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Among the numerous threats to the dentist's health there is one relating to the eye. The paper discusses the impact of selected adverse factors on the eye in connection with dental practice in the surgery.
The article presents in the ophthalmoergonomic aspect data from studies on the character of labour activity, condition of visual organs, vision conditions, and functions of the visual analyzer in dental mechanics. It has been ascertained that during the labour process, it is the functions of accommodation and contrast sensitivity of the eye that bear the highest strain (P < 0.05), and by the vision conditions delineation, the dental mechanic's work is on the list of those jobs requiring high visual efficiency (III B category of visual jobs according to the adopted and enforced standards classification), which facts necessitate ensuring high levels of illumination. Recommendatory measures are presented designed to prevent in dental mechanics general and visual fatigue (eyestrain and to maintain their capacity for work.
Physiological parameters of vision were studied in three professional groups (a total of 1204 subjects): microscope operators, subjects working with magnifying glasses, and computer users. General and specific features of visual system fatigue formation were identified. Because of complete (in microscope operators) or partial (in subjects working with magnifying glasses and display users) "deprivation" of accommodation, these subjects develop early presbyopia (at the age of 30-35 years). In microscope operators long strain of accommodation system leads to professional myopia, while display users develop pseudomyopia. The highest overstrain is observed after 4 years of work in microscope operators, after 5 years in magnifying glass users, and after 6 years in computer users.
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The natural asthenopic pattern of the process of reading shows it necessary to set sanitary standards of publishing production, namely, printing type styling and the printing quality of publications. The necessity of sanitary classification of publishing production stems from the specificity of reading the publications of different functional uses and from the physiological features of vision in different age group readers. The developed sanitary classification of printing production is based on the researches into the actual visual load while reading the publications of different types by readers of different ages.
While working with displays, a combination of white and yellow objects against the black, dark grey, and blue backgrounds was found to be the best in visibility. When the objects were observed against the pale grey and green backgrounds of a display, eye functional changes were minimal, which causes the authors to recommend them as the optimum backgrounds. To reduce visual fatigability when a person works on a computer requires to alternate backgrounds by using white and yellow objects against the black and blue backgrounds for short-term emergency transmissions and green and pale grey backgrounds for presenting continuous current information.
25 Arabic numerals (0-9) lined in a row were displayed with 4 different patterns on CRT. The subjects were asked to find out the one missed numeral in the row and to press the key corresponding to the numeral. The work lasted for 3h. Longitudino-Kinetic visual acuity was measured before and at 30, 60, 80, 100, 120, 150, 180 minutes during the work. The results showed that the Longitudino-Kinetic visual acuity dropped with working time and recovered after work quickly at first and then slowly.
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The difficulty of video display terminal users with bifocal lenses through a traditional workstation increases the complaints and risks for upper extremity cumulative trauma disorders. Furthermore, the regular and no lens users also have problems with traditionally designed workstations over prolonged periods of video display terminal use. A study was conducted on 14 subjects to investigate the effect of computer monitor location for video display terminal users with or without bifocals on subjective assessment and performance. The two monitor locations were 15 degrees and 40 degrees below horizontal eye level. The experimental task consisted of reading words from computer screens and typing them from the reverse side to the next column. Each experimental session lasted one hour. Males with bifocal lenses had less discomfort in the neck, shoulders, forearms, and wrists, less tiredness and eyestrain and higher performance with a 40 degrees angle monitor than with a 15 degrees angle monitor. A similar conclusion has been reached for females. Users with bifocal lenses had significantly higher neck discomfort and lower performance than nonbifocal users. The 40 degrees angle monitor caused less neck discomfort than the 15 degrees angle monitor did. Overall, females had less physical discomfort, less tiredness, and higher performance than males.
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This investigation searched for the relationship between amount of nearwork, asthenopic symptoms and visual function, in a group of office workers engaged in telemarketing. Phoria, monocular accommodative facility with +/- 2 lens flippers and near point of convergence were measured in 100 office workers (mean age 21 +/- 2.6 years) whose uncorrected visual acuity was 20/30 or better. Daily hours of reading hard-copy and of computer use, and the level of asthenopic symptoms, were measured using a questionnaire. In this sample, telemarketers were involved 5.84 +/- 2.02 daily hours in computer use, and 2.87 +/- 2.13 daily hours in reading. The following asthenopic symptoms were present twice or more times in a week: headaches 16%, pain in the eyes 17%, red eyes 18%, blurred vision 10%, double vision 3%, burning eyes 19% and watery eyes 19%. An association was found between the amount of hours using computers and red eyes (chi 2 = 4.4, p = 0.0359) or blurred vision (chi 2 = 8.35, p = 0.0038). And also between deficit of convergence and headaches (chi 2 = 4.3313, p = 0.0374) or red eyes (chi 2 = 3.6416, p = 0.0564). No other associations could be found between the accommodative facility test results, the near point phoria, and the amount of nearwork or the asthenopic symptoms. In conclusion, computer use in telemarketing is associated with few asthenopic symptoms. Near point of convergence should be routinely measured, as it is associated with some asthenopic symptoms.
The article demonstrates analysis of present methods aimed at functional stimulation of vision. The authors show leading role of laser stimulation methods, justify terms--"operative" and "long-term" correction of vision--referring to occupational activities of aviation professionals.
The authors suggest an original method helping to diagnose and prevent visual fatigue and based on PC software. The software enables diagnostic and prophylactic measures conducted directly at the workplace.
PURPOSE: We investigated eyestrain in normal subjects induced by gazing at a random-dot stereogram on a parallax barrier system 3-D display. METHODS: The 41 subjects were divided into 4 groups according to the type of correction. Near point of accommodation, accommodative relaxation, and contraction times were measured with an accommodo-polyrecorder before and after a stereoscopic visual load, and 15 min and 30 min after a rest. The subjective symptoms were assessed by a 7-point rating questionnaire at the same time as the measurements. RESULTS: After 15 min of sustained visual load, the near point of accommodation was prolonged significantly in the groups without correction and with soft contact lenses(SCL), and accommodative contraction and relaxation times were significant delayed in the groups without correction, with hard contact lenses(HCL), and with SCL but not in the group with spectacles. These changed values of accommodation returned to their previous value following the rest. Significant increase in the rating questionnaire was found in the subjective symptoms of "eyestrain", "eye heaviness", "clouding", "eye dryness" and "irritation of eyes" after loading in the groups without correction, with HCL, and with SCL. In the spectacle group, there was no significant change in the subjective symptoms of "clouding" and "eye dryness". CONCLUSION: From these results, it is concluded that gazing at stereoscopic images on the parallax barrier system 3-D display causes severer eyestrain in cases of correction with contact lenses and in uncorrected cases than in cases with spectacles.
OBJECTIVE: To evaluate the visual function of the visual display terminal (VDT) operators under the Multi-user system. METHOD: Subjective symptoms of the VDT operators under the Multi-user system were measured before and after work in the field study. Visual indices were measured at 8:15, 9:15, 10:15, 11:15, or 12:15 a.m. RESULT: No discomfort symptom was observed during the working time, and Longitudino-Kinetic visual acuity, and Critical flicker frequency didn't decrease. Refraction showed no significant decrease as compared with that at 8:15 except that of right eye measured at 12:15. CONCLUSION: The Visual function of the VDT operators remained good in the Multi-user's system.
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PURPOSE: We investigated experimentally the effect on eyestrain of outward-shift stimuli for accommodation. METHODS: Six female students fixed optical outward-shift stimuli for accommodation during 2 min immediately after 15 min of a sustained task on a 3-D display. Before and after the trial, their ocular functions were measured and their subjective symptoms were assessed. The outward-shift stimuli were applied by moving the targets of scenery images from far to near and near to far repetitively at around both eyes' far point position. As a control, stationary targets at the position of 0 D were used instead of moving targets. The same experiment was repeated twice for each subject. RESULTS: In the first experiment, there were significant changes in the accommodative contraction time, the accommodation lag, and the myopic shift, and the subjective symptoms of "eyestrain" and "eye dryness" in the control group, but in the stimulus group there were only increases of the complaint of "eyestrain". In the second experiment, the changed items were the contraction time and the complaints of "eyestrain" and "eye dryness" in both groups. The outward-shift stimuli caused a tendency in the far point to shift outward in the first experiment, and there was a statistically significant inward shift in the second experiment. CONCLUSION: From these results, it is suggested that the outward-shift stimuli for accommodation are effective in relieving eyestrain following the deterioration of ocular functions except when the far point is shifted inward.