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Geraint Griffiths describes the basis of sports vision therapy, including some case studies, and goes on to describe specific appliances available (C3609, one standard CET point)

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Sport is the biggest and most diverse occupation in Britain and every week some 20 million individuals take part. Elite athletes now take specialist advice on their vision as a matter of routine. The England rugby team, Manchester United and Tiger Woods all retain vision specialists.

Where professionals lead, amateurs follow and high street opticians can benefit from a huge business opportunity in recreational sports and second tier professionals.

Recent research,1 from which the 'Laws of Sport Vision', some important basic statements regarding sport and vision, have been derived, has shown that sport vision is very much the province of every optical practice. It presents a wonderful opportunity for dispensers and optometrists to work hand in hand with industry to supply modern sport vision appliances and contact lens materials and solutions, in this important area of occupational optics.

The Laws of Sport Vision

• The primary visual skills in sport are aiming and anticipation (reliant upon depth perception), upon which all other skills are based
•  Visual performance is a controlling external factor (other external factors that can be influenced by coaching procedures include physiology, nutrition and psychology) in the development and maintenance of sporting performance throughout life
•  Sporting performance is usually dependent (according to the visual requirements of the sport) on the maintenance of the normal, established relationship between the two eyes
•  A deficiency in visual performance will inhibit the development of sporting potential through poor eye/hand/body co-ordination, but perfect eyes do not make a perfect athlete. This depends on innate physiology and psychology ('the grit in the oyster', the will to win). Remember, visually impaired but well motivated sports players often achieve remarkable results.

These statements apply where vision is the primary sense and would have special applications in monocular athletes. Although the phrase 'sporting performance' is used in the statements, this could be interchangeable with 'occupational performance' or 'behaviour.' What distinguishes sport from other behaviours and occupations is simply visual demand, which is usually very important in the undertaking of sport.

All sports need a combination of the two primary visual skills of aiming and anticipation. The proportion of one to another varies, from nearly all aiming, in sports like rifle shooting, to nearly all anticipation (reliant on depth perception) in sports like tennis. Golf combines both and is highly visually dependent.

These statements provide a robust model to address problems in sporting performance and resonate with athletes who have an intuitive understanding of this logic. They also support the argument that the best form of eye exercise is playing the game once visual deficiencies have been corrected. Occasionally the establishment of normal binocular vision will need to be reinforced by orthoptic exercises.

Diagnosis of Sporting Deficiency
The cause of deficiencies in these two primary skills can be diagnosed by considering the six elements of visual performance which are common to all sports:

• Refraction
•  High and low contrast vision (as the player presents)
• Eye dominance
• Muscle balance 
•  Fixation disparity 
•  Colour preference and light sensitivity.2

It follows from the laws that vision is the most important consideration in the preparation for competitive sport and that binocular vision is a key competency in optometry and essential to understanding sporting and other occupational deficits.

Case Histories

Archery
Suddenly and inexplicably, an archer started missing the target to the left in a horizontal line level with the gold (centre). This was due to the left non-dominant eye taking over as the aiming eye became more myopic. Correction with a soft contact lens solved the problem.

Goal keeping
The player experienced loss of confidence in catching high balls or going down to the feet of oncoming players. He was found to have incipient myopia and astigmatism and an accommodative spasm with an associated decompensated esophoria. This was masking a convergence insufficiency, which became apparent when the myopia was corrected (the pseudomyopia due to spasm causing convergence, making near point assessment irrelevant). Binocular stability was restored with correction and orthoptic exercises. The player was subsequently sold for a very much increased transfer fee!

Soccer player
Light sensitivity2 was found in a fair skinned blue-eyed player which was disabling the player on bright sunny days. Tinted contact lenses provided some relief and improved playing performance.

Slalom canoeing
Visual assessment showed the athlete had hyperopic anisometropia and residual amblyopia in the non-dominant eye. Full correction improved stereopsis and may encourage some resolution of the amblyopia in normal use. This enabled the athlete to judge the gates much more accurately and improve times.

Tennis
In players with strongly established right eye and hand dominance (Type 1), even small amounts of blur in the non-dominant eye will significantly affect their ability to connect with the ball.1 When the non-dominant eye is blurred, the strength of right dominance 'swamps the visual system', making the athlete effectively monocular.

Judging how far away the ball is and its speed of approach is at its best when it is a stereoscopic function. Interestingly players who are cross dominant, say left eye dominant and right handed appear far less affected by blur of the non-dominant eye. Cross dominance may inhibit the full development of stereopsis3 and forces the visual system to learn and rely more on monocular clues like parallax and magnification.

To a player who can see the incoming object perfectly well (dominant eye clear), inexplicable misses are infinitely frustrating, but easily explained and corrected through an understanding of the visual system. In all these examples, a visual explanation of sporting difficulties gives great confidence to the athlete who is used to dealing with adversity that they understand. It is the inexplicable that has such a profound and psychologically damaging effect.

Modern Sports Optical Appliances
Sport appliance and lenses and contact lenses are the main areas to consider. These are considered with the initial assessment and diagnosis to build a solution tailored to the individual.

Modern sport vision appliances and CLs provide the means to correct, protect and enhance visual performance. Table 1 lists the features and benefits of modern sport vision appliances.

Contact lenses
Modern materials and fitting modalities are giving contact lenses a very important role to play and with an increased awareness of the importance of vision in sport should begin to address the surprisingly low uptake of contact lens options in this country. See Table 2 for advantages of contact lenses in sport.

Specialist appliances

Shooting
Rifle shooting is highly visually dependant as determined by the angular subtense of the target at the eye. The Champion frame by Norville Optical allows for precise alignment of the optical axis and occlusion of the non-aiming eye if necessary.

Swimming
This is the most popular sport in the UK4 where vision and protection from chemical conjunctivitis and water-borne microbes are important. Swimming goggles are available in prescription form and help with judgement of the turns and direction.

Football
It is very important that young athletes are not prevented from developing their sporting skills because of ametropia. The authorities are beginning to accept the wearing of protective and corrective appliances (Edgar Davids, the footballer with glaucoma, being a notable professional example), where there has never been any particular rule preventing them; this is normally left to the referee's discretion. It is important the optical profession leads the way in justifying the use of correction and protection in sport and increasingly the sporting authorities are very willing to take advice.

Squash and Racket sports
(BS British Standard BS 7930 - 1: 1998)
There is risk of ocular trauma in most sports but the close proximity of the players and their rackets on the squash court and the size of the ball make this a particularly visually dangerous sport. The size and velocity of a squash ball make it a perfect cause of blow-out fracture.

Clay shooting
All clay shooters are now required to wear eye protection. These will typically have a distance prescription in them with lenses made of polycarbonate or Trivex material. Shooting appliances tend to have a large navigator type eye size with a high bridge fitting (ideally adjustable).

Snooker
Snooker is another highly visually dependent sport requiring equal levels of aiming and depth perception and a particular consideration of eye dominance. The sport needs high-fitting frames with adjusted pantoscopic angle to allow for the low head position and relative up-gaze.

Skiing
The skiing goggle needs to protect from trauma and ultraviolet radiation. It has to be well ventilated to maximise vision, which may be a matter of life and death.

Conclusion
The principles of visual performance in sport are quite simple in origin and it is from these that the practitioner can build an understanding of the athlete. There is already a bewildering range of optical appliances and contact lens options available, but the best approach is to build up an ideal dispensing solution around the athlete and then go to the manufacturers to find an appliance or contact lens which best meets the need.
Sport vision requires a detailed understanding of the athlete, primarily vision, but also every other aspect of their life, which can all affect sporting performance. It is self evident that the eye is just one part of the whole and cannot be fully understood in isolation.

Acknowledgements
Thanks to: r+h, Adidas, Dailies by CIBA Vision, Sight Care, Optimed, Norville Optical and Caseco for support in preparing this article.

References
1 Griffiths GW. Eye Dominance in Sport - a comparative study 2003 Optometry Today Vol 43:16.
2 Griffiths G.W 2001. Colour Preference - a comparative study. Optometry Today vol 41:20.
3 Griffiths GW. Ametropia its incidence in elite sport. Optometry Today Vol 45:12.
4 Loran and Mac Ewen 1995. Sports Vision, Pub Butterworth Heinemann.
5 Cardell M. CLs in sport. Optician, 2006; 6034, 231, pp 22-26. 

•  Geraint Griffiths is managing director of Sportvision and a former British international high jumper. He is a College examiner and assessor

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