Psychophysics of reading. XVIII. The effect of print size on reading speed in normal peripheral vision

Reading in peripheral vision is slow and requires large print, posing substantial difficulty for patients with central scotomata. The purpose of this study was to evaluate the effect of print size on reading speed at different eccentricities in normal peripheral vision. We hypothesized that reading speeds should remain invariant with eccentricity, as long as the print is appropriately scaled in size--the scaling hypothesis. The scaling hypothesis predicts that log-log plots of reading speed versus print size exhibit the same shape at all eccentricities, but shift along the print-size axis. Six normal observers read aloud single sentences (approximately 11 words in length) presented on a computer monitor, one word at a time, using rapid serial visual presentation (RSVP). We measured reading speeds (based on RSVP exposure durations yielding 80% correct) for eight print sizes at each of six retinal eccentricities, from 0 (foveal) to 20 deg in the inferior visual field. Consistent with the scaling hypothesis, plots of reading speed versus print size had the same shape at different eccentricities: reading speed increased with print size, up to a critical print size and was then constant at a maximum reading speed for larger print sizes. Also consistent with the scaling hypothesis, the plots shifted horizontally such that average values of the critical print size increased from 0.16 deg (fovea) to 2.22 deg (20 deg peripheral). Inconsistent with the scaling hypothesis, the plots also exhibited vertical shifts so that average values of the maximum reading speed decreased from 807 w.p.m. (fovea) to 135 w.p.m. (20 deg peripheral). Because the maximum reading speed is not invariant with eccentricity even when the print size was scaled, we reject the scaling hypothesis and conclude that print size is not the only factor limiting maximum reading speed in normal peripheral vision.     

Color improves object recognition in normal and low vision.

Does color improve object recognition? If so, is the improvement greater for images with low spatial resolution in which there is less shape information? Do people with low visual acuity benefit more from color? Three experiments measured reaction time (RT) and accuracy for naming food objects displayed in 4 types of images: gray scale or color, and high or low spatial resolution (produced by blur). Normally sighted Ss had faster RTs with color, but the improvement was not significantly greater for images with low spatial resolution. Low vision Ss were also faster with color, but the difference did not depend significantly on acuity. In 2 additional experiments, it was found that the faster RTs for color stimuli were related to objects' prototypicality but not to their color diagnosticity. It was concluded that color does improve object recognition, and the mechanism is probably sensory rather than cognitive in origin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Life span changes in visual enumeration: The number discrimination task.

Participants from 5 groups with mean ages of 6, 8, 10, 22, and 72 yrs were tested on a series of speeded number discriminations: 1 vs 2, 3 vs 4, 6 vs 7, and 8 vs 9. The primary measure of interest (response time slope as a function of number size) decreased with age for numbers in the 1–4 range. However, a U-shaped age function emerged in the 6–9 range, with larger slopes for children and senior adults, and the smallest slopes for young adults. These data suggest that different processes are involved in enumerating small and large numbers of items. It is argued that subitizing, the process for small numbers, makes only minimal demands on spatial attention and thus shows developmental improvements without any decline in old age. In contrast, counting, the process for large numbers, requires sophisticated coordination of spatial attention, which has previously been shown first to improve and then decline over the life span. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of certain typographical arrangements upon span of visual comprehension.

A group of 30 Ss read under tachistoscopic exposure material in three typographical styles—conventional, spaced unit, and square-span—and were tested for comprehension. The square-span style yielded comprehension spans significantly superior to the other two styles, which did not differ. "The square-span style used in books and advertising might lead to increased reading and comprehension speed." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How visual imagery interferes with vision.

Mental visual imagery interferes with vision: the Perky (1910) effect. Is the effect optical, sensory, perceptual, attentional, or just a response bias? Acuity was measured (in undergraduates and graduates) using target lines, with and without images (of lines). Optics (fixation, pupil size, accommodation), response bias, global attention (effort, diversion of attention to imagery), perceptual assimilation (target incorporation by imagery) and perceptual masking (of target by imagery) all fail to explain the effect. Foveally, local attention plays a limited role, as the Perky effect in divided attention is half that in focused attention, but this interaction vanishes with extrafoveal targets. Images produce primarily sensory interference, mimicking a reduction in target energy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult life span changes in immediate visual memory and verbal intelligence.

A sample of 558 women and 1,163 men 17 to 102 years old, screened for neurodegenerative and neuropsychiatric disease, was administered tests of immediate visual memory (Benton Visual Retention Test) and crystallized intelligence (Wechsler Adult Intelligence Scale Vocabulary subtest) from 1 to 5 times over 27.7 years. Cross-sectional and longitudinal evidence led to the conclusion that the 65-74-year decade was a watershed for decremental changes in immediate visual memory and verbal intelligence. Age accounted for considerably less variance in vocabulary than in immediate memory. The proportion of individuals whose longitudinal trajectories were contrary to group trends decreased substantially with increased age; observed age changes remained when analyses were restricted to individuals who had perfect or near-perfect mental status scores. Selected neuronal loss and slower reproduction times were considered as possible causes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The comparative study of the macular light threshold in the normal and low visual acuity people]

Hepatitis B recombinant vaccine immunoresponsiveness was studied in 427 preadolescents vaccinated with a 0, 1 and 6 months vaccination schedule. AntiHBs postvaccination titres (measured one month after the last dose) were related to the following variables: sex; weight; height; and Quetelet index. The antiHBs postvaccination titres were used to predict the length of protection induced by the vaccine. All preadolescents developed antiHBs titres 10 IU l-1 and no statistically significant differences could be found between sexes. The relation study between antiHBs postvaccination levels and Quetelet index showed a statistically significant inverse correlation. According to the antiHBs postvaccination titres, the central 50% of the sample distribution would be protected during a period between 7.5 and 10.5 years. In pre-teenagers, the hepatitis B recombinant vaccine has proven to be highly immunogenic, obesity is a predictor of poor immunoresponse and this response is not influenced by sex. According to our results, we would propose the administration of a single booster dose 10 years after primary vaccination and thus protect these subjects during the period of greatest risk.     

A systems model for low vision rehabilitation. II. Measurement of vision disabilities

BACKGROUND: This study presents and tests a method of measuring vision disabilities. Based on the model presented in the first paper of this series, cognitive and motor activities ("tasks") are organized in a hierarchy that identifies the tasks' behavioral goals (purposes) and the social objectives the goals serve. Two latent variables important to the definition of vision disability are identified: "value of living independently" and "visual ability for independent living." The basic principles of the Rasch measurement model are reviewed, and Rasch models are used to measure the two variables that define vision disability. The need for rehabilitation to meet each goal is represented by "rehabilitative demand," a mathematical function of the measurements made of the value and difficulty of achieving each goal independently. METHODS: Over 400 patients with low vision rated both the importance and difficulty of independently achieving each of 24 goals. Rasch analysis was used to derive interval measures of the social value of each goal, the value that individual patients placed on each goal relative to the derived social definition of independence, the visual ability required to achieve each goal without help, and the visual ability of individual patients to live independently. A rehabilitative demand function was ascertained from the judgments of 17 AAO Diplomates in Low Vision through triadic comparisons and multidimensional scaling. RESULTS: Self-care had the greatest "social value" for independence; performing music had the least. Recreational reading required the greatest "visual ability" to accomplish independently; self-care required the least. Rehabilitative demand was linear with value and nonmonotonic with difficulty. CONCLUSIONS: Rehabilitative demand, an algorithm for defining vision disability, incorporates interval measures of visual ability and the value of independent living estimated from patient-based assessments, a social scale of the value of activities relative to independent living, and a consensus opinion of low vision experts on the prioritization of the need for rehabilitation.     

Knowledge-based vision and simple visual machines

The vast majority of work in machine vision emphasizes the representation of perceived objects and events: it is these internal representations that incorporate the 'knowledge' in knowledge-based vision or form the 'models' in model-based vision. In this paper, we discuss simple machine vision systems developed by artificial evolution rather than traditional engineering design techniques, and note that the task of identifying internal representations within such systems is made difficult by the lack of an operational definition of representation at the causal mechanistic level. Consequently, we question the nature and indeed the existence of representations posited to be used within natural vision systems (i.e. animals). We conclude that representations argued for on a priori grounds by external observers of a particular vision system may well be illusory, and are at best place-holders for yet-to-be-identified causal mechanistic interactions. That is, applying the knowledge-based vision approach in the understanding of evolved systems (machines or animals) may well lead to theories and models that are internally consistent, computationally plausible, and entirely wrong.     

Motion parallax: effects of blur, contrast, and field size in normal and low vision

Can people with different forms of low vision use motion parallax to improve depth judgments? We used a staircase method to compare depth thresholds using motion parallax and static viewing. We tested eighteen normal-vision subjects with a range of simulated deficits in acuity, contrast sensitivity, and simulated peripheral-field loss, and ten low-vision subjects with a wide range of acuity, contrast sensitivity, and field loss. Subjects viewed three vertical cylinders monocularly and indicated which one was at a different depth from the other two. For motion-parallax trials, observers moved their heads (in a viewing assembly on rollers) from side to side over a range of 6-12 cm. For static trials, the viewing assembly was fixed in place. Normal-vision subjects' depth thresholds with motion parallax were significantly smaller than those with static viewing by an average factor of 1.95 (p < 0.05) across all levels of acuity and contrast. For low-vision observers, the depth thresholds exhibited large individual differences; however, the motion-parallax thresholds were smaller than the static thresholds by an average factor of 2.05 (p < 0.01). These findings indicate that motion parallax can provide useful depth information for people with low vision.     

A meta-analysis of normal and disordered personality across the life span.

Debate continues about whether personality, both normal and disordered, can change significantly or is mainly stable across the life span. One issue that receives little attention is the degree to which personality stability coefficients may be influenced by attenuation due to measurement error. The current meta-analysis examines the data from recent research on personality stability, reporting both uncorrected and corrected stability coefficients. Attenuation due to measurement error was found to cause a significant reduction in personality stability coefficients, raising the possibility that some studies may conflate personality change with measurement error. Overall, corrected stability coefficients suggested that the stability of personality across adulthood is high, with only modest change. By contrast, personality during childhood is significantly more changeable. Both normal personality and personality disorders were highly stable across the life span, and patients in therapy experienced no more personality change than did nonpatients. Cross-cultural comparisons suggested relatively similar levels of personality stability cross-culturally, although personality stability among people in South Pacific nations is slightly lower than among those in the United States, Canada, or European nations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Display visual angle and attentional scanpaths on the span of apprehension task in schizophrenia.

The effect of display visual angle on span of apprehension (SOA) task performance was investigated in patients with schizophrenia and nonpsychiatric individuals. Narrow and wide visual-angle presentations of 3- and 10-letter arrays were compared. Detection rates were significantly higher with narrow than wide visual angle for nonpsychiatric individuals; the performance of those with schizophrenia was stable across visual-angle conditions. Patients with schizophrenia were best discriminated from nonpsychiatric individuals in the narrow-angle, 10-letter condition. Scanpath analyses, which were based on the pattern of detection rates across different target quadrant locations, suggested that the patients with schizophrenia used a similar number and path of covert scan moves as did the controls. Hypotheses are discussed regarding which of the multiple cognitive processes tapped by the SOA task may be impaired in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nerve fiber layer defects with normal visual fields. Do normal optic disc and normal visual field indicate absence of glaucomatous abnormality?

PURPOSE: When the optic disc has normal appearance with no abnormalities in routine automated perimetry, the subject is not considered to have glaucoma. The purpose of this study is to show how such patients may have localized retinal nerve fiber layer defects with corresponding functional abnormality. METHODS: The authors selected eight eyes of eight patients who had a localized retinal nerve fiber layer defect extending within a few degrees from fovea but in whom the optic disc appearance and Humphrey 30-2 visual fields were normal. Of the eight patients, three had positive family history of glaucoma, two had suspected retinal nerve fiber layer abnormality in routine eye examination, two had increased intraocular pressure (IOP), and one had advanced low-tension glaucoma in one eye with a normal fellow eye. The authors examined the central 10 degrees visual field with 1 degree resolution using Humphrey perimeter and the Ring and Centring programs of the high-pass resolution perimeter. RESULTS: A central field defect corresponding to retinal nerve fiber layer defect was found in six of eight patients: in both 10 degrees Humphrey field and Centring programs (2 eyes), in Humphrey only (2 eyes), and in Centring only (2 eyes). CONCLUSION: The results indicate that retinal nerve fiber layer photographs are helpful in diagnosing glaucoma because early glaucomatous abnormalities cannot be excluded without nerve fiber layer photography. Currently available routine perimetric examination programs do not always detect very early functional damage.     

Active vision: visual activity in everyday life

Recent studies that consider how vision is used in everyday life have led to a new perspective in visual science, in which more emphasis is placed on the active role of the viewer.     

The impact of cataract surgery on low vision patients. A population based study

PURPOSE: To assess the impact of cataract surgery on low vision patients. METHODS: Self-estimated ability to perform visually demanding tasks before and after cataract surgery and expectations and satisfaction with the surgery were analysed in all low-vision patients (n = 52), who during a one-year period underwent surgery at Norrlands University Hospital in Ume?, Sweden. Self-administered questionnaires were used and the records of the patients were studied. RESULTS: The majority (81%) of the low vision patients reported an improved ability to perform visually demanding tasks after surgery. The number of patients who were unable to read newspaper-size print decreased significantly, from 44% to 21% after surgery. The subjectively improved visual ability as well as the augmentation of VA of the operated eye were both significantly related to satisfaction with the outcome of surgery. CONCLUSION: Most low-vision patients with significant cataract benefit from surgery, both subjectively by increased ability to perform visually demanding tasks as well as by an improved visual acuity. Particularly patients with loss of peripheral visual fields subjectively gain in orientation ability. It is important to reduce unreasonable expectations about the outcome of the surgery.     

National survey of blindness and low vision in Lebanon

Here we report a case that presented with sudden onset of neurological symptoms and was treated with ganciclovir. Polymerase chain reaction analysis for human herpes virus-6 (HHV-6) from his cerebrospinal fluid was later found to be positive. He subsequently recovered with minimal residual neurological symptoms. Encephalitis secondary to this virus may be more common than previously thought in patients undergoing bone marrow transplantation. This condition should be considered in the differential diagnosis of sudden onset neurological symptoms after bone marrow transplantation.     

Overview of technology for low vision

This article provides an overview of technology resources and services to assist persons with low vision in maintaining independent function in the home, community, and educational and vocational settings. Case studies are provided to demonstrate the integration of technology into the lives of persons with low vision.     

A multidiscipline approach in low vision rehabilitation

The first low vision clinic was instituted at the Industrial Home for the Blind in 1953 in response to a growing demand that more effective use be made of the residual vision in blind persons. The technology was there. Eye practitioners certainly knew enough about vision problems to offer many of these people an opportunity to enter a new life. The problem was: how to put that knowledge to work through a sound service delivery system. By its twentieth anniversary in 1973 the clinic had seen almost 5,000 patients for low vision evaluation and had built a service which consistently provided substantial and useful improvement in vision through the use of optical aids to a majority of its patients. The low vision optometric staff works as an integral part of a rehabilitation team. That team consists of a number of professionals, including ophthalmologists, social workers, teachers, and a variety of rehabilitation instructors. All members work simultaneously to create a total program of rehabilitation for thepartially sighted. We feel this teamwork approach is of basic importance to effective rehabilitation.