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Strategies & Market Trends : DAYTRADING Fundamentals -- Ignore unavailable to you. Want to Upgrade?

To: Eric P who wrote (4517)	9/30/1999 10:47:00 PM
From: Eric P	Read Replies (1) \| Respond to of 18137

Updated Thread Summary: #reply-11414589

To: Eric P who wrote (4517)	10/1/1999 2:15:00 AM
From: scanshift	Read Replies (1) \| Respond to of 18137

Some comments on viewing distance and viewing angle relative to quote screens If someone is going to watch a quote screen for years on end, then it should be positioned properly. This will reduce viewing mental fatigue that one may not be aware of, until they have tried the ideal viewing angle and screen distance. Watching a quote screen is done at relatively close distance. Factors such as mental fatigue (both realized and unrealized), red or itching eyes, and headaches, can result from improper viewing distance and viewing angle. When an individual watches a quote screen, two things happen to the eyes. They accomodate and converge. Both these reflexes cause eye strain. Accomodation is when the eye lens changes its focus as the viewing object changes distance. The eyes have a resting point of accomodation. This is the distance at which the eye focuses when there is nothing to look at. At one time this resting point was thought to be infinity. Recent studies have shown this is not to be the case. The resting point differs among individuals, but the average is about 31.5 inches. Uninterrupted viewing of a monitor at a distance closer then you resting point of accomodation increases eye strain. The ciliary muscle must work significantly harder to focus on this closer screen than it does to focus on one at the average distance of 31.5 inches. Viewing angle affects the eyes ability to accomodate. A study found that subjects over the age of 42 increased their ability to accomodate by an average of 25 percent by directing their eyes down in the "usual reading position." The improvement for younger subjects was even greater. Also, there is a preference for a greater downward gaze angle when looking at a screen 20 inches away, than one that is at 40 inches. Convergence is another factor in the discussion. The closer the screen, the more the eye muscles move the eyes inward toward the nose. Convergence lets both eyes focus on the object at the same place on the retina. The eyes have a resting point of convergence. This varies among individuals, but the average is around 40 inches. Looking at objects closer than your resting point causes strain on the muscles controlling eye movements. The closer the distance, the greater the strain. The resting point of convergence changes with viewing angle. The lower the gaze angle, the closer resting point of convergence. With a 30 degree upward gaze angle, the unstimulated eyes converge on a target about 53 inches away. Looking horizontally at a screen, the viewing distance would be about 44 inches. When looking down 30 degrees, the resting point of convergence equals about 35 inches of viewing distance. Several studies show more benefits of a downward gaze angle. The studies found that, when looking back and forth between targets placed at eye level, head movements occurred with even very small movements of the eyes. However, when the targets were at a downward gaze angle "head movements hardly participated in the movements." The studies conclude that, given all the above factors, ideally a screen should be 40 inches away and that the gaze angle should be at 30 degrees down.