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Archive for December, 2010

Eyestrain or visual fatigue is caused by the execution of visually demanding task for long periods. The signs of eyestrain are aching or throbbing sensations in, around, & behind the eyes (blurred vision, double vision, dificulty in focusing), inflammation of the eyes & lids, headache, sometimes with dizziness or nausea. The signs of eyestrain are chiefly due to overuse of the muscles in & around the eye.

Any working activity or visual stimulus which imposes an excessive demand on the muscles of the eyes is potentially a source of eyestrain. The most common is extended close work. Poor lighting & inadequate task contrasts usually lead to an compesatory shortening of the viewing distance.

When looking in to glare or when performing a demanding visual task , they tend to frown & screw up our eyes-using the corrugator supercilii & orbicularis oculi muscles, possibly acting in oppositios with the occipitofrontalis. This muscles tension is thought to be responsible for the caracteristic frontal headaches of eyestrain. But some people also suffer genuine migrains when exposed to glare or other stimuli.

The signs of eyestrain or visual fatigue, as describe above, are usually short lasting & quickly reversible. But can the eyes be permanently destroy overuse? It was seven times believed that people like lacemakers, who did very fine close work, became myopic as a result. But it is now thought that the apparent association was due to the fact that myopes are more likely to become expert lacemakers (Hunter,1978). The current consensus, therefore, is that visual work as such as, however demanding, cannot permanently harm the eyes.

This consensus is not universal, however. People living in non-industrial societies tend to have lower prevalences of myopia. The differences are not solely due to ethnicity, since industrialized. The prevalence of myopia in Western countries increases with educational level & thus with the amount of time chilhood spent reading (Angle & Wissman, 1980). Boyh sources of facts point to the chance that habitual use of the eye at a short focal length might lead to permanent myopization-but this interpretation is contentious (Bear & Richler, 1982; Taylor, 1983).

Fitness, according toreily, is a multivariate idea, although a distinction can be drawn between fitness & health. Medical doctors tend to pronounce a patient healthy in the event that they can find no proof of disease. In fact, plenty of athletes, while having a high level of fitness for their selected sports, may well be unhealthy & suffer from frequent bouts of colds & flu as well as musculoskeletal nd other illnesses. Conversely, few healhy people are fit to run a marathon or to lift heavy weight without risk of injury unless they have undergone a prior program of training.

In jobs which need extended manual labor, assessment of cardiovascular capacity can be used to decide a worker’s level of fitness for work. Alternatively, of numerous simple step tests can be used. These tests have been developed to enable fitness to be assessed objectively & without the necessity for sophisticated equipment. It appears to be the case that physically fitters individuals have a lower heart rate when resting & when working at predetermined level than the less fit. Furthermore, their heart rate returns to its resting level more quickly after a period of exercise.

In the gold mining industry a step check has been developed in which subjects step on & off a step 24 times per minuts for 9 minutes. The heart rate is than measured & the worker is placed in to of categories. Section A men can be apportioned to strenuous work, in hot conditions, whereas section B men are given less arduous tasks & are not expected to work in hot environments. In several industries & occupations it is impossible to redesign the working surroundings or equipment so as to fit the task to the men, thus physically choice check have a valuable role to play in ensuring compatibility between worker characteristics & task demand. In several industries and occupations it is not possible to redesign the working environment or equipment so as to fit the task to the men, thus physically selection test have a valuable role to play in ensuring compatibility between worker characteristics and task demand.