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PubMed1986

Tactual habituation and discrimination of form in infancy: a comparison with vision.

Tactual discriminative abilities out of the control of vision are studied in 5-month-old infants, and compared with their visual discriminative abilities. The relevance of a habituation/reaction to novelty procedure in the tactual modality is tested. An infant control procedure is used in both modalities on 2 independent samples of 32 infants each. Habituation and discrimination occur tactually as well as visually, the duration of holds decreasing more than the duration of looks. Accumulated holding time is 3 times longer than accumulated looking time. Analogies and discrepancies between tactual and visual habituations are discussed, and the problem of sensory dominance is raised. Such results are basic to studies on cross-modal transfer, from vision to touch as well as from touch to vision.

Attention↗
PubMed1986

Origins of colour vision standards within the transport industry.

Colour vision standards should reflect changes in our understanding of the nature of these defects as well as technological advances that place less importance upon the visual senses of the human operator. Therefore it is suggested that visual standards be subject to routine reviews in order to assess their suitability for modern work environments. This paper gives a chronological account of the introduction of colour vision standards by several national transport authorities and identifies historical reasons that led to their implementation. It is concluded that the same factors that gave rise to the adoption of early colour vision standards are still relevant for modern transport systems. However the recent deployment of automatic or semi-automatic control or navigational systems has substantially altered man's role from being the primary source of information input to one of a monitoring process. This has generated a good deal of debate and uncertainty regarding the level of responsibility that a human operator has for the control of modern transport vehicles. Nevertheless, it is argued that in the absence of complete automation some type of visual standard is needed whenever visual judgements must be made by human observers.

Aerospace Medicine↗
PubMed1998

A rural vision of a healthy community.

Nurses can take a leadership role in the process of helping rural Americans to recognize and implement their vision of a healthy community. This necessitates an understanding of rural communities' perceptions of health and health care and allows nurses to more appropriately provide primary health care. As defined by the World Health Organization, primary health care is comprised of concepts of essentiality, community participation, intersectorial collaboration, access, and empowerment (Barnes et al., 1995). A focused ethnography involving 150 residents was conducted in a midwestern rural community and included 56 personal and 8 focus group interviews. A qualitative analysis of responses to the question, "What is your vision of a healthy community?" was conducted using Leininger's (1985) categories of economics, social-kinship, cultural, political-legal, religion, technology, and education. An eighth category of environmental concern emerged from the data. Responses were further assimilated into descriptive statements reflecting the community's vision of a healthy community, including issues of accessible and technologically adequate healthcare, job availability, strong community support by schools and churches, a caring community membership, and an attractive, pollution-free environment. This analysis demonstrates the need for application of primary health care at the level of community in designing services to achieve healthy rural communities.

Adult↗
PubMed2006

Treatment of uncorrected refractive error improves vision-specific quality of life.

OBJECTIVES: To evaluate the benefit of eyeglasses and magnifiers in elderly patients with uncorrected refractive errors. DESIGN: A single-center, randomized, prospective, controlled trial (September 2001 to August 2003). SETTING: Los Angeles County, California. PARTICIPANTS: One hundred thirty-one community-dwelling persons aged 65 and older who had habitual distance visual acuity of 20/32 or worse and whose distant visual acuity, near visual acuity, or both could be improved with eyeglasses, a magnifier, or both by two lines of acuity or more. INTERVENTION: Sixty-six were randomized to receive a prescription and voucher for free eyeglasses, a magnifier, or both immediately, and 65 were randomized to receive a prescription and voucher after the 3-month follow-up visit (the control group). MEASUREMENTS: Primary outcome was vision-specific functioning as measured using the 25-item National Eye Institute-Visual Functioning Questionnaire (NEI-VFQ). Secondary outcomes were distance and near visual acuity and overall functioning as measured using the Rosow-Breslau function questionnaire. RESULTS: In the intention-to-treat analysis of 3-month follow-up data, participants who received the eyeglasses prescription and voucher immediately had greater improvement in NEI-VFQ composite scores than the control group (P<.01). They also had greater improvement in perceptions of their general vision (P<.01), distance visual acuity (P=.03), near visual acuity (P=.04), and mental health (P=.02). CONCLUSION: Correction of uncorrected refractive error, one of the leading causes of visual impairment in older people, improved the vision-specific quality of life of community-dwelling older persons.

Aged↗
PubMed1979

The response characteristics of an inhibitory binocular interaction in human vision.

1. The contrast threshold level for visual detection of a linear grating consisting of parallel light and dark bars is increased by adaptation to a high contrast grating of spatial characteristics similar to those of the test grating (e.g. Blakemore & Campbell, 1969). This so-called contrast threshold elevation effect is significantly reduced if two adaptation gratings, with appropriate different spatial characteristics, are presented one to either eye (Ruddock & Wigley, 1976). We have studied the contrast threshold elevation effect obtained with a test and an adaptation grating presented to one eye and a second adaptation grating, referred to as the conditioning grating, presented to the other. 2. Preliminary data are presented for three subjects with normal stereoscopic vision. In each case, the contrast threshold elevation effect for a pair of spatially identical test and adaptation gratings is significantly reduced by a conditioning grating of spatial frequency in the range 1-5 c/deg. 3. Reduction in the contrast elevation effect is observed whether the conditioning and adaptation gratings are of the same or of different wave-lengths and the effect of the conditioning grating increases to a steady-state level over a period of some 30 sec following onset of its presentation. 4. Measurements were made with a 5 deg diameter circular test grating presented at retinal locations up to 8 deg in the horizontal and vertical meridians from a foveal fixation point. It was found that in the horizontal meridian, the amplitude of the suppression effect associated with the conditioning grating falls as the displacement angle of the test field from the fixation point increases. For displacements in the vertical meridian, however, the amplitude of the suppression effect is virtually independent of the retinal location of the test field. 5. Under experimental conditions which yield suppression of the contrast threshold elevation effect for subjects with normal stereoscopic vision, no suppression was found for three subjects who possessed neither global nor fine stereoscopic vision. Results for a subject who possessed fine, but not global stereoscopy, did, however, show the suppression effect.

Adaptation, Ocular↗
PubMed2001

Sound localization in a new-world frugivorous bat, Artibeus jamaicensis: acuity, use of binaural cues, and relationship to vision.

Passive sound-localization acuity and its relationship to vision were determined for the echolocating Jamaican fruit bat (Artibeus jamaicensis). A conditioned avoidance procedure was used in which the animals drank fruit juice from a spout in the presence of sounds from their right, but suppressed their behavior, breaking contact with the spout, whenever a sound came from their left, thereby avoiding a mild shock. The mean minimum audible angle for three bats for a 100-ms noise burst was 10 degrees-marginally superior to the 11.6 degrees threshold for Egyptian fruit bats and the 14 degrees threshold for big brown bats. Jamaican fruit bats were also able to localize both low- and high-frequency pure tones, indicating that they can use both binaural phase- and intensity-difference cues to locus. Indeed, their ability to use the binaural phase cue extends up to 6.3 kHz, the highest frequency so far for a mammal. The width of their field of best vision, defined anatomically as the width of the retinal area containing ganglion-cell densities at least 75% of maximum, is 34 degrees. This value is consistent with the previously established relationship between vision and hearing indicating that, even in echolocating bats, the primary function of passive sound localization is to direct the eyes to sound sources.

Animals↗
PubMed1991

Spectral tuning of pigments underlying red-green color vision.

Variations in the absorption spectra of cone photopigments over the spectral range of about 530 to 562 nanometers are a principal cause of individual differences in human color vision and of differences in color vision within and across other primates. To study the molecular basis of these variations, nucleotide sequences were determined for eight primate photopigment genes. The spectral peaks of the pigments specified by these genes spanned the range from 530 to 562 nanometers. Comparisons of the deduced amino acid sequences of these eight pigments suggest that three amino acid substitutions produce the approximately 30-nanometer difference in spectral peaks of the pigments underlying human red-green color vision, and red shifts of specific magnitudes are produced by replacement of nonpolar with hydroxyl-bearing amino acids at each of the three critical positions.

Amino Acid Sequence↗
PubMed1980

Filter-mediated color vision with one visual pigment.

The compound eye of the grasshopper Phlaeoba has alternating bands that appear clear or brown. Electroretinograms recorded from the individual bands have different action spectra: The spectrum of the clear band peaks at 525 nanometers and that of the brown band at 545 nanometers. Spectrally selective whole-eye adaptation with light of eight long of short wavelength yields identical action spectra. This evidence suggests that this eye has only one visual pigment, whose spectrum is altered in the brown bands by a screening pigment. In behavioral tests of spontaneous choices between stimuli that appear green to the normal human and those that appear red, the green stimuli are preferred even when the relative intensity is varied by 0.9 log units around the equal-brightness level (determined by the electroretinogram). When some red light is mixed with the green light, the preference for the mixture is less than for the green light alone, even though the mixture is more intense. True color vision therefore seems to exist. Painting the bands shows that behavioral color vision requires the presence of both types. These data suggest that Phlaeoba has true color vision mediated by one visual pigment and suitable optical filters.

Animals↗
PubMed2005

Increasing cataract surgery to meet Vision 2020 targets; experience from two rural programmes in east Africa.

BACKGROUND: The numbers of cataract surgeries done in sub-Saharan Africa fall short of Vision 2020 targets. Over a few years, two programmes in rural east Africa both achieved significant increases in the number of cataract surgeries they provide, resulting in cataract surgical rates of 1583 for Kwale District in Kenya and 1165 for Kilimanjaro Region in Tanzania. Key components of success in these two programmes are described. METHODS: Data were collected on standard indicators and key personnel interviewed to describe the results and compare the methods employed to increase cataract surgical rates by the Kwale District Eye Centre programme and the Kilimanjaro regional Vision 2020 programme. RESULTS: Key components of success shared by the programmes included: (1) programmes in the community and at the hospital are closely linked so that they increase capacity together; (2) community programmes are "patient friendly," providing service in one stop; (3) the examination team includes eye workers with enough skill to provide treatment and decide who is operable so that patients are not transported needlessly or sent through a lengthy referral chain; (4) sites for visits in the community are selected according to population distribution and they are visited according to a regular schedule. CONCLUSION: The development of "bridging strategies" that create a strong link between hospitals providing clinical service and communities needing these services is a key component to realising Vision 2020 goals in sub-Saharan Africa.

Cataract Extraction↗
PubMed2005

Night vision in the elderly: consequences for seeing through a "blue filtering" intraocular lens.

Relative scotopic spectral sensitivity depends only on the rhodopsin photopigment and ocular media absorption spectra. Rhodopsin is well characterised so the relative scotopic spectral sensitivity function can be calculated for intraocular lenses (IOLs) of known spectral density. In a recent perspective, Mainster and Sparrow concluded that an IOL with short wave absorbing chromophores would provide more retinal protection than conventional IOLs, but the practical consequences for scotopic vision are unclear. This paper uses published experiments to examine the implications for scotopic vision of the IOLs analysed by Mainster and Sparrow. A 14.6% reduction in scotopic sensitivity is expected for a SN60AT (AcrySof Natural) compared to a SA60AT (Conventional AcrySof) IOL under broadband illumination (equal quantum spectrum). This effect (0.07 log unit) is visually insignificant in relation to the approximately 4.0 log unit range of scotopic sensitivity. More importantly, it is expected that scotopic contrast sensitivity would be reduced by only approximately 0.01 log unit. It is thus improbable that a difference in scotopic vision between observers with the Natural and Conventional IOLs could be reliably detected using broadband stimuli.

Absorption↗
PubMed1995

Colour vision and dark adaptation in high myopia without central retinal degeneration.

Colour vision and dark adaptation of 36 high myopes (68 eyes) without degenerative fundus changes were studied with the standard pseudoisochromatic plates part 2, Farnsworth-Munsell 100 hue (FM 100) test, Nagel anomaloscope, colour vision meter 712-anomaloscope, and Goldmann-Weekers adaptometer. The ages of the myopes ranged from 20 to 49 years, the visual acuity from 6/12 to 6/6, and the refractions from -6.0 to -20.0 D. All the colour vision tests and dark adaptation examination gave normal results. However, the error scores of the myopes in (blue) box III of the FM 100 test were significantly higher than those of the controls matched for age. In dark adaptation, the rod thresholds of the myopes were significantly higher than in the controls. The stretching of the posterior pole of the eye might explain this minimal impairment of the photoreceptor layer of the retina without any visible degenerative changes in the fundus.

Adult↗
PubMedDate not supplied

"Craziness" and "visions": experiences after a stroke.

For a stroke victim there may be at least three types of strange occurrences: incorrect saying, seeing, and thinking. To the patient only the third seems to be "crazy". After a stroke (left hemisphere), which mainly produced serious aphasia, I (the patient) felt crazy two or three times when someone said something I expected him to say. On the other hand, my initial aphasic "gibberish speech" and an occasional false vision did not seem crazy. In my case the vision is always a car or a child, seen on my extreme right, where I am otherwise blind from the stroke. I am always driving when it happens; in recent years this phenomenon occurs when I am tired or tense, or the light is poor. These rapid visions do not seem insane but merely physical problems in my eyes, much like ordinary people's dreams.

Aphasia↗
PubMed2002

Tracheal intubation by novice staff: the direct vision laryngoscope or the lighted stylet (Trachlight)?

OBJECTIVE: To compare the ease of use of the direct vision laryngoscope and the lighted stylet (Trachlight) by novice staff. METHODS: Ten novice medical officers (MOs) performed orotracheal intubations using either the conventional direct vision laryngoscope (DL) or a lighted stylet device (Trachlight). They performed their DL intubations during the first phase of the study, followed by the Trachlight intubations in the subsequent phase. RESULTS: 51 of 54 (94%) of the DL intubation attempts were successful compared with 36 of 54 (67%) of the Trachlight intubations (p<0.001). The mean (SEM) time for intubation was 44 (7) seconds in the DL group and 66 (13) seconds in the Trachlight group (p=0.004). In addition 45 of 54 (83%) of the DL intubations were successful at the first attempt versus 15 of 54 (28%) in the Trachlight group (p<0.001). CONCLUSION: The results show that the use of the conventional direct vision laryngoscope in novices is associated with significantly shorter mean intubation times and higher success rates on the first attempt compared with the Trachlight.

Adolescent↗
PubMedDate not supplied

Common eye diseases of elderly people: identifying and treating causes of vision loss.

Of the 38 million people who are blind, the majority, 22 million, are 60 years of age or older. The most common causes of vision loss in elderly people are age-related macular degeneration (AMD), cataract, glaucoma, and diabetic retinopathy. Of these, AMD is the leading cause of registered blindness in people over the age of 50 years in the western world. However, until recently, the treatment options for people with AMD have been severely limited. Verteporfin therapy is a new treatment that is efficacious and safe in selected patients with AMD who are at high risk of central vision loss. Physicians who are in regular contact with elderly people can help to minimize vision loss in this group of patients by being alert to the symptoms and signs of age-related eye diseases. This paper reviews each of the common eye diseases, with an emphasis on AMD because of the recent advances in treatment.

Aged↗
PubMed1985

Color vision in the ring-tailed lemur (Lemur catta).

Behavioral discrimination tests were used to examine spectral sensitivity and color vision in a pair of ring-tailed lemurs (Lemur catta). Sensitivity tests revealed the presence of a Purkinje shift and a photopic visual system. As measured at increment-threshold, the photopic spectral sensitivity function for the lemur has multiple peaks (at ca. 440-460, 540, and 620 nm). In color vision tests lemurs behave trichromatically in that (a) they show no evidence for a neutral point in the spectral range of 470-510 nm, and (b) they set a unique Rayleigh match (540 nm + 645 nm = 570 nm). Tests of wavelength and colorimetric purity discrimination reveal that although this prosimian has color vision, it is not an acute capacity--thresholds for these color discriminations were consistently much higher for lemurs than for normal human trichromats tested in the same situation.

Animals↗
PubMed2004

Multiscale motion mapping: a novel computer vision technique for quantitative, objective echocardiographic motion measurement independent of Doppler: first clinical description and validation.

BACKGROUND: Objective, quantitative, segmental noninvasive/bedside measurement of cardiac motion is highly desirable in cardiovascular medicine, but current technology suffers from significant drawbacks, such as subjectivity of conventional echocardiographic reading, angle dependence of tissue Doppler measurements, radiation exposure by computer tomography, and infrastructure requirements in MRI. We hypothesized that computer vision technology could represent a powerful new paradigm for quantification in echocardiography. METHODS AND RESULTS: We present multiscale motion mapping, a novel computer vision technology that is based on mathematical image processing and that exploits echocardiographic information in a fashion similar to the human visual system. It allows Doppler- and border-independent determination of motion and deformation in echocardiograms at arbitrary locations. Correctness of the measurements was documented in synthetic echocardiograms and phantom experiments. Exploratory case studies demonstrated its usefulness in a series of complex motion analyses that included abnormal septal motion and analysis of myocardial twisting. Clinical applicability was shown in a consecutive series of echocardiograms, in which good feasibility, good correlation with expert rating, and good intraobserver and interobserver concordance were documented. Separate assessment of 2D displacement and deformation at the same location was successfully applied to elucidate paradoxical septal motion, a common clinical problem. CONCLUSIONS: This is the first clinical report of multiscale motion mapping, a novel approach to echocardiographic motion quantification. For the first time, full 2D echocardiographic assessment of both motion and deformation is shown to be feasible. Overcoming current limitations, this computer vision-based technique opens a new door to objective analysis of complex heart motion.

Algorithms↗
PubMed1993

Local gain control and focal accommodation in the Self Similar Stack vision model.

The aim of this paper is to report an extension to the computationally efficient Self Similar Stack model (Burton et al. Biol., Cybernet. 53, 397-403, 1986) to include the effects of local gain control in the retina. The method employed to do this has been to fit a family of difference-of-Gaussian functions to the human contrast sensitivity function curves of van Nes and Bouman (J. Opt. Soc. Am. 57, 401-406, 1967). The centre frequencies of the DoGs within each family are octave-related, in a simplified manifestation of the DoG channels found by Wilson et al. (Vision Res. 23, 873-882, 1983). The sensitivity of each level, or channel, that formed the original Stack model is modulated individually according to the fitted values, as the local illumination varies within an image. The model was tested against psychometric data obtained by Haig and Burton (Appl. Optics 26, 492-500, 1987) during experiments on visual discrimination. The consistency of the results indicates the validity of the approximations and the robustness of the model, either for machine vision purposes or for predicting human visual performance. A simple algorithm, developed for use with a machine vision application of this model, provides a means by which a TV camera may be focused automatically. The success of this algorithm, using the newly computed channel sensitivities, suggests that human focal accommodation may be regulated by a similar form of mechanism.

Accommodation, Ocular↗
PubMed2002

Suppressive and facilitatory spatial interactions in foveal vision: foveal crowding is simple contrast masking.

Spatial interactions are a critical and ubiquitous feature of spatial vision. These interactions may be inhibitory (reducing sensitivity as occurs in crowding) or facilitatory (enhancing sensitivity). In this work, we had four goals. 1. To test the hypothesis that foveal crowding depends on target size by measuring the extent of crowding for novel targets that were limited in their spatial frequency content. We used a large range of target sizes and spatial frequencies. 2. To assess whether the critical spatial frequency model (Hess, Dakin, & Kapoor, 2000) provides a general model for foveal crowding. To test this model, we measured crowding for a direction-identification task that did not require judging the orientation of the gap. 3. To test the hypothesis that foveal crowding is simply contrast masking by remote flanks we measured and compared crowding in a direction-identification experiment with masking by remote flanks in a detection experiment. In each of the experiments, our targets and flanks were composed of Gabor features, thus allowing us to control the feature contrast, spatial frequency, and orientation. 4. To assess the relationship between suppressive and facilitatory spatial interactions in foveal vision. Our results show that (1) foveal crowding is proportional to feature size over the more than 50-fold range of target sizes that we examined. Over this large range, foveal crowding is scale invariant. Our results also show it is the size of the envelope (SD) rather than the carrier (SF) that determines the extent of crowding in the fovea. 2. Crowding that occurs in the direction-identification task is quite similar to crowding where orientation information is available. Thus we conclude that the critical spatial frequency model does not provide a general explanation for foveal crowding. 3. Threshold elevation for crowding is similar to threshold elevation for masking as predicted by our test-pedestal model. Thus we conclude that foveal crowding is simple contrast masking. 4. Based on our comparison of threshold changes in crowding and masking, we conclude that in foveal vision, the suppressive spatial interactions due to nearby flanks are similar in the two tasks. However, the facilitatory interactions are quite different. In the crowding task, we find very little evidence for facilitation by flankers, whereas in the detection task, we find strong facilitation. We suggest that facilitation of detection by remote flanks may be, at least in part, a consequence of uncertainty reduction.

Contrast Sensitivity↗