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PubMed2000

An early vision-based snake model for ultrasound image segmentation.

Due to the speckles and the ill-defined edges of the object of interest, the classic image-segmentation techniques are usually ineffective in segmenting ultrasound (US) images. In this paper, we present a new algorithm for segmenting general US images that is composed of two major techniques; namely, the early-vision model and the discrete-snake model. By simulating human early vision, the early-vision model can capture both grey-scale and textural edges while the speckle noise is suppressed. By performing deformation only on the peaks of the distance map, the discrete-snake model promises better noise immunity and more accurate convergence. Moreover, the constraint for most conventional snake models that the initial contour needs to be located very close to the actual boundary has been relaxed substantially. The performance of the proposed snake model has been shown to be comparable to manual delineation and superior to that of the gradient vector flow (GVF) snake model.

Algorithms↗
PubMedDate not supplied

Color vision and occupational toluene exposure.

We examined the relationship between acquired color vision loss and exposure to toluene and total hydrocarbons among 125 male workers. Seventy-two toluene-exposed printers were compared with 34 workers from the same photogravure plant with ambient background exposure, and with 19 workers from a bookbinding plant located in the same town (nonexposed). Environmental mean toluene exposure level at workstation was estimated from individual 8-h sampling. Historic exposure data from the last 30 years were used to construct two cumulative exposure indices, one for toluene and one for total hydrocarbons. Airborne toluene levels were overall lower than the current Threshold Limit Value (TLV) of 50 ppm. Color vision was assessed by the Lanthony D-15 desaturated panel. Color vision loss was quantitatively established by the Color Confusion Index (CCI) and classified by type of acquired dyschromatopsia according to Verriest's classification. CCI was positively related to current airborne toluene levels, and cumulative exposure indices for toluene and total hydrocarbons (.18< or =r< or =.35). Odds ratios of acquired dyschromatopsia were significant for current airborne toluene, toluene, and total hydrocarbon past exposure (1.27 [1.02-1.58], 1.21 [1.04-1.39], 1.15 [1.02-1.31], respectively). In conclusion, this study suggests that the Lanthony D-15 desaturated panel detects early neurotoxic effects among workers exposed to toluene.

Adult↗
PubMedDate not supplied

A new framework for vision-enabled and robotically assisted minimally invasive surgery.

This paper presents our on-going research at bringing the state-of-the-art in vision and robotics technologies to enhance the emerging minimally invasive surgery, in particular the laparoscopic surgical procedure. A framework that utilizes intelligent visual modeling, recognition, and serving capabilities for assisting the surgeon in maneuvering the scope (camera) in laparoscopy is proposed. The proposed framework integrates top-down model guidance, bottom-up image analysis, and surgeon-in-the-loop monitoring for added patient safety. For the top-down directives, high-level models are used to represent the abdominal anatomy and to encode choreographed scope movement sequences based on the surgeon's knowledge. For the bottom-up analysis, vision algorithms are designed for image analysis, modeling, and matching in a flexible, deformable environment (the abdominal cavity). For reconciling the top-down and bottom-up activities, robot servoing mechanisms are realized for executing choreographed scope movements with active vision guidance. The proposed choreographed scope maneuvering concept facilitates the surgeon's control of his/her visual feedback in a handless manner, reduces the risk to the patient from inappropriate scope movements by an assistant, and allows the operation to be performed faster and with greater ease. In this paper, we describe the new framework and present some preliminary results on laparoscopic image analysis for segmentation and instrument localization, and on instrument tracking.

Humans↗
PubMedDate not supplied

"One voice-one vision" for Wisconsin pharmacy.

OBJECTIVE: To describe how a new organization, reflecting a new vision and unifying the pharmacists of Wisconsin, was created by bringing together organizationally the resources and memberships of the Wisconsin Pharmacists Association and the Wisconsin Society of health-System Pharmacists. SETTING: State of Wisconsin. DESCRIPTION: The boards of directors of the two precursor organizations initiated an exploration of the desirability and feasibility of creating a single, new organization to represent, with a unified voice, all of Wisconsin's pharmacists. This two-year effort resulted in the creation of the Pharmacy Society of Wisconsin (PSW) on January 1, 1998. INNOVATION: The new organization builds on the strengths and resources of two pharmacy organizations that previously represented divergent views and practice settings. PSW offers a new vision and level of service to its members and to pharmacy students. It presents a single voice to patients, other health care providers, and governmental agencies. RESULTS: The creation of the Society was supported unanimously by the two boards of directors and by 98% of the voting membership of the two previous organizations. CONCLUSION: Through a deliberate and extensive planning and organizational process, two vigorous professional organizations were able to recognize the importance of combining their resources into a new single organization. The pharmacists of Wisconsin responded to a call for a new vision and a unified voice. The opportunity exists for American pharmacy to examine how it will be best served by its professional organizations.

Humans↗
PubMed2001

The role of color in high-level vision.

Traditional theories of object recognition have emphasized the role of shape information in high-level vision. However, the accumulating behavioral, neuroimaging and neuropsychological evidence indicates that the surface color of an object affects its recognition. In this article, we discuss the research that examines the conditions under which color influences the operations of high-level vision and the neural substrates that might mediate these operations. The relationship between object color and object recognition is summarized in the 'Shape+Surface' model of high-level vision.

Journal Article↗
PubMed2001

Vision of low astigmats through thick and thin lathe-cut soft contact lenses.

Distance and near visual acuity of 13 low astigmats were determined in a double-masked experiment through thick and thin (centre thickness 0.12 mm and 0.06 mm, respectively) spherical lathe-cut soft lenses. For each lens type, distance and near LogMAR VA and over-refraction were assessed with different logMAR VA charts. For 70% of the subjects, the residual astigmatism was significantly lower than the refractive astigmatism with thicker lenses. No statistically significant differences in the distance and near logMAR VA was found between the two lens types using any of the charts used, though, in general, logMAR VA obtained through the thicker lens was better than logMAR VA through the thinner lens. The variabilities in distance and near logMAR VA between the two lens types increased with decreased contrast. The variabilities in distance logMAR VA were greater with Chinese charts than with English charts, and LogMAR VA with Chinese charts were significantly worse for both lens types. Based on the results of this study, we concluded that thicker spherical lathe-cut soft lenses provide better vision in low astigmats. The Snellen acuity test is inadequate for vision assessment of soft contact lens wearers. When a patient wearing thin soft contact lenses complains of poor vision in spite of 6/6 or 6/5 Snellen acuity, changing to thicker lenses may be considered.

Journal Article↗
PubMed2004

The effect of add power on distance vision with the acuvue bifocal contact lens.

PURPOSE: This study was designed to determine if subjective evaluation of quality of distance vision with the Acuvue Bifocal contact lens could be correlated with high- and low-contrast acuity scores. METHODS: LogMAR visual acuities of 20 non-presbyopic subjects were measured using high and low-contrast Bailey-Lovie charts. Each subject wore an Acuvue Bifocal contact lens with add powers +1.00, +1.50, +2.00, and +2.50, each optimized for best distance acuity. RESULTS: Subjects showed significantly decreased acuities with increasing add; a low-contrast target heightened this effect. Subjects reported a reduction in quality of distance vision, increasing fluctuation, ghosting/shadows, and halos around lights that correlated with increasing add power. CONCLUSIONS: Our findings suggest that the Acuvue Bifocal contact lens may be expected to perform best for presbyopes with low-to-moderate bifocal add requirement, and that clinicians should anticipate decreased low-contrast acuity and reduced overall quality of vision as add powers are increased.

Adult↗
PubMed2004

M-cell deficit and reading disability: a preliminary study of the effects of temporal vision-processing therapy.

BACKGROUND: This study examines the following questions: In moderately disabled readers, will temporal vision-processing therapy procedures that benefit reading comprehension, visual attention, and oculomotor skills ameliorate M-cell processing deficits as measured with coherent motion threshold testing? And will the results show a corresponding improvement in oral reading and verbal skills? METHOD: A sample of 16 moderately disabled readers, evaluated in a study completed 6 months earlier, were retested with another form of the Gates-MacGinitie Reading Test. Each participant was additionally tested for coherent motion, oral reading, and word attack skills. During the succeeding 6 months, fifteen 45-minute therapy sessions were administered once a week (as the school schedule permitted). After completing 15 therapy sessions, the initial testing procedures were repeated. RESULTS: All four variables--namely, Gates-MacGinitie Reading Test, Coherent Motion Threshold Test, Gray Oral Reading Test, and Woodcock-Johnson Word Attack Test--revealed significant improvements after temporal vision therapy. Half of the 16 participants improved 2 or more years in reading comprehension, compared to no significant mean difference following the 6-month "control period" before the onset of therapy. CONCLUSIONS: This research supports the value of rendering temporal vision therapy to children identified as moderately reading disabled (RD). The diagnostic procedures and the dynamic therapeutic techniques discussed in this article have not been previously used for the specific purpose of ameliorating an M-cell deficit. Improved temporal visual-processing skills and enhanced visual motion discrimination appear to have a salutary effect on magnocellular processing and reading comprehension in RD children with M-cell deficits.

Child↗
PubMed1989

Color vision in the dog.

The color vision of three domestic dogs was examined in a series of behavioral discrimination experiments. Measurements of increment-threshold spectral sensitivity functions and direct tests of color matching indicate that the dog retina contains two classes of cone photopigment. These two pigments are computed to have spectral peaks of about 429 nm and 555 nm. The results of the color vision tests are all consistent with the conclusion that dogs have dichromatic color vision.

Animals↗
PubMedDate not supplied

FDA regulation of labeling and promotional claims in therapeutic color vision devices: a tutorial.

The Food and Drug Administration (FDA) is responsible for determining whether medical device manufacturers have provided reasonable assurance, based on valid scientific evidence, that new devices are safe and effective for their intended use before they are introduced into the U.S. market. Most existing color vision devices pose so little risk that their manufacturers are not required to submit a premarket notification [510(k)] to FDA prior to market. However, even low-risk devices may not be acceptable if they are marketed on the basis of misleading or excessive claims. Although most color vision devices are diagnostic, two types that are therapeutic rather than diagnostic are colored lenses intended to improve deficient color vision and colored lenses intended to improve reading performance. Both of these devices have presented special regulatory challenges to FDA because the intended uses and effectiveness claims initially proposed by the manufacturers were not supported by valid scientific evidence. In each instance, however, FDA worked with the manufacturer to restrict labeling and promotional claims in ways that were consistent with the available device performance data and that allowed for the legal marketing of the device.

Color Perception↗
PubMed1991

Design, chemical synthesis, and expression of genes for the three human color vision pigments.

Color vision in humans is mediated by three pigments from retinal cone photoreceptor cells: blue, green, and red. We have designed and chemically synthesized genes for each of these three pigments. The genes were expressed in COS cells, reconstituted with 11-cis-retinal chromophore, and purified to homogeneity using an immunoaffinity procedure. To facilitate the immunoaffinity purification, each pigment was modified at the carboxy terminus to contain an additional eight amino acid epitope for a monoclonal antibody previously used to purify bovine rhodopsin. The spectra for the isolated pigments had maxima of 424, 530, and 560 nm, respectively, for the blue, green, and red pigments. These maxima are in excellent agreement with the maxima previously observed by microspectrophotometry of individual human cone cells. The spectra are the first to be obtained from isolated human color vision pigments. They confirm the original identification of the three color vision genes, which was based on genetic evidence [Nathans, J., Thomas, D., & Hogness, D.S. (1986) Science 232, 193].

Amino Acid Sequence↗
PubMed1993

Haptic exploration in the presence of vision.

Two experiments addressed initiation of haptic exploration to encode object properties when vision is present. Ss compared pairs of objects on designated properties, using only vision or with touch permitted. Tough initiation, reach, contact, and visual responses were timed. With difficult material judgments, tough occurred frequently and was initiated faster than the time to respond by vision alone. With geometric judgments, touch was rarely used and then was initiated at the typical time for a visual response. Imposing a visual preview before allowing touch did not reduce the incidence of touch but did speed its initiation. Results support a model in which preliminary visual processing quickly initiates haptic exploration for material judgments that are visually or semantically difficult.

Adult↗
PubMed1994

Spectral sensitivity, photopigments, and color vision in the guinea pig (Cavia porcellus).

Behavioral discrimination tests and electroretinogram (ERG) flicker photometry were used to measure spectral sensitivity and to define the spectral mechanisms of the guinea pig (Cavia porcellus). Results from these 2 approaches converge to indicate that guinea pig retinas contain rods with peak sensitivity of about 494 nm and 2 classes of cone having peak sensitivities of about 429 nm and 529 nm. The presence of 2 classes of cones suggests a retinal basis for a color vision capacity. Behavioral tests of color vision were conducted that verified this prediction: Guinea pigs have dichromatic color vision with a spectral neutral point centered at about 480 nm. The cone pigment complement of the guinea pig is different from that known to characterize other rodents.

Animals↗
PubMedDate not supplied

Polymorphism of the long-wavelength cone in normal human colour vision.

Colour vision is based on the presence of multiple classes of cone each of which contains a different type of photopigment. Colour matching tests have long revealed that the normal human has three cone types. Results from these tests have also been used to provide estimates of cone spectral sensitivities. There are significant variations in colour matches made by individuals whose colour vision is classified as normal. Some of this is due to individual differences in preretinal absorption and photopigment density, but some is also believed to arise because there is variation in the spectral positioning of the cone pigments among those who have normal colour vision. We have used a sensitive colour matching test to examine the magnitude and nature of this individual variation and here report evidence for the existence of two different long-wavelength cone mechanisms in normal humans. The different patterns of colour matches made by male and female subjects indicate these two mechanisms are inherited as an X-chromosome linked trait.

Color Perception↗
PubMed1994

Disturbances in night vision after excimer laser photorefractive keratectomy.

Eighty-four patients with up to -6.00 dioptres of myopia underwent photorefractive keratectomy (PRK), using 5.00 mm ablation zones. Three months post-operatively 38 (45%) complained of disturbances in night vision, compared with 21 (25%) pre-operatively. In the majority, these disturbances were regarded as negligible. However, 9 (11%) reported significant problems, defined as an inability to drive safely at night with the treated eye. At 12 months, 32 patients (38%) complained of impaired night vision, 4 (5%) of whom had significant problems. A series of measurements were performed to investigate the origins of these disturbances, especially in patients reporting significant problems. Visual impairment from forward scattered light was investigated using a computerised technique. Back scattered light was measured with a charge coupled device-camera system and a computer program was used to assess the degree of halation around a bright light source on a high-resolution monitor. Pupillary diameters were measured by infrared television pupillometry. At 6 months, those reporting a starburst effect around lights at night had small hyperopic shifts, minimal halos and high forward and back light scatter measurements. Patients who reported halo phenomena had large hyperopic shifts, little light scatter and large pupillary diameters. Of the 4 patients who reported significant disturbances at 12 months, all had persistent halo problems. Those with starburst effects in the early post-operative period noticed an improvement with time as their corneal haze gradually improved. Perturbations of night vision after PRK manifest as starbursts and halos around lights.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Evolution of colour vision in vertebrates.

The expression of five major families of visual pigments occurred early in vertebrae evolution, probably about 350-400 million years ago, before the separation of the major vertebrate classes. Phylogenetic analysis of opsin gene sequences suggests that the ancestral pigments were cone pigments, with rod pigments evolving last. Modern teleosts, reptiles and birds have genera that possess rods and four spectral classes of cone each representing one of the five visual pigment families. The complement of four spectrally distinct cone classes endows these species with the potential for tetrachromatic colour vision. In contrast, probably because of their nocturnal ancestry, mammals have rod-dominated retinas with colour vision reduced to a basic dichromatic system subserved by only two spectral classes of cone. It is only within primates, about 35 millions years ago, that mammals 're-evolved' a higher level of colour vision: trichromacy. This was achieved by a gene duplication within the longer-wave cone class to produce two spectrally distinct members of the same visual pigment family which, in conjunction with a short-wavelength pigment, provide the three spectral classes of cone necessary to subserve trichromacy.

Animals↗
PubMed1992

Defective colour vision associated with a missense mutation in the human green visual pigment gene.

All red/green colour vision defects described so far have been associated with gross rearrangements within the red/green opsin gene array (Xq28). We now describe a male with severe deuteranomaly without such a rearrangement. A substitution of a highly conserved cysteine by arginine at position 203 in the green opsins presumably accounted for his colour vision defect. Surprisingly, this mutation was fairly common (2%) in the population but apparently was not always expressed. In analogy with nonexpression of some 5'green-red hybrid genes in persons with normal colour vision, we suggest that failure of manifestation occurs when the mutant gene is located at a distal (3') position among several green opsin genes. This mutation might also predispose to certain X-linked retinal dystrophies.

Amino Acid Sequence↗
PubMed2003

Profile of eye lesions and vision loss: a cross-sectional study in Lusambo, a forest-savanna area hyperendemic for onchocerciasis in the Democratic Republic of Congo.

OBJECTIVE: To determine baseline data regarding eye lesions and vision loss in five villages of Lusambo, an onchocerciasis-hyperendemic forest-savanna area in the Democratic Republic of Congo (DRC), in preparation of mass ivermectin distribution. METHODS: Five villages were selected by simple randomization. Through a cross-sectional design, 750 subjects were examined ophthalmologically. The eye examination included acuity visual measurement, slit-lamp examination, ophthalmoscopy, intraocular pressure measurement, and visual field assessment by the Wu-Jones test. RESULTS: There was a high prevalence of onchocerciasis-related eye lesions compared with non-onchocercal lesions. Chorioretinitis (20%) was the most frequent disease, others were punctate keratitis and microfilariae in the anterior chamber in equal frequency (13.8%), white intraretinal deposits (10.4%) and iridocyclitis (8%). Vision loss was discovered in 8.5% of the subjects, of whom 0.5% had bilateral blindness, 2.2% had monocular blindness and 5.7% had visual impairment. Vision loss was mostly caused by onchocerciasis-related diseases, especially those affecting the anterior segment of the eye. CONCLUSION: Features of ocular onchocerciasis usually described in forest and savanna areas were both found in this forest-savanna zone of the DRC.

Adolescent↗