About
141
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Introduction
My research focus on understanding vision related behaviors, performance and mechanism in people with eye diseases. We develop technologies to help them to overcome problems in daily life.
Additional affiliations
January 2016 - present
May 2013 - present
June 2011 - December 2015
Publications
Publications (141)
Objective: Micro-navigation poses challenges for blind and visually impaired individuals. They often need to ask for sighted assistance. We explored the feasibility of utilizing ChatGPT as a virtual assistant to provide navigation directions. Methods: We created a test set of outdoor and indoor micro-navigation scenarios consisting of 113 scene ima...
Purpose:
The purpose of this study was to investigate gaze-scanning by pedestrians with homonymous hemianopia (HH) when walking on mid-block sidewalks.
Methods:
Pedestrians with right homonymous hemianopia (RHH), and left homonymous hemianopia (LHH) without and with left spatial neglect (LHSN) walked on city streets wearing a gaze-tracking syste...
Background
While it is treatable, uncorrected refractive error is the number one cause of visual impairment worldwide. This eye condition alone, or together with ocular misalignment, can also cause amblyopia, which is also treatable if detected early but still occurs in about 4% of the population. Mass vision screening is the first and most critica...
Purpose:
GPS location-based navigation apps are insufficient to aid blind and visually impaired (BVI) travelers for micro-navigation tasks, such as finding the exact location of bus stops. The resulting large gaps could lead to BVI travelers missing their bus. We evaluated the ability of a signage detection mobile app, All_Aboard, to guide BVI tra...
We present clinical evaluation of a mobile app for dark adaptation (DA) measurement in age-related macular degeneration (AMD) patients and in older adults (age > 50 years) without AMD or other retinal disorders (NV). The outcome measures were the area under dark adaptation curve (AUDAC) and the time for visual sensitivity to recover by 3 log units...
Purpose:
To investigate compensatory gaze-scanning behaviors during street crossings by pedestrians with homonymous hemianopia (HH) and hemispatial neglect (HSN).
Methods:
Pedestrians with right homonymous hemianopia (RHH) and left homonymous hemianopia without (LHH) and with left spatial-neglect (LHSN) walked on city streets wearing a gaze-trac...
The pervasiveness of mobile devices and other associated technologies has affected all aspects of our daily lives. People with visual impairments are no exception, as they increasingly tend to rely on mobile apps for assistance with various visual tasks in daily life. Compared to dedicated visual aids, mobile apps offer advantages such as affordabi...
Purpose: Pupil center is an important anchor point in corneal refractive surgery, which may affect by body position. This study investigated the feasibility of using a smartphone application in measurement of posture-related pupil center shifts.
Methods: Images of undilated eyes were captured for 25 participants (age: 18–38 years) at a distance of...
The regular full-length version of the letter paper "Low-cost real-time VLSI system for high-accuracy optical flow estimation using biological motion features and random forests"
This study proposes a low-cost, real-time, very large-scale
integration (VLSI) architecture for optical flow estimation.
The architecture adopts parallel spatiotemporal filters to extract bio-inspired motion features at each pixel location and
uses hardware random forests to infer the motion speed.
Our system achieves higher estimation accuracy at...
Purpose:
Individuals with amblyopia are known to have functional vision deficits (e.g., reduced reading speed) in spite of good visual acuity in the nonamblyopic eye. We studied and compared eye movements in children with and without amblyopia to examine how a visual scene is explored during visual search.
Methods:
Children (six to 16 years of a...
Significance:
Peripheral prisms (p-prisms) improve blind-side detection of hazards in hemianopia by shifting the image of the hazard into the intact visual field. Collision judgments can be made accurately after detection by using a gaze shift to fixate the hazard in the prism-free portion of the lens, but this is slow relative to normal periphera...
Introduction
This study aimed to compare compliance between pediatric patients with amblyopia undergoing a smartphone virtual reality-based training method (EYEBIT) and those receiving traditional patching method training.
Methods
A crossover design was adopted in this study. The enrolled children (n = 76) were randomized into the traditional patc...
Purpose
To investigate whether head-mounted vision assistance devices may address a different set of visual needs as compared to handheld video magnifiers.
Methods
Daily app usage data (e.g. launch frequency, duration, among others) across 8 months was collected from tens of thousands global active users of two mobile vision assistance apps: handh...
Tracking head movement in outdoor activities is more challenging than in controlled indoor lab environments. Large-magnitude head scanning is common under natural conditions. Compensatory gaze (head and eye) scanning while walking may be critical for people with visual field loss. We compared the accuracy of two outdoor head tracking methods: diffe...
Purpose:
The purpose of this study was to evaluate the potential feasibility of using a smartphone app in myopia screening.
Methods:
The app estimates myopic refractive error by measuring the far point distance for reading three 20/20 Tumbling E letters. In total, 113 myopic subjects with astigmatism no greater than -1.75 diopters (D) were enrol...
For embedded, mobile and edge-computing intelligent applications, this brief proposes a low-cost real-time neuromorphic hardware system of spiking Extreme Learning Machine (ELM) equipped with on-chip triplet-based reward-modulated spike-timing-dependent plasticity (R-STDP) learning capability. Our design employs a time-step pipelined dual-core arch...
Importance:
There is scant rigorous evidence about the real-world mobility benefit of electronic mobility aids.
Objective:
To evaluate the effect of a collision warning device on the number of contacts experienced by blind and visually impaired people in their daily mobility.
Design, setting, and participants:
In this double-masked randomized...
Purpose:
Quantification of dark adaptation (DA) response using the conventional rod intercept time (RIT) requires very long testing time and may not be measurable in the presence of impairments due to diseases such as age-related macular degeneration (AMD). The goal of this study was to investigate the advantages of using area under the DA curve (...
Background:
Millions of visually impaired use mobile vision assistance apps to help with their daily activities. The most widely used vision assistance apps are magnifier apps. It is still largely unknown what the apps are used for. Lack of insight in the visual needs of visually impaired people is a hurdle for development of more effective assist...
Purpose
To evaluate the effect of central serous chorioretinopathy (CSCR) on retinal function using dark adaptation in a human subject, and to follow it through resolution of the disease.
Patients
Single patient, 50 years old male patient, with acute CSCR in one eye and resolved old CSCR in the other eye.
Observations
Observational study in patie...
Background
Strabismus is the leading risk factor for amblyopia, which should be early detected for minimized visual impairment. However, traditional school screening for strabismus can be challenged due to several factors, most notably training, mobility and cost. The purpose of our study is to evaluate the feasibility of using a smartphone applica...
Purpose:
Mobile video magnifier apps are used by many visually impaired people for seeing details that are beyond their visual capacity. Understanding the common types of visual targets will be importantly informative for low-vision research and assistive technology development. This study addressed this question through analysis of images capture...
Purpose:
To assess the relationship between baseline age-related macular degeneration (AMD) and disease stage, as well as optical coherence tomography (OCT) features seen in AMD, with three-year changes in dark adaptation (DA).
Methods:
Prospective longitudinal study including patients with AMD and a comparison group (n=42 eyes, 27 patients). At...
Purpose:
To investigate the roles of motion perception and visual acuity in driving hazard detection.
Methods:
Detection of driving hazard was tested based on video and still-frames of real-world road scenes. In the experiment using videos, 20 normally sighted participants were tested under four conditions: with or without motion interruption by...
Background: Strabismus is the leading risk factor for amblyopia, which should be early detected for minimized visual impairment. However, traditional school screening for strabismus can be challenged due to several factors, most notably training, mobility and cost. The purpose of our study is to evaluate the feasibility of using a smartphone applic...
BACKGROUND
Millions of individuals with visual impairment use vision assistance apps to help with their daily activities. The most widely used vision assistance apps are magnifier apps. It is still largely unknown what the apps are used for. Lack of insight into the visual needs of individuals with visual impairment is a hurdle for the development...
Objective
To describe and evaluate a secure video call system combined with a suite of iPad vision testing apps to improve access to vision rehabilitation assessment for inpatients.
Design
Retrospective.
Setting
Two acute care inpatient rehabilitation hospitals (AR1 and AR2) and 1 long-term acute care hospital (LTAC).
Participants
Records of inp...
Brain-inspired spiking neural networks (SNNs) have become a research hotspot in recent years. These SNNs communicate and process information in a form of spatiotemporally sparse spikes, leading to high energy efficiency and low computational cost for object classification tasks. To reduce computational complexity while maintain SNN classification a...
A normally sighted person can see a grating of 30 cycles
per degree or higher, but spatial frequencies needed for
motion perception are much lower than that. It is
unknown for natural images with a wide spectrum how
all the visible spatial frequencies contribute to motion
speed perception. In this work, we studied the effect of
spatial frequency co...
Significance:
To judge the feasibility of virtual reality (VR) headsets for vision testing and treatment of binocular vision disorders and low vision, angular resolution (logMAR) and field of view must be known and may not be reliably provided. This is the first study to measure the limitations of VR systems for eye care applications.
Purpose:
T...
Purpose:
Visually impaired people may be allowed to drive if they wear bioptic telescopes. Bioptic driving safety is debatable, especially given that the telescopes are seldom used by most bioptic drivers. This preliminary study examined bioptic safety based on critical events that occurred in naturalistic daily driving.
Methods:
Daily driving a...
Purpose:
Evaluating mobility aids in naturalistic conditions across many days is challenging owing to the sheer amount of data and hard-to-control environments. For a wearable video camera-based collision warning device, we present the methodology for acquisition, reduction, review, and coding of video data for quantitative analyses of mobility ou...
Purpose:
In most states, people with reduced visual acuity may legally drive with the aid of a bioptic telescope. However, concerns have been raised that the ring scotoma may impair detection of peripheral hazards. Using a driving simulator, we tested the hypothesis that the fellow eye would be able to compensate for the ring scotoma when using a...
A smartphone app has been developed to perform the automated photographic Hirschberg test for objective measurement of ocular misalignment. By computing the difference in corneal reflection generated by the phone camera flash relative to the iris center based on high resolution images, the app can measure misalignment with a much higher precision t...
Purpose:
The purpose of this study was to investigate the telescope use behaviors in natural daily driving of people with reduced visual acuity licensed to drive with a bioptic (a small spectacle-mounted telescope).
Methods:
A large dataset (477 hours) of naturalistic driving was collected from 19 bioptic drivers (visual acuity 20/60 to 20/160 w...
SIGNIFICANCE To judge the feasibility of virtual reality (VR) headsets for vision testing and treatment of binocular vision disorders and low vision, angular resolution (LogMAR) and field of view must be known and may not be reliably provided. This is the first study to measure the limitations of VR systems. PURPOSE To measure, in a sample of VR he...
Gaining environmental awareness through lateral head scanning (yaw rotations) is important for driving safety, especially when approaching intersections. Therefore, head scanning movements could be an important behavioral metric for driving safety research and driving risk mitigation systems. Tracking head scanning movements with a single in-car ca...
Background:
Controlled naturalistic driving for examining impacts of cognitive impairment on driving safety is rare.
Objective:
Evaluating the safety among drivers with mild cognitive impairment based on near collision incidents using naturalistic driving, and investigating its correlation with cognitive measures.
Methods:
Frequency of near co...
Background:
Smartphone video magnifier apps are being used by millions of people to assist their vision. To understand the behaviour of app users, an exploratory investigation was conducted based on 'big data' collected from their daily uses.
Method:
A mobile magnification app was developed with embedded analytics data collection modules. Seven...
This paper proposes a pixel-parallel Eulerian Video Magnification (EVM) algorithm for vision chips. The proposed algorithm is optimized for the stereotyped programmable pixel-parallel array processor architecture favored by high-speed vision chips. We also propose an improved pixel-parallel array processor with alternative image border padding mode...
Local features have widely been used in visual tracking to improve robustness in the presence of partial occlusion, deformation, and rotation. In this paper, a local fragment-based object tracking algorithm is proposed. Unlike many existing fragment-based algorithms using all the fragments and allocating the weight to each fragment according to sim...
Keyword search in a cluttered environment is difficult in general, and even more challenging for people with low vision. While magnification can help in reading for low vision people, it does not facilitate efficient visual search due to the constriction of the field of view. The motivating observation for this study is that, in a large number of v...
This work proposes a hardware-friendly, dense optical flow-based Time-to-Collision (TTC) estimation algorithm intended to be deployed on smart video sensors for collision avoidance. The algorithm optimized for hardware first extracts biological visual motion features (motion energies), and then utilizes a Random Forests regressor to predict robust...
Purpose:
We evaluate a smartphone application (app) performing an automated photographic Hirschberg test for measurement of eye deviations.
Methods:
Three evaluation studies were conducted to measure eye deviations in the horizontal direction. First, gaze angles were measured with respect to the ground truth in nonstrabismic subjects (n = 25) as...
Purpose:
We evaluated the feasibility of a smartphone application-based dark adaptation (DA) measurement method (MOBILE-DA).
Methods:
On a Samsung Galaxy S8 smartphone, MOBILE-DA presented a 1.5° flashing stimulus (wavelength = 453 nm) between -1.15 and -4.33 log candela (cd)/m2 at 8° eccentricity using an adaptive staircase, and logged timing o...
Significance:
This work describes a preliminary evaluation of a wearable collision warning device for blind individuals. The device was found to provide mobility benefit in subjects without (or deprived of) vision. This preliminary evaluation will facilitate further testing of this developmental stage device in more naturalistic conditions.
Purpo...
PURPOSE
There are many visually impaired people who can drive legally with bioptic telescope. Drawing on the experience of drivers with reduced vision, this study investigated the role of motion perception and visual acuity in driving, under simulated low visual acuity.
METHODS
Twenty normally sighted participants took part in a driving hazard perc...
Purpose: Recently we developed a driving simulator paradigm to evaluate detection of road hazards when using a bioptic telescope and conducted an initial study using normally-sighted observers with simulated vision loss. We now extend our investigation to quantifying the extent to which visually impaired bioptic users are able to use their fellow (...
Optomotor response/refex (OMR) assays are emerging as a powerful and versatile tool for phenotypic study and new drug discovery for eye and brain disorders. Yet efcient OMR assessment for visual performance in mice remains a challenge. Existing OMR testing devices for mice require a lengthy procedure and may be subject to bias due to use of artifci...
Speed perception is an important task performed by our visual system in various daily life tasks. In various psychophysical tests, relationship between spatial frequency, temporal frequency, and speed has been examined in human subjects. The role of vision impairment in speed perception has also been previously examined. In this work, we examine th...
Significance:
A new driving simulator paradigm was developed and evaluated that will enable future investigations of the effects of the ring scotoma in bioptic drivers with diverse vision impairments and different telescope designs.
Purpose:
The ring scotoma may impair detection of peripheral hazards when viewing through a bioptic telescope. To...
This paper presents a lightweight statistical learning framework potentially suitable for low-cost event-based vision systems, where visual information is captured by a dynamic vision sensor (DVS) and represented as an asynchronous stream of pixel addresses (events) indicating a relative intensity change on those locations. A simple Random Ferns cl...
This paper proposes a bio-inspired visual motion estimation algorithm based on motion energy, along with its compact VLSI architecture using low-cost embedded systems. The algorithm mimics motion perception functions of retina, V1 and MT neurons in primate visual system. It involves operations of ternary edge extraction, spatiotemporal filtering, m...
Significance:
In general, young adults with normal vision show the best visual search performance when compared with children and older adults. Through our study, we show that this trend is not observed in individuals with vision impairment. An interaction effect of vision impairment with visual development and aging is observed.
Purpose:
Perfor...
Analyzing naturalistic driving behavior recorded with in-car cameras is an ecologically valid method for measuring driving errors, but it is time intensive and not easily applied on a large scale. This study validated a semi-automated, computerized method using archival naturalistic driving data collected for drivers with mild Alzheimer’s disease (...
Lane changes are important behaviors to study in driving research. Automated detection of lane-change events is required to address the need for data reduction of a vast amount of naturalistic driving videos. This paper presents a method to deal with weak lane-marker patterns as small as a couple of pixels wide. The proposed method is novel in its...
Gaze-contingent displays have been widely used in vision research and virtual reality applications. Due to data transmission, image processing, and display preparation, the time delay between the eye tracker and the monitor update may lead to a misalignment between the eye position and the image manipulation during eye movements. We propose a metho...
This paper proposes a modified Eulerian Video Magnification (EVM) algorithm and a hardware implementation of a motion magnification core for smart image sensors. Compared to the original EVM algorithm, we perform the pixel-wise temporal bandpass filtering only once rather than multiple times on all scale layers, to reduce the memory and multiplier...
Enhancement of non-uniformly illuminated images often suffers from over-enhancement and produces unnatural results. This paper presents a naturalness preserved enhancement method for non-uniformly illuminated images, using a priori multi-layer lightness statistics acquired from high-quality images. Our work makes three important contributions: desi...
Purpose
Speed estimation of drivers’ own vehicles and other vehicles on the road is an important task for drivers and is also crucial to the roadway safety. The objective of the study was to examine the effects of multiple factors such as image scale, speed, road type, driving experience, and gender on the speed perception of drivers’ own vehicles....
Twenty-seven observers performed intensive visual search tasks with curved and flat monitors. Based on a 22-item eyestrain questionnaire, fewer subjects reported eyestrain, difficulty-to-focus and blurred-vision symptoms with a curved monitor than with a flat monitor. Fewer subjects had reduced saccade peak speed following the curved monitor use.