[Accommodation asthenopia and convergence asthenopia].
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Accommodation, Ocular↗
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Asthenopia induced by computer-generated fusional vergence targets.
A questionnaire was used to evaluate asthenopia in 30 normal subjects (Ss). Then, each S experienced 3 min of continuous alternating convergent and divergent fusional vergence or a control condition which was identical to the experimental condition, but without any vergence demand, i.e., version. The stimulus was a computer-generated flat fusion red-blue anaglyph picture of a horse. The order of vergence and version conditions were randomized. Asthenopia measures and maximal fusional vergence ranges measures were repeated immediately after each condition. Results indicated a significantly higher rating of asthenopia after induced vergence than version. There were no differences in maximal fusional vergence ranges or recovery values after the two conditions. Correlations between pretreatment asthenopia scores and asthenopia scores after either induced vergence or version were also not significant. Post hoc analyses of Ss grouped as having either high or low asthenopia, according to baseline ratings, revealed no significant differences in vergence or version conditions. Alternative hypotheses for these results are presented.
Adult↗
Asthenopia and the dark focus of accommodation.
To study asthenopia, we compared the dark focus of accommodation of 54 symptomatic and 56 asymptomatic control subjects. The two groups were matched for age and cycloplegic refractive error. Symptomatic subjects were defined as those who complained of asthenopia daily even though their refractive error had been corrected. Subjects with other eye diseases that could produce asthenopia such as strabismus or aniseikonia were excluded. Using a Nidek Autorefractometer AR1600, we first measured non-cycloplegic refractive error (Non-Cyclo R) in a bright room, then the dark refractive state (Dark R) in complete darkness using the instrument with the optical target light extinguished and, finally, determined the cycloplegic refractive error (Cyclo R) after instilling cyclopentolate hydrochloride. The difference between Dark R and Cyclo R was defined as DFcus (Cyclo R) and that between Dark R and Non-Cyclo R as DFcus (Non-Cyclo R). We found both DFcus (Cyclo R) and DFcus (Non-Cyclo R) to be smaller in the symptomatic than in the asymptomatic subjects, indicating that asthenopia is associated with a low rather than a high level of tonic accommodation.
Accommodation, Ocular↗
A novel in vitro model for screening and evaluation of anti-asthenopia drugs.
Patients suffering asthenopia are steadily increasing with an expanding use of visual display terminals such as computers. An attempt was made to develop an in vitro model for asthenopia. Ciliary muscle removed from eyeballs of a rabbit was stimulated with acethylcholine, resulting in contraction of the muscle. Repeated stimulations caused decreased contraction, which may be related to fatiguing of ciliary muscle and hence asthenopia. Treatment of the repeatedly stimulated muscle with cyanocobalamin restored contraction dose-dependently. Thus, the model developed in this study can be used to screen drug candidates for treating asthenopia.
Acetylcholine↗
Muscular asthenopia and eccentric ablation after photorefractive keratectomy.
PURPOSE: To investigate the relationship between muscular asthenopia and eccentric ablation after photorefractive keratectomy (PRK). METHODS: Sixteen eyes of eight myopic patients whose muscular asthenopia was corrected by subjectively accepted spectacle prism after PRK, with visual acuity better than 0.8, were followed for 6 to 14 months. On the basis of preoperative and post-operative data and corneal topography, we calculated the total corrected corneal power using the Holladay formula and then measured the ablation eccentricity (h, millimeters) and its direction. According to the formula delta approximately equals Dh, the prism effective value (delta) caused by the eccentric ablation was computed and compared with the objectively accepted spectacle prism. RESULTS: The subjectively accepted spectacle prisms were similar to calculated values from the formula. Mean difference was 0.10 +/- 0.25delta. The direction of the subjectively accepted prism was in the direction of the ablation deviation. CONCLUSIONS: Eccentric ablation is an important cause of muscular visual asthenopia after PRK. The asthenopia may be corrected by spectacle prism. The spectacle prism value may be estimated by the formula delta approximately equals Dh.
Adult↗
Post-PRK muscular asthenopia and eccentric ablation.
OBJECTIVE: To investigate the relationship between muscular asthenopia post photorefractive keratectomy (PRK) and eccentric ablation. METHODS: 16 eyes of 8 myopia cases whose muscular asthenopia was corrected by subjectively accepted triangular prism after PRK with vision more than 0.8 were followed up for 6-14 months. On the basis of data provided by the pre-PRK, post-PRK and their difference corneal topography, we calculated the real corrected corneal diopter (D) with the Holladay formula and measured the ablating eccentricity (h) and its direction. According to the formula delta approximately Dh, the prism effective value (delta) caused by the eccentric ablation was computed and compared with objectively accepted triangular prism. RESULTS: The subjectively accepted prism was similar to values calculated from the formula. Their mean difference is 0.10 +/- 0.25. The direction of the subjectively accepted prism was in the direction of ablation deviation. CONCLUSIONS: Eccentric ablation was the chief cause of post-PRK muscular visual asthenopia. The triangular prism effective value from eccentric ablation may be estimated by the formula delta approximately Dh. We must pay attention to the diagnosis, treatment and prevention of post-PRK muscular asthenopia.
Adult↗
[Relation of asthenopia and some ophthalmological, neuropsychological, and musculoskeletal parameters in workers assigned to video display terminals].
BACKGROUND: Since the use of video display units (VDU) has become widespread in the workplace, more and more research has been conducted to evaluate the possible onset of adverse effects. OBJECTIVES: We carried out a multidisciplinary investigation on a group of 660 VDU operators working for a service agency, aimed at analysing the relationship between ophthalmological, musculoskeletal and neuropsychological parameters and asthenopia. METHODS: In this study we propose a method for a qualitative and quantitative evaluation of the asthenopic syndrome based on data collected with an easy semi-structured questionnaire. RESULTS AND CONCLUSIONS: No relationship between asthenopia and refractive alteration was noted, whereas a significant association was observed between a lengthened convergence near point and the average time of daily VDU exposure. A significant relationship was also shown between asthenopia, cervical and lumbar disorders, and neuropsychological symptoms. The method for evaluation of asthenopia and the results of this study suggest useful implications in health surveillance programs. After an appropriate validation procedure, this method could represent a useful screening tool and a valid support for preventive interventions. The use of this instrument in longitudinal studies will also provide the opportunity of verifying the existence of long-term effects due to VDU exposure.
Adult↗
[Changes in the dark focus of accommodation in patients with asthenopia].
The authors studied tonic accommodation in cases of asthenopia. The subjects consisted of ten college students, aged 20 to 22 years old as normal control and seven patients with asthenopia, aged 20 to 27. The dark focus of accommodation was measured with the infrared optometer before and after a 15 min sustained visual task. No significant differences were found between the two groups on the pre-task dark focus of accommodation. After the task, significant differences were found between the pre- and post-task dark focus of accommodation in patients with asthenopia. The results suggest that the patients with asthenopia are more susceptible to autonomic nervous system imbalance than healthy persons.
Accommodation, Ocular↗
[Risk factors for asthenopia among computer terminal operators].
OBJECTIVE: To study the incidence of asthenopia among computer terminal operators as compared to unexposed administrative workers and to identify the risk factors associated with this condition. MATERIAL AND METHODS: A sample of 35 computer terminal operators and 70 unexposed administrative workers from eight computing centers at an educational institution were included in the study. The risk factors studied were: lighting, contrast, type of lighting, screen type, electrostatic field, eye to monitor distance, time and number of hours worked, age, use of corrective lenses, seniority and overtime. Asthenopia was clinically identified as the presence of at least one sign and symptom present in a given workday. RESULTS: Asthenopia was found in 68.5% of the exposed group and in 47.7% of the unexposed group (p < 0.05). Among the risk factors studied, working for more than four hours at the video display terminal was shown to have a significant association with asthenopia (p < 0.05). CONCLUSIONS: A recommendation is made to take breaks during the workday at computer terminals in order to avoid visual fatigue. Also, more extensive studies should be carried out in our population to establish safety criteria and to standardize work activities using computer terminals.
Adolescent↗
Reduction of asthenopia in patients with convergence insufficiency after fusional vergence training.
Seven patients with convergence insufficiency and related asthenopia underwent automated fusional convergence training. A matched-subjects control group crossover design was used to reduce placebo effects. All patients showed significant increases in vergence ranges with concurrent marked reduction of symptoms after training. All patients showed a flattening of and an increase in the base-out portion of their fixation disparity curve. Our results demonstrated the effectiveness of fusional vergence training in reducing asthenopia in these patients. Subsequent accommodation and vergence training using traditional orthoptic procedures yielded further reduction of asthenopia, as well as an increase in the base-out fusional range.
Adolescent↗
Reduction of asthenopia after accommodative facility training.
Five patients reporting asthenopia secondary to accommodative deficiencies underwent automated accommodative facility training. A matched-subjects, crossover design was used to control for placebo effects. All patients receiving automated accommodative training showed a marked increase in accommodative amplitude along with a concurrent reduction of asthenopia. Decreases of blur and increases of reading time were the most frequently reported changes by patients. This experiment shows the effectiveness of automated accommodative training in reducing asthenopia and improving accommodative facility.
Accommodation, Ocular↗
Is all asthenopia the same?
PURPOSE: Any of several conditions can cause asthenopia. The purpose of this study was to determine whether the particular sensations or their location vary dependent on the symptom-inducing condition. METHODS: Twenty subjects with good vision performed eight reading tasks in random order during different conditions. Each condition used different stimuli to induce asthenopia. The eight conditions were mixed astigmatism, close viewing distance, upward gaze, dry eyes, lens flipper, small font, glare, and flickering light. Subjects were asked to read until attaining a level of discomfort self-defined as "barely tolerable." After each task, subjects rated the magnitude of several symptom descriptors (burning, ache, strain, irritation, tearing, blurred vision, double vision, dryness, and headache) and their location. RESULTS: Analysis of variance with repeated measures was used to determine that all of the individual symptom sensation measures (except blur) were significantly related (p values ranged from 0.003 to <0.0001) to the inducing condition. Principal factor analysis with orthogonal varimax rotation was used to test symptom by condition relationships and determined two latent factors, designated external and internal symptom factors (ESF and ISF), that related symptoms to inducing condition. The ESF pattern comprises burning, irritation, tearing, and dryness located in the front and bottom of the eye. ESF is caused by holding the eyelid open, glare, up gaze, small font, and flickering. ESF seems highly related to dry-eye symptoms. The ISF pattern comprises ache, strain, and headache located behind the eyes. ISF is caused by the close viewing distance, lens flipper, and mixed astigmatism conditions and is likely related to accommodative and vergence stress. CONCLUSIONS: Symptom descriptors and locations were able to distinguish discomfort on the basis of causative condition. Results support two different symptom constellations and, hence, at least two different afferent pathways for symptoms of asthenopia.
Accommodation, Ocular↗
Visual evoked potential in patients with cerebral asthenopia.
Cerebral asthenopia is often overlooked as a symptom in diffuse brain lesion. An objective correlate of this symptom has so far never been demonstrated. Averaged visual evoked potential (VEP) in 10 patients with asthenopia was compared with 20 normal subjects. Both eyes and each eye alone were stimulated using bipolar recording in the midline and over each of the occipital lobes. There was no difference of latency of the VEPs in the two groups, but the amplitude of the most prominent component was significantly reduced in the patients. There was also a difference in the two groups regarding habituation and lateralisation. No amplitude difference could be found in the somatosensory evoked potential. The amplitude difference in VEP, as an objective correlate of asthenopia, is probably modal specific and suggests involvement of the visual cortex. VEP is unsuitable as a diagnostic tool due to the great overlap between amplitudes in asthenopic patients and control subjects.
Adult↗
Accommodative microfluctuation in asthenopia caused by accommodative spasm.
BACKGROUND: Although many patients complain of eye fatigue caused by accommodative spasm, there have been no reports of a good objective examination method to diagnose it. PURPOSE: The spectral power of the high frequency component of the accommodative microfluctuation (spectral power of HFC) differs according to the constrictive degree of the accommodation. In this paper, we expatiated upon our previously reported analyzing processes of the spectral power of HFC, and we investigated the relationship between normal subjects and subjects with asthenopia. METHOD: The accommodative microfluctuation were recorded when the subjects were looking at a stable target. The waves of the accommodative microfluctuation were analyzed by FFT. RESULTS: The spectral power of HFC for the distant target was 50-60 in the subjects with normal vision, but it was higher in the subjects with asthenopia. CONCLUSION: Our results suggested that the ciliary muscle was also actively working in asthenopia caused by accommodative spasm even if the patient was looking at a distant target.
Accommodation, Ocular↗
[The Pola-test in asthenopia (author's transl)].
Seventy-three patients with asthenopia and 43 control subjects were examined with the Pola-Test. The two populations showed a significantly different frequency of pathologic results on the four test patterns. The so-called "stereo test" seems to be the most important test pattern. Patients with a pathologic stereo pattern reported asthenopic symptoms significantly more frequently than the control subjects who were questioned for similar symptoms. However, since 30% of the asthenopic patients showed normal results on the four Pola-Test patterns, the indication for treatment can be based only on a combined evaluation of binocular tests and asthenopic symptoms. In asthenopia visual and conjunctival symptoms are more prominent than headache. At times they may be masked by psychogenic factors. In a double-blind study on 12 asthenopic patients symptoms improved significantly during treatment with prisms.
Adult↗
An attempt at preventing asthenopia among VDT workers.
We report the results of 3 surveys of visual display terminal (VDT) users who took a minibreak during which they viewed a stereoscopic image of a repeating parallel pattern showing planets. The single image stereogram method employed is called Stretch Eye (TM), and we evaluated the effects of Stretch Eye (TM) on asthenopia. An accommodative relaxation of about 1 D was observed in participants while they were gazing at the image. The employees of 2 information technology companies were evaluated according to a visual analogue scale (VAS) for subjective symptoms of asthenopia and eyesight. The results showed that Stretch Eye (TM) was effective in easing visual fatigue due to VDT work and it improved eyesight under working conditions.
Asthenopia↗
Is the type of VDT work important in asthenopia?
The Authors studied the relationship between visual fatigue (or asthenopia) and different types of work with display units on about 30,000 videoterminal (VDT) operators of the Italian telecommunication company. Visual fatigue was reported with data entry, data checking, word processing, dialogue enquiry, and various services. The Chi-square test showed that asthenopia was not related to any particular type of VDT work, comparing subjects working at the VDT for similar times each week. These findings provide further confirmation that the main factor determining visual fatigue in VDT operators is the amount of time spent at the display units.
Adult↗
Protective filters in the prevention of asthenopia at a video display terminal.
In this work 25,064 employees were studied with the aim of investigating whether the video display terminal (VDT) equipped with filters reduces the incidence of asthenopia with reference to weekly time spent at a VDT and duration of work at a VDT. Analysis showed that the filters themselves do not reduce the occurrence of asthenopia consequent to various factors (refractive defects, time spent at a VDT, and monitors' characteristics).
Adult↗