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

●Issues with artificial lighting (color perception and glare)

●Temperature issues that may affect ophthalmic products

●Humidity conditions, especially low humidity with contact lens wear

●Altitude factors that may affect oxygen transmission in contact lens wear

●Dust and foreign body potential

●Sweat, fogging, and precipitation effects with ophthalmic products

●The need for product flexibility because of environmental variability

These environmental factors will be addressed in the following sections to assist the practitioner in determining the advantages and disadvantages of the available options. Each athlete has specific variables that affect ophthalmic recommendations. The gender, age, level of participation, combination of sports activities, and previous history of product use influence the choice of available options. Some athletes seek a single product to meet all visual performance needs, whereas others seek the optimal products for a variety of highly specific uses. Effective patient counseling begins with a thorough history to determine the specific needs and profile for the individual. Many patients would like to make informed decisions about the use of ophthalmic products; therefore a thorough case history coupled with comprehensive education and recommendations establish the practitioner as a valuable resource for the athlete.

REFRACTIVE COMPENSATION

The incidence of refractive error and visual symptoms found at the Junior Olympic Games is similar to that found in the general population (approximately 20%), dispelling the idea that athletes have a lower incidence of refractive error and vision problems.1 Athletes who currently use vision correction require an evaluation to determine whether the prescription is providing optimal visual performance for the specific sport demands. A task analysis of the sport will assist in determining the specific visual demands, and a careful refractive analysis can establish the best refractive compensation for use in that sport. For example, a myopic baseball player may benefit from an additional 0.25 D of minus to improve contrast judgment or when playing in twilight conditions. This prescription becomes the sportspecific prescription and is not intended for general use. Other sports, such as billiards, have specific viewing distances that should be considered, especially for the presbyopic athlete. The eye care practitioner should advise athletic patients about the advantages and disadvantages of spectacles, contact lenses, and refractive surgery. The athlete should be able to make an informed decision about the best option for his or her individual needs. If spectacles are an option, the athlete should be counseled on the best lens characteristics, frame designs, tint characteristics, and protection factors. Contact lenses offer a method to minimize many of the disadvantages found with most spectacle corrections, specifically poor optics, distortion, lack of safety, and frame comfort.2-4 Refractive surgery offers the potential advantage of eliminating the need for optical devices; however, surgical procedures have safety and suboptimal vision performance outcome concerns. Orthokeratology offers an option to refractive surgery for some athletes.

For the approximately 80% of athletes who do not use vision correction, some may benefit from a sport-specific refractive prescription. To determine the possible benefits of a refractive prescription, the eye care provider should consider the athlete’s entering unaided visual acuities, the visual demands of the sport, and the effort exerted by the athlete to

TABLE 6-1 Guidelines for Refractive Compensation in Athletes

*Against-the-rule and oblique astigmatism are more detrimental than with-the-rule astigmatism.

†Consider meridional effects with asymmetric astigmatism.

achieve clarity. For example, a golfer with unaided visual acuities of 20/25 (6/7.5) may appreciate the improved ability to judge the terrain of the course and find the ball when wearing a −0.25 DS prescription. This amount of myopia is typically insignificant, but the lack of compensation may have an impact on golf performance. Similarly, an uncorrected hyperope may find relief from eye strain with a prescription when playing tennis.

Guidelines have been published to assist the practitioner in determining when refractive compensation should be considered5 (Table 6-1). Any patient with myopia of −0.25 D or more should be counseled on the possible benefits of refractive compensation. Astigmatism has a similar effect on visual resolution as does myopia, especially against-the-rule and oblique astigmatism. Refractive compensation should be considered with −0.50 D or more astigmatism, although with-the-rule astigmatism compensation may not yield as much improvement on clinical measures. Low amounts of hyperopia are often well tolerated without correction; however, hyperopia of +1.00 D or greater may require a significant amount of effort from the athlete to achieve and maintain clarity. Low amounts of anisometropia are not always compensated for, especially when the refractive errors are low. Anisometropia of 0.50 D or more can have a detrimental effect on depth perception, and some athletes may be sensitive to that effect. In addition, the effects of meridional anisometropia should be considered in athletes with asymmetric astigmatism. The guidelines are useful for the practitioner to trigger the discussion of the potential benefits of a refractive prescription; the athlete ultimately makes the decision whether to experiment with the prescription.

When an athlete decides to experiment with a refractive prescription and he or she has not previously worn a correction, the timing of the experimentation should be discussed. The best time to experiment is during the off season. The athlete is typically not competing at that time, so adaptation to the prescription will not directly affect critical performance. Athletes generally use the off season to rest, work on biomechanical skills, and prepare their physical conditioning for the next season. This presents a perfect opportunity to experiment with refractive compensation. If a new prescription is introduced during the competitive season, the athlete may find that performance is negatively affected during the adaptation to the magnification effects induced by spectacle lens wear. For example, a basketball player who wears a myopic prescription for the first time will need to adjust to the change in spatial perception induced by the lenses (e.g., the basket can appear closer).

Presbyopia potentially presents a prescribing challenge in some sports activities. In many sports, a near addition is unnecessary because near visual acuity has a minimal impact on performance.

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In tennis, for example, clarity of near vision provides no advantage to performance. In golf, near visual acuity does not affect performance; however, clear near vision is desirable for seeing the score card and identifying one’s ball during play. A spectacle prescription with near addition lenses can interfere with the golfer’s view when addressing the ball and adjusting swing mechanics. A small, low-set segment set in one lens in the opposite viewing direction from the putting view angle has been recommended as a solution to this problem. For example, offset the segment in right gaze (lower temporal corner of the lens) for a right-handed golfer.6 A better option may be contact lenses for playing the game and a near prescription (e.g., half eyes) to use when scoring. Alternatively, a progressive addition lens (PAL) may be prescribed with a short corridor and narrow near zone set low to minimize peripheral distortion effects. Pilots and boat operators may require a double segment design, with positioning of the near additions to allow them to read instruments in downgaze and upgaze positions. Placing a small segment at the top of the lens and a traditional segment at the bottom of the lens typically provides a solution to the near vision challenge (although this lens design is not currently available with polycarbonate lenses). Billiards players often use a single-vision intermediate-distance prescription for use during play, and the optical centers may need to be carefully measured in the billiards viewing position with strong prescriptions to minimize induced prism effects. Scuba divers may need a multifocal contact lens or prescription bonded to the face mask or attached as an insert within the mask to allow the diver to see the equipment, instruments, and underwater environment clearly. In these cases, the prescription must be adjusted for the significant increase in vertex distance created by the mask. For reactive sports, spectacle lenses produced better reaction times at near in presbyopes than do contact lenses.7 Several companies offer PALs in high base (wrap) designs for use in sports.

The toughest challenge with presbyopia is created by shooters. Shotgun shooters are not significantly affected by the loss of accommodation because the task does not require critical alignment of sights on the target.8 Rifle shooting requires that the shooter clearly focus the target at a far distance while carefully aligning the front and rear sights of the rifle with the target. For the presbyope, the rifle’s front sight (intermediate distance) and rear sight (just beyond the spectacle plane) cannot be viewed with the same clarity as they were before the onset of presbyopia, and bifocal, trifocal, and multifocal lens designs do not offer an effective solution. Some shooters are happy with the distance correction slightly overplussed, creating a tolerable amount of blur for both the target and sights.9 Telescopic sights also have been recommended for this situation to allow clarity and accurate alignment without the need for near accommodation.8 Aiming scopes are available for archery as well; however, the increased magnification offered by these converging lenses does not improve visual acuity of the target because of the presence of significant dioptric blur.10 If spectacles are worn by the shooter, the lens material should protect the athlete and the eye relief distance should be sufficient to protect against rifle recoil.8,9 As described with billiards, the optical centers may need to be carefully marked with the athlete in the shooting position(s) with a strong refractive prescription to minimize the induced prism effects.

Pistol shooters are particularly affected by presbyopia because the front and rear sights must be aligned with exacting precision as a result of the shorter length of the weapon. Again, the front sight is positioned at an intermediate distance from the eyes, and the difference in accommodative demand between the sights and the far target creates significant blur for one distance when focusing at the other. Presbyopic pistol shooters are particularly disturbed

by the loss of image clarity and often want a solution that provides image clarity at both distances. A pinhole aperture can be created by punching a tiny hole in black electrical tape and carefully aligning the tape on the spectacle lens of the aiming eye to allow adequate acuity at both distances for the early presbyope.8 As the pistol shooter approaches absolute presbyopia, the pinhole will no longer provide adequate relief, and a bifocal spectacle will need to be carefully measured to allow clarity of the distant target through the upper lens and clarity of the pistol sights through the near addition lens. This movement between the distance correction and near correction should occur with 1 mm of head movement up or down when in the shooting position, and the practitioner should meticulously measure this position (with clear tape to simulate the add position) for a special-purpose shooting prescription.8 An executive or FT40 segment design will not induce a vertical image jump when moving into the near segment. A flip-down lens design that would allow clarity at two distances also has been recommended,8,9 but the effect on alignment created by flipping the lenses may be unacceptable.

NONPROTECTIVE SPORTS EYEWEAR

A nonprotective spectacle correction is recommended only for use in noncontact sports. In sports with a low incidence of contact (e.g., volleyball), other risks for eye injury exist, such as injury from the ball. In most sports the use of contact lenses or appropriate protective eyewear is preferred over the use of dress eyewear. Dress eyewear does not offer the impact resistance necessary to protect the wearer from the possible hazards encountered in many sports.

The American National Standards Institute (ANSI) has established industry standards for the impact resistance of ophthalmic lenses. Dress eyewear performance standards are detailed in the ANSI Z80.1 standard,11 and the industrial strength (safety) eyewear standards are detailed in the ANSI Z87.1 standard.12 The use of polycarbonate, Trivex (PPG Industries, Pittsburgh, Penn.), or NXT (Intercast Europe, Parma, Italy) lens materials can provide significantly improved impact attenuation properties over conventional glass and CR-39 lens materials.6,13-17 However, the frame construction of fashion eyewear does not withstand the forces encountered in many sports. The ANSI Z80.3 standard for nonprescription sunglasses and fashion eyewear and standards for sports protective eyewear are discussed later in this chapter.

Spectacle prescriptions are not commonly recommended for use in sports. The main concerns in addition to the lack of adequate eye protection provided by dress eyewear are the potential impact of optical aberrations of the lenses and visual field restriction created by the frames. Four of the seven monochromatic, or Seidel, lens aberrations can degrade the optical image transmitted through the off-center portions of the lens; radial or oblique astigmatism, power error caused by the curvature of the lens, lateral chromatic aberration, and distortion can each decrease the useful field of view through a lens.15,18 The reduction in the useful field of view can have a detrimental impact on performance in sports. For example, a right-handed golfer viewing the hole during a putt looks through the left field portions of his or her spectacle lenses, and the image can be significantly altered in large refractive errors because of these aberrations. Stronger refractive prescriptions also produce larger amounts of prismatic effects when viewing away from the optical centers of the lenses, and the effect is increased with larger angles of view as approximated by Prentice’s rule.15,19 Therefore lens design and optical center measurements are critical features of crafting the optimal spectacle

correction for an athlete. Wrap lens designs potentially can eliminate or reduce some of the aberration and visual field problems found in nonwrap lenses; however, these designs are more commonly found in performance sun eyewear rather than dress eyewear.

Spectacle lenses may be a good prescribing option for noncontact sports and recreational athletes who do not require high-performance optics. Many who participate in golf, tennis, running, cycling, fishing, archery, and shooting sports perform satisfactorily with spectacle corrections. These athletes should be prescribed a suitable impact-resistant lens material and counseled regarding the risks of eye injury with dress eyewear. These athletes also may appreciate the visual performance benefits of contact lenses, such as elimination of the four field-of-view aberrations and expanded visual fields. Many shooters and archers prefer spectacles over contact lenses because of the stability of clear vision obtained with spectacle lenses. Because peripheral vision is not a significant factor in most aiming sports, the enhanced visual field does not offer a significant benefit. In addition, contact lens movement on the eye can produce undesirable visual fluctuations during the prolonged gaze behavior (without blinking) that many shooters and archers develop. The shooter or archer is not typically bothered by lens aberrations off the optical center; however, the lenses may need to be fit with the optical centers set for eye position used when aiming with strong prescriptions. The athlete should bring the weapon, carefully unloaded, to the office for this measurement. The practitioner can also arrange to meet the athlete at his or her training facility to make the measurement to generate interest in sports vision services.

Lens Treatment Options

Ophthalmic lenses are available with a variety of lens treatment options. Most athletes will be bothered by reflections from the lens surface, and reflections off the back surface of the lens are particularly distracting. For example, the golfer who sees a reflection of the leaves on a tree behind him or her fluttering in a breeze will not be pleased by this distraction during a critical putt. Antireflective coatings are a particularly valuable lens treatment option, and the improvements in technology that allow multilayer antireflective coating have improved the performance of this lens option.15 The athlete should be warned that antireflective coatings are easy to scratch if the spectacles are not cleaned properly or not kept in a protective case when not in use and that the coating will make dirt and smudges more visible. If polycarbonate lenses are prescribed, an abrasion-resistant coating is provided by the manufacturer because polycarbonate is an inherently soft material and is easily scratched.

Lens fogging and precipitation are two other factors that should be considered in spectacle wearers who compete in predisposing environmental conditions. Condensation appears on spectacle lenses when the temperature of the lenses is lower than the dew point of the surrounding air.15 Rain, fog, and other moisture in the environment also will produce water drops on the lens surface that can dramatically degrade the athlete’s vision through the lenses. Antifog coatings are available to make the lens surface more wettable so that the moisture forms a thin film on the lens rather than droplets.15 These coatings also help slough water off the lens surface quicker in wet environments. An antifog coating does, however, interfere with the efficacy of an antireflective coating.

Lens coatings reduce the impact resistance properties of the lens because of the change in surface tension created by the coatings. Polycarbonate and Trivex lens materials with antireflection coatings have reduced penetration resistance to sharp objects, especially in lenses with reduced center thickness.17,20

102 CHAPTER 6 PRESCRIBING FOR THE ATHLETE

(A) (B)

Figure 6-1. Certifying logos from the Protective Eyewear Certification Council (A), Hockey Equipment Certification Council (B), Canadian Standards Association (C), and National Operating Committee on Standards for Athletic Equipment (D).

(Courtesy Paul Vinger, MD, Concord, Mass.)

tennis; the CSA and ASTM F803 standard is designed to provide protection for any racquet sport. The ball or shuttlecock is hit with tremendous force and can travel at dramatic speeds (Table 6-4). As previously mentioned, the eyewear must protect the eye and orbit from a squash or racquetball projected at 90 mph from several angles, including the side. The hinges are also tested to ensure protection from the forces directed at this potentially weak area. Hingeless frames with straps are recommended when feasible.

Even though the balls used in some racquet sports are larger than the average orbital opening, the compression forces can push the ball deep inside the orbit.25 The first protective eyewear was designed for use in handball and consisted of a lensless rubber-covered wire frame to reduce the orbital opening (Fig. 6-4). These open eye guards were subsequently

*Joint policy statement of the American Academy of Pediatrics Board of Directors, February 1996, and the American Academy of Ophthalmology Board of Trustees, February 1995. Revised and approved by the American Academy of Pediatrics Board of Directors, October 2003, and the American Academy of Ophthalmology Board of Trustees, November 2003.

†Javelin and discus have a small but definite potential for injury. However, good field supervision can reduce the extremely low-risk injury to near negligible.

used for protection in squash and racquetball. Studies demonstrated that the lack of a protective lens allowed penetration of the ball, potentially resulting in significant eye trauma.53-58 The ability of the lensless eye guard to compress the ball actually may increase the risk to the ocular tissues by essentially funneling the ball into the orbit.56,58 In addition, lensless eye guards offer only limited protection from a racquet injury and are never recommended for use.

Many have advocated for protective eyewear use in squash and racquetball and promote education regarding the ineffective protection provided by dress eyewear.52-69 Dress eyewear with glass or CR39 lenses may increase the risk of severe ocular trauma in racquet sports if the lens shatters on impact.48,54,59,62,70,71 Most racquet sport organizations for handball,