used it.

CONCLUSION

Dynamic visual acuity of forwards is lower than that of other players. Twenty-five per cent of players who need to use visual correction to practice sports actually use it.

What do cyclists need to see to avoid single-bicycle crashes?

The number of single-bicycle crash victims is substantial in countries with high levels of cycling. To study the role of visual characteristics of the infrastructure, such as pavement markings, in single-bicycle crashes, a study in two steps was conducted. In Study 1, a questionnaire study was conducted among bicycle crash victims (n = 734). Logistic regression was used to study the relationship between the crashes and age, light condition, alcohol use, gaze direction and familiarity with the crash scene. In Study 2, the image degrading and edge detection method (IDED-method) was used to investigate the visual characteristics of 21 of the crash scenes. The results of the studies indicate that crashes, in which the cyclist collided with a bollard or road narrowing or rode off the road, were related to the visual characteristics of bicycle facilities. Edge markings, especially in curves of bicycle tracks, and improved conspicuity of bollards are recommended. STATEMENT OF RELEVANCE: Elevated single-bicycle crash numbers are common in countries with high levels of cycling. No research has been conducted on what cyclists need to see to avoid this type of crash. The IDED-method to investigate crash scenes is new and proves to be a powerful tool to quantify 'visual accessibility'.

Attentional and visual demands for sprint performance in non-fatigued and fatigued conditions: reliability of a repeated sprint test

Background

Physical performance measures are widely used to assess physical function, providing information about physiological and biomechanical aspects of motor performance. However they do not provide insight into the attentional and visual demands for motor performance. A figure-of-eight sprint test was therefore developed to measure the attentional and visual demands for repeated-sprint performance. The aims of the study were: 1) to assess test-retest reliability of the figure-of-eight sprint test, and 2) to study the attentional and visual demands for sprint performance in a non-fatigued and fatigued condition.

Methods

Twenty-seven healthy athletes were included in the study. To determine test-retest reliability, a subgroup of 19 athletes performed the figure-of-eight sprint test twice. The figure-of-eight sprint test consisted of nine 30-second sprints. The sprint test consisted of three test parts: sprinting without any restriction, with an attention-demanding task, and with restricted vision. Increases in sprint times with the attention-demanding task or restricted vision are reflective of the attentional and visual demands for sprinting. Intraclass correlation coefficients (ICCs) and mean difference between test and retest with 95% confidence limits (CL) were used to assess test-retest reliability. Repeated-measures ANOVA were used for comparisons between the sprint times and fatigue measurements of the test parts in both a non-fatigued and fatigued condition.

Results

The figure-of-eight sprint test showed good test-retest reliability, with ICCs ranging from 0.75 to 0.94 (95% CL: 0.40-0.98). Zero lay within the 95% CL of the mean differences, indicating that no bias existed between sprint performance at test and retest. Sprint times during the test parts with attention-demanding task (P = 0.01) and restricted vision (P < 0.001) increased significantly compared to the base measurement. Furthermore the sprint times and fatigue measurements increased significantly in fatigued condition. There was a significant interaction effect between test part and level of fatigue (P = 0.03).

Conclusions

High ICCs and the absence of systematic variation indicate good test-retest reliability of the figure-of-eight sprint test. The attentional and visual demands for sprint performance, in both a non-fatigued and fatigued condition, can be measured in healthy team-sport athletes with the figure-of-eight sprint test.

Designing contact lenses for a wide field of view via ocular wavefront tomography

Purpose

Correcting the off-axis wavefront aberration is potentially important for peripheral vision, for diagnostic imaging of the retina, and for influencing refractive development. A new technique called ocular wavefront tomography (OWT) was adapted to optimize the design of contact lenses to improve the eye's peripheral optical quality.

Methods

OWT is a technique for customizing a multi-surface model eye to mimic the off-axis wavefront aberrations for an individual eye. This technique was adapted for contact lens design by establishing clear design goals for the eye + contact lens system. To demonstrate the method we optimized the shape of an aspheric and bifocal contact lens to correct a wide angle model eye with −2D foveal myopia. Two strategies for correction reflected alternative design goals: 1) to fully correct central vision while also improving optical quality peripherally to enhance vision and retinal imaging, or 2) fully correct central vision while introducing a degree of peripheral myopia relative to central vision in order to slow myopia progression.

Results

The OWT technique successfully produced aspheric and bifocal contact lens designs over a wide field of view. In addition to correcting foveal vision, the optimized contact lens designs either 1) improved the retinal image quality across the visual field (< 45°) significantly to obtain a visual performance and retinal imaging benefit or 2) produced the desired level of myopia in the peripheral field to obtain a refractive development benefit.

Conclusion

The OWT technique is a validated tool to optimize contact lens design over a wide field.

Design and validation of a scanning Shack Hartmann aberrometer for measurements of the eye over a wide field of view

Peripheral vision and off-axis aberrations not only play an important role in daily visual tasks but may also influence eye growth and refractive development. Thus it is important to measure off-axis wavefront aberrations of human eyes objectively. To achieve efficient measurement, we incorporated a double-pass scanning system with a Shack Hartmann wavefront sensor (SHWS) to develop a scanning Shack Hartmann aberrometer (SSHA). The prototype SSHA successfully measured the off-axis wavefront aberrations over +/- 15 degree visual field within 7 seconds. In two validation experiments with a wide angle model eye, it measured change in defocus aberration accurately (<0.02microm, 4mm pupil) and precisely (<0.03microm, 4mm pupil). A preliminary experiment with a human subject suggests its feasibility in clinical applications.