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PubMed2001

Characteristics of the pediatric/adolescent low-vision population at the Illinois School for the Visually Impaired.

BACKGROUND: There are few descriptive studies of children and adolescents with low vision in the United States. Our study describes a pediatric/adolescent population at the Illinois School for the Visually Impaired (ISVI), detailing the etiologies of low vision and the devices prescribed. METHODS: A retrospective record review was conducted of 260 consecutive students who had been examined at the twice-yearly Lions of Illinois Low Vision Clinic at ISVI between the years 1991 and 1999. Data collected included age, race, sex, best-corrected visual acuity, ocular diagnoses, the etiology of low vision (if known), and low-vision devices prescribed. RESULTS: The population was 60% male. Ages ranged from less than 1 year to 20 years of age. The mean best-corrected distance visual acuity was approximately 20/200. Optic atrophy, cataracts, and retinopathy of prematurity were significant etiologies of low vision; however, the largest group of patients had a diagnosis classified as "other." Hand-held telescopes, bifocals/high adds, and tinted lenses were the major low-vision devices prescribed. CONCLUSIONS: While optic atrophy, cataracts, and retinopathy of prematurity were common causes of vision impairment among students at ISVI, the largest group of students had an etiology from a wide range of disorders. Information on the causes of low vision can help with decisions on the allocation of research funds and resources for low-vision devices.

Adolescent↗
PubMed2007

[Parallel processing of motion vision].

Several neuropsychological studies have reported dissociation between motion vision and object vision. One patient with motion blindness had a bilateral MT/V5 lesion and could see objects, but could not see the motion of the objects (Zihl et al, 1983). By contrast, some blindsight patients with primary visual cortex lesions cannot see objects but can see their movement (e.g. Riddoch, 1917). These results imply that movement vision and form vision rely on independent mechanisms. However one patient with motion blindness had controversial symptoms concerning motion vision. She could not perceive the movement of objects, although she could walk without colliding with obstacles and could catch incoming objects. It has also been reported that patients with a bilateral parietal lesion had well-preserved primary motion vision, but had problems walking and catching a ball (Vaina, 1998). Therefore, motion for vision and motion for action might have independent mechanisms. Such dissociation has also been noted in patients with Bálint syndrome. Some patients behave like a blind person but can walk and catch a ball, while other patients bump into obstacles while walking. These results indicate that the neural bases of motion vision are distinct from those of form vision and that there are subdivisions of motion vision.

Agnosia↗
PubMed1988

The efficacy of optometric vision therapy. The 1986/87 Future of Visual Development/Performance Task Force.

Vision is not simply the ability to read a certain size letter at a distance of 20 feet. Vision is a complex and adaptable information gathering and processing system which collects, groups, analyzes, accumulates, equates, and remembers information. In this review, some of the essential components of the visual system and their disorders which can be physiologically and clinically identified, i.e., the oculomotor, the accommodative, and the fusional vergence systems have been discussed. Any dysfunctions in these systems, can lessen the quality and quantity of the initial input of information into the visual system. Deficiencies in one or more of these visual subsystems have been shown to result in symptoms, such as blurred or uncomfortable vision or headaches, or behavioral signs such as rubbing of the eyes, eyes turning inward or outward, reduced job efficiency or reading performance, or simply the avoidance of near point tasks. In addition, these signs/symptoms may contribute to reducing a person's attention and interest in near tasks. The goal of vision therapy is to eliminate visual problems, thereby reducing the frequency and severity of the patient's signs and symptoms. Vision therapy should only be expected to be of clinical benefit to patients who have detectable visual deficiencies. In response to the question, "How effective is vision therapy in remediating visual deficiencies?," it is evident from the research presented that there is sufficient scientific support for the efficacy of vision therapy in modifying and improving oculomotor, accommodative, and binocular system disorders, as measured by standardized clinical and laboratory testing methods, in the majority of patients of all ages for whom it is properly undertaken and employed. The American Optometric Association reaffirms its long-standing position that vision therapy is an effective therapeutic modality in the treatment of many physiological and information processing dysfunctions of the vision system. It continues to support quality optometric care, education, and research and will cooperate with all professions dedicated to providing the highest quality of life in which vision plays such an important role.

Accommodation, Ocular↗
PubMed1992

Negative predictive value of a population-based preschool vision screening program.

BACKGROUND: The Enhanced Vision Screening Program is a population-based vision screening program that has, at present, examined 59,782 children. Its main goal is to detect amblyopia, strabismus, and high refractive errors. An average of 11,910 4 1/2- to 5 1/2-year-old children are screened yearly. The current study determines the negative predictive value of the screening program: For a subject having passed the vision screening test, what is the probability of not having amblyopia, strabismus, or high refractive errors? METHODS: Of the 11,734 subjects who passed the vision screening, 200 were randomly chosen to undergo a strictly defined gold standard examination by an orthoptist and an ophthalmologist. RESULTS: Of the 200 randomly chosen subjects, 157 underwent the gold standard evaluation. The negative predictive value of the Enhanced Vision Screening Program was 97.6% for any potentially vision-threatening ocular condition. It was 98.7% if we considered only the visually significant ocular problems that the test was designed to detect. CONCLUSION: Because the negative predictive value of the Enhanced Vision Screening Program is not 100%, some children with amblyopia, strabismus, or refractive errors are missed. Occasionally, a rare, potentially vision-threatening condition may go undetected. Parents should be made aware of this when they receive the results of the vision screening.

Child↗
PubMed2003

Sports vision testing of selected athletic participants in the 1997 and 1998 AAU Junior Olympic Games.

BACKGROUND: Sports vision researchers have attempted to establish the need for vision care services for athletes and the relationship between visual skills and athletic success. METHODS: Data collected from sports vision screenings at the 1997 and 1998 Amateur Athletic Union AAU Junior Olympic Games was compiled for analysis. Four hundred forty-nine athletes, ranging in ages from 5 to 19 years old and representing 12 sports, were part of the sports vision epidemiology project conducted by the American Optometric Association Sports Vision Section. Protocols from the AOA Sports Vision Section were used to assess the visual systems of athletes participating in the games. The history included evaluation of the use of vision care services, refractive correction type, and symptomology. The screening assessed visual acuity, contrast sensitivity, ocular alignment, eye-hand dominance, handspeed, footspeed, speed of stereopsis, speed of recognition, eye movements, hand-eye coordination, anterior-segment health, and posterior-segment health. Performance testing was analyzed by age group and sport. RESULTS: In this population of athletes, eye care was under-utilized. The performance testing indicated an increase in performance with increasing age for most tests. With increasing age, there was a decrease in the number of fixation losses, an increase in footspeed, and a decrease in handspeed. The norms for the performance tests are reported by age group and by sport. CONCLUSIONS: The results of this study imply that athletic populations at all levels are in need of eye care services. The norms derived from this investigation act as a standard for the evaluation of vision performance using the AOA Sports Vision Testing Battery.

Adolescent↗
PubMed2005

Prevalence of abnormal vision in one-year-old Thai children, based on a prospective cohort study of Thai children (PCTC).

OBJECTIVES: To collect preliminary data on the prevalence of abnormal vision in one-year-old Thai children. MATERIAL AND METHOD: A retrospective study was conducted using data collected from a prospective cohort study of Thai children (PCTC) carried out during 2000-2002, to examine the prevalence of abnormal vision in one-year-olds. Data from five districts in five provinces were examined. One-year-old children in the present study underwent vision screening and eye examination performed by non-medical research assistants. RESULTS: There were records from 3,898 children in five districts, 49.7% females and 50.2% males. Their eye examinations showed very good vision in 77.8% (9.8 cy/cm at 38 cm), good vision in 21.5% (6.5 cy/cm at 38 cm), and fair vision in 0.7% (< or = 1.6 cy/cm at 38 cm). Normal ocular motility was found in 99.7% and 99.9% had normal anterior segment and lens. No strabismus was found in 99.4%, 99.9% had normal pupil light reflex, 99.8% had normal red reflex, 93.6% could fix and follow at 3 months of age, 85.7% could detect a falling object at 6 months, and 78.5% of mothers and 46.5% of fathers regularly played with the children. Logistic regression analysis indicated that some factors had statistical significance, such as "fix and follow" by 1 month of age, and lack of father-child interaction, but these were not clinically significant. Using Kappa analysis, the authors combined groups 1 (very good vision) and 2 (good vision) to create a "normal vision" category. If children had 2 abnormal eye examinations (eye exam for strabismus, cornea, anterior chamber, lens, pupil and red reflex), the authors recommended sending them to a specialist. The sensitivity and specificity of the visual screening and eye examination instruments were 19.23% and 99.38%, respectively. The Kappa statistic was 0.17. These instruments are not appropriate for eye screening in one-year-old children. CONCLUSION: More than 99% of the children examined had normal results. The majority of children could fix and follow from 2-3 months of age. The early fix and follow development may be related to better visual acuity. The interaction between father and child may be associated with eye development. However, eye screening of one-year-old children by assistant researchers may be inappropriate due to lack of expertise and experience.

Age Factors↗
PubMed1992

The role of vision in the temporal and spatial control of handwriting.

The general observation that handwriting is not noticeably impaired by the withdrawal of vision can be explained in two ways. One might argue that vision is not needed during the act of writing. Micro-analyses should then reveal that spatial as well as temporal writing features are identical in conditions of vision and no vision. Alternatively, it is possible that vision is needed during the act of writing, but that without vision possible errors and inaccuracies have to be prevented. Assuming that the latter would place an extra demand on movement control, this should be revealed by an increase in processing time. We have found evidence for the latter view in the present study in which 12 subjects wrote a nonsense letter sequence with and without vision. Close examination showed that writing shapes remained equally invariant under both vision conditions, suggesting that spatial control was unaffected by withdrawing vision. The prediction that invariance of shapes is preserved in the absence of vision at the expense of processing time increments was confirmed. The increase of reaction time observed when visual guidance was withdrawn suggests that more processing time was needed prior to the movement start. Moreover, the RT increment was larger when a short writing duration was instructed. The present findings will be discussed in light of the remarkable flexibility of writing as a motor skill in which writers appear to be able to employ specific strategies to preserve shape in the absence of visual guidance.

Adult↗
PubMed2005

What aspects of vision facilitate haptic processing?

We investigate how vision affects haptic performance when task-relevant visual cues are reduced or excluded. The task was to remember the spatial location of six landmarks that were explored by touch in a tactile map. Here, we use specially designed spectacles that simulate residual peripheral vision, tunnel vision, diffuse light perception, and total blindness. Results for target locations differed, suggesting additional effects from adjacent touch cues. These are discussed. Touch with full vision was most accurate, as expected. Peripheral and tunnel vision, which reduce visuo-spatial cues, differed in error pattern. Both were less accurate than full vision, and significantly more accurate than touch with diffuse light perception, and touch alone. The important finding was that touch with diffuse light perception, which excludes spatial cues, did not differ from touch without vision in performance accuracy, nor in location error pattern. The contrast between spatially relevant versus spatially irrelevant vision provides new, rather decisive, evidence against the hypothesis that vision affects haptic processing even if it does not add task-relevant information. The results support optimal integration theories, and suggest that spatial and non-spatial aspects of vision need explicit distinction in bimodal studies and theories of spatial integration.

Adult↗
PubMed2006

The contribution of peripheral and central vision in the control of movement amplitude.

Past research has revealed that central vision is more important than peripheral vision in controlling the amplitude of target-directed aiming movements. However, the extent to which central vision contributes to movement planning versus online control is unclear. Since participants usually fixate the target very early in the limb trajectory, the limb enters the central visual field during the late stages of movement. Hence, there may be insufficient time for central vision to be processed online to correct errors during movement execution. Instead, information from central vision may be processed offline and utilised as a form of knowledge of results, enhancing the programming of subsequent trials. In the present research, variability in limb trajectories was analysed to determine the extent to which peripheral and central vision is used to detect and correct errors during movement execution. Participants performed manual aiming movements of 450 ms under four different visual conditions: full vision, peripheral vision, central vision, no vision. The results revealed that participants utilised visual information from both the central and peripheral visual fields to adjust limb trajectories during movement execution. However, visual information from the central visual field was used more effectively to correct errors online compared to visual information from the peripheral visual field.

Adolescent↗
PubMed2001

Psychophysics of reading. XX. Linking letter recognition to reading speed in central and peripheral vision.

Our goal is to link spatial and temporal properties of letter recognition to reading speed for text viewed centrally or in peripheral vision. We propose that the size of the visual span - the number of letters recognizable in a glance - imposes a fundamental limit on reading speed, and that shrinkage of the visual span in peripheral vision accounts for slower peripheral reading. In Experiment 1, we estimated the size of the visual span in the lower visual field by measuring RSVP (rapid serial visual presentation) reading times as a function of word length. The size of the visual span decreased from at least 10 letters in central vision to 1.7 letters at 15 degrees eccentricity, in good agreement with the corresponding reduction of reading speed measured by Chung and coworkers (Chung, S. T. L., Mansfield, J. S., & Legge, G. E. (1998). Psychophysics of reading. XVIII. The effect of print size on reading speed in normal peripheral vision. Vision Research, 38, 2949-2962). In Exp. 2, we measured letter recognition for trigrams (random strings of three letters) as a function of their position on horizontal lines passing through fixation (central vision) or displaced downward into the lower visual field (5, 10 and 20 degrees ). We also varied trigram presentation time. We used these data to construct visual-span profiles of letter accuracy versus letter position. These profiles were used as input to a parameter-free model whose output was RSVP reading speed. A version of this model containing a simple lexical-matching rule accounted for RSVP reading speed in central vision. Failure of this version of the model in peripheral vision indicated that people rely more on lexical inference to support peripheral reading. We conclude that spatiotemporal characteristics of the visual span limit RSVP reading speed in central vision, and that shrinkage of the visual span results in slower reading in peripheral vision.

Analysis of Variance↗
PubMed1996

Primate photopigments and primate color vision.

The past 15 years have brought much progress in our understanding of several basic features of primate color vision. There has been particular success in cataloging the spectral properties of the cone photopigments found in retinas of a number of primate species and in elucidating the relationship between cone opsin genes and their photopigment products. Direct studies of color vision show that there are several modal patterns of color vision among groupings of primates: (i) Old World monkeys, apes, and humans all enjoy trichromatic color vision, although the former two groups do not seem prone to the polymorphic variations in color vision that are characteristic of people; (ii) most species of New World monkeys are highly polymorphic, with individual animals having any of several types of dichromatic or trichromatic color vision; (iii) less is known about color vision in prosimians, but evidence suggests that at least some diurnal species have dichromatic color vision; and (iv) some nocturnal primates may lack color vision completely. In many cases the photopigments and photopigment gene arrangements underlying these patterns have been revealed and, as a result, hints are emerging about the evolution of color vision among the primates.

Animals↗
PubMed2004

Effect of laser photocoagulation treatment for diabetic macular oedema on patient's vision-related quality of life.

PURPOSE: To evaluate the effect of laser photocoagulation for diabetic macular oedema (DME) on patients' Vision Related Quality Of Life (VR-QOL) and to investigate associations between changes in self reported VR-QOL and changes in visual acuity following application of laser treatment. METHODS: Prospective cohort study of 55 subjects who underwent laser treatment for DME. Eligible patients with no history of previous laser photocoagulation self-administered the 51-item field-test version of the National Eye Institute Visual Function Questionnaire (NEI-VFQ) prior to treatment and 3 months following the last session of laser application. Visual acuity was measured by means of the Early Treatment of Diabetic Retinopathy (ETDRS) chart. Multi-item scales rating different aspects of VR-QOL were compared prior and after photocoagulation and the change in questionnaire's composite score following treatment was correlated to change in visual acuity and other determinants previously reported as risk factors in the diabetic population. RESULTS: Scale scores associated with general vision, near vision, distance vision, peripheral vision, vision-specific social functioning, vision-specific mental health, expectations for visual function and dependency due to vision were significantly improved following laser treatment. Multivariate models revealed that improvement of the NEI-VFQ composite score was significant in subjects younger than 65 years of age (p = 0.04) who received more laser burns (p = 0.02) and had worse vision-related QOL prior to laser treatment as expressed by the baseline NEI- VFQ composite score (p = 0.03). There was no statistically significant association between change in the composite score following laser treatment and stage of diabetic retinopathy, duration of diabetes or laser settings used during photocoagulation. CONCLUSIONS: Photocoagulation for DME has a beneficial effect on patients' subjective perception of visual function. The use of vision-targeted health status questionnaires in conjunction with the clinical examination appears to provide a more comprehensive overview of individuals' daily well- being following laser treatment.

Aged↗
PubMed2005

A randomized clinical trial of vision therapy/orthoptics versus pencil pushups for the treatment of convergence insufficiency in young adults.

PURPOSE: : The purpose of this article is to compare vision therapy/orthoptics, pencil pushups, and placebo vision therapy/orthoptics as treatments for symptomatic convergence insufficiency in adults 19 to 30 years of age. METHODS: : In a randomized, multicenter clinical trial, 46 adults 19 to 30 years of age with symptomatic convergence insufficiency were randomly assigned to receive 12 weeks of office-based vision therapy/orthoptics, office-based placebo vision therapy/orthoptics, or home-based pencil pushups. The primary outcome measure was the symptom score on the Convergence Insufficiency Symptom Survey. Secondary outcome measures were the near point of convergence and positive fusional vergence at near. RESULTS: : Only patients in the vision therapy/orthoptics group demonstrated statistically and clinically significant changes in the near point of convergence (12.8 cm to 5.3 cm, p = 0.002) and positive fusional vergence at near (11.3Delta to 29.7Delta, p = 0.001). Patients in all three treatment arms demonstrated statistically significant improvement in symptoms with 42% in office-based vision therapy/orthoptics, 31% in office-based placebo vision therapy/orthoptics, and 20% in home-based pencil pushups achieving a score <21 (our predetermined criteria for elimination of symptoms) at the 12-week visit. DISCUSSION: : In this study, vision therapy/orthoptics was the only treatment that produced clinically significant improvements in the near point of convergence and positive fusional vergence. However, over half of the patients in this group (58%) were still symptomatic at the end of treatment, although their symptoms were significantly reduced. All three groups demonstrated statistically significant changes in symptoms with 42% in office-based vision therapy/orthoptics, 31% in office-based placebo vision therapy/orthoptics, and 20% in home-based pencil push-ups meeting our criteria for elimination of symptoms.

Adult↗
PubMedDate not supplied

Description and measurement of handicap caused by vision impairment.

To develop an instrument to describe and quantify handicap caused by vision impairment an item pool was derived from focus groups and from a review of vision-related quality-of-life questionnaires. Only items related to handicap were included and grouped into five subscales. The 76-item 'Impact of Vision Impairment' was administered to 95 people who were vision impaired. Content validity was established by consultation with professionals and with people with impaired vision. Forty-six items remained after the elimination of those found to be irrelevant and others with inter-item correlation coefficients of > or = 0.7. Univariate and multivariate analyses revealed an association between visual acuity and type and degree of handicap on subscales, except emotional reaction to vision loss, which is related to cause of vision impairment. The instrument is responsive to the level of vision loss and discriminates the different performances of people with different causes of vision loss.

Activities of Daily Living↗
PubMed2000

Detection of vision impairment in people admitted to aged care assessment centres.

Vision is not routinely tested when the health of older people is assessed, and the aim of this study was to detect older people with vision impairment for referral to appropriate eye care services. People admitted for assessment and or rehabilitation in three aged care assessment centres had distance and near visual acuity assessed with a simplified vision test. A pinhole test was used when necessary. Referral criteria were distance visual acuity of less than 6/12; near vision of less than N8, and people with diabetes who had not attended a dilated fundus examination in the last 2 years. Visual acuity results were obtained in 93% of patients (685/735). Those unable to perform the vision test were very ill or had severe cognitive impairment. Forty-three per cent of patients (266/646) had impaired vision and, of these, 70.6% (188/266) were referred to eye care specialists. Forty-five per cent were referred to ophthalmologists, 36% to optometrists and 20% to low vision services. This significant proportion of patients with poor vision suggests that vision screening is warranted.

Aged↗
PubMed2002

The measurement of vision disability.

The American Medical Association's (AMA) visual efficiency scale, a vision disability metric based on visual impairment measurements, was adopted in 1925. That scale was based on a 30-year history of theoretical models in vision economics, a misinterpretation of Snellen notation for visual acuity, and an erroneous application of Weber's psychophysical law. The AMA visual efficiency scale survived uncontested for 75 years. In 2001, the AMA adopted a new vision disability scale based on logarithmic transformations of visual acuity and visual field diameter. Like the earlier visual efficiency scale, the new scale is theoretical-it is not supported by any data that speak to the relationship between vision disability and visual impairments. Attempts to measure vision disability date to the early 1980s with the development of self-assessment visual function rating scale questionnaires. Nearly all of the questionnaires developed over the last 20 years use Likert scales, but use them incorrectly. The development of a vision disability metric based on Likert scaling parallels the historical development of other forms of measurement. A tutorial review of psychometrics-classical test theory, item response theory, and Rasch analysis-shows how vision disability measurement scales can be estimated from Likert-type visual function rating scales. We conclude that preliminary data relating measures of vision disability to measures of visual acuity and visual fields support the new AMA vision disability scale.

Algorithms↗
PubMedDate not supplied

Vision screening in a national sample of 11-year-old children.

This report describes the results of vision screening carried out by local health authorities on a national sample of 11-year-old schoolchildren using a standard Snellen chart. Of the 12 772 children tested, 78% had an unaided distant visual acuity of 6/6 or better in both eyes (optimal vision), 10% had a distant visual acuity of 6/9 in the worse or both eyes (near-optimal vision) and 12% had a visual acuity of 6/12 or worse in one or both eyes eyes (definite visual defect). In addition, near visual acuity was tested for 12 737 children and 5% were found to have defective near vision. Glasses had been prescribed for current use in 12% of children but a quarter of those prescribed glasses did not have them available at the time of the test. Testing revealed that 22% of children whose glasses were available had optimal or near-optimal unaided distant vision, the number increasing to 98% when retested wearing glasses. In contrast, 43% of the children who were without their glasses had optimal or near-optimal vision; 27% had a bilateral defect. Amongst the children for whom glasses had not been prescribed 4-6% had a visual defect. A higher proportion of children from non-manual family background than from manual family background had visual impairment and had been prescribed glasses, but there was no significant social class difference amongst the children with visual defects for whom no glasses had been prescribed. A defect of red/green colour vision was recorded in 6% of boys and 1% of girls. The proportion of children with poor visual acuity was similar in the group of children with defective colour vision and the group with normal colour vision.

Child↗
PubMed2006

Outcomes of low-vision services using optometric and multidisciplinary approaches: a non-randomized comparison.

Consecutive patients (n = 215) who were referred to optometric (55%) or multidisciplinary (45%) low-vision services and above 50 years of age were recruited from four hospitals in the Netherlands. They completed two vision-related quality of life questionnaires, the Vision Quality of Life Core Measure (VCM1) and the Low Vision Quality of Life Questionnaire (LVQOL), before their first visit with low-vision services and 1 year later. At follow-up, patients referred to multidisciplinary low-vision services had lower scores on the mobility subscale of the LVQOL than patients referred to optometric low-vision services [5.3 points; 95% confidence interval (CI): 0.2-10.5]. Paired sample t-tests for the two groups of patients taken together show improvement for the VCM1 (3.1 points; 95% CI: 0.6-5.6) and deterioration for the basic aspects of vision (3.5 points; 95% CI: 1.1-5.9) and the mobility (6.6 points; 95% CI: 3.7-9.5) subscales of the LVQOL. In conclusion, people referred to optometric services showed less deterioration in mobility than those referred to multidisciplinary services. No differences were observed for any of the other subscales of the LVQOL and the VCM1. Future research in this field should include randomized controlled designs comparing low-vision services with no treatment or placebo.

Aged↗