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PubMed1995

A history of low vision and blind rehabilitation in the United States.

The author presents a history of services for the blind and those with low vision in the United States focusing on the areas of orientation and mobility, and rehabilitation teaching. The controversies involving the development of these specialties are discussed. Emphasis is placed on the role of Father Thomas Carroll in the establishment of low vision and blind services for the military and veterans administrations. Published data regarding the past role of ophthalmologists in obtaining low vision services for patients is reviewed. The opportunity for a more active role for ophthalmologic involvement in the rehabilitation of the low vision and blind patient is discussed.

Blindness↗
PubMed2003

[Influence of long term occupational exposure to solvents on colour vision].

BACKGROUND: The study was designed to determine the influence of chronic occupational exposition of organic solvent mixtures on colour vision of car painters. SUBJECTS AND METHODS: The 123 subjects (2 groups differing in organic solvents exposure and 1 control group) were examined using Ishihara-Panel, Lanthony Desaturated Panel D-15, Velhagen-Panel, and Tritan-Album. RESULTS: In the Velhagen-Panel 3% of the probands currently exposed to organic solvents, and 11% of formerly exposed probands developed a blue/yellow vision defect for the right eye. All control subjects perfectly finished this panel. In the Tritan-Album 3% of currently exposed subjects and 26% of formerly exposed painters expressed a blue/yellow vision defect for the right eye, but also 7% of controls showed anomalies. Similar results were found for both panels with the left eye. The CCI difference in the D-15 test was significant between all three groups. CONCLUSION: The impaired colour vision may also be an important indicator of neuro-ophthalmological effects after long-term occupational exposure to organic solvents.

Adult↗
PubMed2001

Quality of vision with presbyopic contact lens correction: subjective and light sensitivity rating.

PURPOSE: To quantify the quality of vision achieved with multifocal and bifocal contact lenses. METHODS: We analyzed differential light sensitivity by computerized automatic perimetry in 21 patients wearing monofocal soft contact lenses (group 1, controls) and multifocal and bifocal contact lenses (groups 2 and 3, respectively). Seven patients each were fitted with multifocal or bifocal contact lenses; seven patients were without contact lenses (without correction for testing the visual periphery and with near-vision correction using monofocal contact lens for testing the central 30 degrees of vision). The type of correction was randomly changed in a crossover fashion so that each eye was examined at different times with different corrections. Humphrey 640 VFA computerized automated perimetry was used to test visual fields at baseline, 45 days, and 3, 4.5, and 6 months. RESULTS: A statistically significant difference was found between the global sensitivities (GS) of the central visual field in patients with near-vision monofocal contact lenses and with bifocal contact lenses (P=0.0273) and between the GS of the central visual fields with multifocal contact lenses and with bifocal contact lenses (P=0.0261). In both cases, the GS were significantly reduced with bifocal contact lenses (total GS: group 1, 11256 dB (Decibels); group 2, 11154 dB; group 3, 10679 dB). CONCLUSIONS: The results indicate that there is reduced differential light sensitivity in the central 30 deg of the visual field with bifocal contact lenses compared with multifocal contact lenses and monofocal contact lenses (controls).

Contact Lenses, Hydrophilic↗
PubMed1998

Qualitative color vision impairment in toluene-exposed workers.

OBJECTIVE: The aim of this study was to evaluate whether toluene, like many other organic solvents and solvent mixtures, could impair color vision. SUBJECTS AND METHODS: We investigated color vision impairment in three groups of workers, two groups occupationally exposed to toluene and a nonexposed group. The first exposed group, group E1, comprised 41 workers (median value of toluene in air 35.00 ppm, range 11.3-49.3 ppm) and the second exposed group, group E2, comprised 32 subjects (median value of toluene in air 156.00 ppm, range 66.0-250.0 ppm). The nonexposed group, group NE, comprised 83 subjects. Color vision was evaluated by the Lanthony D-15 desaturated test according to Verriest's classification: type I, loss in the red-green range; type II, loss in the blue-yellow and red-green ranges, and type III, loss in the blue-yellow range. Subjects were classified as dyschromates if specific acquired loss was determined in at least one eye. In both exposed groups, exposure was evaluated by measurement of the concentration of toluene in the ambient air and in the blood. In group E2, level of hippuric acid and orthocresol in urine after the work shift were also determined. The Mann-Whitney U-test, t-test, chi 2-test, and Spearman's rank correlation and multiple regression analysis were used for statistical analysis. RESULTS: Type III dyschromatopsia was detected in all groups examined: 26.6% of the workers in group NE, 31.7% of those in group E1, and 50% of those in group E2. As many as 15.6% of the workers in group E2, 4.8% of those in group E1, and only 1.2% of those in group NE had type II dyschromatopsia. A statistically significant difference in the prevalence of total dyschromatopsia (type III + type II) was established among the three examined groups together (chi 2 = 14.13; df = 2; P < 0.01), between group E2 and group E1 (chi 2 = 4.96; P < 0.05), and between group E2 and group NE (chi 2 = 12.50; P < 0.005), whereas no significant difference was found between groups E1 and NE. Type III dyschromatopsia was significantly correlated with age in group NE (P < 0.01) and in group E1 (P < 0.005). In group E2, both type II (P < 0.05) and type III dyschromatopsia correlated with toluene in ambient air and with the duration of exposure to toluene (both P < 0.005). In group E2, total dyschromatopsia correlated significantly with toluene in ambient air and in blood (both P < 0.05) as well as with hippuric acid in urine after the work shift (P < 0.001). CONCLUSION: This study suggests that toluene can impair color vision.

Adult↗
PubMed1997

Vitamin A deficiency and nocturnal vision in teenagers with cystic fibrosis.

UNLABELLED: The aim of this study was to document plasma retinol status and nocturnal vision in ten eutrophic adolescents with cystic fibrosis (CF) receiving daily retinol supplementation. Plasma retinol, alpha and beta carotenes and retinol binding protein were measured in ten clinically stable CF patients (mean age: 14.3 years; Shwachman score: 80-100). Nocturnal vision evaluation was performed with a Beyne optometer. Plasma retinol (mean 0.42 +/- 0.16 mg/l), alpha carotene and beta carotene levels were below the lower limit of normal in all but one patient. Five out of ten patients with normal standard opthalmological examination presented a poor (n = 3 patients) or a pathological (n = 2) dark adaptation test. These two patients showed a dramatic increase in nocturnal vision after 1 year of adapted retinol supplementation. CONCLUSION: Low vitamin A levels occur frequently in clinically stable, eutrophic and retinol supplemented CF adolescents. Since vitamin A deficiency is associated with poor nocturnal vision and since this pattern can be reversed by adapted retinol supplementation, we recommend monitoring plasma vitamin A levels in CF patients and evaluation of dark adaptation in retinol deficient patients.

Adaptation, Physiological↗
PubMed1995

The effects of vision and task complexity on Hoffmann reflex gain.

Previous research demonstrates modulation of the Hoffmann reflex amplitude and gain during changes in environmental conditions. H-reflex gain (defined in this study as the ratio of H-reflex amplitude to average soleus background EMG) is considered a functional measure of reflex modulation. In this study the effects of manipulating visual input and surface stability were to investigated in 17 subjects under four experimental conditions: (1) vision-stable surface, (2) no vision-stable surface, (3) vision-unstable surface, and (4) no vision-unstable surface. In each condition, subjects performed fifteen trials of a single leg stance for 7 s. The H-reflex was electrically elicited at the end of each trial by delivering a 1 ms square wave stimulation to the tibial nerve in the popliteal online for each trial (sampling rate = 2 kHz). An analysis of variance revealed significant decreases in H-reflex gain for the visual (F1.16 = 4.71, P < 0.05) and, surface conditions (F1.16 = 7.67, P < 0.05), however there was no interaction (F1.16 = 0.48, P < 0.05), between these variables. These results suggest that supraspinal mechanisms, possibly presynaptic inhibition, modulate H-reflex gain across environmental conditions. We conclude that visual and possibly cutaneous inputs were responsible for driving presynaptic inhibition and thus decreasing H-reflex gain.

Analysis of Variance↗
PubMed1993

Do postural responses to transient and continuous perturbations show similar vision and amplitude dependence?

This study compares the influence of vision and perturbation amplitude on postural center-of-pressure responses to transient (acceleration pulse) versus continuous (pseudorandom acceleration) platform-translation perturbations. To control possible confounding effects, efforts were directed at making the perturbations unpredictable and matching the transient and continuous waveforms in terms of frequency content and level of challenge to stability. It was hypothesized that, under these conditions, the same control mechanisms would be activated; hence, responses to transient and continuous perturbations would show similar vision and amplitude dependence. A repeated-measures experimental design was used to test 12 healthy males. The transient and continuous perturbations were each administered at three acceleration amplitude levels, in random order, and the tests were repeated under eyes-open and blindfolded conditions. When order-of-testing effects were taken into account, the results failed to demonstrate any differences between transient and continuous postural control with regard to the influence of vision, as both types of response were unaffected by vision deprivation. This finding is consistent with the experimental hypothesis. Responses to the two types of perturbation did appear to differ, however, with regard to the influence of perturbation amplitude, as the transient-perturbation responses showed greater evidence of nonlinearity. This finding would seem to reject the hypothesis that the responses to transient and continuous perturbations would show similar amplitude dependence. However, it is suggested that the amplitude distribution of the particular continuous waveform that was used, rather than the continuous nature of the perturbation per se, may have led to the greater linearity in the continuous-perturbation responses. Although the present results fail to provide unequivocal support for the hypothesis that the same control mechanisms are utilized in transient and continuous balance recovery, they do demonstrate that distinctions between these two types of postural task are not nearly so clearcut as has been suggested. Nonetheless, from a practical perspective, the findings of substantial nonlinearity indicate that attempts to predict responses to transient perturbations from continuous-perturbation tests should be performed with caution.

Acceleration↗
PubMedDate not supplied

Uses of vision by rats in play fighting and other close-quarter social interactions.

Enucleated juvenile rats were compared to sighted juveniles, and tested over six trials. In some of these trials, the vibrissae were clipped and the test chamber was flooded with white noise. Even though the enucleated rats played, they did so in an atypical manner. They tended to initiate more playful and other social contacts, and were more likely to defend themselves if contacted. When they did defend themselves, they adopted behavior patterns that were more likely to evade the partner's attack. In addition, the enucleated rats were hypersensitive to the partner, being more likely to respond defensively when contacted further from the nape (the main play target). All these changes in play fighting by nonsighted rats suggest that the loss of vision leads to motivational changes in activity and reactivity, and so has an indirect effect on play behavior. In addition, direct evidence is also provided to show that vision is used to orient attacks to the nape. When the vibrissae were closely clipped, the sighted rats continued to make direct attacks on the partner's napes, whereas the nonsighted rats did not. Rather, they first contacted some other part of the partner's body and then oriented to the nape. Another test paradigm was used to determine whether vision is used to trigger defensive responses. The rats were partially food deprived as adults and were filmed in a food wrenching and dodging situation where one rat was given a food pellet and the other allowed to steal it. Measurement of the distance at initiation of the lateral swerve away from the approaching partner (i.e., dodge) showed that when the vibrissae are clipped, the sighted rats continued to initiate dodges at the same distance, whereas the nonsighted rats could not. Therefore, vision appears to have an active role in organizing movement sequences of attack and defense in play fighting and other close-quarter interactions.

Aggression↗
PubMedDate not supplied

Preschool vision screening for amblyopia and strabismus. Programs, methods, guidelines, 1983.

Amblyopia and strabismus, which afflict at least 5% of children, require treatment early in life for best visual results. At present, many such children are treated late or not at all. Mass screening at preschool age, and perhaps ultimately of infants, appears the only viable solution to this problem. To ascertain the present status of preschool screening in the United States, on-site visits, mail questionnaires and telephone interviews were used to study existing preschool vision screening programs at the federal, state and private organization levels. We estimate that, at most, 21% of preschool children receive any form of vision screening. Only two states, Michigan and Minnesota, have legislated requirements for such screening. Several organizations have attempted to establish screening guidelines, with suggestions of specific test and referral criteria. These guidelines are reviewed. The guidelines are of particular interest because screening programs following them typically indicate far lower prevalence rates than most studies indicate actually exist, suggesting that the guidelines result in underreferrals. In order to assess this matter, vision screening methods appropriate for preschoolers or infants, based on current evidence, are reviewed. Stereoscopic testing, utilizing a random dot stereogram format, appears the best instrument available for amblyopia and strabismus screening, but large scale comparative studies of the different test methods are needed to arrive at a final determination. Suggestions are made for the physician interested in initiating preschool vision screening programs.

Amblyopia↗
PubMed1994

Ultraviolet vision in birds: what is its function?

Although UV vision was first demonstrated in birds in the early 1970s, its function is still unknown,. Here we review the evidence for UV vision in birds, discuss the special properties of UV light, lay out in detail hypotheses for the function of UV vision in birds and discuss their plausibility. The main hypotheses are that UV vision functions: (i) in orientation, (ii) in foraging and (iii) in signaling. The first receives support from studies of homing pigeons, but it would be unwise to conclude that orientation is UV's primary function in all birds. It is especially important to test the signalling hypothesis because bird plumage often reflects UV and tests of theories of sexual selection have virtually always assumed that birds perceive plumage "colours" as humans do. A priori this assumption is unlikely to be correct, for unlike humans, birds see in the UV, have at least four types of cones and have a system of oil droplets which filters light entering individual cones.

Animals↗
PubMedDate not supplied

The influence of vision on computerized neurobehavioral test scores: a proposal for improving test protocols.

Computerized tests of neurobehavioral function are frequently administered in neurotoxicological studies with little attention given to the optical properties of test stimuli or to the vision of subjects. Yet many test stimuli are small or briefly presented, and test endpoints often involve short reaction times. Stimulus detection and reaction time are known to be strongly dependent upon stimulus luminance, contrast, and size, as well as on the subject's visual abilities. The current study assessed the influence of visual contrast sensitivity on Neurobehavioral Evaluation System 2 (NES2) test results in three data sets. Analyses indicated that vision was associated with up to 24% of the variance (Hand Eye Coordination test) in NES2 scores, even when visual acuity was normal, and that vision often influenced the significance of group differences. It is suggested that researchers measure the luminance, contrast, and size of test stimuli, the distance from the subject's eyes to the monitor, and the subject's visual contrast sensitivity. The measurement and control of stimulus parameters and the inclusion of visual function scores in analysis models could reduce the variability among computerized test scores both within and between studies. Models that assess the influence of vision on computerized test results may help to identify the CNS domains and specialized functions adversely affected by neurotoxicant exposures.

Adolescent↗
PubMed2006

Patient perceptions of discomfort and changes in vision and functional status associated with intravitreal triamcinolone injection.

PURPOSE: To assess patient perceptions concerning discomfort and changes in vision associated with intravitreal triamcinolone injections (IVTA). DESIGN: Prospective consecutive case series. METHODS: Fifty patients treated with IVTA between June 2003 and February 2005 were interviewed by telephone 10 to 12 weeks after injection. Each question was answered on a 1 to 5 scale. RESULTS: There was no significant difference in reported amount of ocular discomfort pre-injection vs post-injection (1.0 vs 1.1, respectively). Expected pain level (2.9) was higher than the actual pain level (1.6; P < .001). Patients' self-reported vision improved from 2.7 to 3.7 (P < .001). Thirty (60%) patients reported improved vision and 20 (40%) reported no change. Thirty-three (66%) patients reported more visual improvement than expected. CONCLUSIONS: Patient expectation of discomfort during IVTA was greater than their actual experience; approximately two-thirds of patients reported improved vision and about one-third reported improved functional status after injection.

Adult↗
PubMed2005

Pharmacological properties of motion vision in goldfish measured with the optomotor response.

In goldfish, the retinal pathways involved in motion coding have been demonstrated to have an L-cone dominated action spectrum (S. Schaerer, C. Neumeyer, Motion detection in goldfish investigated with the optomotor response is "color blind", Vision Res. 36 (1996) 4025-4034). The neurotransmitters involved in retinal motion coding mechanisms, and the relevance of these retinal motion coding mechanisms for motion perception, are little investigated in fish. In this study, the optomotor response was used to investigate the effect of antagonists on different receptor types for acetylcholine (ACh), GABA, for the dopamine D2-receptor (D2-R) - which is known to modulate the action spectrum in motion coding (C. Mora-Ferrer, K. Behrend, Dopaminergic modulation of photopic temporal transfer properties in goldfish retina investigated with the ERG, Vision Res. 44 (2004) 2067-2081) - and of an agonist for against the mGluR6-receptor (mGluR6) on goldfish motion vision in the photopic range. Blockade of nicotinic ACh-R, GABAa-R and both GABAa- and GABAc-R eliminated the optomotor response completely. Neither a muscarinic ACH-R antagonist, a D2-R antagonist or a mGluR6-agonist affected goldfish motion vision. The pharmacological profile of the goldfish optomotor response resembles the pharmacological profile of direction-selective ganglion cells (DS-GC) described for vertebrate retinas in electrophysiological experiments, e.g. (S. Weng, W. Sun, S. He, Identification of ON-OFF direction-selective ganglion cells in the mouse retina, J. Physiol. 562 (2005) 915-923). This indicates that cells with direction-selective receptive field properties exist in the goldfish retina. It is proposed that these cells provide the input for the full field motion perception in goldfish.

Acetylcholine↗
PubMed2005

The effects of blurred vision on the mechanics of landing during stepping down by the elderly.

Visual impairment is an important risk factor for falls. However, relatively little is known about how visual impairment affects stair or step negotiation. The aim of the present study was to determine the effects of blurred vision on the mechanics of landing during stepping down by the elderly. Twelve elderly subjects (72.3 +/- 4.7 year) stepped down from three levels (7.2 cm, 14.4 cm and 21.6 cm). Step execution time, ankle and knee joint angular displacements at the instance of ground contact, and vertical landing stiffness and the amount of bodyweight supported by the contralateral (support) limb during the initial contact period were recorded. Measurements were repeated with vision blurred by light scattering lenses. With blurred vision, step execution time increased (P < 0.05), knee flexion and ankle plantar-flexion increased (P < 0.05), vertical stiffness decreased (P < 0.01), and the amount of bodyweight being supported by the contralateral leg increased (P < 0.05). These findings suggest that under conditions of blurred vision, subjects were more cautious and attempted to 'feel' their way to the floor rather than 'drop' on to it. This may have been an adaptation to increase the kinaesthetic information from the lower limb to make up for the unreliable or incomplete visual information. Correcting common visual problems such as uncorrected refractive errors and cataract may be an important intervention strategy in improving how the elderly negotiate stairs.

Accidental Falls↗
PubMed2005

ASCRS Binkhorst lecture 2004: the search for perfect vision: ophthalmology's Holy Grail?

Wavefront technology and wavefront-based vision correction are major advances but will not, in isolation, achieve the goal of perfect vision. Study of the animal kingdom teaches lessons of adaptation, leading to the conclusion that the human visual system is probably optimized for our ancestral hunter-gatherers, but today's visual demands have developed faster than the pace of evolution. Psychophysical studies of perception emphasize the importance of the visual processing system in the totality of visual function, with application today in areas such as multifocal intraocular lenses. The goal of "perfect vision" is more than optimized optics. A better understanding of visual function can be achieved only by a cooperative effort of ophthalmologists, vision scientists, and psychophysicists.

Animals↗
PubMed2006

Batting with occluded vision: an in situ examination of the information pick-up and interceptive skills of high- and low-skilled cricket batsmen.

The capability of cricket batsmen of different skill levels to pick-up information from the pre-release movement pattern of the bowler, from pre-bounce ball flight, and from post-bounce ball flight was examined experimentally. Six highly skilled and six low-skilled cricket batsmen batted against three different leg-spin bowlers while wearing liquid crystal spectacles. The spectacles permitted the specific information available to the batsmen on each trial to be manipulated such that vision was either: (i) occluded at a point prior to the point of ball release (thereby only allowing vision of advance information from the bowler's delivery action); (ii) occluded at a point prior to the point of ball bounce (thereby permitting the additional vision of pre-bounce ball flight); or (iii) not occluded (thereby permitting the additional vision of post-bounce ball flight information). Measurement was made on each trial of both the accuracy of the definitive (forward-backward) foot movements made by the batsmen and their success (or otherwise) in making bat-ball contact. The analyses revealed a superior capability of the more skilled players to make use of earlier (pre-bounce) ball flight information to guide successful bat-ball interception, thus mirroring the greater use of prospective information pick-up by skilled performers observed in other aspects of batting and in other time-constrained performance domains.

Humans↗
PubMed2006

Vision as Bayesian inference: analysis by synthesis?

We argue that the study of human vision should be aimed at determining how humans perform natural tasks with natural images. Attempts to understand the phenomenology of vision from artificial stimuli, although worthwhile as a starting point, can lead to faulty generalizations about visual systems, because of the enormous complexity of natural images. Dealing with this complexity is daunting, but Bayesian inference on structured probability distributions offers the ability to design theories of vision that can deal with the complexity of natural images, and that use 'analysis by synthesis' strategies with intriguing similarities to the brain. We examine these strategies using recent examples from computer vision, and outline some important implications for cognitive science.

Algorithms↗
PubMed2005

A mutation in the silver gene leads to defects in melanosome biogenesis and alterations in the visual system in the zebrafish mutant fading vision.

Forward genetic screens have been instrumental in defining molecular components of visual function. The zebrafish mutant fading vision (fdv) has been identified in such a screen due to defects in vision accompanied by hypopigmentation in the retinal pigment epithelium (RPE) and body melanocytes. The RPE forms the outer most layer of the retina, and its function is essential for vision. In fdv mutant larvae, the outer segments of photoreceptors are strongly reduced in length or absent due to defects in RPE cells. Ultrastructural analysis of RPE cells reveals dramatic cellular changes such as an absence of microvilli and vesicular inclusions. The retinoid profile is altered as judged by biochemical analysis, arguing for a partial block in visual pigment regeneration. Surprisingly, homozygous fdv vision mutants survive to adulthood and show, despite a persistence of the hypopigmentation, a partial recovery of retinal morphology. By positional cloning and subsequent morpholino knock-down, we identified a mutation in the silver gene as the molecular defect underlying the fdv phenotype. The Silver protein is required for intralumenal fibril formation in melanosomes by amylogenic cleavage. Our data reveal an unexpected link between melanosome biogenesis and the visual system, undetectable in cell culture.

Amino Acid Sequence↗