Gordon E Legge

• PhD
• Professor (Full) at University of Minnesota

Purpose Reading is slow and difficult for many people with central vision loss. Numerous studies have used peripheral vision in normally sighted individuals without ocular disease as a model for reading with central vision loss. In this study, we tested the validity of this model. Methods Oral reading speed was measured for a range of print sizes...

Purpose: This study explored whether visual acuity (VA) can be inferred from self-reported ability to recognize everyday objects using a set of yes/no questions. Methods: Participants answered 100 yes/no questions designed to assess their ability to recognize familiar objects at typical viewing distances, such as distinguishing between a full mo...

SIGNIFICANCE Poor visibility of indoor features such as steps and ramps can pose mobility hazards for people with low vision. For purposes of architectural design, it is important to understand how design parameters such as the illumination level of an indoor space affect the visibility of steps and ramps. PURPOSE This study was aimed to examine t...

Spatial localization is important for social interaction and safe mobility, and relies heavily on vision and hearing. While people with vision or hearing impairment compensate with their intact sense, people with dual sensory impairment (DSI) may require rehabilitation strategies that take both impairments into account. There is currently no tool f...

Reading is a primary concern of patients with central field loss (CFL) because it is typically performed with foveal vision. Spatial remapping offers one potential avenue to aid in reading; it entails shifting occluded letters to retinal areas where vision is functional. Here, we introduce a method of creating and testing different remapping strate...

When an observer moves in space, the retinal projection of a stationary object either expands if the motion is toward the object or shifts horizontally if the motion contains a lateral component. This study examined the impact of expansive optic flow and lateral motion parallax on the accuracy of depth perception for observers with normal or artifi...

Purpose In the United States, AMD is a leading cause of low vision that leads to central vision loss and has a high co-occurrence with hearing loss. The impact of central vision loss on the daily functioning of older individuals cannot be fully addressed without considering their hearing status. We investigated the impact of combined central vision...

The Low Vision History Timeline is an ongoing project to chronicle important events in the history of the field which have contributed to or been critical in changing knowledge and practice.

Braille reading and other tactile discrimination tasks recruit the visual cortex of both blind and normally sighted individuals undergoing short-term visual deprivation. Prior functional magnetic resonance imaging (fMRI) work in patient ‘S’, a visually impaired adult with the rare ability to read both highly magnified print visually and Braille by...

Significance: Digital reading devices have become increasingly popular among people with low vision. Because displays come in many sizes ranging from smart watches to large desktop computer displays, it is important to have principles to guide people with low vision in selecting suitable displays for reading. Purpose: The selection of effective...

Visual and auditory localization abilities are crucial in real-life tasks such as navigation and social interaction. Aging is frequently accompanied by vision and hearing loss, affecting spatial localization. The purpose of the current study is to elucidate the effect of typical aging on spatial localization and to establish a baseline for older in...

Pedestrians with low vision are at risk of injury when hazards, such as steps and posts, have low visibility. This study aims at validating the software implementation of a computational model that estimates hazard visibility. The model takes as input a photorealistic 3D rendering of an architectural space, and the acuity and contrast sensitivity o...

Purpose: Binocular summation refers to better visual performance with two eyes than with one eye. Little is known about the mechanism underlying binocular contrast summation in patients with common eye diseases who often exhibit binocularly asymmetric vision loss and structural changes along the visual pathway. Here we asked whether the mechanism...

Introduction: We compared the print-to-speech properties and human performance characteristics of two artificial intelligence vision aids, Orcam MyEye 1 (a portable device) and Seeing AI (an iPhone and iPad application). Methods: There were seven participants with visual impairments who had no experience with the two reading aids. Four participants...

Purpose Low vision reduces text visibility and causes difficulties in reading. A valid low-vision simulation could be used to evaluate the accessibility of digital text for readers with low vision. We examined the validity of a digital simulation for replicating the text visibility and reading performance of low-vision individuals. Methods Low-vis...

Research has examined the nature of visual imagery in normally sighted and blind subjects, but not in those with low vision. Findings with normally sighted subjects suggest that imagery involves primary visual areas of the brain. Since the plasticity of visual cortex appears to be limited in adulthood, we might expect imagery of those with adult-on...

Significance Accessibility of digital text is essential in modern society. The growing use of small mobile displays forces attention to the competing requirements for adequate print size and adequate screen real estate. As print size gets larger, the number of characters per line and the number of lines per screen shrinks, ultimately affecting read...

Purpose Visual acuity (VA) and contrast sensitivity (CS) characterize different aspects of visual function. Whereas VA is a standard test in routine eye exams and clinical trials, CS is often not included. We investigated the pathology-specific dissociation between VA and CS by quantifying and comparing the relationship between these two measures i...

Significance: Access to digital text is increasingly widespread, but its impact on low-vision reading is not well understood. Purpose: We conducted an online survey of people with low vision to determine what assistive technologies they use for visual reading, their preferred text characteristics, and the time they devote to reading digital and...

A previous study from our lab demonstrated retention of high tactile acuity throughout the lifespan in blind subjects in contrast to the typical decline found for sighted subjects (Legge, Madison, Vaughn, Cheong & Miller, Percept Psychophys, 70 (8), 1471-1488, 2008). We hypothesize that preserved tactile acuity in old age is due to lifelong experie...

We used a letter transposition (LT) technique to investigate letter position coding during reading in central and peripheral vision. Eighteen subjects read aloud sentences in a rapid serial visual presentation task. The tests contained a baseline and three LT conditions with initial, internal, and final transpositions (e.g., "reading" to "erading",...

The MNREAD chart consists of standardized sentences printed at 19 sizes in 0.1 logMAR steps. There are 95 sentences distributed across the five English versions of the chart. However, there is a demand for a much larger number of sentences: for clinical research requiring repeated measures, and for new vision tests that use multiple trials at each...

Navigating unfamiliar indoor spaces while visually searching for objects of interest is a challenge faced by people with visual impairment. We asked how restricting visual acuity of normally sighted subjects would affect visual search and navigation in a real world environment, and how their performance would compare to subjects with naturally occu...

Significance: Digital reading displays provide opportunities for enhancing accessibility of text for low vision. How are these displays used by people in their daily lives? Purpose: Subjects responded to an online survey concerning their vision history, reading technology, display preferences, and reading habits. Here, we report on findings conc...

Evaluating the effects of print size and retinal eccentricity on reading speed is important for identifying the constraints faced by people with central-field loss. Previous work on English reading showed that 1) reading speed increases with print size until a critical print size (CPS) is reached, and then remains constant at a maximum reading spee...

The mnreadR R package provides functions for analyzing and plotting data obtained with the MNREAD acuity chart, a standardized reading test commonly used in vision research and clinical settings to assess one’s reading performance. mnreadR implements two interlinked toolsets to calculate the reading parameters measured with the MNREAD test: 1) a...

Purpose: People with central field loss (CFL) lose information in the scotomatous region. Remapping is a method to modify images to present the missing information outside the scotoma. This study tested the hypothesis that remapping improves reading performance for subjects with simulated CFL. Methods: Circular central scotomas, with diameters r...

Our purpose was to compare reading performance measured with the MNREAD Acuity Chart and an iPad application (app) version of the same test for both normally sighted and low-vision participants. Our methods included 165 participants with normal vision and 43 participants with low vision tested on the standard printed MNREAD and on the iPad app vers...

The visual span refers to the number of adjacent characters that can be recognized in a single glance. It is viewed as a sensory bottleneck in reading for both normal and clinical populations. In peripheral vision, the visual span for English characters can be enlarged after training with a letter-recognition task. Here, we examined the transfer of...

PURPOSE. Most people with low vision experience difficulty with reading. Reading assessment can provide guidance for prescription of reading aids and strategies for reading rehabilitation. Here we investigate the effectiveness of letter acuity (LA) and reading acuity (RA) as predictors of low-vision reading performance. METHODS. Low-vision subjects...

The visual span is hypothesized to be a sensory bottleneck on reading speed with crowding thought to be the major sensory factor limiting the size of the visual span. This proposed linkage between crowding, visual span, and reading speed is challenged by the finding that training to read crowded letters reduced crowding but did not improve reading...

Central-field loss necessitates the use of peripheral vision which makes reading slow and difficult. Slower temporal processing of letter recognition has been shown to be a limiting factor in peripheral letter recognition and reading. Previous studies showed that perceptual learning can increase the number of letters recognized on each fixation and...

Individuals with macular degeneration often develop a Preferred Retinal Locus (PRL) used in place of the impaired fovea. It is known that many people adopt a PRL left of the scotoma, which is likely to affect reading by occluding text to the right of fixation. For such individuals, we examined the possibility that reading vertical text, in which wo...

Purpose Spatial updating is the ability to keep track of position and orientation while moving through an environment. We asked how normally sighted and visually impaired subjects compare in spatial updating and in estimating room dimensions. Methods Groups of 32 normally sighted, 16 low-vision, and 16 blind subjects estimated the dimensions of si...

Low vision is any type of visual impairment that affects activities of daily living. In the context of low vision, we define plasticity as changes in brain or perceptual behavior that follow the onset of visual impairment and that are not directly due to the underlying pathology. An important goal of low-vision research is to determine how plastici...

Letter recognition and reading in peripheral vision is limited by crowding. It has been proposed that the spatial extent of crowding corresponds to a fixed distance on primary visual cortex (Pelli, Current Opinion in Neurobiology, 2008). Hypothetically, if peripheral letter recognition is only determined by crowding, then same target-flanker cortic...

Purpose: The continuous-text reading-acuity test MNREAD is designed to measure the reading performance of people with normal and low vision. This test is used to estimate maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and the reading accessibility index (ACC). Here we report the age dependence of these measures for no...

Purpose: Spatial updating refers to the ability to keep track of position and orientation while moving through an environment. People with impaired vision may be less accurate in spatial updating with adverse consequences for indoor navigation. In this study, we asked how artificial restrictions on visual acuity and field size affect spatial updat...

Importance We define a Reading Accessibility Index for evaluating reading in individuals with normal and low vision.Objective To compare the Reading Accessibility Index with data from the Impact of Cataracts on Mobility (ICOM) study.Design, Setting, and Participants This investigation was a secondary data analysis from the ICOM study performed b...

Purpose The contrast sensitivity function (CSF) provides a detailed description of an individual's spatial-pattern detection capability. We tested the hypothesis that the CSFs of people with low vision differ from a “normal” CSF only in their horizontal and vertical positions along the spatial frequency (SF) and contrast sensitivity (CS) axes. Met...

This paper discusses issues of importance to designers of media for visually impaired users. The paper considers the influence of human factors on effectiveness of presentation as well as the strengths and weaknesses of tactile, vibrotactile, static pins, haptic, force feedback, and multimodal methods of rendering maps, graphs and models. The autho...

Yu, Legge, Park, Gage, and Chung (2010) suggested that the neural bottleneck for slow peripheral reading is located in nonretinotopic areas. We investigated the potential rate-limiting neural site for peripheral reading using fMRI, and contrasted peripheral reading with recognition of peripherally presented line drawings of common objects. We measu...

The visual span-the number of adjacent text letters that can be reliably recognized on one fixation-has been proposed as a sensory bottleneck that limits reading speed (Legge, Mansfield, & Chung, 2001). Like reading, searching for a face is an important daily task that involves pattern recognition. Is there a similar limitation on the number of fac...

Reading speed for English text is slower for text oriented vertically than horizontally. Yu, Park, Gerold, and Legge (2010) showed that slower reading of vertical text is associated with a smaller visual span (the number of letters recognized with high accuracy without moving the eyes). Three possible sensory determinants of the size of the visual...

Purpose: English-language text is almost always written horizontally. Text can be formatted to run vertically, but this is seldom used. Several studies have found that horizontal text can be read faster than vertical text in the central visual field. No studies have investigated the peripheral visual field. Studies have also concluded that trainin...

Low vision may be defined as any chronic form of vision impairment, not correctable by glasses or contact lenses, that adversely affects everyday function. Visual accessibility refers to factors that make an environment, device, or display usable by vision. In this article, I discuss the concept of visual accessibility with special reference to low...

THE VISUAL SPAN FOR READING IS THE NUMBER OF LETTERS THAT CAN BE RECOGNIZED WITHOUT MOVING THE EYES AND IS HYPOTHESIZED TO IMPOSE A SENSORY LIMITATION ON READING SPEED FACTORS AFFECTING THE SIZE OF THE VISUAL SPAN HAVE BEEN STUDIED USING ALPHABET LETTERS THERE MAY BE COMMON CONSTRAINTS APPLYING TO RECOGNITION OF OTHER SCRIPTS THE AIM OF THIS STUDY...

Effects of context on the perception of, and incidental memory for, real-world objects have predominantly been investigated in younger individuals, under conditions involving a single static viewpoint. We examined the effects of prior object context and object familiarity on both older and younger adults' incidental memory for real objects encounte...

Background / Purpose: To design and test a digital version of the MNREAD acuity chart on an iPad3. Main conclusion: The iPad version and the printed chart yield similar estimates of the MNREAD parameters (Maximum Reading Speed, Critical Print Size and Reading Acuity) when tested on both a normally-sighted population and a low-vision population...

There is a need for adaptive technology to enhance indoor wayfinding by visually-impaired people. To address this need, we have developed and tested a Digital Sign System. The hardware and software consist of digitally-encoded signs widely distributed throughout a building, a handheld sign-reader based on an infrared camera, image-processing softwa...

This study investigated the interaction between remembered landmark and path integration strategies for estimating current location when walking in an environment without vision. We asked whether observers navigating without vision only rely on path integration information to judge their location, or whether remembered landmarks also influence judg...

Spatial updating refers to the ability to keep track of one’s position and orientation in an environment. Does visual (and auditory) perception of the size and shape of an indoor space facilitate spatial updating? How are people with impaired vision hindered in spatial updating? To begin addressing these issues, we tested 19 normally sighted young...

The visual span for reading is defined as the number of adjacent letters that can be correctly identified without eye movements, and may impose a sensory bottleneck on reading speed. In this study, we extended the concept of visual span to Chinese characters. We investigated the effect of complexity on the size of the visual span for alphabetic and...

Reading speed in normal peripheral vision is slow but can be increased through training on a letter-recognition task. The aim of the present study is to investigate the sensory and cognitive factors responsible for this improvement. The visual span is hypothesized to be a sensory bottleneck limiting reading speed. Three sensory factors-letter acuit...

Background / Purpose: The visual span for reading is the number of text letters that can be recognized accurately without eye movements, and may limit reading speed (the visual-span hypothesis) (1) . Peripheral visual span can be enlarged through perceptual training, accompanied by an increase in reading speed (2) . Letter acuity, crowding, and m...

Background / Purpose: Reading speed in peripheral vision improves with practice, but the cortical site of this improvement is not understood. Using psychophysics and fMRI, we investigated the potential training-related functional changes in retinotopic and non-retinotopic cortical areas. Main conclusion: Our behavioral data confirm the existen...

Should people with central field loss (CFL) be on the road driving? Independent travel is an important prerequisite for full participation in modern society. Reduced mobility and its associated social isolation and depression are among the most severe consequences of vision impairment. Research on mobility with vision impairment has focused primari...

Kwon and Legge (2011) found that high levels of letter recognition accuracy are possible even when letters are severely low-pass filtered (0.9 cycles per letter). How is letter recognition possible with such severe reduction in the spatial resolution of stimulus letters? Clues may come from understanding the possible interaction between contrast an...

Purpose: Detection and recognition of ramps and steps are important for the safe mobility of people with low vision. Our primary goal was to assess the impact of viewing conditions and environmental factors on the recognition of these targets by people with low vision. A secondary goal was to determine if results from our previous studies of norma...

Purpose: Detecting and recognizing three-dimensional (3D) objects is an important component of the visual accessibility of public spaces for people with impaired vision. The present study investigated the impact of environmental factors and object properties on the recognition of objects by subjects who viewed physical objects with severely reduce...

Examined reading with a central scotoma using 2 complementary approaches: ideal-observer analysis and visual-span simulation with human readers. The authors formulated Mr. Chips, an ideal-observer computer program that combines visual and lexical information optimally to read simple texts in the minimum number of saccades. To study human performanc...

Reading speed matters in most real-world contexts, and it is a robust and easy aspect of reading to measure. Theories of reading should account for speed.

Background / Purpose: Practicing a perceptual task often leads to improved performance, termed perceptual learning. Here, we focus on perceptual learning with eccentric reading. Is perceptual learning in eccentric reading transferable to an untrained retinal location or a task non-related to reading? Is visual span size affected by perceptual lea...

Detecting and recognizing steps and ramps is an important component of the visual accessibility of public spaces for people with impaired vision. The present study, which is part of a larger program of research on visual accessibility, investigated the impact of two factors that may facilitate the recognition of steps and ramps during low-acuity vi...

Blur is one of many visual factors that can limit reading in both normal and low vision. Legge et al. [Legge, G. E., Pelli, D. G., Rubin, G. S., & Schleske, M. M. (1985). Psychophysics of reading. I. Normal vision. Vision Research, 25, 239-252.] measured reading speed for text that was low-pass filtered with a range of cutoff spatial frequencies. A...

An environment is visually accessible if a person can rely on vision to travel efficiently and safely through it, to perceive its spatial layout, and to update location and orientation within the environment. We are studying how architectural and interior design decisions and viewing conditions interact with vision deficits of people with low visio...

Activity in visual cortex with tactile perception has been observed in people with normal or impaired vision. The functional significance of this activity is unclear. In this fMRI study, we ask whether different tactile stimuli produce distinguishable multi-voxel activation patterns in occipitotemporal cortex, and whether these patterns differ for...

It is well known that object recognition requires spatial frequencies exceeding some critical cutoff value. People with central scotomas who rely on peripheral vision have substantial difficulty with reading and face recognition. Deficiencies of pattern recognition in peripheral vision, might result in higher cutoff requirements, and may contribute...

Background / Purpose: Visual accessibility is the use of vision to travel efficiently and safely through an environment, to perceive the spatial layout of the environment, and to update one’s location in the layout.The present study extends the findings of Legge et al 2010 who described the effects of lighting, geometry, and surface properties on...

Eccentric viewing in macular disease has been described for half a century. However, a clear definition of eccentric viewing and preferred retinal locus (PRL) does not exist. Here, we determine how the PRL in macular disease is defined by researchers active in this field and, based on the responses received, propose a standardized definition of the...

The size and shape of printed symbols determine the legibility of text. In this paper, we focus on print size because of its crucial role in understanding reading performance and its significance in the history and contemporary practice of typography. We present evidence supporting the hypothesis that the distribution of print sizes in historical a...

The Low Vision Timeline update.

To make a successful reach, the visual system must take into account the accuracy of its knowledge of the location and size of an object. The spatial certainty of a target's location with respect to the hand is limited by the eccentricity of viewing (Hess & Hayes, 1994), and by the ability to convert a target in retinal coordinates to arm-centered...

Purpose: In order to better understand the interactions of spatial memory and visual information in spatial navigation, we have developed an ideal navigation model called ANTIE (Acme Navigation Through Indoor Environments) that uses visual and geometric information optimally during spatial navigation. By comparing humans with ANTIE, we have investi...

At ARVO 1997, Majaj, Kurshan, & Pelli used critical-band masking to show that letter identification is not scale invariant. They found that channel frequency grows as the 2/3 power of line-frequency, a unit for measuring target spatial frequency. (Scale invariance would produce a value of 1.) At the same meeting, Chung & Legge presented data on con...

Activity in regions of the visual cortex corresponding to central scotomas in subjects with macular degeneration (MD) is considered evidence for functional reorganization in the brain. Three unresolved issues related to cortical activity in subjects with MD were addressed: Is the cortical response to stimuli presented to the preferred retinal locus...

Purpose. Information in an image can be represented in separate spatial-frequency bands, or spatial scales. If non-redundant information is available in different spatial scales, access to multiple scales should provide better recognition performance than access to a single scale. An image can also be divided into different spatial regions. If ther...

Purpose: Vision is routinely used to walk from one nearby location to another, e.g. crossing at intersections. Motivated by the mobility problems of visually impaired people, we asked: 1) How accurately can people walk a straight line without vision? 2) Is this capacity affected by long-term vision loss? 3) Is such ability related to sensitivity in...

Purpose. Visual span profiles are plots of letter-recognition accuracy as a function of letter position left or right of the midline. We hypothesize that the size of the visual span, summarized as the area under the profile, limits reading speed in normal and low vision. We tested this hypothesis by measuring the correlation between size of the vis...

At VSS 2001, we reported that the spatial-frequency tuning characteristics for letter identification could be accounted for by the product of a function describing letter-identity information vs. spatial frequency and an observer's contrast sensitivity function (CSF). This result obviates the need to invoke specific channels for letter identificati...

Previous studies have shown that people make letter-reversal errors in identifying strings of letters in peripheral vision. These errors contribute to a rapid fall-off of letter-recognition performance away from fixation. This study tests the hypothesis that these errors are due to decreased precision (increased "noise") in the coding of letter pos...

Purpose. We are developing a method for retinotopic mapping of the visual cortex in people with central field loss. Retinotopic mapping based on polar coordinates uses rotating wedges and expanding rings, which assume stable foveal fixation. However, people with central field loss usually adopt a non-foveal retinal location for fixation and that lo...

The current study investigates the cognitive limitations associated with navigating through familiar indoor environments. To better address this question we developed an ideal navigator to measure human action efficiencies. Previous studies have found that humans are inefficient at navigating through large-scale indoor environments. The current stu...

The visual accessibility of a space refers to the effectiveness with which vision can be used to travel safely through the space. For people with low vision, the detection of steps and ramps is an important component of visual accessibility. We used ramps and steps as visual targets to examine the interacting effects of lighting, object geometry, c...

Purpose: Age-related macular degeneration (AMD) afflicts the central 5° to 10° of the retina. Studies of retinotopy of the primary visual cortex (V1) among normally sighted humans have shown that the central retinal area projects to a disproportionately large area at the posterior end of V1. It is not yet known what happens to the retinotopy in AMD...

Letter recognition is usually thought to rely on the shape and arrangement of distinctive pattern features such as line segments and curves. In findings to be reported, we have found that high levels of letter-recognition accuracy are possible when low-pass filtering reduces the spatial bandwidths of letters to levels not expected to support adequa...

Temporal feature binding is the ability to distinguish a combination of features shown simultaneously from other binding possibilities. Temporal binding is vital because visual scenes are often dynamic and people constantly move their eyes. In the current study, we investigated properties of binding spatially separated features. In the first experi...

The detection of ramps and steps is important for the safe mobility of people with low vision. We used ramps and steps as stimuli to examine the interacting effects of lighting, object geometry, contrast, viewing distance and spatial resolution. Gray wooden staging was used to construct a sidewalk with a transition to one of five targets: a step up...

Visual texture on floors may facilitate safe mobility by providing information to pedestrians about surface slant and discontinuities. Often, ground plane texture is composed of fine detail and is beyond the acuity limit or below the contrast threshold of people with low vision. Consequently, we investigated whether a surface with large, high-contr...