The nature and basis of age-related changes in dynamic visual acuity.

The ability of observers to resolve moving targets, or dynamic visual acuity (DVA), was determined for a group of young adults (M age?=?19.6 years) and a group of older adults (M age?=?67.6 years). Targets were presented at two luminance levels over a range of velocities (30, 60, 90, and 120 deg/s) and at 2 durations (200 and 600 ms). The younger subjects exhibited superior DVA under nearly all conditions, but this effect was essentially eliminated by the luminance adjustment. These results are interpreted in terms of decreased retinal illumination in the older subjects rather than in terms of age-related changes in the underlying eye movement systems. Practical and theoretical implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Occupation and visual/vestibular interaction in vestibular rehabilitation

Otolaryngologists often prescribe head movement exercise programs for patients with vestibular disorders, although the effectiveness of these programs and the critical features of the exercises are poorly understood. Because many patients who dislike exercising do not follow through with their exercises, alternatives to the traditional repetitive exercises would be useful. Subjects diagnosed with vestibular disorders were treated for 6 weeks with either an outpatient exercise program that incorporated interesting, purposeful activities or a simple home program of head movements, comparable with the exercises otolaryngologists often give their patients when they do not refer to rehabilitation. Both treatments incorporated repetitive head movements in all planes in space, graduated in size and speed. Subjects were all tested before and after treatment with standard measures of vestibulo-ocular reflex and balance, level of vertigo, gross motor skills, and self-care independence. Subjects in both groups improved significantly on the functional measures, with slightly greater improvements in the occupational therapy group. The results were maintained 3 months after the cessation of intervention. These data suggest that graded purposeful activities are a useful alternative for treating this patient population and that the essential factor in any exercise program is the use of repetitive head movements.     

Comparison of measures of visual acuity in infants: Teller acuity cards and sweep visual evoked potentials

PURPOSE: This study compares the development of acuity in the same infants during one testing session using Teller acuity cards (TAC) and sweep visual evoked potentials (sVEP). We asked whether different testing methods in two centers would produce different developmental time courses. METHODS: Forty-eight infants were tested in two centers. The standard procedure for TAC was used. For sVEP acuity, the amplitude response curve derived from time-locked cortical activity was used to extrapolate to zero response, giving an acuity estimate for each infant. RESULTS: sVEP acuity was generally higher than TAC acuity. The rate of development was steeper for TAC than sVEP acuity with TAC starting at a much lower level. The ratio of sVEP to TAC acuity decreased exponentially with age reaching an asymptote of about 1.44 at 6 months. CONCLUSIONS: Results were indistinguishable between centers suggesting that comparison of acuity measures obtained using variations of these methods across centers is possible.     

Table for assessing visual acuity in children]

The effect of vegetable (peach kernel) oil on the somatic development and puberty of female rats was studied. The oil was injected (0.2 ml) once intramuscularly into the prepuberty (aged 35 days) or (at the age of 31-35 days) five times. The oil inhibited dose-dependently the somatic development of the rats before puberty. It inhibited the ovarian endocrine function, significantly delayed the initial (opening of the vagina) and terminal (ovulation) stages of puberty or suppressed it completely (in 30% of cases).     

Effect of levodopa therapy on visual evoked potentials and visual acuity in amblyopia

Between 10 and 11 years after children were vaccinated with Vi capsular polysaccharide of Salmonella typhi or meningococcal A + C control vaccine in a double blind randomized trial, we traced 83 subjects, aged 16-20 years. A blood sample was taken for determination of Vi antibody titres in both groups by radioimmunoassay. TO and TH titres were also done to assess if the participants had had recent exposure to typhoid fever. Fifty-eight percent of subjects in both groups had protective levels of Vi antibody against Salmonella typhi (a titre greater than 1 microgram ml-1). There was no significant difference in the levels of Vi antibodies in the cases versus the controls (p = 0.5). Two of the children who had received meningococcal A + C vaccine had recently had typhoid fever. Our data show that adolescents in typhoid endemic areas have high levels of Vi antibodies regardless of previous vaccination status, suggesting that Vi antibodies are acquired in adolescence by a large percentage of the population in this area. Moreover, Vi vaccination has led to ongoing antibody production in greater than 50% of Vi vaccinated children in an endemic area for a period of 10 years. Ongoing antigenic exposure may have contributed to these antibody levels.     

Compared optical performances of multifocal and monofocal intraocular lenses (contrast sensitivity and dynamic visual acuity)

The functional results (contrast sensitivity and dynamic visual acuity) of 19 multifocal (3M design) and 14 all polymethylmethacrylate biconvex monofocal intraocular lenses (IOLs), 6 mm in optical diameter were compared. Best corrected visual acuity was > or = 8/10 (Monoyer chart) Parinaud 2 in all cases. Major differences of functional performance in favour of monofocal IOLs were found outside standard conditions of vision (low contrast and illumination levels). A significant difference in contrast sensitivity was found for each spatial frequency in favour of multifocal IOLs (0.0016 < p < 0.05). Mesopic vision was statistically higher in the monofocal IOL group (p = 0.0015). Moreover, dynamic visual acuity allowed accurate evaluation of the difference in performance between these two models of implant. In view of these results multifocal IOLs should be reserved for patients with normal psychosensitive adaptation; an ocular pathology that could alter contrast sensitivity or mesopic vision is a contraindication for multifocal IOLs.     

Computerized tomography in the assessment of metastatic facial adenopathy

The facial lymph nodes are classified in five groups: mandibular, buccinator, infraorbital, malar and retrozygomatic nodes. This paper reports the CT appearance of neoplastic involvement of these nodes, an unusual and not well documented event. The CT examinations of 62 patients with a history of primary or recurrent cancer of the epidermal structures of the face, oral cavity and sinonasal region were retrospectively reviewed to assess the presence of facial adenopathy. Nine cases of neoplastic involvement of facial nodes were found. Most commonly the buccinator nodes (4 cases) were involved, the infraorbital, mandibular (2 cases) and retrozygomatic nodes (1 case) being less commonly involved. No malar nodes were found. Neoplastic involvement of these nodes was caused by squamous cell carcinoma in 6 cases, by adenocarcinoma in 2 cases and by a lymphoma in 1 case. Normal nodes could not be confidently identified on CT studies. CT diagnosis of neoplastic involvement of facial nodes is based on the presence of a nodular lesion which lies along the lymphatic pathways of the primary neoplasm in an anatomically compatible location. CT diagnosis of facial nodes is very important for treatment planning if the nodes are deep or at a distance from primary cancer. This is especially true for retrozygomatic and buccinator nodes.     

Systematic analysis of deficits in visual attention.

A variety of impairments in visual attention can follow damage to the brain. The authors develop systematic methods for analyzing such impairments in terms of C. Bundesen's (see record 1991-03287-001) Theory of Visual Attention and apply these in a group of 9 patients with parietal lobe lesions and variable spatial neglect. In whole report, patients report letters from brief, vertical arrays in left or right visual field. The results show substantial, largely bilateral impairments in processing capacity, implying a major nonlateralized aspect to neglect. In partial report, arrays contain 1 or 2 letters in red and/or green. The task is to report only those letters in a specified target color. In addition to the expected bias against left-sided letters, patients show striking, bilateral preservation of top-down control, or attentional priority for targets. The results show how differentiation of attentional impairments can be informed by a theory of normal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The visual acuity for the lateral visual field of the pigeon (Columba livia)

Previous studies on pigeons indicated that the visual acuity for the frontal visual field was much higher than that for the lateral one. Suspecting that the poor values for the lateral field were due to suboptimal testing conditions, we determined the lateral field acuity in eight head-fixed pigeons with high-contrast square-wave gratings. An instrumental conditioning task with water as reinforcer and mandibulation as an operant was used. Subjects achieved a mean acuity value of 12.6 c/deg. The results show that the acuity of the lateral visual field is only slightly lower than that of the frontal field. These data provide a psychophysical basis for ecological observations that pigeons and most other birds gaze laterally when scrutinizing small and distant objects.     

Design of an Arabic near visual acuity chart

This paper describes the design of an Arabic test chart for measurement of visual acuity at near. The chart was designed employing specially selected Arabic letters and was based on the logMAR principle devised by Bailey and Lovie. Ten Arabic letters of nearly equal legibility values (0.92-1.05) (mean = 1.00), (SD = 0.05) were used in the design of the chart. Each row of the chart has 5 letters and row legibility values range from 4.82 to 5.03 with a mean of 4.92 (SD = 0.06). The logMAR method of visual acuity scaling was used, hence the sizes of letters in the rows progress in a uniform step of 0.1 log unit. The inter-letter spacing is equal to the width of each letter in the row, while inter-row spacing is equal to the height of letter in the subjacent row. The height of letters ranged from 3.67 to 0.46 mm corresponding to visual acuity of 2.4 M to 0.3 M which is equivalent to reduced Snellen 6/36 to 6/4.5 at 0.4 m. The chart is designed for use at 40 cm with a recommended luminance level of 160 cd/m2.     

Computerized tomographic assessment of the composition of gallstones

We present the results of an in vitro study of biliary lithiasis (n = 106) with computerized tomography (CT). We analyzed the correlation between composition of gallstones (crystallographic analysis of thin sections and atomic absorption spectrophotometric analysis of total calcium content) with CT patterns (densitometry) and their corresponding attenuations. Six main CT patterns were distinguished: hypodense (homogeneous and heterogeneous), dense, homogeneous hyperdense, ringed hyperdense and irregular hyperdense. Statistically significant differences (p < 0.05) were found between attenuations for cholesterol (mixed and pure) and pigmentary stones. We found a good inverse correlation between attenuations and cholesterol content; the contents of pigment, inorganic calcic salts and total calcium content also showed significant direct correlations (p < or = 0.01). Of the samples classified as pure cholesterol type stones, 86.4% showed hypodense patterns, and the remaining 13.6% showed irregular hyperdense patterns. Of the pigmentary stones, 80% showed homogeneous hyperdense images. All stones that contained more than 3% calcium produced hyperdense patterns, whereas 72.4% of the stones that contained less calcium produced hypodense images. Tomodensitometric measurements provided more information than simple radiography, and made it possible to distinguish a greater variety of gallstone types based on structural complexity.     

Evaluation of vestibular and visual oculomotor function

The visual system interacts synergistically with the vestibular system. A normally functioning vestibulo-ocular reflex is necessary but not sufficient for optimum visual acuity during head motion. Studies of dynamic visual acuity, the acuity achieved during relative motion of visual targets or of the observer, indicate that motion of images on the retina markedly compromises vision. The vestibulo-ocular reflex normally provides a substantial measure of stabilization of the retina during head movements, but purely vestibular compensatory eye movements are not sufficiently precise for optimal vision under all circumstances. Other mechanisms, including visual tracking, motor preprogramming, prediction, and mental set, interact synergistically to optimize the gain (eye velocity divided by head velocity) of compensatory head movements. All of these mechanisms are limited in their capacity to produce effective visual-vestibular interaction at higher rotational frequencies and velocities. It is under these conditions that vestibular deficits give rise to symptoms of oscillopsia. Patients having vestibular lesions exploit mechanisms of visual-vestibular interaction to compensate by substitution for deficient vestibular function. Thus, for accurate topographic clinical diagnosis of vestibular lesions, testing conditions should isolate purely vestibular responses. This may be done by testing reflex eye movements during passively generated rotations in darkness, or perhaps by testing during other types of motion under conditions of extreme frequency and velocity sufficient to attenuate the effects of visual-vestibular interaction. This article reviews clinical tests of vestibular function in relation to synergistic interactions with vision.     

Study of "retinal" visual acuity in eye diseases

Nitrobacter agilis was grown autotrophically on nitrite, mixotrophically on nitrite together with either acetate or pyruvate and heterotrophically on acetate and casamino acids, pyruvate and casamino acids or pyruvate and nitrate. The enzymatic activities differed most in the key enzymes of lithotrophic metabolism. Nitrite oxidase was repressed 90% in 10 days after transition to heterotrophic growth and was no longer detectable after several transfers. The induction of nitrite oxidase began after a lag of 2 days and reached the autotrophic level after 7 days when pyruvate was the carbon and energy source and after 9 days using acetate.     

Theories of visual acuity and their physiological bases.

An orientation into the problem of visual acuity and of the size and distribution of retinal receptors precedes a discussion of the principal theories of visual acuity. The 2 static theories covered are Hartridge's and Hecht's, including a critique of Hetcht's theory where evidence is cited that fails to support his position. The 2 dynamic theories discussed are those of Weymouth and his colleagues, and of Marshall and Talbot. The Marshall-Talbot theory, accounting for visual phenomena other than acuity alone, is viewed as the best existing theory, and is evaluated in terms of the principal physiological mechanisms on which the theory is based. 84 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced visual acuity in elderly people: the role of ergonomics and gerontechnology

Branch pulmonary artery stenosis is a common problem in pediatric cardiology. Treatment has included surgery, balloon angioplasty, and balloon expandable stent placement. It was the purpose of this investigation to demonstrate the cost-effectiveness of each of these modes of treatment. From 1983 to 1994 there were 30 patients admitted for treatment of branch pulmonary artery stenosis only. Data included age at procedure, sex, primary diagnosis, acute and intermediate term success, and complications. Acute success was defined by results at the end of the procedure where intermediate term (IT) success was defined by results at follow-up. Success of a procedure was defined by at least one of the following: an increase in vessel diameter by >/=50% of predilation diameter, a decrease in right ventricular to left ventricular or aortic systolic pressure ratio by >/=20%, or a decrease in peak to peak pressure gradient by >/=50%. The procedure was considered a failure if the previously mentioned criteria were not met or if the patient required a second procedure for the same stenosis. The expense of the procedure (estimated by using the patient charges) were collected from the time of the procedure until December 1994. Because of differing lengths of follow-up, the patients were analyzed separately for procedures and outpatient charges. The total charges were corrected to 1994 dollars using the Medical Consumer Price Index. Thirty patients had 46 separate procedures (12 patients had >1 procedure and 3 had >2 procedures). There were 13 surgeries, 13 balloon angioplasties, and 20 stents. Stents were the most successful (90% acute and 85% IT), but were not statistically superior to surgery (62% acute and IT). Balloon angioplasty was significantly less successful as compared with stents (31% acute and 23% IT), and was not statistically different from surgery over the acute and intermediate term. The charge data showed balloon angioplasty was the least expensive followed by stents and then by surgery. The average total charges per procedure, including outpatient charges, were: surgery $58,068 +/- $4372 (standard error), balloon $21,893 +/- $5019, stents $33,809 +/- $3533 (p < 0.001); excluding outpatient charges: surgery $52,989 +/- $3649, balloon $15,653 +/- $1691, and stents $29,531 +/- $2241 (p < 0.001). Average total charges per patient, including all procedure types and grouped by initial procedure, were: surgery $53,707 +/- $6388, balloon $50,040 +/- $8412, and stent $34,346 +/- $3488 (p = 0.047). Stents were at least as effective as surgery and were more effective than balloon angioplasty in both acute and intermediate term follow-up. Balloon angioplasty was least expensive per procedure but was also least effective. Therefore, intravascular balloon expandable stents are the most cost-effective means available in the treatment of branch pulmonary artery stenosis.