Virtual reality for interactive binocular treatment of amblyopia

Amblyopia, or ‘lazy eye’, is currently treated by wearing an adhesive patch over the nonamblyopic eye for several hours per day, over a period of many months. Non-compliance with patch wearing is a significant problem. Our multi-displinary team involved clinicians and technologists to investigate the application of VR technology in a novel way. We devised a binocular treatment system in which children watch a video clip of a cartoon on a virtual TV screen, followed by playing an interactive computer game to improve their vision. So far the system has been used to treat 39 children of which 87% have shown some improvement in vision. Vision improvement tended to occur within the first 3-4 treatment sessions. This paper describes research development of the I-BiTTM system. We present a summary of results from clinical case studies conducted to date and discuss the implications of these findings with regard to future treatment of amblyopia. 1. WHAT IS AMBLYOPIA? Amblyopia, or ‘lazy eye’, is reduced corrected visual acuity which exists in the absence of any detectable organic disease. Amblyopia can be the result of a squint (strabismic amblyopia), in which both eyes are not straight, a difference of the refractive state of each eye (anisometropic amblyopia) or the result of both squint and refractive inequality (mixed amblyopia, combined anisometropic and strabismic amblyopia), in which there is a squint as well as a stronger corrective glasses lens for one eye. This condition affects 2-5% of the population (Hillis, 1986; Thompson et al., 1991) and is currently treated by wearing an adhesive patch over the non-amblyopic eye for several hours per day, over a period of many months (Cleary, 2000). Although this form of occlusion therapy is successful, success rates are variable (Hiscox et al., 1992) and noncompliance with patch wearing is a problem that can result in unsuccessful treatment (Louden, Polling and Simonsz, 2002). Standard teaching has been that amblyopia caused by strabismus and anisometropia should be treated before a child is 7 years of age (von Nooden and Crawford, 1979) and research studies have found that screening at a younger age (i.e. under 3 years) leads to better treatment outcomes (Williams et al., 2003). Children who are not successfully treated within this critical period will be left to cope with their condition into adulthood. Whilst, not disabling in itself, having one weak eye can prohibit people from some occupations such as those driving professions which require a HGV licence, the police force and ambulance driver, and there is also a higher risk of losing the good eye in later life due to injury or eye disease. The UK visually impaired register consists of large numbers of people who are amblyopic, but have lost their remaining ‘good’eye through injury or disease (Rahi et al., 2002; Tommila and Tarkkanen, 1981). 2. INTERACTIVE BINOCULAR TREATMENT A research collaboration between orthoptists, ophthalmologists and the virtual reality applications research team (VIRART) examined the potential application of VR technology to treatment of amblyopia. Our multidisplinary team considered how the features of VR could be used to provide a new way to treat amblyopia that young children would find interesting and so encourage them to comply with treatment. Together we