Evidence-based classification for athletes with a vision impairment in goalball

In Paralympic sport, classification systems aim to ensure that athletes compete against others who have impairments that similarly impact on their ability to perform in a given sport. This promises that Paralympic success reflects sporting prowess, not just having a less severe impairment. Every classification system must state both the ‘Minimum Impairment Criteria’, which reflects the least impairment an athlete can have to be considered eligible, and the ‘Class Structure’, which determines whether eligible athletes are further divided into different competition groups to maximise fair play. Historically, many sports have used the same medical definitions to determine eligibility, despite different impairments having varying impact on a person’s ability to perform each sport’s specific tasks. Subsequently, the International Paralympic Committee published the Athlete Classification Code (2007, 2015) which required all Paralympic sports to develop sport-specific, evidence-based classification systems which reflect the extent to which a specific impairment impacts on performance in a given sport. This triggered the initiation of research programmes across Paralympic Sport, each aiming to highlight a sport’s unique impairment performance relationship to inform new, code-compliant, classification systems.

This thesis examined the relationship between vision impairment and individual performance in the Paralympic sport of goalball, to underpin an updated classification system. Goalball is an indoor, court-based sport where two teams of three players aim to throw an audible ball into the opposition’s 9m wide goal, situated at the end of an 18m-by-9m court. During competition, all athletes are required to wear blackout eyeshades, and hence use tactile court markings and the audible ball to orientate during play. Currently, athletes are eligible for competition based on definitions of low vision and blindness (I.e., focusing on levels of visual acuity and visual field), not based on how a vision impairment impacts the ability to compete in the sport.

To start the process of investigating the impairment performance relationship in goalball, expert opinions surrounding the current, and future, goalball classification system were gathered using a Delphi Study (Chapter 2). This provided insight into the challenges of developing a new classification system and informed later empirical investigation. Notably, the lack of an able-bodied (i.e., fully sighted) equivalent sport and the requirement for all players to compete whilst wearing eyeshades, were highlighted as key areas of consideration for goalball classification research. Several measures of visual function (visual acuity, visual field, contrast sensitivity, motion perception and visual search) were also suggested as potentially relevant for classification. In addition, the Goalball Performance Model was developed, highlighting the key performance determinants of individual goalball performance.

Second, to inform the development of a new class structure, the relationship between vision impairment and performance whilst players compete wearing eyeshades was assessed. In Chapter 3, data from the last two Paralympic Games (Rio 2016 and Tokyo 2020) was analysed to determine whether individual performance was related to severity of vision impairment. No significant relationships were found between vision impairment and performance for five out of six performance indicators, with decision-tree analysis further suggesting that one class remains appropriate.

Chapter 4 also assessed the impairment performance relationship under eyeshaded conditions, extending the range of participants’ vision beyond the current eligibility boundary by including those not considered eligible by the current system. More importantly, Chapter 4 also saw the development of the Goalball Performance Test, the first test of comprehensive individual goalball performance, and testing across several measures of visual function for the first time. In line with findings from Chapter 3, no relationship between vision (across all measures) and performance (measured across attacking, defending and orientation tasks) was found. In sum, findings from Chapter 3 and Chapter 4 suggested that one class remains suitable for all athletes during competition, regardless of where the Minimum Impairment Criteria is set.

Third, investigation aimed to contribute to the determination of an appropriate Minimum Impairment Criteria. Results from Chapters 3 and 4, which identified no relationship between vision and performance whilst players wear eyeshades, cannot be used to inform eligibility as there is no obvious point at which a vision impairment negatively impacts performance. To understand how vision impacts on a players’ ability to perform goalball-specific skills, investigation described in Chapter 5 took place without eyeshades, using a simulation study protocol. Here, fully-sighted participants completed an adapted version of the Goalball Performance Test under increasingly severe simulated vision impairment. Youden’s J analysis, assuming equal weighting of sensitivity and specificity, suggested that performance became significantly worse when visual acuity was reduced to 1.25LogMAR (specifically for orientation performance), which is more severe than the current cut-off of 1.0LogMAR. However, it remains unclear whether it is appropriate to give equal weighting to the classification system’s sensitivity and specificity for goalball. Arguably, a greater weighting may be favoured for sensitivity, as as all athletes compete wearing eyeshades, the chance of someone with less impairment having an advantage during competition is reduced. When determining the final cut-off, consideration must be given to whether the sensitivity or the specificity of goalball’s classification system should be preferred.

Ultimately, it is clear that a one class structure is suitable for goalball, but that further guidance is needed from the International Paralympic Committee and International Federation of Blind Sports (IBSA) as to how to approach determining the Minimum Impairment Criteria. This thesis presents evidence showcasing the impairment performance relationship in goalball whilst athletes compete both with and without eyeshades, to assist with the development of a new, evidence-based classification system.