Paula Waddingham describes the results of recent trials using modified virtual reality technology and computer games in the treatment of amblyopia
Amblyopia is reduced corrected visual acuity which exists in the absence of any detectable organic disease. Typically, amblyopia is present in only one eye and is usually as a result of strabismus or anisometropia. This condition affects 2-3 per cent of the population.1
Current Management
Current management commences with a comprehensive orthoptic assessment, a cyclopentolate refraction and funduscopy.
If glasses are required, the full prescription should be prescribed and be worn full time. It is now recognised that a period of time is required to settle into the new glasses, during which the vision progressively improves without any other intervention. This is termed ‘refractive adaptation’ and may take up to 18 weeks2 or more.3 In various trials, about a quarter of the children referred with reduced vision, required refractive correction as the only treatment.3 When the vision no longer improves, the most commonly prescribed treatment for amblyopia is by wearing an occlusive patch on the non-amblyopic eye.
Understandably, being prescribed an occlusive patch to wear for several hours a day for many weeks and sometimes months is a difficult undertaking which requires commitment from both the child and the parent. Non-compliance with patch wearing is the main reason why treatment can be unsuccessful.4 There are variations of the occlusive patch, namely the use of an extension patch which fits over the glasses or ‘blenderm’ (the translucent patching tape used for dressings) which is attached to the lens of the glasses in front of the non-amblyopic eye. The former is popular as the patch is not sticky and blenderm is not as obvious as a patch on the face. Glasses must fit well, otherwise the motivation to ‘peep’ over the top of the glasses can be too tempting.
Avoiding a patch all together is the reason why pharmacological penalisation with atropine is seen as a more acceptable alternative for some parents and children.
Atropine is used as a primary treatment in those with vision of 6/30 or more,5 otherwise the non-amblyopic eye can still be used for fixation. Atropine is typically used when children are not compliant with occlusion.3 However, atropine has been found to be just as successful as patching5,6 and has better patient compliance which can be easily checked by observation of the pupil. It should be remembered that atropine is a potentially toxic drug and for that reason regular follow-up is required. In Nottingham, we have a protocol in place to ensure frequent appointments with the orthoptist and ophthalmologist are made and that a child has an initial 12 weeks of treatment, followed by a drug-free period.
The age at which children are offered visual screening varies throughout the country and some pre-school programmes have been stopped due to lack of evidence for its effectiveness.7 The age at which to screen for visual defects is much debated. It generally depends upon whether it is believed that the treatment of amblyopia should be carried out earlier within the critical period and will result in a more successful treatment.8 However, evidence shows that treatment effectiveness did not vary with age 9 and that improvements in vision are still achievable in older children10,11 and even adults.12,13 The gold standard which is advocated is examination of all children between the age of 4-5 years of age.14
Regardless of the timing of screening, if untreated, amblyopia is taken into adulthood and can result in exclusion from various professions15 but more significantly can lead to a dramatic lifestyle change if the non-amblyopic eye is lost through injury or pathology. A small but significant number on the partially sighted register have their amblyopic eye as their only remaining eye.16, 17 Adults with amblyopia do re-present to clinic hoping to have their amblyopia treated, typically because they wish to gain entry to the ambulance or police service.
Upon questioning it is often revealed that they remember not wearing their patch as they disliked it so much or they wore the patch but peeped. As mentioned in the preceding paragraph some evidence exists that treating amblyopia in adults may lead to visual gain. However, at present, adult amblyopia therapy is not typically offered by the majority of clinicians practising in this country.
The I-Bit system
Poor compliance, outcomes and the unpopularity of occlusion were starting points to make amblyopia treatment more exciting for children. 
Our multi-displinary team involved orthoptists and ophthalmologists from the hospital and virtual reality (VR) technologists from the university. Together we devised a novel virtual reality-based system, the I-BiT system, in which children play interactive computer games.18 Figure 1 shows the experimental I-BiT research system with the clinician interface on the desktop PC and the game being played by a child. The child looks down the cyberscope to see the game and interacts with it using a game pad or joy stick.
The racing game has an egocentric viewpoint and was designed so that the two viewpoints were completely different but complementary, with each eye seeing images that constructed the full, final, image. Figure 2 shows the racing game image as presented to each eye and the composite image when both eyes are being used. To get the child to concentrate on the game, each eye is presented with half a target and alternating white lines in the centre of the road. This means that one eye sees a white line and the other eye sees the next white line. To play the game, the child is told to drive the car around the track and collect the icons within the game. There are an equal number of icons for the right and left eyes. 
This allows the clinician to confirm that the amblyopic eye is being used. A total score for each eye comes up at the end of each circuit, in addition to a lap time. As well as the use of the specially designed games, video clips were also used in which the clip was presented preferentially to the amblyopic eye but still in a binocular context. Treatment consisted of watching the video clip for 15-20 minutes, followed by the game for a further 5-10 minutes.
Results
The children and parents were keen to participate in the research. They were happy to do anything which did not involve wearing a patch, especially those children who had had previous experience of patching.
Of the children who were treated in Nottingham, all but one enjoyed the treatment. Parents attended for every treatment appointment as requested. Children were enthusiastic and made suggestions on how to improve the game and the research prototype. Early clinical trials have showed encouraging results.
In total, 87 per cent of the children in the trial responded to the treatment. This improvement varied from half a line to five lines on the Glasgow Acuity Cards. Even children with poor levels of vision, (less than 6/60) were able to use their amblyopic eye on the binocular system and responded to treatment. Our results showed that if the treatment is going to work, it usually worked within the first 3-4 sessions, which equates to about two hours of treatment in total.
This equates to less than one daily patching treatment. Typically, most children had one treatment session a week for six weeks. In the first pilot study, children attended twice a week, but parents were happier to attend on a weekly basis. In the second trial centre in Glasgow, 12 children received treatment via a 3-D headset. All children in this trial had failed to improve with previous traditional treatment. The oldest child to respond to treatment was 11 years of age.19
The innovation with the I-BiT system is that the game is played with both eyes open and the amblyopic eye is given additional visual stimuli to encourage the eye to be used and hence improve the vision. This treatment, with both eyes open, is a world first and this new technology has an international patent. The treatment worked for newly diagnosed children and those in whom previous occlusion therapy had failed.19, 20 This binocular treatment also has the potential to benefit those children whose amblyopia has been detected late and would otherwise go untreated and those with very poor levels of vision.
The technology has been licensed to a UK commercial partner, Carleton. The company is currently developing new prototypes (Figure 3) and games to trial within a clinical setting.
References
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18 Eastgate RM, Griffiths GD, Waddingham PE et al. Modified virtual reality technology for treatment of amblyopia. Eye, 2006 Mar;20(3):370-4.
19 Cleary M, Moody A D, Buchanan A et al. Assessment of a computer-based treatment for older amblyopes: the Glasgow Pilot Study. Manuscript in preparation.
20 Waddingham P E, Butler T K H, Cobb S V et al. Preliminary results from the use of the novel Interactive Binocular Treatment (I-BiTTM) system, in the treatment of strabismic and anisometropic amblyopia. Eye, 2006 Mar;20(3):375-378.
Paula Waddingham is orthoptist and research fellow at VIRART, University of Nottingham and the Amblyopia Research Team, Ophthalmology Directorate, Queen’s Medical Centre, Nottingham