Advances in vision impairment research

Sight is one of the five basic human senses and is generally considered as the most valued sense.1 A cross-sectional survey with 250 adults between the age of 22 and 80 years revealed that people would, on average, choose 4.6 years of perfect health over 10 years of life with complete vision loss.1 It is therefore not surprising that vision impairment is associated with a lower quality of life.2–4 Vision impairment typically results from eye disorders or diseases that could have an onset earlier or later in life, and many eye diseases that lead to vision impairment have a genetic predisposition (e.g., retinitis pigmentosa, Stargardt disease). Additionally, injuries to the brain can also lead to vision impairment, for example, traumatic brain injuries and strokes. Advances in medical interventions have made early detection possible for several sight debilitating diseases, and in some cases, they are even capable of slowing down the progression of eye diseases. A success story of advances in medical intervention in reversing vision loss is cataract surgery. Cataract is once a leading cause of vision impairment, but it is now a condition that can be treated with a high level of success, with vision returning to normal in most cases. Yet, even with advances in medical interventions, according to the Global Burden of Disease Study, there were approximately 600 million of people with reduced vision ranging from mild vision loss to total blindness in 2020, with the number projected to reach almost 900 million by the year 2050.5 Impairment to vision is often manifested as a reduction in visual acuity, contrast sensitivity, or visual field—the three primary facets of vision. Previous research in the field of vision impairment has focused on the development of more effective tools to assess vision, especially in relation to one of the three primary facets of vision, better designs of optical magnifiers, and characterizing certain visual capabilities in patients with specific types of eye diseases. Since the last Feature Issue on Low Vision (Vision Impairment) published in Optometry and Vision Science in 2012, we have seen significant advancements across various fronts related to research in vision impairment, all with the ultimate goal of improving the quality of life for individuals with vision impairment. As scientific research becomes increasingly interdisciplinary in nature, we have also seen a substantial increase in research that applies cutting-edge methods or technologies to research in vision impairment, for example, the incorporation of augmented reality or virtual reality in assistive devices, sensory substitution for people with ultra-low vision, or the use of data science to analyze big data and to extract insights and patterns of knowledge from structured and unstructured data. We are excited to showcase the 18 papers in this Feature Issue, many of which made use of novel research techniques or tools. These papers are evidence that research in vision impairment has made significant strides in the past decade of years. A major contributor to the advances in research in vision impairment is the advances in the field of computing technologies. With more powerful computing infrastructure, cheaper storage solutions, and faster Internet, some tasks that were daunting and tedious in the past now become more feasible and practical. For instance, analyzing a large volume of data would be an intimidating and impractical task in the past, but now big data have become a mainstream way of extracting information from large-scale population data set. Stolwijk et al.6 used the Dutch national health insurance claims database to identify the barriers and enablers for accessing low vision services in the Netherlands. They found that various sociodemographic, clinical, and contextual patient characteristics and patients' general health care utilization all had an impact on patients' access to low vision services. An impediment to patients with vision impairment receiving quality low vision services is the availability of professionals who are capable of providing the services. With an increase in the average age of the population worldwide, the number of individuals with mild to moderate vision loss is also on the rise. Recruiting practitioners of other rehabilitative professions to help screen for mild to moderate vision impairment and to manage these patients within their scope of practice might help. Nemargut et al.7 evaluated rehabilitation professionals' perceptions of their competency in identifying and treating patients with mild to moderate vision impairment in Quebec. They found that rehabilitation professionals in Quebec are not confident in identifying or treating patients with mild to moderate vision impairment but that they expressed an interest in attending continuing education courses offered by optometrists or low vision professionals. Our profession may wish to provide continuing education courses to other professionals in relation to management of patients with vision impairment. In low vision clinics, training is often used as a tool to help patients learn something new. Some examples include learning how to use optical magnifiers (e.g., the distance at which a handheld magnifier has to be held from the page), how to direct their gaze for eccentric viewing, how to improve saccade accuracy, and how to scan the visual scenes in the case of hemianopia. A somewhat related concept but one that focuses more on the sensory experience and neural plasticity based on repeated exposure to sensory stimuli8 is perceptual learning. Perceptual learning has been shown to be effective in improving visual functions for participants with vision impairment in laboratory settings.9–11 Park et al.12 systematically reviewed 50 studies that used different perceptual learning inventions in participants with various vision impairments. Although the meta-analysis results were mostly inconclusive, the narrative synthesis showed improvements in visual functions following perceptual learning, consistent with the reports from individual studies. As in the field of general medicine, eye care professionals have also seen a paradigm shift from treating specific symptoms or diseases of patients to holistic medicine—an approach that considers the whole person. In relation to eye care services, the holistic approach may be especially important for patients with vision impairment because most of the patients are older in age and that their vision impairment might present barriers for them to fully participate in the modern society. Bittner et al.13 explored whether demographics, vision, and/or health characteristics were related to older adults with vision impairment to decide whether or not to travel and the distances that they traveled. They found that minority race, reduced vision, self-efficacy, and physical health were related to how much and how far their participants traveled and that loneliness was greater among those who did not leave town. Another way to interact with the modern society, besides traveling, is through social media. Subramanian et al.14 reported a high proportion of social media usage among adults with vision impairment in India and identified accessibility issues of having to rely on audio over vision to navigate social media. In a study that focused on achromatopsia, Andersen et al.15 investigated the vision-related quality of life, the impact of photoaversion on daily living, the effect of filters on vision, and patients' preferences of filters. The authors found that their cohort had a relatively high vision-related quality of life compared with other inherited retinal diseases and that, contrary to the belief that red light–attenuating filters are better for achromatopsia, these filters were generally not preferred by patients with achromatopsia. As mentioned earlier, research in vision impairment has benefited a great deal from advances and developments in technologies. One such technology is the head-mounted wearable devices. The first generation of such a wearable device was the Low Vision Enhancement System,16 which was developed in the 1990s. Although the Low Vision Enhancement System did not gain widespread popularity, efforts in making head-mounted wearables useful and usable for individuals with visual impairment continued. Currently, there are a number of commercial head-mounted headsets on the market with improved image processing algorithms and better functionality, and are lighter in weight. Chun et al.17 evaluated the effectiveness of two magnification strategies in a head-mounted virtual reality display—the full-field magnification display versus the virtual bioptic telescope mode—and found that both magnification strategies significantly improved functional vision outcomes for self-reported reading ability in a cohort of 88 participants with vision impairment. Besides the traditional assistive devices such as portable electronic magnifiers or wearable headsets, mobile phones have become a popular type of “assistive device” as a majority of people carry a mobile phone with them on a daily basis, and major brands of mobile phones have built-in accessibility functions to assist visually impaired users to navigate the complexity of using modern mobile phones. Malkin et al.18 conducted a clinical trial in which participants with vision impairment were randomized to use one of three mobile apps (SuperVision+, SeeingAI, or Aira). These authors compared the amount of training time and proficiency and found that age, mild cognitive loss, or level of vision impairment did not preclude proficiency in using the three apps with training, although those factors were associated with longer training times. These authors also concluded that telerehabilitation could be a viable option in providing app training remotely for visually impaired seniors. Advances in technology have also provided us with means to help individuals with ultra-low vision to function better, including the use of prostheses or retinal/cortical implants or sensory substitution. Jin et al.19 showed that a prototype vibrotactile sensory substitution device was effective in improving functional performance of people with profound vision loss in a face detection and an obstacle avoidance task. Visual midline shifts can be a result of a range of neurological conditions, including stroke and traumatic brain injury, and it could be a risk factor for falls. Stalin et al.20 evaluated the parameters of a novel visual midline gauge and compared the results with the current clinical method. They found that the measurement of visual midline was tolerant of target speeds, testing methods, and age of participants, and they demonstrated good repeatability of the novel visual midline gauge. There is an explosion of current interest in using artificial intelligence in eye care and vision research. He and Chung21 developed a framework that combines Natural Language Processing and machine learning to analyze narratives in electronic medical records obtained from a cohort of patients attending low vision examinations. They demonstrated that the proposed framework was able to extract the semantic patterns embedded within the medical narratives, which comprised qualitative and unstructured data, and to predict patients' sentiments toward using certain assistive tools and their quality of vision. Their framework may also be adopted to analyze big data in other areas of optometric research. Mobility, or the ability to travel independently, is an important task of daily activity for people with vision impairment. Knights et al.22 reviewed the current literature in search of evidence linking mobility aids for people with vision impairment to the functions, activities, and participation domains of the International Classification of Functioning, Disability and Health. These authors found only three observational studies in the literature that satisfied their inclusion criteria and that the findings were inconclusive; thus, they identified this as an important knowledge gap for determining the most suitable mobility aids to best facilitate health-supporting activities. People with vision impairment may rely more on auditory cues for path planning, navigation, and obstacle avoidance. Pardhan et al.23 investigated whether there exist differences in sound distance estimation in people with early-onset compared with late-onset vision impairment. Their findings suggest that early-onset vision impairment results in significant changes in judged auditory distance, especially for close and intermediate distances, whereas late-onset vision impairment does not have much of an impact on judging auditory distance. Their results were discussed in relation to the Perceptual Restructuring Hypothesis. When navigating indoor or outdoor spaces, very often we need to negotiate steps and ramps. Poor visibility of steps and ramps can pose significant hazards to individuals with vision impairment. Lei et al.24 examined the effect of illumination on the visibility of steps and ramps in an indoor environment. Although the authors found that changes in photopic illumination over a range of two log units had minimal effect on the objective visibility of steps and ramps for participants with vision impairment, changes in illumination affected participants' confidence in hazard recognition. These findings suggest that architectural design decisions should consider the consequences of certain parameters such as illumination level on both the objective and subjective accessibility of space. Another challenge for people with vision impairment in walking around in the real world is to avoid colliding with obstacles or other people. Bowers et al.25 presented preliminary results comparing the effectiveness of two types of prism glasses on blind-side collision detection performance in six participants with homonymous hemianopia, using a test that simulated walking through a busy shopping mall. Many people with vision impairment are unable to drive because of their vision limitations. Bioptic telescopes enable some people with vision impairment to drive, but there remain unanswered questions about their contributions to driving safety. Oberstein et al.26 measured the performance of participants with vision impairment using a bioptic telescope to recognize road signs, traffic lights, and hazards while they sat in the front passenger seat of a moving car. The authors found that road signs were recognized at significantly longer distances when participants used a bioptic telescope. Future work is needed to determine whether the effect also applies to bioptic telescope drivers. Another technology that could address the driving issue for people with vision impairment is self-driving cars, also known as driverless cars or autonomous cars. Despite the perceived promises of autonomous cars as an alternative transportation solution for people with vision impairment, it is unclear how they are perceived by the visually impaired community. Kuborn and Hassan27 administered a survey to people with vision impairment, people who were blind, and people with normal vision and asked about their perceptions and concerns regarding autonomous cars. She found that individuals with vision loss expressed more acceptance of autonomous cars despite their concerns, and how positive someone is toward autonomous cars appears to be dependent upon their visual field and driving status. In the real world, whether we are driving, sitting in a car as a passenger, walking, or simply sitting still, there is always retinal image motion caused by moving objects around us. How well can we see a moving object, and does it matter if we try to follow it? And how about in the presence of vision loss? Shanidze and Verghese28 examined whether the characteristics of smooth pursuit (continuous tracking of a moving object with the eyes) changed when the task required dynamic visual acuity in the presence of macular degeneration. They found that compromised pursuit gain in participants with macular degeneration likely further compromised their dynamic visual acuity and their ability to view moving targets. The research highlighted in this Feature Issue represents significant advances in the field of vision impairment research. However, many knowledge gaps remain, and future research must continue to address the challenges faced by individuals with vision impairment in their daily lives, devise tools and rehabilitative strategies, and embrace new technology to improve the quality of life of these individuals.

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