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PubMedDate not supplied

Vision testing of young children in the age range 18 months to 4 1/2 years.

Four hundred and twenty-five normal children in the age range 18 months to 4 1/2 years have been studied to determine the percentage of children according to age who can be expected to cooperate in a letter-matching vision test using a key card; to see whether the use of plastic letters to replace the key card lowers the age at which a letter-matching test can be achieved, and to show that children in this age range can do a vision test at 20ft (6m). Acceptance of occlusion using a patch occluder was also examined. The study shows that children effectively begin to cooperate in letter-matching vision tests using a key card from 33 months of age. Replacement of the key card with plastic letters lowers the age to 30 months and thereafter there is a gain of some 25% of children up to 39 months. All children were successfully tested at 20ft (6m). The most difficult age for occlusion was in the age group around the second birthday.

Age Factors↗
PubMed2006

The impact of cataract surgery on visual functioning, vision-related disability and psychological distress: a randomized controlled trial.

PURPOSE: Determine whether there are changes in visual functioning, vision-related disability, health status and mood after cataract surgery. METHODS: 45 adults (mean age = 73.7 years) with bilateral cataract needing surgery for the first eye were recruited from public ophthalmology clinics. The Visual Functioning-14 survey assessed visual disability. Minimal angle of resolution tested visual acuity, and the Melbourne Edge Test examined contrast sensitivity. Demographic, psychological, health and medication use variables were examined. Participants were randomized to either an intervention or control arm. Controls were assessed on two occasions at a 3-month interval before having surgery. The intervention group was assessed 1-2 weeks before surgery and then reassessed 3 months after surgery. RESULTS: Visual functioning improved for those who had cataract surgery with better visual acuity in the better (P = 0.010) and worse (P = 0.028) eye compared with controls. The intervention group reported fewer difficulties with overall vision-related disability (P = 0.0001), reading (P = 0.004) and instrumental activities of daily living (P = 0.010) post-surgery compared with controls. People with improved depression scores (P = 0.048) after surgery had less difficulty with reading compared with those with unchanged or worsened depression scores. Cataract surgery did not improve health status. CONCLUSIONS: First eye cataract surgery is effective in improving outcomes in visual functioning and disability. Improved mood after surgery was related to less vision-related disability compared with unchanged or worse depression.

Aged↗
PubMed2002

Aging, driving and vision.

Older people constitute the fastest growing sector of the driving population and are believed to represent a high risk to road safety, given their high crash rate per distance travelled. The crash characteristics of the elderly also differ from those of younger drivers and generally involve multiple vehicles and more complex driving situations. Although the reasons for this deterioration in driving performance are multi-factorial, the age-related changes in vision are likely to be a significant factor, given the important role of vision in driving. This paper provides an overview of some of the complex issues associated with older drivers and considers how the aging changes in visual function might impact on driving performance. Particular emphasis is placed on the literature linking vision to driving, with emphasis on more recent research. The implications of this research for driver licensing and self-regulation of older drivers are also discussed.

Accidents, Traffic↗
PubMed2002

Protan colour vision deficiency and road accidents.

BACKGROUND: Protans are precluded from holding a commercial driver's licence in Australia because they have a substantially reduced ability to see red lights and have more road accidents involving signal lights. This exclusion has been in place since 1994 but is likely to be abandoned following a current review of medical standards for commercial drivers. This paper reviews the level of risk of road accidents due to protan colour vision deficiency. It also addresses the question of whether it is fair to regard all protans as having a higher risk of road accident because some protans might have a sensitivity to red light that is as good as that of some people with normal colour vision. METHODS: Data of two studies by Verriest and co-workers are re-analysed to estimate the degree of overlap of the protan and colour normal distributions of sensitivity to red light. RESULTS: Field trial data show that protans have a very reduced visual range for red signals compared to colour normal observers but there is considerable variability among both classes of observers and the distributions do overlap. However, some variability is due to differences in observers' choices of a detection criterion, their speed of response and the measurement method. A laboratory study of the spectral sensitivity of protan and colour normal subjects that largely removes these sources' variability shows that all protans have a sensitivity to red light that is less than that of the least sensitive colour normal. CONCLUSION: It is reasonable to conclude that all protans, regardless of the severity of their defect, have a lesser ability to see red signals than colour vision normal observers and for that reason will have a higher risk of road accident.

Accidents, Traffic↗
PubMed2004

Clinical colour vision tests.

The structure and function of the available and significant clinical colour vision tests are reviewed in the light of the needs in the clinical examination of congenital and acquired colour vision deficiencies. The tests are grouped and described as pseudo-isochromatic plates, arrangement tests, matching tests and vocational tests. The colorimetric constructions of the test types are described and the efficiency of their performance and usefulness discussed. Recommendations are made for basic and extended test batteries, when examining of congenital and acquired colour vision deficiencies in the consulting room.

Color Perception Tests↗
PubMed2004

The description of physical signs of illness in photographs by physicians with abnormal colour vision.

BACKGROUND: Physicians with congenital colour vision deficiency (CCVD) have reported difficulties recognising certain physical signs of illness, for example, jaundice, red rashes and pallor, and interpreting coloured charts, diagrams and slide projections. However, there has been little study of the effects of CCVD on the performance of medical practitioners. AIM: The aim of this study was to look for evidence of the effect of CCVD on the ability of physicians to recognise and describe physical signs of illness that have colour as either the main or an important feature. METHOD: Twenty-three general practitioners with CCVD were shown 11 colour photographs depicting colour signs of illness and were asked to describe the signs they saw and rate their confidence in making their descriptions. Their responses were compared to those of 23 age-matched general practitioners with normal colour vision. RESULT: General practitioners with CCVD compared to those with normal colour vision had less ability and confidence in detecting physical signs in the photographs and naming the colours. CONCLUSIONS: The results of this study support other evidence that physicians with CCVD have difficulties detecting some colour signs of illness and naming the colours. Because of the use of photographs the extent of the problem in clinical practice is unknown but medical practitioners with CCVD should be aware of the possibility of failing to detect or correctly assess physical signs that are characterised by colour.

Color Vision Defects↗
PubMed2005

Five cricketers with abnormal colour vision.

Five cricketers with abnormal colour vision, all of whom had mild deuteranomaly, reported occasions when they had lost sight of the ball when the background was the green grass of the playing field or the green of grassy banks or trees surrounding the playing field. While these five cricketers demonstrate that mild deuteranomaly does not preclude playing cricket successfully at a competitive level, their responses to questions at interview suggest that those with more severe forms of abnormal colour vision may be at a disadvantage. This conclusion is consistent with the under-representation of abnormal colour vision in a sample of first class county cricketers in England reported by Goddard and Coull (BMJ 1994; 309 1684-1685).

Adult↗
PubMed2006

Mobility performance of low-vision adults using an electronic mobility aid.

Visually impaired people rank obstacle location and identification as two of the most important mobility problems faced. Traditional mobility aids (the long cane) provide information about where an object is located but only within their limited (one metre) range. Although objects are located when traditional aids are used, it is unlikely that they are identified. The Bristol Mobility Aid (BMA) is an electronic travel aid that presents scene images to remaining residual vision in a number of view formats. Previous work has suggested visually impaired observers have better static object recognition using this aid. We investigated the mobility performance of subjects with retinitis pigmentosa using the BMA by determining the percentage preferred walking speed (PPWS), and the number of errors made with three different BMA headset views on an indoor mobility course. We found low-vision subjects had significantly reduced PPWS in two of the three headset views and interestingly, sighted subjects had significantly reduced PPWS when using the BMA in all three views. The numbers of errors made were significantly higher across all vision groups when the BMA was worn. We found that the BMA does not currently increase mobility in the visually impaired. Results are discussed in terms of modifications that could be made to the aid and methodological limitations.

Aged↗
PubMed2006

Short periods of concordant binocular vision prevent the development of deprivation amblyopia.

Based in part on deprivation studies, it is generally agreed that the development of vision and of the central visual pathways of higher mammals such as cats and primates is experience-dependent. Past deprivation experiments employed periods of exclusively abnormal early visual input. Because of the absence of any normal visual input, such studies indicate only the extremes to which the visual system can change in response to visually driven activity (i.e. its capabilities) rather than provide insight into the role of early visual input in normal development (i.e. what it actually does). We examined the possibility that certain visual input, i.e. normal concordant binocular vision, may be more efficacious than others with respect to its effects on the developing visual system and on vision. On a daily basis, one type of visual input, i.e. normal binocular experience (BE), was pitted against abnormal (monocular exposure, ME) input in order to see if one was more effective. We show that 2 h of daily normal concordant, but not discordant, BE outweighs or protects against as much as 5 h of daily abnormal input to permit the development of normal grating acuity and alignment accuracy in the two eyes. Further, we show that splitting the period of BE into two 1-h periods straddling the period of ME was ineffective, thereby indicating the 2 h of BE each day must be continuous to protect against the development of amblyopia.

Adaptation, Physiological↗
PubMed2004

Self-optimised vision correction with adaptive spectacle lenses in developing countries.

It is estimated by the World Health Organization that about 1 billion people in the developing world would benefit immediately from distance vision and near vision correction if it were available to them. Here we address this problem and provide a solution by correcting vision in the field with adaptive liquid-filled variable focus lenses. We describe the details of the lens and present the results of a series of experiments performed in Ghana, Nepal, Malawi and South Africa that demonstrate that it is possible by simple means to self-determine and obtain correct refraction using such lenses.

Adolescent↗
PubMed2004

Low vision services in South Devon: a multi-agency, multi-disciplinary approach.

Since 1994, the Low Vision Service in South Devon has been provided by a multi-agency, multi-disciplinary team. The team comprises of staff from Devon Social Services Sensory Team, Optima Low Vision Services Ltd, Royal National Institute for the Blind (RNIB) Manor House, Devon and Torbay Special Education Services and South Devon Healthcare Trust. In the 9 years of operation this service has been independently audited twice for patient satisfaction levels and compliance level in the use of low vision aids (LVAs). The results of the most recent service audit questionnaire reveal a high and constant patient satisfaction level with 92% of patients who answered the question reporting that the service was sufficient to meet their needs. The number of patients who used LVAs at least weekly was 88% of those answering the question. Plans for the future expansion of the service include the further development of interdisciplinary working.

Charities↗
PubMed2004

Evaluation of a prototype Minified Augmented-View device for patients with impaired night vision.

An evaluation was carried out of the first prototype (LV-3) of a new night vision device, which incorporates visual field expansion through minification (Minified Augmented-View), to provide feedback for continuing development. Six subjects with night blindness completed visual function measurements and indoor mobility assessments without a device, with the LV-3 and with a commercially available comparison device (the Multi-Vision) at light levels representative of well lit and poorly lit streets. Device performance and potential benefits in real-world situations were evaluated at four outdoor locations (well lit to very dark). Results indicate that the see-through nature and spectacle-frame mounting of the LV-3 address some of the cosmetic and ergonomic disadvantages of currently available devices; however insufficient light sensitivity of the prototype camera limited LV-3 performance. With improved camera sensitivity and full implementation of the Minified-Contours Augmented-View concept in the next prototype, patients might be able to make better use of the novel field expansion and vision multiplexing features to aid outdoor night mobility.

Adult↗
PubMed1976

A low-vision clinic at a home for the aged.

The objective of a low-vision clinic developed at the Jewish Home and Hospital for Aged was to improve the visual capabilities of the residents who were not helped by the regular eye clinics. Eighty-three patients (72 women, 11 men) were examined the first year. Ages ranged from 71 to 101 years. The causes of poor vision were mainly senile macular degeneration, cataract formation, chronic glaucoma, severe myopia, aphakia, and combinations of these diseases. Vision ranged from 10/50 at 10 feet (20/100 at 20 feet) in the better eye, to only the ability to distinguish hand movements or to perceive light. With the use of visual aids such as distance or reading glasses and various forms of magnifying glasses, some improvement occurred in 61 of the 83 patients. The follow-up examination was within one year in most cases. It was concluded that in order to examine and treat such patients properly, much more time and patience were required than is usually possible in a regular eye clinic. This involved the help of more social workers and volunteer assistants. Nevertheless, the results were worthwhile for this type of patient.

Aged↗
PubMed1998

Barriers to seeking care following school vision screening in Rochester, Minnesota.

School vision screening provides an effective way to identify children who require vision therapy, usually glasses. To benefit from screening, children with abnormal screening test results must receive follow-up eye care, but care may be delayed for months or years. This project used community focus groups in Rochester, Minn., to identify barriers that may delay seeking professional care following school vision screening. Major barriers identified included lack of community awareness about the frequency and potential effect of refractive errors in children, a parental perception of inadequate communication between schools and the parents and community, high cost of corrective lenses, limited availability of convenient eye care appointments, and adolescents reluctance to wear glasses. Program planners developed a community action plan to address the perceived barriers.

Adolescent↗
PubMed1992

Scotopization and pseudoprotanomaly in blue-yellow/colour vision defects.

With a routine clinical colour vision test battery we found scotopization in 32% of retinal diseases presenting with pseudoprotanomaly as sign of an acquired type III blue-yellow colour vision defect. In blue-yellow colour vision defects of retinal origin scotopization is a transient phenomenon, present in early stages of the disease, but it is not an obligatory finding. There is no evident relationship between visual acuity and scotopization.

Color Perception Tests↗
PubMed1988

Spatial vision of the achromat: spatial frequency and orientation-specific adaptation.

1. The psychophysical technique of selective adaptation to stationary sine-wave gratings of varying spatial frequency and orientation was used to investigate the central processing of spatial information in the visual system of the complete achromat. 2. For adapting spatial frequencies of 1 and 2 cycles/deg, the spatial frequency and orientation selectivity of contrast threshold elevation is similar for achromatic and trichromatic vision. 3. For adapting frequencies below 1 cycle/deg, the achromat shows threshold elevations of normal magnitude with symmetrical spatial frequency and orientation tuning for adapting frequencies as low as 0.09 cycles/deg with 'bandwidth' estimates similar to those found at high frequencies in the trichromat. Below 0.66 cycles/deg no after-effect could be obtained in the trichromat, and the frequency tuning at 0.66 cycles/deg was skewed towards higher frequencies. 4. The interocular transfer of low-frequency adaptation in the achromat was 50%, which is the same value obtained at higher frequencies. 5. The time course of the decay of low spatial frequency adaptation in the achromat was similar to that found at higher frequencies. 6. Control experiments show no low-frequency adaptation in peripheral vision or in central vision in the dark-adapted trichromat indicating that low spatial frequency adaptation cannot be elicited through the rod system of the trichromat. 7. It is proposed that the observed range shift of adaptable spatial frequency mechanisms in the achromat's visual cortex is the result of an arrest at an early stage of sensory development. The visual cortex of the achromat is comparable, with respect to spatial processing, to that of the young, visually normal human infant.

Adaptation, Ocular↗
PubMed2000

Sparse coding and decorrelation in primary visual cortex during natural vision.

Theoretical studies suggest that primary visual cortex (area V1) uses a sparse code to efficiently represent natural scenes. This issue was investigated by recording from V1 neurons in awake behaving macaques during both free viewing of natural scenes and conditions simulating natural vision. Stimulation of the nonclassical receptive field increases the selectivity and sparseness of individual V1 neurons, increases the sparseness of the population response distribution, and strongly decorrelates the responses of neuron pairs. These effects are due to both excitatory and suppressive modulation of the classical receptive field by the nonclassical receptive field and do not depend critically on the spatiotemporal structure of the stimuli. During natural vision, the classical and nonclassical receptive fields function together to form a sparse representation of the visual world. This sparse code may be computationally efficient for both early vision and higher visual processing.

Action Potentials↗
PubMed1995

Numbers and ratios of visual pigment genes for normal red-green color vision.

Red-green color vision is based on middle-wavelength- and long-wavelength-sensitive visual pigments encoded by an array of genes on the X chromosome. The numbers and ratios of genes in this cluster were reexamined in men with normal color vision by means of newly refined methods. These methods revealed that many men had more pigment genes on the X chromosome than had previously been suggested and that many had more than one long-wave pigment gene. These discoveries challenge accepted ideas that are the foundation for theories of normal and anomalous color vision.

Base Sequence↗