Introduction
A significant proportion of the population participates in sports or leisure-time physical activities. For example, a world-wide metaanalysis found that among adults, walking was the most popular activity in the Americas (19% of the population), Eastern Mediterranean (15%), Southeast Asia (39%) and Western Pacific (42%). In Europe and Africa, soccer (10%) and running (9%), respectively, were top activities ( ).
Sport and recreation are often cited as the reason for seeking contact lenses. surveyed 1573 people engaged in sport and found that contact lens penetration in the sample was 18.7%. Contact lenses were reported to be the favourite system of correction among people interviewed, compared to spectacles and refractive surgery.
With modern contact lens technology, there is no reason why an ametropic sportsperson cannot compete with a normally sighted opponent on an equal basis from the standpoint of visual function. For example, daily disposable lenses offer flexibility and convenience for those playing sports. They are available in hydrogel and silicone hydrogel materials and in a wide range of parameters that will correct almost all potential sportspersons.
This chapter presents an overview of factors that should be considered when prescribing contact lenses for those participating in various sports. Although the emphasis is on competitive sports, the principles outlined are applicable to all forms of sport and recreational activity.
Deciding on the Best Form of Correction
The primary vision correction options are soft contact lenses, rigid contact lenses, orthokeratology, refractive surgery or spectacles. Rigid lenses can be made in corneal, corneo-scleral or scleral designs. Scleral lenses are usually prescribed only in very demanding circumstances; they will therefore not be considered in detail in this chapter (see Chapter 17 ).
Refractive surgery represents the most radical alternative. The benefits are that no correction needs to be worn for sport, and problems of lens loss, lens movement and lens maintenance are obviated. Although it might seem to be a perfect solution, laser correction is not without potential drawbacks. Corneal haze and regression can lead to less than perfect visual acuity, especially during the first few months following surgery. There is also potential for flap damage in patients who have had laser in situ keratomileusis (LASIK). reported on a case where the left eye of a 39-year-old man was struck by the finger of a friend while the two were practising karate, resulting in loss of the flap, which occurred 3 years and 5 months after LASIK. noted that a 38-year-old man sustained a dislocated flap after being struck in the left eye with a football more than 30 months after uneventful LASIK. These cases illustrate the need for LASIK patients to wear protective eyewear when participating in contact sports.
A comparison of the key features of the primary options for vision correction for sport is presented in Table 24.1 .
| Characteristic | Soft Lenses | Rigid Lenses | Orthokeratology | Spectacles | Refractive Surgery |
|---|---|---|---|---|---|
| Field of view | Full | Full | Full | Restricted | Full |
| Stability of vision (postblink) | Excellent | Good | Excellent | Excellent | Excellent |
| Glare | None | In low light | None | None | Some postsurgery |
| Glare protection tint possible | Cosmetic only | No | No | Yes | N/A |
| Ultraviolet protection possible | Yes | Yes | No | Yes | N/A |
| Initial comfort | Good | Poor | Fair | Good | Fair |
| Long-term comfort | Good | Good | Excellent | Good | Excellent |
| Adaptation required | Very little | Yes | Yes | Sometimes | N/A |
| Suitability for intermittent use | Yes | Not usually | No | Yes | No |
| Disposability viable | Yes | No | N/A | No | N/A |
| Risk of loss | Low | Moderate | N/A | Low | N/A |
| Risk of dislodgement during wear | Low | Moderate | Nil | High | N/A |
| Risk of damage during wear | Low | Low | Nil | High | Moderate (LASIK flap mislocation) |
| Risk of damage with handling | High | Low | Low | Low | N/A |
| Ease of care | Simple (nil for daily disposable) | Simple | Simple | Simple | N/A |
| Initial cost | Low | Moderate | High | Moderate | High |
| Ongoing costs | High | Moderate | Moderate | Nil | Nil |
| Cost to correct astigmatism | High | Low | Only limited correction possible | Low | High |
| Bifocal correction possible | Compromise | Very difficult | No | Yes | Monovision |
| Use in rain | Good | Good | Excellent | Poor | Excellent |
| Susceptibility to fog up | No | No | No | Yes | No |
| Susceptibility to dirt up | No | No | No | Yes | No |
| Risk of complication | Low | Negligible | Low | None | Moderate |
Do Contact Lenses Enhance Sporting Performance?
Some clinicians have offered the anecdotal opinion that, compared with spectacles, contact lenses enhance the visual skills of the ametropic sportsperson; however, properly controlled clinical trials do not support these claims. applied a battery of tests (including measurement of high- and low-contrast visual acuity, assessment of lens fit and subjective assessment of visual performance) to ametropic athletes wearing their spectacle correction versus low-water-content soft contact lenses. The authors found that, although contact lenses did not offer a measurable advantage over spectacles in terms of visual performance under these testing conditions, the psychological advantages were significant, and in this way, contact lenses may enhance overall sports-oriented visual performance.
There have been suggestions that specially tinted contact lenses can enhance sporting performance. For example, have demonstrated that the now-discontinued Maxsight Amber lenses (50% visible light transmission) and grey-green lenses (36% visible light transmission) provide better contrast discrimination in bright sunlight, better contrast discrimination when alternating between bright and shaded target conditions, better speed of visual recovery in bright sunlight and better overall visual performance in bright and shaded target conditions compared with clear lenses. However, the extent to which these visual performance attributes translate to enhanced sports performance is less clear ( ). The prescription of performance-enhancing tinted contact lenses for sport is discussed further in Chapter 21 .
Environmental and Physical Constraints
The choice of contact lens for use in a given sport must be made with reference to the length of time that it takes to play the sport, the environment in which it is played and the general physical demands of the sport. The majority of sports are completed within 2 hours, which equates to a total period of lens wear of 4 hours, allowing for pre- and postmatch activity during which lens insertion and removal would be impractical and/or undesirable. Even when these factors are understood, the lens of the first choice may not be obvious. The most appropriate lens is sometimes determined only by trial and error.
Environmental Conditions
Contact lens wear is often associated with signs and symptoms of ocular dryness. These drying effects can be exacerbated by certain environmental factors, such as low humidity, wind and visual tasks. Wearing silicone hydrogel contact lenses may provide greater relief of subjective ocular discomfort in adverse environmental conditions than that afforded by both the habitual lenses of contact lens wearers or no contact lens wear ( ).
Sports are played in almost every environment. Climatic conditions play a role in disease severity and causative organism in contact-lens-related microbial keratitis and therefore have implications for practitioners involved in contact lens care of wearers who may be engaging in sporting activities in the tropics ( ). The following environmental conditions are considered as they will directly affect the choice of lens for the sportsperson.
Cold
Many sports take place in cold environments, typically in close proximity to ice and snow. Because the intrinsic temperature of the eye and tear film is around 34°C ( ), contact lenses cannot freeze up in the eye. In an extensive survey of 105 contact lens wearers who were frequently engaged in cold-weather sports, found no evidence of eye injury or disease. ‘Eye redness’ was the most common complaint of rigid lens wearers; soft lens wearers most frequently complained of slightly reduced vision. Large-diameter, medium-water-content hydrogel or silicone hydrogel soft lenses may provide the best results in cold conditions.
Altitude
The ability of oxygen to reach the cornea through a contact lens, which is a key prerequisite to sustain good ocular health during lens wear, is a function of the oxygen transmissibility of the contact lens and the partial pressure of oxygen in the atmosphere. This argument is particularly relevant to sports that are played at altitude. The partial pressure of oxygen in the atmosphere decreases with altitude, which effectively means that the tolerance of the eye to a lens of given oxygen performance will decrease with increasing altitude. In addition, the temperature falls about 10°C per 1500 m increase in altitude, to a minimum of −50°C; the effects of extreme cold on the cornea were dealt with in the previous section. There appears to be a significant connection between the level of available oxygen during contact lens wear and patient symptoms of comfort ( ). In view of the rarified oxygen atmosphere at high altitude, and the length of time lenses may be worn, high-oxygen-performance silicone hydrogel lenses are indicated.
surveyed the experience of 158 contact lens wearers while trekking at high altitude in Nepal. The majority of the participants (78%) reported no problems with their lenses (daily disposables, soft lenses, extended-wear lenses, hard/rigid lenses) during their stay, although dry air, dust, wind, cold temperatures and difficult hygiene maintenance were challenging. Freezing lenses and freezing solutions were additional challenges. Almost 60% of participants had not sought any pretravel health advice, and 22% of trekkers experienced a variety of problems. concluded that remote and wilderness areas provide a challenge for appropriate contact lens wear and care. Based on the findings of his survey, made the following recommendations:
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Lodges should provide better access to clean water, mirrors and lighting.
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The decision between the potential risk of infection due to touching lenses (daily disposables, soft/hard lenses) and the potential risk of corneal erosion (extended-wear lenses) needs to be made in pretravel consultations.
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Travel health professionals and travel agencies should remind contact-lens-wearing trekkers to assess carefully their wear and care routine so as to accommodate potentially challenging conditions.
Dirt and Dust
Rigid contact lenses are prone to trap debris beneath the lens and are clearly contraindicated in dirty and dusty environments. Also, dirty and dusty sporting environments are typically associated with intense physical activity and a greater risk of dislodging the lens, which are further factors contraindicating the use of rigid lenses. Large-diameter soft lenses are the lens of the first choice in such environments. Lens water content and oxygen transmissibility are less critical factors. Orthokeratology has a distinct advantage in such environments, in that the lenses are not present in the eyes to trap dirt or dust or to become dislodged.
Aquatic Environments
Aquatic sports are defined here as those that take place immediately above or in water, but generally not deeper than 2 m. has suggested that sportspersons engaged in aquatic activities be advised of the following strategies for avoiding lens loss and preserving eye health:
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Close eyes on impact with the water.
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Do not open eyes fully when under water; instead, squint and maintain a head position in the direction of gaze.
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Upon surfacing, gently wipe water from closed lids before opening eyes.
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Irrigate eyes with fresh saline upon leaving the water.
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Remove and disinfect lenses shortly thereafter.
Contact lens wear is known to increase the risk of infection slightly, and the use of lenses in aquatic environments must be considered as an additional risk factor. found that wearing a hydrophilic lens while swimming in a chlorinated pool allows the accumulation of microbial organisms on or in the lens, in both hydrogel and silicone hydrogel materials. reported that the wearing of goggles over contact lenses reduced the number of bacterial colonies found on the lens surface. However, infections are rare, and the risk of lens-related eye disease can be reduced to almost zero if lenses are removed, cleaned and disinfected in the prescribed manner soon after leaving the water. Ideally, daily disposable lenses can be worn and then discarded.
Larger lenses provide the greatest on-eye stability, which is of particular benefit when engaged in dynamic water sports ( ). Goggles worn over contact lenses, in the same way as worn by a nonlens wearer, will ensure good vision, help preserve ocular health and help reduce lens loss.
reported that, over the previous 20 years, Japanese water polo players were increasingly using contact lenses for this sport, presumably as a result of the increasing availability and affordability of disposable lenses. In 2011, 86% of Japanese water polo players wore contact lenses during games, and 96% wore soft lenses.
A survey of coaches involved in a number of different sports found that swimming was the sport associated with the lowest level of recommendation for contact lenses, although this trend was reversed with appropriate education ( ).
Subaquatic Environments
Various authors advocate the use of both rigid lenses ( ) and soft lenses ( ) for scuba diving. All seem to agree that the use of contact lenses with a standard facemask is preferred to the use of prescription facemasks. As a result of the increased physical pressure experienced during deep dives, inert atmospheric gases, in particular nitrogen, dissolve in body tissues. As the diver returns to the surface slowly, these gases are released and become trapped as minute bubbles beneath the lens ( ). This problem is especially acute with rigid lenses because of the extremely low permeability of rigid lens materials to nitrogen; the nitrogen gas cannot escape by permeating through the lens ( Fig. 24.1 ). This phenomenon can be alleviated by fitting lenses of very high gas permeability, such as silicone hydrogel lenses, and encouraging the diver to concentrate on blinking. concluded there are no compelling reasons to change lens types in patients who are already fully adapted, lens wearers. Nevertheless, silicone hydrogel lenses are the modality of choice.
