Virtual Reality-based Perceptual Learning Therapy for Visually Impaired Population

Primary outcome is the visual area measured using the HVF (24-2, SITA-standard), where sensitivity increased by 6 dB or more relative to baseline in the defective hemifield or whole field.

Visual search: Perceptual processing efficiency will be assessed using a visual search task - spatial configuration search task (Wolfe et al., 2010). In this task, participants were instructed to fixate on the centre of the screen and to locate a target. Each trial began with a short tone, followed after 500 ms by a search display. Participants pressed a key to report whether the target was present (in 50% of trials) or absent, responding as quickly and accurately as possible. Feedback-indicating response correctness-appeared for 500 ms after each trial. Trials were separated by a 1000-ms inter-trial interval. Set size was systematically varied across two conditions-6 items (1 target + 5 distractors) and 18 items (1 target + 17 distractors)-to quantify search efficiency. For each participant, reaction time (RT) was regressed on set size, and the resulting slope served as the primary index of perceptual processing efficiency: shallower slopes indicate higher efficiency.

Balance: The Bertec Balance Advantage™ system is used to assess participants' balance before and after training. During the test, participants are asked to stand under different challenging conditions. Balance-challenging conditions include (1) standing on a firm or foam surface (Fi/Fo); (2) standing surface with backward or forward translation (BT/FT); and (3) standing with their eyes close (EC). Outcome measures, including root mean square sway of the center of pressure in the anterior - posterior and medial -lateral directions (mm/s), total sway path length (mm), and maximum CoP displacement in the AP and ML directions (mm)

Fear of fall: The English & Chinese version of the Falls Efficacy Scale-International (FES-I) is a validated and reliable questionnaire used to assess fear of falling in everyday life. The FES-I total score ranges from 16 to 64. Higher scores indicate greater concern about falling and therefore a worse outcome.

The National Eye Institute 25-Item Visual Function Questionnaire (NEI-VFQ-25), English and Chinese versions. The NEI VFQ-25 scores range from 0 to 100. Higher scores indicate better visual functioning and better vision-related quality of life and therefore represent a better outcome.

The Chinese version of the Low Vision Quality of Life Questionnaire (CLVQOL) is used to assess vision-related quality of life. The CLVQOL contains 25 items, each scored from 0 to 5, resulting in a theoretical total score ranging from 0 to 125. Higher scores indicate fewer vision-related difficulties and better vision-related quality of life and therefore represent a better outcome.