Simulating Macular Degeneration to Investigate Activities of Daily Living: A Systematic Review

Purpose: Investigating difficulties during activities of daily living is a fundamental first step for the development of vision-related intervention and rehabilitation strategies. One way to do this is through visual impairment simulations. The aim of this review is to synthesize and assess the types of simulation methods that have been used to simulate age-related macular degeneration (AMD) in normally sighted participants, during activities of daily living (e.g., reading, cleaning, and cooking).Methods: We conducted a systematic literature search in five databases and a critical analysis of the advantages and disadvantages of various AMD simulation methods (following PRISMA guidelines). The review focuses on the suitability of each method for investigating activities of daily living, an assessment of clinical validation procedures, and an evaluation of the adaptation periods for participants.Results: Nineteen studies met the criteria for inclusion. Contact lenses, computer manipulations, gaze contingent displays, and simulation glasses were the main forms of AMD simulation identified. The use of validation and adaptation procedures were reported in approximately two-thirds and half of studies, respectively.Conclusions: Synthesis of the methodology demonstrated that the choice of simulation has been, and should continue to be, guided by the nature of the study. While simulations may never completely replicate vision loss experienced during AMD, consistency in simulation methodology is critical for generating realistic behavioral responses under vision impairment simulation and limiting the influence of confounding factors. Researchers could also come to a consensus regarding the length and form of adaptation by exploring what is an adequate amount of time and type of training required to acclimatize participants to vision impairment simulations

A Systematic Review of Extended Reality (XR) for Understanding and Augmenting Vision Loss

Over the past decade, extended reality (XR) has emerged as an assistive technology not only to augment residual vision of people losing their sight but also to study the rudimentary vision restored to blind people by a visual neuroprosthesis. To make the best use of these emerging technologies, it is valuable and timely to understand the state of this research and identify any shortcomings that are present. Here we present a systematic literature review of 227 publications from 106 different venues assessing the potential of XR technology to further visual accessibility. In contrast to other reviews, we sample studies from multiple scientific disciplines, focus on augmentation of a person's residual vision, and require studies to feature a quantitative evaluation with appropriate end users. We summarize prominent findings from different XR research areas, show how the landscape has changed over the last decade, and identify scientific gaps in the literature. Specifically, we highlight the need for real-world validation, the broadening of end-user participation, and a more nuanced understanding of the suitability and usability of different XR-based accessibility aids. By broadening end-user participation to early stages of the design process and shifting the focus from behavioral performance to qualitative assessments of usability, future research has the potential to develop XR technologies that may not only allow for studying vision loss, but also enable novel visual accessibility aids with the potential to impact the lives of millions of people living with vision loss

Keep Your Eyes above the Ball: Investigation of Virtual Reality (VR) Assistive Gaming for Age-Related Macular Degeneration (AMD) Visual Training

Humans are beyond all visual beings since most of the outside information is gathered through the visual system. When the aging process starts, visual functional damages become more and more common and the risk of developing visual impairment is higher. Age-related macular degeneration (AMD) is one of the main afflictions that leads to severe damage to the optical system due to the aging process. The ones affected lose the ability to use the central part of vision, essential for accurate visual information processing. Even if less accurate, peripheral vision remains unaffected, hence medical experts have developed training procedures to train patients to use peripheral vision instead to navigate their environment and continue their daily lives. This type of training is called eccentric viewing. However, there are several shortcomings in current approaches, such as not being engaging or individualizable enough nor cost and time-effective. The main scope of this dissertation was to find out if more engaging and individualizable methods can be used for peripheral training of AMD patients. The current work used virtual reality (VR) gaming to deliver AMD training; the first time such an approach was used for eccentric viewing training. In combination with eye-tracking, real-time individualized assistance was also achieved. Thanks to an integrated eye-tracker in the headset, concentric gaze-contingent stimuli were used to redirect the eyes toward an eccentric location. The concentric feature allowed participants to choose freely and individually their peripheral focus point. One study investigated the feasibility a VR system for individualized visual training of ophthalmic patients, two studies investigated two types of peripheral stimuli (three spatial cues and two optical distortions) and the last study was a case study looking into the feasibility of such an approach for a patient with late AMD. Changes in gaze directionality were observed in all the last three studies for one specific spatial cue, a concentric ring. In accordance with the literature, the gaze was directed spontaneously toward the most effective peripheral position. The last study additionally proved gaming feasible for future testing of the elderly AMD population. The current work opened the road to more individualized and engaging interventions for eccentric viewing training for late AMD

Eye movements in hemianopia and the rehabilitation of hemianopic dyslexia

This thesis is a study of the nature and rehabilitation of the functional impairments in unilateral homonymous hemianopia (HH), with a major focus on hemianopic dyslexia. The reading, visual exploration and line bisection impairments associated with homonymous visual field loss are frequent and well-established clinical phenomena. Yet, it is still unknown whether the reading and visual exploration impairments are caused by the visual field defect or by additional extrastriate injury preventing efficient spontaneous oculomotor adaptation. It is also unclear whether the line bisection impairment directly arises from the visual field defect or its adaptive oculomotor consequences, or whether it indicates an associated visual-spatial deficit that is caused by injury to regions involved in visual-spatial perception (Introduction). Based on a critical review of research into hemianopic dyslexia since its original description in 1881, it is suggested that the visual field defect is a major component of hemianopic dyslexia but possibly not its sole cause (Chapter 1). This assumption was confirmed in six experiments whose purpose was to establish the extent to which the reading, visual exploration and line bisection impairments associated with HH are purely visually elicited. To study the behavioural changes associated with the visual field defect that are not caused by brain injury, a gaze-contingent display paradigm was used to simulate HH in healthy participants. Simulated HH induced the reading and visual exploration impairments of hemianopic patients. However, all participants showed efficient spontaneous oculomotor adaptation to simulated HH which was associated with highly specific and task-dependent improvements in reading and visual exploration (Chapters 2 and 3). Moreover, simulated HH did not induce the main feature of the hemianopic line bisection impairment, i.e., the contralateral line bisection error, albeit it nevertheless impaired line bisection performance (Chapter 4). The final study investigated the basis and specificity of the therapeutic effect of an efficient compensatory oculomotor treatment method for hemianopic dyslexia in patients with unilateral homonymous visual field loss. The results demonstrate that using text-material and, thus, lexical-semantic processes, is not critical to the treatment effect, which was also found to be specific to reading (Chapter 5). The concluding chapter reviews the main findings and suggests that the functional impairments associated with visual field loss may not simply be failures of vision. Although the hemianopic visual field defect is a major component of hemianopic dyslexia and possibly contributes to the visual exploration and line bisection impairments, additional injury to specific extrastriate regions seems to be the critical causative factor. The implications for understanding, assessing and rehabilitating functional impairments in homonymous visual field disorders are discussed. The important future research directions arising from this thesis are also identified and presented (Conclusion)

Head Mounted Eye Tracking Aid for Central Visual Field Loss

University of Minnesota M.S.M.E. thesis. July 2016. Major: Mechanical Engineering. Advisor: Arthur Erdman. 1 computer file (PDF); viii, 137 pages.Age-Related Macular Degeneration results in central visual field loss (CFL) due to formation of central blind-spots or scotomas. Activities like reading are affected. We hypothesize that real-time remapping of lost information due to CFL onto a functional portion of the retina will improve visual performance. We have developed two hardware prototypes using a head-mounted display, integrated eye-tracker, and computer to remap and display images in real-time to the wearer. To test, in three different studies, normally-sighted subjects were asked to wear the head-mounted display with the built-in eye tracker. CFL was simulated by placing artificial circular scotomas ranging from 2° to 16° diameter over the gaze position, and reading speed was measured for the remapped and unremapped condition. We observed a statistically significant increase in mean reading speeds for the larger scotomas. Results indicate that the device shows promise for use with CFL patients

Scanpath Eye Movements during Visual Mental Imagery in a Simulated Hemianopia Paradigm

Several studies have shown that eye movements (EM) are functionally involved in visual imagery. In this study we investigate the impact of a simulated homonymous hemianopia paradigm (SH) with and without foveal masking on scanpath eye movements during visual mental imagery. EM of twenty subjects were recorded under SH condition during viewing and subsequent visual imagery of complex pictures. Using evaluated string editing methods viewing and imagery scanpaths were compared. Our results show that scanpath EM are involved in visual mental imagery and reflect the picture content even under SH. In contrast, additional foveal masking significantly reduces the similarity between viewing and imagery scanpath. This points toward a detrimental effect of foveal masking on subsequent visual imagery performance

Training Reading Skills in Central Field Loss Patients: Impact of Clinical Advances and New Technologies to Improve Reading Ability

The primary goal of patients with central field loss attending to visual rehabilitation (VR) offices is to get adapted to daily life activities in near vision, mainly looking for recovering their ability to read again. The disparity in the functionality of these patients, due to the new advances in medical treatment and the increasing number of new apps and technological devices in the market, implies a heterogeneity in the reading training programs to be applied, and consequently a variability in the results obtained. Currently, with the increasing access to information and communication technologies and social networks, the opportunities for improving their access to information and communication is taken an important role. For this reason, the basis of ad-hoc evidence-based reading training programs is needed to standardized the clinical practice in reading rehabilitation for visual impaired and blind patients. This chapter will go in depth into these topics offering an exhaustive state of the art of reading rehabilitation for central field loss patients that will be useful for clinicians dedicated to the rehabilitation of visual impaired and blind people

A Covered Eye Fails To Follow an Object Moving in Depth

To clearly view approaching objects, the eyes rotate inward (vergence), and the intraocular lenses focus (accommodation). Current ocular control models assume both eyes are driven by unitary vergence and unitary accommodation commands that causally interact. The models typically describe discrete gaze shifts to non-accommodative targets performed under laboratory conditions. We probe these unitary signals using a physical stimulus moving in depth on the midline while recording vergence and accommodation simultaneously from both eyes in normal observers. Using monocular viewing, retinal disparity is removed, leaving only monocular cues for interpreting the object\u27s motion in depth. The viewing eye always followed the target\u27s motion. However, the occluded eye did not follow the target, and surprisingly, rotated out of phase with it. In contrast, accommodation in both eyes was synchronized with the target under monocular viewing. The results challenge existing unitary vergence command theories, and causal accommodation-vergence linkage

Evidence-Based Practice and Trends in Visual Rehabilitation for Patients with Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a common, chronic, and progressive eye disease that is considered the leading cause of visual loss among the elderly in developed countries. Advanced AMD, including choroidal neovascularization (CNV) or geographic atrophy (GA), is associated with substantial and progressive visual impairment that can lead to a significant reduction in functional independence and quality of life (QoL) for affected individuals, whose number is expected to increase in the coming years in line with population growth and ageing. In this context, while an important part of medical care is focused on preventing the progression of the disease, Visual Rehabilitation (VR) aims to address its consequences by providing these patients with a number of strategies to achieve their goals and participate autonomously, actively and productively in society. This chapter aims to provide an update on evidence-based practices in the field and how modern technologies play an important role in the development of new VR approaches

Seuratun kappaleen poikkeuttaminen silmänräpäysten aikana: käyttäytymis- ja neuromagneettisia havaintoja

The visual world is perceived as continuous despite frequent interruptions of sensory data due to eyeblinks and rapid eye movements. To create the perception of constancy, the brain makes use of fill-in mechanisms. This study presents an experiment in which the location of an object during smooth pursuit tracking is altered during eyeblinks. The experiment investigates the effects of blink suppression and fill-in mechanisms to cloud the discrimination of these changes. We employed a motion-tracking task, which promotes the accurate evaluation of the object’s trajectory and thus can counteract the fill-in mechanisms. Six subjects took part in the experiment, during which they were asked to report any perceived anomalies in the trajectory. Eye movements were monitored with a video-based tracking and brain responses with simultaneous MEG recordings. Discrimination success was found to depend on the direction of the displacement, and was significantly modulated by prior knowledge of the triggered effect. Eye-movement data were congruent with previous findings and revealed a smooth transition from blink recovery to object locating. MEG recordings were analysed for condition-dependent evoked and induced responses; however, intersubject variability was too large for drawing clear conclusions regarding the brain basis of the fill-in mechanisms.Visuaalinen maailma koetaan jatkuvana, vaikka silmänräpäykset ja nopeat silmänliikkeet aiheuttavat keskeytyksiä sensoriseen tiedonkeruuseen. Luodakseen käsityksen pysyvyydestä, aivot käyttävät täyttömekanismeja. Tämä tutkimus esittelee kokeen, jossa kappaleen seurantaa hitailla seurantaliikkeillä häiritään muuttamalla sen sijaintia silmänräpäysten aikana. Tämä koe tutkii, kuinka silmänräpäysten aiheuttama suppressio ja täyttömekanismit sumentavat kykyä erotella näitä muutoksia. Käytimme liikeseurantatehtävää, joka vastaavasti edistää kappaleen liikeradan tarkkaa arviointia. Kuusi koehenkilöä osallistui kokeeseen, jonka aikana heitä pyydettiin ilmoittamaan kaikki havaitut poikkeamat kappaleen liikeradassa. Silmänliikkeitä tallennettiin videopohjaisella seurannalla, ja aivovasteita yhtäaikaisella MEG:llä. Erottelykyvyn todettiin riippuvan poikkeutuksen suunnasta, sekä merkittävästi a priori tiedosta poikkeutusten esiintymistavasta. Silmänliikedata oli yhtenevää aiempien tutkimusten kanssa, ja paljasti sujuvan siirtymisen silmänräpäyksistä palautumisesta kappaleen paikallistamiseen. MEG-tallenteet analysoitiin ehdollisten heräte- ja indusoitujen vasteiden löytämiseksi, mutta yksilölliset vaste-erot koehenkilöiden välillä olivat liian suuria selkeiden johtopäätösten tekemiseksi täyttömekanismien aivoperustasta