The reliability of the built-in assessments in DREX training app

App-based perimetry has been introduced recently for screening stroke-related visual impairments (Spofforth, Codina, & Bjerre, 2017) and diagnosing hemianopia (Koiava et al., 2012). One study comparing the results of app-based perimetry and

conventional Humphrey Visual Field analyser (HVF) revealed that app-based perimetry is effective to detect moderate to severe visual field loss, and both findings were highly

35 correlated (Johnson et al., 2017). In terms of the sensitivity and specificity of the app-based perimetry in detecting visual field loss, Koiava et al. (2012) found that the app-based version is highly sensitive and specific for the undamaged field, but the values slightly reduced for the damaged field and thus the suggestion to add more testing stimuli to the present version to improve detection of visual field loss has been made. Other than perimetry, wed-based visual search assessment has also been introduced to evaluate the outcome of visual search therapy which was completed online (Ong et al., 2015), and this assessment was validated previously (Jacquin-Courtois, Bays, Salemme, Leff, & Husain, 2013). The study demonstrated that the app-based visual search assessment was able to accurately measure the visual search performance indicating the effectiveness and usefulness of the app-based assessment in assessing visual search. Although the ADL scales were included in the study as a part of the assessments, the validity of the scales is unknown. There is very little information about the use of self-assessment in HVFD rehabilitation as most of the treatments were done in clinic or laboratory such that the conventional assessments which require supervision and input from therapist were used.

In the DREX training app there are four main self-assessments that have been incorporated to measure the extent of visual field loss (perimetry), visual search, reading, and quality of life. These assessments will allow the user to monitor their own progress and understand the benefits they have gained. Furthermore, there is also a mechanism whereby this data can be shared with the clinical team, such as doctors, optometrists and

occupational therapists, enabling them to track patients’ progression remotely and make suggestions to improve training experience. The aim of Chapter 5 (Studies 4 to 6) is to validate the assessment measures that have been built into the app by comparing

improvements on these with other standardised and previously used outcome measures.

Validating the assessment measures that have been built into the app will allow us to

36 determine if these can be used effectively for monitoring the benefits of the training

remotely.

1.3.5 The efficacy of DREX training for other partial visual field defects The behavioural consequences of visual field loss appear to be comparable

regardless of the cause. Impairment of visual search among those with other partial visual field defects such as glaucoma, retinitis pigmentosa and age-related macular degeneration (AMD) has been demonstrated (Jacko et al., 2000; Smith, Glen, & Crabb, 2012; Vargas-Martin & Peli, 2006; Whittaker, Cummings, & Swieson, 1991); patients were unable to effectively scan their surroundings, read and mobilise independently as a consequences of impaired visual search, and their visual search was described as slow and longer than the normal subjects (Kuyk, Liu, & Fuhr, 2005). The visual field loss not only impaired their behavioural function but also their quality of life (Taylor, Hobby, Binns, & Crabb, 2016) which has a wider impact on patients participation in society, emotional well-being, and independence.

In 2015, there were an estimated 253 million people with visual impairment globally, and around 3 to 4% of them suffered from either glaucoma or AMD (Ackland, Resnikoff, & Bourne, 2017) that affects mainly the elderly population. These estimates indicate the substantial global burden of these diseases that suggests immediate

improvement of eye care service as well as the provision of effective rehabilitation strategies to ameliorate visual disabilities (Wong et al., 2014). Therefore, numerous treatment options have been introduced to rehabilitate glaucoma, retinitis pigmentosa and AMD including compensatory training which was found to be clinically effective (Ivanov et al., 2016; Janssen & Verghese, 2016; Liu, Kuyk, & Fuhr, 2007; Parmeggiani et al., 2011). For example, the study on the effects of visual compensatory training on retinitis pigmentosa patients was recently conducted in a controlled trial by Ivanov and co-workers

37 (2016). They reported a positive therapeutic impact of exploratory saccade training on mobility among retinitis pigmentosa patients such that patients demonstrated faster visual search and improved ability to avoid obstacles which were persistent up to 6 weeks post-training. Despite promising effects of compensatory training, it is not widely offered and accessible to many patients. At present, the training was done in a specialised clinic which is both costly and laborious. Therefore, the DREX app, which is free and accessible, could be advantageous to these patients.

Study 7 (Chapter 6) reports a proof of principle case series investigating the effect of DREX training in the rehabilitation of visual exploration and reading impairments in patients with tunnel vision, central visual field loss and bitemporal visual field loss. If successful, DREX could be offered to many patients at no cost. The outcomes of this study will also allow us to make specific modifications where necessary to the training itself in order to optimise the efficacy of training for these patient populations.

1.3.6 The effects of blurred vision on the outcomes of visual exploration training