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At least 343 records · Page 19Linked to original sources
PubMed1978

Autokinetic movement of an induced afterimage.

Thirty-two female Ss participated in an experiment in which autokinetic movement (AKM) direction change frequency of an induced afterimage was assessed as a function of stimulus afterimage color (yellow or blue-green) and the presence or absence of eye strain. Afterimage color was found not to affect AKM frequency reports. However, eye strain significantly (p less than .002) affected such reports, with the fewest AKM direction changes reported when strain was present. These results were explained in terms of an error signal and noise analysis of AKM.

Afterimage↗
PubMed1992

Video display terminal operation: a potential risk in the etiology and maintenance of temporomandibular disorders.

Surveys indicate over 50 million Americans, mostly women, currently operate video display terminals (VDTs) at home or in the workplace. Recent epidemiological studies reveal more than 75% of approximately 30 million American temporomandibular disorder (TMD) sufferers are women. What does the VDT and TMD have in common besides an affinity for the female gender? TMD is associated with numerous risk factors that commonly initiate sympathetic nervous system and stress hormone response mechanisms resulting in muscle spasms, trigger point formation, and pain in the head and neck. Likewise VDT operation may be linked to three additional sympathetic nervous system irritants including: (1) electrostatic ambient air negative ion depletion, (2) electromagnetic radiation, and (3) eyestrain and postural stress associated with poor work habits and improper work station design. Additional research considering the roles these three factors may play in the etiology of TMD and other myofascial pain problems is indicated. Furthermore, dentists are advised to educate patients as to these possible risks, encourage preventive behaviors on the part of employers and employees, and recommend workplace health, safety, and ergonomic upgrades when indicated.

Air Ionization↗
PubMed2005

The relationship between convergence insufficiency and ADHD.

BACKGROUND: Children being evaluated for attention deficit hyperactivity disorder (ADHD) often have an eye exam as part of their evaluation. The symptoms of convergence insufficiency (CI) can make it difficult for a student to concentrate on extended reading and overlap with those of ADHD. METHODS: A retrospective review of 266 patients with CI presenting to an academic pediatric ophthalmology practice was performed. All patients included were diagnosed with CI by one author (DBG) and evaluated for the diagnosis of ADHD. A computerized review was also performed looking at the converse incidence of CI in patients carrying the diagnosis of ADHD. RESULTS: We reviewed 266 charts of patients with CI. Twenty-six patients (9.8%) were diagnosed with ADHD at some time in their clinical course. Of the patients with ADHD and CI, 20 (76.9%) were on medication for ADHD at the time of diagnosis for CI while 6 (23.1%) were either not on medication or the medication was discontinued several months before the diagnosis of CI. The review of computer records showed a 15.9% incidence of CI in the ADHD population. CONCLUSION: We report an apparent three-fold greater incidence of ADHD among patients with CI when compared with the incidence of ADHD in the general US population (1.8-3.3%). We also note a seeming three-fold greater incidence of CI in the ADHD population. This may simply represent an association and not be a causative relationship. Until further studies are performed, however, patients diagnosed with ADHD should be evaluated to identify the small subset that may have CI -- a condition that responds well to treatment at home.

Adolescent↗
PubMed2006

Are orthoptic exercises an effective treatment for convergence and fusion deficiencies?

PURPOSE: To investigate whether orthoptic exercises are an effective way to influence the near point of convergence, fusion range and asthenopic symptoms. METHODS: Seventy-eight patients met the inclusion criteria of visual acuity 6/9 or better, no history of orthoptic treatment, squint surgery or Meares Irlen syndrome/dyslexia. Information was collected from case records related to diagnosis, near point of convergence, fusion range, prism and cover test measurements and symptoms. Type, duration and frequency of exercises were also recorded. Non-parametric statistics were applied. RESULTS: Patients ranged in age from 5 to 73 years (mean 11.9). Females outnumbered males (46:32). The diagnoses were: decompensating heterophoria (n = 50) or convergence insufficiency (n = 28: primary 27; secondary 1). Exophoria was more common (n = 65), than esophoria (n = 11) or orthophoria (n = 1). Treatments were aimed at improving near point of convergence and/or reduced fusional reserves. The mean treatment period was 8.2 months. Reduced near point of convergence normalized following treatment in 47/55 cases, and mean near point of convergence improved from 16.6 to 8.4 cm (p = 0.0001). Fusional reserves normalized in 29/50. Fusional convergence improved significantly for those with exodeviation (p > 0.0006). Asthenopic symptoms improved in 65 patients. A reduction in deviation of 5 pd or more occurred in 20 patients. CONCLUSIONS: Orthoptic exercises are an effective means of reducing symptoms in patients with convergence insufficiency and decompensating exophoria, and appear to target the proximal and fusional components of convergence. Their role in esophoria is unclear and needs further study.

Adolescent↗
PubMed1999

Luminance of the surround and visual fatigue of VDT operators.

Luminance distribution in the visual field is considered as one of causal factors with a significant influence on visual fatigue, especially for intensive and extended Video Display Terminal (VDT) work. The aim of the study was to define visual fatigue of VDT operators for different values of surrounding luminance. Experiments were carried out in laboratory conditions under 3 lighting conditions. Only 1 lighting parameter--the luminance of the wall behind the display (surrounding luminance)--changed. Visual fatigue was measured both by a subjective evaluation of different visual complaints (asthenopic symptoms) and by objective measurements of changes in the following visual functions: accommodation, convergence, habitual horizontal phoria, critical fusional frequency (CFF), and visual acuity. The same experiments were done for CRT (Cathode Ray Tube) and LCD TFT (Liquid Crystal Display with Thin Film Transistor) screens. The results of the study have shown that there was no significant influence of the value of surrounding luminance on the asthenopic symptoms for either type of screen. A general tendency towards bigger visual complaints for LCD TFT than for CRT participants was found. An objective evaluation of visual fatigue demonstrated a tendency towards bigger changes in visual functions with an increase of surrounding luminance for both screens. Statistical analysis of the results has shown that surrounding luminance influences significantly the reduction of the accommodation amplitude (significance level <.05).

Adolescent↗
PubMed2003

Visual strain and lighting preferences of VDT users under different lighting systems.

Lighting influences users' visual strain and well-being. Therefore creating lighting that ensures visual work conditions do not result in visual fatigue is a preventive activity. The aim of the study was to model different lighting systems for visual display terminal (VDT) work and to determine their influence on users' visual strain and preferences. The results of the study showed that visual fatigue was lowest for indirect and compound lighting systems. On the other hand, in general, direct lighting realized by "dark-light" luminaires was the most preferred lighting system. Some interesting differences related to age, gender, and VDT work experience were found. On the basis of the obtained results lighting designers can be provided with some guidance.

Adolescent↗
PubMed2004

True three-dimensional displays that allow viewers to dynamically shift accommodation, bringing objects displayed at different viewing distances into and out of focus.

Under natural viewing conditions, viewers do not just passively perceive. Instead, they dynamically scan the visual scene by shifting their eye fixation and focus between objects at different viewing distances. In doing so, the oculomotor processes of accommodation (eye focus) and vergence (angle between lines of sight of two eyes) must be shifted synchronously to place new objects in sharp focus in the center of each retina. Accordingly, nature has reflexively linked accommodation and vergence, such that a change in one process automatically drives a matching change in the other. Conventional stereoscopic displays force viewers to try to decouple these processes, because while they must dynamically vary vergence angle to view objects at different stereoscopic distances, they must keep accommodation at a fixed distance--or else the entire display will slip out of focus. This decoupling generates eye fatigue and compromises image quality when viewing such displays. In an effort to solve this accommodation/vergence mismatch problem, we have built various prototype displays that can vary the focus of objects at different distances in a displayed scene to match vergence and stereoscopic retinal disparity demands and better simulate natural viewing conditions. By adjusting the focus of individual objects in a scene to match their stereoscopic retinal disparity, the cues to ocular accommodation and vergence are brought into agreement. As in natural vision, the viewer brings different objects into focus by shifting accommodation. As the mismatch between accommodation and vergence is decreased, natural viewing conditions are better simulated and eye fatigue should decrease.

Accommodation, Ocular↗
PubMed2004

Photometry in the workplace: the rationale for a new method.

OBJECTIVES: The assessment of lighting conditions in workplaces has traditionally focused on the measurement of illuminance. The rationale for a new method for the detailed evaluation of natural and artificial light in 'near work' situations, involving the assessment of luminance, is described. METHODS: The procedure comprises four successive phases: (1) identify object/images observed during work tasks; (2) outline the area of the operator's visual field where gaze is predominantly directed; (3) measure luminances in the visual field, pin-pointing all sources of primary and secondary luminance, and constructing iso-luminance maps; and (4) compare luminance ratios. RESULTS: The procedure was illustrated using the common example of near work in an office environment. Illuminance was found to be inadequate to evaluate the effects of natural and artificial environmental light in the workplace. This is due to the fact that the luxmeter is designed to integrate the light detected over a large angle, whereas in near work the operator's retina is mainly stimulated by light originating from objects/images placed in the occupational visual field. CONCLUSIONS: A detailed measurement of luminance within the occupational visual field is consistent with ocular anatomy and physiology, and can be used as part of a risk assessment for visual disturbances and to rationalize lighting at workstations.

Asthenopia↗
PubMed1994

Objective evaluation of visual fatigue in VDU workers.

Prolonged work with visual display units (VDUs) may result in a wide range of subjective complaints of visual fatigue and somatic disorders. Accepted tests for measuring the physiological correlates of eye discomfort are lacking. In this study, we tested accommodation and convergence, which are most often linked experimentally with VDU work. The tests were carried out on 16 VDU and 13 control workers aged 24 to 43 years, before work at the beginning of the week (first examination) and again four days later at the end of the work day (second examination). The results in VDU workers showed that both accommodation and convergence range significantly decreased. In addition, those workers with powerful accommodative or convergence ranges at the initial examination had a higher decrease. We suggest that accommodation and convergence measurements can be used to evaluate visual fatigue objectively in VDU workers.

Accommodation, Ocular↗
PubMed2005

Musculoskeletal disorders and visual strain in intensive data processing workers.

BACKGROUND: This study was conducted for a UK Trade Union in response to increasing numbers of health complaints among intensive computer workers in a data processing environment. AIM: To estimate prevalence of musculoskeletal pain/discomfort and visual strain symptoms among data processing workers and to explore associations with work factors. METHODS: A self-report questionnaire was distributed to data processors (n = 175) and a control group (n = 129) in the same organization. RESULTS: Eighty-six per cent of data processors reported musculoskeletal pain/discomfort in the previous year, with the highest prevalence rate found for the neck (58%). The 12 month reported prevalence for visual strain symptoms was 47%, tired eyes (41%) was the most commonly reported symptom. In the last week, 56% reported pain/discomfort and 25% visual strain symptoms. Data processors reporting pain in the previous year were more likely to be dissatisfied with their jobs (P < 0.01), to report a lack of choice in deciding what they did at work (P < 0.02), to have insufficient time to complete work (P < 0.05) or to receive help from others when time was limited (P < 0.03). CONCLUSION: The prevalence of self-reported musculoskeletal pain/discomfort and visual strain symptoms was high among data processors. A systematic approach to risk reduction addressing organizational, psychosocial and physical work factors is required. This study has implications for reorganization of this and other intensive computer work, given the increasing requirement for intensive computing work in many industrial sectors. More research is needed to investigate interactions between job demands and support systems for these workers.

Adult↗
PubMed2001

Health tips for computer users.

Computers have changed everything about our world. Any change of this magnitude brings new challenges and new concerns for the long-term effects of exposure to the product. Computers especially pose specific risks to home care workers. This article reviews health and safety practices related to desktop and hand-held computers.

Anxiety↗
PubMed1950

Visual fatigue.

Explore the source record for details and available documents.

Asthenopia↗
PubMed1975

Evaluation of the status of binocularity in the non-strabismic and strabismic with regular and prolonged testing.

The need for "in-depth" study of the status of binocularity in true space of both the non-strabismic and strabismic before orthoptics is discussed. Vectogram tests to ascertain the status of binocularity of the non-strabismic and the strabismic are explained. With the strabismic, the Single Oblique Mirror Stereoscope is used and the tests with it are enumerated. Significant enhancement of diagnosis of the status of binocularity in the non-strabismic is obtained by testing over a prolonged period of time, instead of relying only upon tests based upon instantaneous response. Prolonged testing techniques utilizing Vectograms in which the patient used alternating saccadic, jump, oculo-rotary fusional movements from the straight ahead position into the lower reading field are used.

Asthenopia↗
PubMed1976

Eye movements during reading: case reports.

Since the time of Javal, it has been well established that normal reading eye movement patterns have 3 principal components: (1) small saccades that move the eyes from word to word, (2) large saccades that return the eyes to the beginning of the next line, and (3) fixation pauses between each saccade for information processing. We discuss the vision analysis results and show the quantitative reading eye movement records, measured with the infrared photoelectric method, of 5 patients examined in the Neuro-optometry Clinic. The reading records showed a wide variety of behavior: 1 patient performed normal reading movements, 1 "slow reader" manifested an excessive number of fixations as well as extended fixational durations, another "slow" reader only exhibited an excessive number of fixations, a patient with dyslexia performed backward reading movements, and 1 patient exhibited nystagmus superimposed upon the reading pattern.

Adult↗
PubMed1978

Association of symptoms with measures of oculomotor deficiencies.

Phoria, vergence, and fixation-disparity were measured at near working distances for a nonclinical sample of 3rd-yr optometry students. A questionnaire divided the sample into 33 symptomatic and 44 asymptomatic subjects. Discriminant analysis was used to determine which clinical measures best predicted the group to which each subject belonged. Sheard's criterion was a good discriminator for exo deviations, and a variant of Percival's criterion was good for eso deviations. Fixation-disparity variables proved to be valuable diagnostically. The best fixation-disparity measures were the curve slope, curve type, and amount of fixation disparity.

Asthenopia↗
PubMed1984

Relation of symptoms to accommodative infacility of school-aged children.

Conventional optometric wisdom holds that accommodative infacility may result in asthenopic symptoms, yet the literature contains little support for this belief. We determined whether failure to achieve 8 cycles per minute of binocular accommodative facility or 11 cycles per minute of monocular accommodative facility tends to be associated with symptoms. Sixty subjects were given questionnaires to determine whether they were symptomatic. Monocular and binocular accommodative rock using plus and minus 2 D lenses was performed. Statistical analysis indicates that symptomatic subjects performed significantly poorer than asymptomatic subjects on both monocular and binocular facility tests. Patients presenting with asthenopic symptoms should therefore be tested for accommodative infacility.

Accommodation, Ocular↗