Ординатура / Офтальмология / Английские материалы / Sports Vision Vision Care for the Enhancement of Sports Performance_Erickson_2007

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The search for the association between visual abilities and sports performance has a long, rich history. Many researchers and clinicians have sought to discover the vision skills that correlate to success in sports and to refine the procedures to assess the quality of those vision skills. In a 1982 literature review, the authors concluded that ample evidence supported the contention that athletes typically have better visual abilities than nonathletes and that top athletes benefit from visual abilities that often are superior to lower-level athletes.1 In another extensive review of the literature in 1993, the authors agreed with these contentions but cautioned that the visual skills related to successful athletic performance are specific to the sport being investigated.2 The authors further cautioned that attributes such as size, speed, quickness, psychological status, experience level, and influence of coaches confound the ability to predict performance quality solely based on an evaluation of visual skills. Further caution is warranted because a small percentage of top athletes demonstrate poor performance on some aspects of vision skills.

The quest for understanding all the elements that play a role in athletic success is being conducted globally across many disciplines. Each discipline seeks to identify factors that contribute to peak human performance by isolating and measuring specific functions, and most sports vision evaluations attempt the same approach.3-5 The sports vision practitioner must identify the vision factors essential to performance of the visual tasks critical for success in the sport and evaluate the quality of those skills in the most appropriate, accurate,

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The athlete should be evaluated with the habitual correction used for sports participation. Interestingly, a large percentage of athletes have been reported to have a significant uncorrected refractive error; those athletes who do wear refractive correction either do not wear that correction for sports, or the athlete is undercorrected.7,37 A measurement of SVA should also be performed with the best optical correction in place to assess any change in visual acuity produced by that correction. Recommendations for the use of, or change in, vision correction during sports participation are discussed in Chapter 6.

The measurement of SVA is an essential element of any vision evaluation because degraded visual acuity can have a detrimental effect on many other aspects of visual performance. Reduced visual acuity has been shown to affect dynamic visual acuity,38 depth perception,39,40 and accommodative accuracy.41 Some studies have found better static visual acuity in athletes than in nonathletes,3,28,42-44 and some have found no difference.27 Some athletes may perform at a high level despite having deficient visual acuity.14-16,18,43-45 Although the expected level of visual acuity depends on the visual task demands of each sport situation, at least 20/15 (6/4.5) static visual acuity OD, OS, OU has been recommended as a desired standard for competitive athletes.3

DYNAMIC VISUAL ACUITY

Many of the visual demands in sports require discrimination of information that is moving, such as judging the speed and trajectory of a tennis serve. Traditional static visual acuity measurements do not fully address the visual demands encountered in some types of sports, especially those in which judgments about rapidly moving objects are important. A significant amount of early research investigated the physiologic parameters of resolving visual targets in motion, referred to as dynamic visual acuity (DVA).38,46-67 Ludvigh and Miller48,50-53 were the first to use the term DVA, and it has been defined as the ability to resolve detail when relative movement exists between the observer and the test object.68

Many variables in the stimulus parameters can affect DVA, including target luminance, angular velocity, and the time exposure of the target.38,46-67 Human attributes that can affect DVA include the resolving power of the retina, peripheral awareness, oculomotor abilities, and psychological functions that affect interpretation of visual information.38,46-67,69,70 Several conclusions have been made concerning DVA that have emerged from the research:

(1)Visual acuity for a moving target is reduced compared with that of a stationary target, and acuity becomes progressively more reduced with increasing velocity of the target.

(2)The correlation between static visual acuity and DVA decreases with increasing target velocity. (3) A progressive decline in acuity occurs with advancing age that accelerates in older age groups and is more pronounced with DVA than SVA. (4) Males, in general, perform consistently better than females on DVA tasks.59,61,62,71

DVA research was stimulated by the theory that, for many activities, discrimination of moving objects (or stationary objects while the person is in motion) is a critical element of human performance.62 This concept applies to sport situations as well as common daily tasks such as driving.55,58,59,62 Several attempts have been made to determine the relation between DVA and visual task performance; however, further investigation is necessary to correlate clinical measurements of DVA with visual task performance.*

*References 19-23, 44, 48, 50-53, 55, 58, 59, 62, 71-76.

Figure 4-1. Wayne Robot Rotator with visual acuity chart for dynamic visual acuity testing.

Despite the significant amount of research conducted with DVA parameters and the many applications of DVA features to daily activities, limited resources are available to assess this ability. DVA is a widely recommended visual function to evaluate in athletes.* Significant variations in the clinical measurement of DVA have included the type of target, the size of the target, the direction of the stimulus movement (or subject movement), and the amount of time that the stimulus is exposed. This variability in measurement parameters has lead to several different recommendations for normative performance in athletes, as well as different performance characteristics for athletes compared with nonathletes.† Few DVA measurement systems are currently available, and most use a predictable rotator device (Fig. 4-1). Rotators are available from Wayne Engineering (www.wayneengineering.com) and JW Engineering (www.jtac.com), as well as other retailers. The inVision package from NeuroCom (www.onbalance.com) is a system that “quantifies a patient’s ability to maintain visual acuity and stable gaze while actively moving the head” (Fig. 4-2).87 This system has shown promise as an effective diagnostic tool in a study to establish preliminary normative data88 and has demonstrated acceptable test-retest reliability.89

CONTRAST SENSITIVITY

Contrast sensitivity measures the visual system’s ability to process spatial or temporal information about objects and their backgrounds under varying lighting conditions.68 Measurement of contrast sensitivity function (CSF) has been recommended in athletes because many sports involve visual discrimination tasks in suboptimal lighting because of environmental variability.2,3,5 Snellen-type visual acuity measurements may not be sensitive to the subtle visual discrimination tasks inherent in many sports because the acuity task is usually performed only under high-contrast conditions. Consider the decreased contrast

*References 3-6, 13, 19-23, 26, 27, 30-33, 35, 36, 42, 44, 69, 77-82.

†References 3, 5, 13, 31-33, 37, 79-81, 83-86.

Figure 4-2. inVision package to assess dynamic visual acuity.

effect of a white, cloudy sky as a background when judging the trajectory of a fly ball in baseball when the ball is also predominantly white. Ginsburg90,91 has suggested that lower spatial frequencies provide spatial localization information about objects and that higher spatial frequencies are the first to be affected by poor illumination, movement, and increased viewing distance. In sports in which the athlete must process visual information from an object in motion (e.g., a baseball pitch), evaluation of CSF at high spatial frequencies may provide vital diagnostic information.

Several investigations have compared CSF in athletes by using gratings of varying spatial frequency.3,31,42,92-100 The general results from these studies demonstrate elevated CSF across all spatial frequencies for athletes. Athletes may have a positive benefit in CSF with aerobic excercise.101 Contrast sensitivity also may be degraded in contact lens wearers if the lenses are not optimal, even when visual acuity appears acceptable.102-105 Therefore contrast sensitivity measurement is an essential part of the evaluation of athletes who wear contact lenses during sports participation.

Many systems are commercially available to measure CSF. Most use grating patterns that vary in spatial frequency and contrast level; however, fixed-chart and computer-generated symbols of varying contrast levels are also available. Contrast sensitivity measurements usually involve detection of a threshold contrast level at each spatial frequency, with the resultant CSF plotted on a graph.106 The principal instruments used to measure CSF in athletes have been the Vistech Contrast Test System (www.vistechconsultants.com) and Vector Vision contrast sensitivity test (www.vectorvision.com). These systems were primarily chosen for the speed of test administration and portability of the tests.* The Vistech system

*References 3-5, 13, 31, 33, 42, 94-103, 105.

Figure 4-3. The CSV-1OOOE contrast sensitivity chart.

is externally lit and requires a light meter to calibrate, whereas the Vector Vision test is internally illuminated and somewhat self-calibrating (Fig. 4-3). Major concerns have been reported regarding the reliability and repeatability of the Vistech Contrast Test System for measuring CSF, although other studies have demonstrated adequate reliability and repeatability.107-110

Whatever CSF test system is chosen, evaluation is often recommended for athletes and should be performed binocularly with habitual sports correction in place.* If contact lenses are used in sports, or if more than a one-line difference in monocular static visual acuities exists, CSF testing should also be performed monocularly. A measurement of CSF should also be performed with the best optical correction in place to assess any change in CSF produced by that correction and with any performance tints used during sports participation (e.g., ski goggles).111 The practitioner is encouraged to assess filter performance in natural sunlight because light levels are much more intense outdoors than under artificial lighting. Recommendations for the use of, or change in, vision correction or contact lenses used during sports participation is discussed in Chapter 6.

REFRACTIVE STATUS

Assessment of refractive status is an essential element of the visual evaluation of the athlete. Interestingly, it is such a basic element of a vision evaluation that it is rarely directly discussed in the extensive literature describing evaluation procedures for athletes. Ample data

*References 3-6, 13, 30, 31, 33, 42, 78, 80, 82.

are available concerning visual acuity performance, which has obvious implications for uncorrected refractive errors, but refractive status of the athletes is presented infrequently.* Therefore limited information is available concerning the percentage of athletes who have significant uncorrected refractive errors.7,113

Only a few reports in the literature concern the percentage of athletes who use vision correction (spectacles or contact lenses).7,15,17,26 Beckerman and Hitzeman7 recently found at the Junior Olympic Games that, of the approximately 20% of athletes who wore vision correction, 28% had less than 20/25 (6/7.5) visual acuity through their habitual sports correction. They found that 35% of right eyes had greater than ±0.75 D of uncorrected spherical refractive error, and 64% of right eyes had greater than −0.75 D of uncorrected astigmatism. The incidence of refractive error and visual symptoms found by Beckerman and Hitzeman is similar to that found in the general population, dispelling the perception that athletes have a lower incidence of refractive error and vision problems. In contrast, those athletes with significantly above-average visual acuity demonstrate corneae relatively free of high-order aberrations on videokeratography.114

Standardized examination procedures to evaluate refractive status are recommended for athletes, and prescribing recommendations are addressed in Chapter 6. The need for cycloplegic examination is left to the discretion of the practitioner and is usually based on concerns regarding latent hyperopia in the athlete. Of note, most young athletes are also students, and vision conditions that can affect school performance should be addressed as well.

EYE/HAND/FOOT PREFERENCE

The phenomenon of ocular dominance was first described by Giovanni Battista della Porta in 1593,115 and interest in the relation between ocular dominance and performance has been active ever since. Dominance has been defined as any sort of physiologic preeminence, priority, or preference by one member of any bilateral pair of structures in the body when performing various tasks.116 Many studies have attempted to determine the best method for assessing the types of eye dominance,117-135 but tests of sighting preference are the most frequently used.

Many studies have investigated the relation between hand and foot preference and eye preference.120,121,128,134,136-140 The preferred eye does not always correspond to the preferred hand or foot, and when they are different the condition is referred to as crossed dominance. Duke-Elder137 reported that 33% of right-hand dominant people are left-eye dominant, 50% of left-hand dominant people are right-eye dominant, and an estimated 20% to 40% of the general population is crossed eye and hand dominant. Entangled in the issue of testing methods to determine eye preference are reports of dominance switching with hand used when sighting, and issues of central dominance in which neither eye is aligned with the sighted target (also sometimes referred to as ambiocular).31,135,141-143

Many theories have proposed advantages or disadvantages of having crossed eye and hand dominance in sports performance.28,112,116,135,141-161 These speculations were further inspired by the findings of Coren and Porac,133 who found that information from the dominant eye

*References 7, 11, 15-17, 26, 28, 30, 33, 36, 112.