The effect of letter-stroke boldness on reading speed in central and peripheral vision

Luciole, a new font for people with low vision

Low vision affects the ability to read and can be a major barrier to educational success and insertion into the workplace. We designed a new font (Luciole) to improve the readability and comfort for people with low vision. In this study, we analyze the effect of the font type on readability. Luciole was compared to five other fonts (Arial, OpenDyslexic, Verdana, Eido and Frutiger) in 145 French readers (73 with low vision, and 72 normal sighted), aged 6 to 35 years old and divided into four reading expertise groups. Participants completed two tasks, first reading texts on paper and then reading false-words on screen using eye tracking. About half of the participants with low vision had a subjective preference for Luciole when reading on paper and on the screen; lower preference is noted for participants with normal vision. Other readability criteria show a slight advantage of the Luciole font over some fonts (e.g., Eido and OpenDyslexic) in both groups. The results obtained when taking into consideration the level of reading expertise confirm this trend.

The dispute about sans serif versus serif fonts: An interaction between the variables of serif and stroke contrast

AIM

It is a long-lasting dispute whether serif or sans serif fonts are more legible. However, different fonts vary on numerous visual parameters, not just serifs. We investigated whether a difference in word identification can be attributed to the presence or absence of serifs or to the contrast of the letter stroke.

METHOD

Participants performed a word-recognition two-interval, forced-choice task (Exp. 1) and a classic lexical decision task (Exp. 2). In both experiments the word stimuli were set with four new fonts, which were developed to isolate the stylistic features of serif and letter-stroke contrast. Two measures (i.e., font-size threshold & sensitivity) were analysed.

RESULTS

The threshold measure of both experiments yielded a single significant main effect of stroke contrast such that low stroke contrast elicited lower than high stroke contrast. The sensitivity measure of Experiment 1 yielded a single significant effect of the interaction between serifs and stroke contrast. Specifically, at the sans-serif level, low stroke contrast revealed better sensitivity, relative to high stroke contrast. At the serif level, the opposite stroke contrast pattern was observed.

CONCLUSION

Sans serif fonts with low stroke contrast yield better performance and if a serif font is used, high stroke contrast yields better performance than low stroke contrast. Limitations and future directions are discussed.

High letter stroke contrast impairs letter recognition of bold fonts

To make graphical user interfaces look more fashionable, designers often make use of high-stroke-contrast fonts. We are yet to understand how these fonts affect reading. We examined the effect of letter-stroke contrast on three bold fonts, one with extreme contrast between thick and thin strokes, one with no contrast, and one in between. The fonts were designed for this experiment to enable control of font variables. Participants identified the middle letter in a lowercase letter trigram in each trial, briefly presented in the parafovea (at 2° left and right of fixation) and at the foveal fixation point. There was evidence for letter recognition impairment for the font with high stroke contrast compared to the fonts with low and medium stroke contrast, while there was no significant difference in performance between the medium- and low-stroke-contrast fonts. The results suggest that bold fonts with high stroke contrast should not be considered for designs where letter recognition is a priority.

The effect of character stroke width on legibility: The relationship between duty ratio and contrast threshold

Stroke width is an important factor affecting letter legibility. Although there seems to be a critical or optimal value for stroke width, it has been difficult to estimate quantitatively because shape deterioration and the increase of stroke width are covariates. This study attempted to predict the optimal value of stroke width considering it as a duty ratio. The duty ratio is related to the amplitude of the fundamental frequency, with the maximum amplitude of the fundamental frequency occurring at a duty ratio of 0.5. The fundamental frequency decreases when the duty ratio is set either lower or higher than 0.5. Based on previous research indicating that letters also have a critical band (CB), or the frequency band which contributes most to letter recognition, which corresponds to their fundamental frequency, we hypothesized that the amplitude of CB is related to the legibility of letters. We measured the contrast thresholds using square-wave gratings and letters of differing duty ratios. In both the grating and letter stimuli, the amplitude of CB reached its maximum when the duty ratio was around 0.5. Contrast thresholds for stimuli with various duty ratios were accurately predicted by the amplitudes of CB and the contrast thresholds in the individual's sine-wave grating. Our results suggest that the amplitude of a single critical component contributes significantly to the legibility of letters, even though they contain diverse frequency components.

Visual Demand and Acuity Reserve of Chinese versus English Newspapers

SIGNIFICANCE

This study suggests that Chinese newspaper characters are more legible than English newspaper letters. Characters in Chinese newspapers have higher acuity reserve than English newspapers.

PURPOSE

The purpose of this study was to evaluate visual demand and acuity reserve for Chinese newspapers in comparison with published data on U.S. newspapers.

METHODS

The test distances for visual acuity in Chinese clinical studies were reviewed systematically. Characters from different sections of newspapers printed in simplified Chinese were evaluated. The character height, frequency, and visual demand and acuity reserve of each newspaper section were determined for Chinese characters of the six different levels of complexity.

RESULTS

More than 70% of Chinese clinical studies measure near visual acuity at either 33 or 40 cm. The height of Chinese characters ranged from 1.95 to 3.28 mm across different sections of five newspapers compared with 1.0 to 2.0 mm for English letters. The frequency of Chinese characters from least to most complex ranged from 7 to 34% across 12 sections of one Chinese newspaper. The angular threshold across the six complexity levels of Chinese characters ranged from 4.62 to 5.93 arcmin (0.54 to 0.69 mm at 40-cm reading distance) with a weighted angular threshold of 5.18 arcmin compared with 3.37 arcmin (0.39 mm) for the English letters. For Chinese newspapers, at 40-cm reading distance, the acuity reserve for the smallest and largest median size was 3.55 and 4.61, respectively.

CONCLUSIONS

Chinese characters are larger than English characters in all newspaper sections newspapers by a factor of 1.60 to 2.34. Given that Chinese characters need to be 1.54 times larger than English letters to provide the same acuity reserve, on average, Chinese newspapers are more legible than U.S. English newspapers.

Effects of Task on Reading Performance Estimates

Reading is a primary problem for low vision patients and a common functional endpoint for eye disease. However, there is limited agreement on reading assessment methods for clinical outcomes. Many clinical reading tests lack standardized materials for repeated testing and cannot be self-administered, which limit their use for vision rehabilitation monitoring and remote assessment. We compared three different reading assessment methods to address these limitations. Normally sighted participants (N = 12) completed MNREAD, and two forced-choice reading tests at multiple font sizes in counterbalanced order. In a word identification task, participants indicated whether 5-letter pentagrams, syntactically matched to English, were words or non-words. In a true/false reading task, participants indicated whether four-word sentences presented in RSVP were logically true or false. The reading speed vs. print size data from each experiment were fit by an exponential function with parameters for reading acuity, critical print size and maximum reading speed. In all cases, reading speed increased quickly as an exponential function of text size. Reading speed and critical print size significantly differed across tasks, but not reading acuity. Reading speeds were faster for word/non-word and true/false reading tasks, consistent with the elimination of eye movement load in RSVP but required larger text sizes to achieve those faster reading speeds. These different reading tasks quantify distinct aspects of reading behavior and the preferred assessment method may depend on the goal of intervention. Reading performance is an important clinical endpoint and a key quality of life indicator, however, differences across methods complicate direct comparisons across studies.

Reading in the presence of macular disease: a mini-review

Purpose

Reading is vital to full participation in modern society. To millions of people suffering from macular disease that results in a central scotoma, reading is difficult and inefficient, rendering reading as the primary goal for most patients seeking low vision rehabilitation. The goals of this review paper are to summarize the dependence of reading speed on several key visual and typographical factors and the current methods or technologies for improving reading performance for people with macular disease.

Important findings

In general, reading speed for people with macular disease depends on print size, text contrast, size of the visual span, temporal processing of letters and oculomotor control. Attempts at improving reading speed by reducing the crowding effect between letters, words or lines; or optimizing properties of typeface such as the presence of serifs or stroke‐width thickness proved to be futile, with any improvement being modest at best. Currently, the most promising method to improve reading speed for people with macular disease is training, including perceptual learning or oculomotor training.

Summary

The limitation on reading speed for people with macular disease is likely to be multi‐factorial. Future studies should try to understand how different factors interact to limit reading speed, and whether different methods could be combined to produce a much greater benefit.

Smaller visual angles show greater benefit of letter boldness than larger visual angles

Research has shown that fonts viewed at a smaller visual angle benefit from greater letter boldness. Since small and large visual angles operate on different spatial frequencies, we examined whether the effect was dependent on font size. By applying a paradigm of single-letter exposure across two experiments, we showed that fonts of thinner letter strokes and of extreme boldness decreased recognition for all tested font sizes, and that there was a positive effect of boldness at small visual angles which did not occur at large visual angles. The paper provides evidence that bolder fonts are less effective at improving recognition at larger visual angles, and that over a scale of font weights there is a drop-off at the lightest and the heaviest extremes at all tested font sizes.

Typeface features and legibility research

In the early 20th century, reading researchers expressed optimism that scientific study of reading would improve the legibility of typefaces. Font-making was, however, complex, expensive and impractical for reading research, which was therefore restricted to standard commercial fonts. The adoption of computer typography in legibility studies makes the measurement, modification and creation of experimental fonts easier, while display of text on computer screens facilitates reading studies. These technical advances have spurred innovative research. Some studies continue to test fonts for efficient reading in low vision as well as normal vision, while others use novel fonts to investigate visual mechanisms in reading. Some experimental fonts incorporate color and animation features that were impractical or impossible in traditional typography. While it is not clear that such innovations will achieve the optimistic goals of a century ago, they extend the investigation and understanding of the nature of reading.

Bolder print does not increase reading speed in people with central vision loss

Patients with central vision loss are often advised by low vision rehabilitation professionals to read bolder print to ameliorate their reading difficulties. Is boldface print really effective in improving reading performance for people with central vision loss? In this study, we evaluated how reading speed depends on the stroke-width of text in people with central vision loss. Ten participants with long-standing central vision loss read aloud single, short sentences presented on a computer monitor, one word at a time, using rapid serial visual presentation (RSVP). Reading speed was calculated based on the RSVP word exposure duration that yielded 80% of words read correctly. Text was rendered in Courier and at six boldness levels, defined as the width of the letter-strokes normalized to that of the standard Courier font: 0.27, 0.72, 1, 1.48, 1.89 and 3.04× the standard. Reading speed was measured for two print sizes - 0.8× and 1.4× the critical print size (the smallest print size that can be read at the maximum reading speed). For all participants and both print sizes, reading speeds were essentially the same for text with stroke-width boldness ranging from 0.72 to 1.89× the standard, and were significantly lower for the thinnest and the boldest print. Most importantly, reading speed was not higher for bolder print than for the standard one. Despite the clinical wisdom that patients with central vision loss might benefit from bolder print, print with stroke-widths larger than the standard does not significantly improve reading speed for participants with central vision loss.

Korean reading speed: Effects of print size and retinal eccentricity

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 speed (MRS), and 2) as eccentricity increases, MRS decreases and CPS increases. Here we extend this work to Korean, a language with more complex orthography. We recruited 6 Korean native speakers (mean age = 22) and measured their reading speed in central vision (0°) and peripheral vision (10° in the lower field). 900 Korean sentences (average 8.25 words) were created with frequently-occurring beginner-level words, presented using a rapid serial visual presentation (RSVP) paradigm. Data for English reading were obtained from Chung, Mansfield & Legge, Vision Research, 1998, for comparison. MRS was similar for Korean and English at 0° (713 vs. 787 wpm), but decreased faster with eccentricity for Korean. CPS was larger for Korean than for English regardless of eccentricity, but increased with eccentricity similarly for both languages. From 0 to 10°, MRS decreased by a factor of 6.5 for Korean and 2.8 for English, and CPS increased by a factor of 11.7 for Korean and 10.2 for English. Korean reading speed is more affected by retinal eccentricity than English, likely due to additional within-character crowding from more complex orthography. Korean readers with central-field loss may experience more difficulty than English readers.

Fonts Designed for Macular Degeneration: Impact on Reading

Purpose

People with macular degeneration (MD) experience difficulties in reading due to central-field loss. Two new fonts, Eido and Maxular Rx, have been designed specifically for individuals with MD. We have compared reading performance of these new fonts with three mainstream fonts (Times-Roman, Courier, and Helvetica).

Methods

Subjects with MD (n = 19) and normally sighted subjects (n = 40) were tested with digital versions of the MNREAD test using the five fonts. Maximum reading speed (MRS), critical print size (CPS), and reading acuity (RA) were estimated to characterize reading performance. Physical properties of the fonts were quantified by interletter spacing and perimetric complexity.

Results

Reading with MD showed font differences in MRS, CPS, and RA. Compared with Helvetica and Times, Maxular Rx permitted both smaller CPS and RA, and Eido permitted smaller RA. However, the two new fonts presented no advantage over Courier. Spacing, but not Complexity, was a significant predictor of reading performance for subjects with MD.

Conclusions

The two fonts, designed specifically for MD, permit smaller print to be read, but provide no advantage over Courier.

Impact of simulated micro-scotomas on reading performance in central and peripheral retina

Observers with central field loss typically fixate within a non-foveal region called the preferred retinal locus, which can include localized sensitivity losses, or micro-scotomas (Krishnan and Bedell, 2018). In this study, we simulated micro-scotomas at the fovea and in the peripheral retina to assess their impact on reading speed. Ten younger (<36 years old) and 8 older (>50 years old) naïve observers with normal vision monocularly read high and/or low contrast sentences, presented at or above the critical print size for young observers at the fovea and at 5 and 10 deg in the inferior visual field. Reading material comprised MNREAD sentences and sentences taken from novels that were presented in rapid serial visual presentation (RSVP) format. Randomly distributed 13 × 13 arc min blocks corresponding to 0-78% of the text area (corresponding to ∼0-17 micro-scotomas/deg²) were set to the background luminance to simulate micro-scotomas. A staircase algorithm estimated maximum reading speed from the threshold exposure duration for each combination of retinal eccentricity, contrast and micro-scotoma density in both age groups. Log₁₀(RSVP reading speed) decreased significantly with simulated micro-scotoma density and eccentricity. Across conditions, reading speed was slower with low-compared to high-contrast text and was faster in younger than older normal observers. For a given eccentricity and contrast, a higher density of random element losses maximally affected older observers with normal vision. These outcomes may explain some of the reading deficits observed in older observers with central field loss.

The effect of letter string length and report condition on letter recognition accuracy

PURPOSE

Letter sequence recognition accuracy has been postulated to be limited primarily by low-level visual factors. The influence of high level factors such as visual memory (load and decay) has been largely overlooked. This study provides insight into the role of these factors by investigating the interaction between letter sequence recognition accuracy, letter string length and report condition.

METHODS

Letter sequence recognition accuracy for trigrams and pentagrams were measured in 10 adult subjects for two report conditions. In the complete report condition subjects reported all 3 or all 5 letters comprising trigrams and pentagrams, respectively. In the partial report condition, subjects reported only a single letter in the trigram or pentagram. Letters were presented for 100ms and rendered in high contrast, using black lowercase Courier font that subtended 0.4° at the fixation distance of 0.57m.

RESULTS

Letter sequence recognition accuracy was consistently higher for trigrams compared to pentagrams especially for letter positions away from fixation. While partial report increased recognition accuracy in both string length conditions, the effect was larger for pentagrams, and most evident for the final letter positions within trigrams and pentagrams. The effect of partial report on recognition accuracy for the final letter positions increased as eccentricity increased away from fixation, and was independent of the inner/outer position of a letter.

CONCLUSIONS

Higher-level visual memory functions (memory load and decay) play a role in letter sequence recognition accuracy. There is also suggestion of additional delays imposed on memory encoding by crowded letter elements.

Reading Digital with Low Vision

Reading difficulty is a major consequence of vision loss for more than four million Americans with low vision. Difficulty in accessing print imposes obstacles to education, employment, social interaction and recreation. In recent years, research in vision science has made major strides in understanding the impact of low vision on reading, and the dependence of reading performance on text properties. The ongoing transition to the production and distribution of digital documents brings about new opportunities for people with visual impairment. Digital documents on computers and mobile devices permit customization of print size, spacing, font style, contrast polarity and page layout to optimize reading displays for people with low vision. As a result, we now have unprecedented opportunities to adapt text format to meet the needs of visually impaired readers.

A New Font, Specifically Designed for Peripheral Vision, Improves Peripheral Letter and Word Recognition, but Not Eye-Mediated Reading Performance

Reading speed is dramatically reduced when readers cannot use their central vision. This is because low visual acuity and crowding negatively impact letter recognition in the periphery. In this study, we designed a new font (referred to as the Eido font) in order to reduce inter-letter similarity and consequently to increase peripheral letter recognition performance. We tested this font by running five experiments that compared the Eido font with the standard Courier font. Letter spacing and x-height were identical for the two monospaced fonts. Six normally-sighted subjects used exclusively their peripheral vision to run two aloud reading tasks (with eye movements), a letter recognition task (without eye movements), a word recognition task (without eye movements) and a lexical decision task. Results show that reading speed was not significantly different between the Eido and the Courier font when subjects had to read single sentences with a round simulated gaze-contingent central scotoma (10° diameter). In contrast, Eido significantly decreased perceptual errors in peripheral crowded letter recognition (-30% errors on average for letters briefly presented at 6° eccentricity) and in peripheral word recognition (-32% errors on average for words briefly presented at 6° eccentricity).

IURead: a new computer-based reading test

PURPOSE

To develop a computer-based single sentence reading test especially designed for clinical research enabling multiple repeat trials without reusing the same sentences.

METHODS

We initially developed 422 sentences, with an average of 60 characters and 12 words. Presentation controls were improved by employing computer-based testing and the oral reading was recorded by visual inspection of digital audio recordings. Variability in reading speed of normally sighted adults between sentences, between charts, between subjects, between formats, and between display devices was quantified. The impact of display size and pixel resolution on test geometry was assessed, and the impact of reduced retinal image quality and retinal illuminance were compared for reading and standard letter acuities. Eleven visually normal subjects (age: 18-60 years) participated in this study.

RESULTS

Stopwatch timing of sentences reliably underestimated reading times by about 0.3 s, and exhibited coefficients of repeatability 17 times larger than those estimated from visual inspection of digital recordings. A slight relaxing of the lexical content constraints had no effect on reading speed; neither did sentence format (single vs three lines) or display size or distance. Within subject standard deviations of reading speed for different sentences were small (between 6% and 9% of the mean speed) requiring only small samples sizes to achieve typical statistical reliability and power when comparing conditions within individual subjects. The greater variability associated with stopwatch timing necessitates larger sample sizes. As defocus and light level were varied, reading acuity and standard letter acuity were highly correlated (r(2)  = 0.99), and reading acuity was slightly better.

DISCUSSION

A computer-based IURead reading test provides a useful reading speed and reading acuity tool for clinical research involving multiple conditions and repeat testing of individual subjects. Ready to use IURead files for use with a computer, tablet or cell phone can be downloaded from our lab website (https://www.opt.indiana.edu/Bradley/Downloads.aspx).

A matter of font type: The effect of serifs on the evaluation of scientific abstracts

Text-based communication is one of the substantial ways of spreading scientific information. While the content and contextual aspects of written words have been widely researched, the impact of font characteristics on text perception is an almost blank page. The following study deals with the influence of serifs on the evaluation of online-presented scientific abstracts. Yet there is only evidence for faster reading times when texts are presented in sans-serif fonts, although the opposite is stated in parts of the literature. The present work examines if the presence or absence of serifs also have an impact on the appraisal of scientific texts when all other important font characteristics do not change. For this purpose, 188 university students participated in an online experiment and rated different aspects of scientific abstracts as well as of the research outlined in the abstracts. The results show that missing serifs led to increased reading speed. However, and in contrast to the perceptual fluency hypothesis, the presence of serifs had a positive effect on all evaluation dimensions. The results of a second study with 187 participants also indicated that reading fluency counteracted the liking of texts. Implications for future studies and media production are discussed.