Research: Specific Issues

From Low Vision Accessibility Task Force

This page is to collect relevant research on specific low vision issues. Please include a summary (paragraph or bullets) of the research. Please conscult the Research page for all research gathered.

Legibility and Readability and ???

current draft section, revision suggestion

Elizabeth Russell-Minda, Jeffrey W. Jutai, J. Graham Strong, Kent A. Campbell, Deborah Gold, Lisa Pretty, and Lesley Wilmot

One concept of the legibility of print specifies that the test material should be performed under “threshold seeing conditions,” a psychophysical acuity measurement that defines a threshold value at which a majority of subject responses are accurate. Another concept is elated to the performance of various typeface designs when they are presented at sizes that are well above the reader’s threshold. One aspect to be considered may be simply which font design is the most appealing or comfortable to the reader, often described as “readability” Arditi, 2005; Kitchel, 2002). A significant problem arises when one font design “A” is found to be more legible than another font design “B,” but font “B” is found to be more readable than “A.” The apparent contradiction may be explainable by the inconsistent use of terms. Other criteria that are used to determine the legibility of typefaces are reading speed and critical print size (Chung et al., 1998; Mansfield et al., 1996). The critical print size is the smallest print size at which individuals can read with their maximum reading speed. This is an important measure because it indicates the minimum magnification that is required for effortless reading.

Compares normal and low vision reading across (A) reading acuity, (B) critical print size, (C) maximum reading rate. But, doesn't necessarily define them.

When one examines readability, the ease (speed and comfort) with which an individual reads and comprehends text, it is important to first determine legibility, the ability of an individual to distinguish characters. The legibility of text influences its readability (Erdmann & Neal, 1968), which in turn influences ease of comprehension of written material.

Minnesota Laboratory for Low-Vision Research. 1999

"Reading speed is an objective measure of reading performance. Research has shown that patients (with either normal or low vision) often require letters that are two or three times larger than their acuity limits before they can achieve their maximum reading speeds."

"The critical print size is the smallest print size at which patient's can read with their maximum reading speed. This is an important measure as it indicates the minimum magnification required for effortless reading. The critical print size is most easily identified from a plot of the patient's reading speed at each print size."

Gordon E. Legge; Charles A. Bigelow
fluent print size—the range over which text can be read at maximum speed

  • Tinker, Miles A. (1963). Legibility of Print. Iowa: Iowa State University Press.
    Note: In his seminal research, Tinker used only the term legibility to avoid confusion with readability formulas for the level of difficulty of the language; however, most recent literature distinguishes between legibility and readability as explain on this page. —
  • Gradisar, Humar, and Turk. The Legibility of Colored Web Page Texts 2007.

Readability is the ability to recognize the form of a word or a group of words for contextual purposes [17]...

In this paper, legibility is understood as a group of visual properties of a character or symbol that determine the ease with which it can be recognized, with respect to ANSI/HFS 100-1988 standard. In principle, legibility is affected only by observer’s spatial vision abilities. Up to some asymptotic level, legibility is enhanced by high luminance and color contrast, larger targets, and increased inter- and intra- target spacing [21].

  • Nielsen, Jakob. Legibility, Readability, and Comprehension: Making Users Read Your Words, 2015.
    • "Legibility Definition: Legibility is the lowest-level consideration in content usability: its whether people are able to see, distinguish, and recognize the characters and words in your text. Legibility is thus mainly determined by visual design, specifically typography..."

    • "Readability Definition: Readability measures the complexity of the words and sentence structure in a piece of content. The assumption behind this metric is that complex sentences are harder to parse and read than simpler ones. Its usually reported as the reading level (stated as years of formal education) needed to easily read the text. For example, a 12th grade reading level means that somebody with a good high-school diploma will be able to read the text without difficulty..."

    • "Comprehension Definition: Comprehension measures whether a user can understand the intended meaning of a text and can draw the correct conclusions from the text. In the case of instructional or action-oriented content, we also want users to be able to perform the intended actions after reading the text..."

Movement and Low Vision

  • VA is visual acuity, DVA dynamic visual acuity

    "Identifying targets or letters in mobile environment, such as in driving, flying, and some special exercises, requires excellent dynamic VA because of high tactile skill requirement [37,38]. Dynamic VA is also significantly better among student athletes than among their non-athletic peers [39]. Many clinical physicians focus on diagnosing dynamic VA without using magnetic resonance imaging (MRI), electronystagmography, or other complicated instruments. Patients are requested to see a visual chart before and after head movement. Thus, static and dynamic VA can be easily obtained for further evaluation. For example, patients with dizziness, labyrinthitis, head trauma, multiple sclerosis, and optic neuritis can be easily diagnosed through decreased visual acuity during head motion (a minimum of two-line reduction in dynamic VA). Studies also demonstrated a five-line difference between dynamic and static VA (decline in dynamic VA in these diseases) [40,41]. In addition, dynamic VA remarkably declines during head motion in patients with focal peripheral lesions and aminoglycoside toxicity [42]. Therefore, dynamic VA in patients with vestibular deficits may primarily reflect the degree of vestibular loss [43]."

    Effects of Horizontal Acceleration on Human Visual Acuity and Stereopsis
  • "balance, clear vision during head movements and correct spatial orientation entail the processing of visual, vestibular and somatosensory afferent input to produce adaptive eye and body movements and a correct spatial sensation. Disequilibrium, blurred vision and dizziness or vertigo may ensue, if there is any sensory deficit, abnormal stimulation or defective central processing..."

    - E. Mira

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