Maria Beatriz G. Villanueva

Adjustments of posture and viewing parameters of the eye to changes in the screen height of the visual display terminal

To understand the motions caused by the interaction among the different body parts, adjustments of both eye position and body posture to screen height settings of 80, 90, 100, 110 and 120 cm were determined in 10 subjects. The subjects engaged in a non-keyboard, interactive computer game requiring constant visual monitoring. Changes in body positions were determined by video image analysis for the posture parameters and by video frame analysis for the eye parameters. Analysis of variance and correlation analysis showed that neck angle, thoracic bending and vertical eye position were significantly affected by changes in the screen height of the VDT. The study of the interrelationship of eye position and body posture suggested that changes in body positions served to complement the eye position in attaining a better view of the visual target. Viewing angle was observed to be decided mainly by inclination of the neck and the eye. Thoracic bending was also noted to contribute in setting the viewing angle, although to a lesser extent. On the other hand, viewing distance and trunk inclination showed significant correlation.

Analysis of ocular surface area for comfortable VDT workstation layout

This paper proposes a comfortable visual display terminal (VDT) workstation layout based on an analysis of ocular surface area (OSA). A large OSA induces eye irritation and eye fatigue because the eye surface is highly sensitive to various stimuli. The authors considered that OSA must be one of the useful indices of visual ergonomics and applied it to evaluate VDT workstation layout. Each subject was asked to perform a word processing task using four different VDT workstation layouts. It was found that the main factor affecting OSA was not cathode ray tube (CRT) height itself but the distance between the CRT and keyboard. Thus the following workstation layout is recommended to realize comfortable VDT operation: (1) the desk height should be adjusted to the users height; and (2) the CRT display should be set closer to the keyboard to provide a smaller OSA.

Effects of the liquid crystal display tilt angle of a notebook computer on posture, muscle activities and somatic complaints

Abstract More con strained posture and higher neck muscle activities have been reported among users of notebook computers than those of desktop computers. Complaints of eye and musculoskeletal d iscomfort as well as di fficulty of keying were greater during work with notebook computers. These reports ascribed the findings to the differences in the size of desktops and notebooks. Another ergonomic aspect of the notebook computer distinct from the CRT is its angle-dependent luminance contrast. The present study investigated the effects of liquid crystal display (LCD) tilt angle of a notebook computer on posture, muscle activities and somatic complaints in 10 subjects. At the tilt angle of 100°, the subjects were noted to have relatively less neck flexion. The static neck extensor muscle activity was also lowest at this tilt angle. Nonetheless, the complaint survey revealed higher rates of discomfort while viewing and using the LCD set at the tilt angle of 100°. The findings of this study strongly suggested that the ergonomic features and problems attributable to notebook computers are distinct from the desktop computers. The points of interest raised in this paper should be considered when contemplating the use of notebook computers. Relevance to industry The use of notebook computers has increased steadily over the last 5 years , especially in Japan. Few authors have ventured to study the problems associated with these smaller computers . The results and suggestions of this stu dy may contribute to improve the design of notebook computers and the workstations .

Toxic effects of hexane derivatives on cultured rat Schwann cells

The cytotoxic effects of the following five hexane-related compounds were examined on Schwann cell DNA synthesis: 2,5-hexanedione (2,5-HD), 2-hexanol (2-OH), 2-hexanone (MnBK), 2,5-dimethylfuran (DF) and gamma-valerolactone (VL). Schwann cells were isolated from the sciatic nerves of neonatal Sprague-Dawley rats and cultured. [(3)H]-thymidine incorporation into Schwann cell nuclei was measured by scintillation spectrometry and autoradiography when hexane derivatives were added to the culture medium. All of the hexane-related compounds suppressed [(3)H]-thymidine incorporation in a concentration-dependent manner. DF was the most cytotoxic for the inhibition of Schwann cell DNA synthesis among the compounds. The finding suggests that DF-mediated cytotoxicity should be taken into account as a possible additional mechanism of hexane intoxication, especially in the impairment of mitotic cells.

Correlation analysis between visual acuity and sitting postural parameters of young students

The relationship between failing eyesight and the sitting posture of young students while studying was studied quantitatively. Among the 19 students who participated in this study, 9 were classified as emmetropic and 10 were myopic. The mean age was 13.2 +/- 2.2 (mean +/- standard deviation) years. Viewing distance, neck angle, viewing angle, vertical gaze direction, and ocular surface area while studying were measured from the lateral and frontal view images of video recordings of the posture. Viewing distance, accommodative power, neck angle, viewing angle, near point, and log transformed visual acuity showed significant differences between these two groups (p < 0.001). Viewing distance of myopes (15.0 +/- 1.9 cm) (mean +/- standard desviation) is shorter than that of emmetropes (30.2 +/- 4.1 cm). Accommodative power of myopes was lower than that of emmetropes. Correlation analysis revealed that the viewing distance of students significantly correlates to neck angle, viewing angle, accommodative power, near point, and visual acuity (p < 0.01). It can be surmised that the failing eyesight of young students results from postural problems such as shortness of viewing distance and increased neck flexion.

Urinary metabolite levels and symptoms in Filipino workers using organic solvents

SummaryTo compare symptoms with urinary metabolite levels, 900 workers from 7 organic solvent-using industries were studied. Urinary metabolites were determined using a high performance liquid chromatograph. Urinary hippuric acid concentrations exceeding the reference value (2.5 g/g creatinine) were found in 78 (8.7%) workers. However, only 3 (0.3%) and 1 (0.1%) of the participants exceeded the reference value for mandelic (0.8 g/g creatinine) and total methylhippuric acid (1.5 g/g creatinine), respectively. The sum of the values of the ratio of measured urinary metabolite concentration to the corresponding ACGIHs biological exposure indices (BEI) [(HA/ BEI of HA + MHA/BEI of MHA + MA/BEI of MA)] exceeded 1.0 in 166 (18.4%) workers. Majority of them were from the footwear manufacturing industry (63/129 or 49.2%). Questionnaire interviews were also administered to determine the prevalence of symptoms while at work (acute symptoms) or within the past 6 months (chronic symptoms). Urinary metabolite levels of individual and mixed solvents were compared with the symptoms of all workers. Analysis using Spearmans rank correlation showed in workers whose urinary hippuric acid exceeded 3.75 g/g creatinine (1.5x BEI), significant correlation between their hippuric acid levels and subjective complaints. Workers whose sum of the values of the ratio of measured urinary metabolite concentration to corresponding BEI exceeded 1.5 were selected and comparing this level with their symptoms, significant correlation was also noted in some complaints.

Evaluation of the Ergonomic Aspects of Portable Personal Computers with Flat Panel Displays (PC-FPDs)

Adverse effects may accompany the increased popularity of portable computers (PC-FPDs). This paper evaluated the ergonomic aspects of PC-FPD use in two (2) experiments. The first phase studied the posture, muscle load, complaints and performance of the subjects. Ten subjects performed a text-entry task for 5 minutes using a desktop computer and 4 PC-FPDs of various sizes. Viewing and neck angles were lower and the trunk was more forward inclined while using the PC-FPDs. Muscle activities of the neck extensor during work with PC-FPDs were also higher than for the desktop computer. Increasing discomfort and difficulty of keying validated by decreasing performance with smaller PC-FPDs were noted. The second experiment looked at the effect of FPD tilt on body and eye positions and luminance. Another 10 subjects were asked to transcribe sentences using a 13.3-inch FPD with the screen set at tilt angles from 100 to 140 degrees. The results showed that at a 100-degree tilt, the subjects assumed a relatively upward gaze, longer viewing distance, wider elbow angle and forward trunk inclination with the chair height set the lowest and the computer set farthest from the edge of the table. These findings may be explained by the intent of the subjects to obtain the best viewing parameters. The subjects had the greatest difficult using the computer at this tilt angle. This setting was also least preferred during the experiment. Our studies show the need for ergonomic guidelines specific for PC-FPD use.

Relationship Between Posture and Myopia Among Students

The purpose of this study was to determine the posture of young students while studying and its relation to the degradation of unaided vision. The subjects were 19 young students (mean age, 13.2 ± 2.2 years). Quantitative analysis of posture while studying was done, and comparison was made with visual functions. The subjects’ posture was monitored from front and lateral views using a video camera. Measurements were made of viewing distance, neck angle, vertical gaze direction, and viewing angle by frame analysis of the video images. There was a significant relation between the viewing distance and eye accommodation, near point, viewing angle, and neck angle (P < 0.01). It was concluded that poor posture, especially decreased neck angle, has a significant relation to the degradation of unaided vision.