In this study, 8 clusters or groups of vision-related activities related to challenges under low luminance were identified by both expert low vision professionals and patients with vision impairment (from highest to lowest importance ratings): hazard detection and safety outside; social interactions; navigation; near reading; selfcare and safety at home; distance spotting; searching around the home; and cooking and cleaning. The clusters that included the most activity statements were hazard detection and safety outside, near reading, and cooking and cleaning. Many of the clusters and individual activity statements rated most highly for importance seem to be those that might pose greater risk to personal safety. Clusters with lower importance ratings (searching around the home and cooking and cleaning), comprise household activities where lighting can usually be increased. Although low vision professionals and patients differed slightly in their perceived relative importance of the clusters of activity statements, any differences were not significant.
The hazard detection and safety outside and navigation clusters were rated as highly important and were located next to each other on the cluster map, indicating a close relationship, as expected. Several activities within these clusters related to crossing the road, driving (either as a driver or passenger), and walking around the environment (mobility). This is consistent with the literature (where these activities are frequently reported as challenging for adults with vision impairment), and the focus of low luminance PROMs.
5,8,13,15,16 These activities are not easily standardized and could present safety issues in a set of tasks that might be included in a performance-based measure. An option for both crossing the road and driving could be a carefully designed computer-based “hazard perception test” (HPT).
32,33 HPTs typically involve real video or static images that require the viewer to identify a range of potential hazards or traffic conflicts (e.g. cars and pedestrians). To date, no studies have investigated performance on HPTs simulating mesopic or night-time conditions. However, performance on daytime HPTs has been associated with crash risk and on-road driving performance.
34–36 Although HPTs have been mostly used to evaluate driving, there are a few studies that have used HPTs to investigate the ability to cross the road safely during the daytime.
33,37,38 With regard to walking around the environment, a number of standardized, relatively safe and compact laboratory courses, typically seeded with hazards simulating the real world, have been designed to evaluate mobility performance under a range of luminance levels,
23,24,26,39–41 and could incorporate many of the activities identified in this study. An additional activity in the hazard detection and safety outside cluster that warrants specific consideration for inclusion in a comprehensive performance-based measure is adapting to changes in light levels. To date, adaptation to light levels has been limited to a few performance-based mobility
41–43 and driving studies
41–46 investigating glare disability, in spite of it being such a frequently reported problem for patients with vision impairment.
3,5,16,17,47
The second most important cluster comprised the fewest activity statements, mostly related to identifying faces and facial expressions. Diverse approaches have been used in previous studies to measure the ability of persons with vision impairment to identify faces and facial expressions, several that could be included as a low luminance performance-based measure, each with advantages and disadvantages. Some studies have simply used printed or projected famous faces.
48,49 However, even famous faces might not be familiar to everyone. Other studies have either used faces that were photographed for the purpose of the study,
50–52 or faces from validated standardized databases (originally assembled to investigate prosopagnosia).
53–55 Regardless, it is challenging to standardize images of faces with respect to features, such as expression, head posture, hair, etc. Facial expressions used are typically neutral, sad, anger, fear, happy, surprise, and disgust, as these are consistently found within most cultures.
56 For face recognition, matching and odd-one-out methods have been used to evaluate performance (with several trials to account for variability in faces and guessing), and for facial expressions, simple naming has been used.
49,51,52,57 Even so, no studies have assessed the effect of low luminance on face perception in adults with vision impairment.
The near reading cluster in this study comprised a large number of activity statements, mostly related to reading small text, such as medicine labels, mobile phone texts, computer use, shopping labels, food/ingredient labels, books, menus, and brochures, as well as writing and identifying money. Some of these are more likely to be undertaken in low luminance than others (e.g. reading a book in bed or a menu in a dimly lit restaurant). Most are easily replicated and standardized, and, indeed, many have been included as part of performance-based measures designed for photopic conditions,
48,58,59 as well as low luminance PROMs.
5,13,15,17 Similarly, many of the activities in the distance spotting cluster could be easily replicated and standardized (e.g. identifying the correct public restroom, reading bus numbers, and road signs).
Three clusters, self-care and safety at home, searching around the home, and cooking and cleaning, were positioned close to each other on the cluster map, and therefore closely related, as the named themes suggest. Indeed, some of the activities could easily belong in one cluster or the other (e.g. finding/cleaning spills, and using controls on the stove/cooktop). However, given the large number of activities in these clusters and that the 8-cluster map made most conceptual sense for all other clusters, these were not combined. Activities in the self-care and safety at home cluster were mostly related to managing medications, checking that foods are safe for consumption, and safe use of appliances (e.g. checking the gas on the stove/cooktop). Relatively few activities were in the searching around the home cluster and included finding things dropped on a floor and inserting a key into a lock. Although cooking and cleaning comprised the largest number of activities and was of some importance, it was rated least important compared with all other clusters. Although some of the activities in these 3 clusters are less likely to occur in low luminance (and hence not commonly included in low luminance visual function research to date), are impractical or unsafe to include in a performance-based measure (e.g. cutting of food, and making a cup of tea/coffee). To be comprehensive, a few could be considered for inclusion in a low luminance performance-based measure and have been used previously (e.g. finding food in a cupboard and inserting a key into a lock
5,58–60).
The strengths of this study were use of group concept mapping and inclusion of both expert low vision professionals and patient stakeholder groups. In contrast, existing low luminance PROMS were developed using parts of other PROMS in the literature,
15,16 or focus groups and interviews with predominantly patients with macular degeneration.
5,17 However, there were some limitations. Although participants were asked to generate a list of “…activities a person with vision impairment might find challenging under low light conditions, such as in a poorly lit room or outside at dusk,” several of the activities reported are not usually performed under low luminance conditions. However, for the purpose of designing a low luminance performance-based measure, having a wide range of potential tasks from which to select is useful at this stage. In addition, a smaller number of participants went on to complete the sorting and rating components of the study. Understandably, participants with vision impairment found it challenging to sort the large number of statements into groups of similar activities, even with assistance, producing less consistent sorting of similar activities compared with the low vision professionals. Therefore, the clusters were based on the sorting completed by the professional group. Perhaps having a larger number of participants with vision impairment involved in sorting may have resulted in an equal or better goodness-of-fit compared to the low vision professionals.
In conclusion, this study has defined a conceptual framework using the group concept mapping approach and identified activities that present challenges under low luminance for patients with vision impairment. The most important activities were related to hazard detection, and safety outside and social interactions. These findings can inform the design of a performance-based measure of low luminance visual function.