Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – With antiglare or shading
Reexamination Certificate
2001-04-03
2002-05-14
Mai, Huy (Department: 2873)
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
With antiglare or shading
C351S158000
Reexamination Certificate
active
06386701
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to eyewear directed to relieving eye-related problems such as, eye muscular fatigue, headaches, and eye redness, such problems generally being identified as computer vision syndrome (“CVS”), or asthenopia, resulting from the use of a video display terminal. The visual science dictionary defines asthenopia as the subjective complaint of uncomfortable, painful, irritable vision.
BACKGROUND OF THE INVENTION
Computers have equaled the telephone in becoming the most indispensable piece of office equipment. Because computer use is such a visually demanding task, vision problems and symptoms have become very common in today's workplace. A survey of optometrists indicated that 10 million eye examinations are given annually in this country, primarily because of vision problems related to visual display terminals (VDT) use. This series of eye symptoms has became known as computer vision syndrome (CVS). This condition most commonly occurs when the viewing demand of the task exceeds the visual abilities of the VDT user. Almost three-quarters of people suffering from the condition are those who use corrective eyeglasses. The physiological implications for the disparity in those suffering from the condition continues to confound professionals in the field. The problem purportedly is exacerbated by the reflections produced by the lenses of the eyeglasses.
CVS is a byproduct of excessive VDT screen viewing without regard to practical visual hygiene. The symptoms of CVS can be diminished, or eliminated, if proper equipment is employed. The American Optometric Association defines CVS as that complex of eye and vision problems related to near work which are experienced during or related to computer use. The symptoms can vary, but they include eyestrain, headaches, blurred vision (distance, near, or both), dry and irritated eyes, slowed refocusing, neck ache, backache, sensitivity to light, and double vision.
The eyes are designed to be stimulated by light and to control the amount of light entering through the pupil. The predominant cause of CVS is the overwhelming extraneous light and information entering the eye when a person is using a VDT. Limiting the extraneous light coming from overhead lights can result in an immediate improvement in comfort. Controlling the amount of light that enters the eye from different directions when the operator is using the VDT will result in optimal eye relief. Limiting the light will allow the operator's eyes to concentrate on the task at hand. As a consequence, blocking the light and information coming to the eye from different directions, except for the computer screen, makes it the single most critical parameter requiring control in order to minimize CVS.
A person engaging in near vision work is at a great risk of experiencing discomfort glare when the source of light is brighter or closer to the point of attention. This same principal applies when the light coming from behind the person, reflects on the glasses and enters the eye from a close proximity. Another significant contributor to CVS are veiling reflections, those images that are repeatedly transmitted between the computer screen and the lenses of the eyeglasses.
All segments and age ranges of society are experiencing exposure to VDTs and engaging in activities using computers such for shopping, playing games, corresponding and performing research. This increasing exposure is occurring all over the world resulting in an explosion of the numbers of individuals suffering from CVS. According to an Occupational Safety and Health Administration report published in November of 1999 the U.S. government estimates that 90% of the 70 million US workers using computers for more than 3 hours per day experience CVS in some form. In addition, a study conducted by the Department of Human Factors Engineering, University of Occupational and Environmental Health, Japan, reported that visual strain occurred as quickly as 60 minutes after commencing VDT operation.
The eyelids and tissue above the eyes contain glands which secrete tears. These tears cover the eye surface and maintain moisture for normal eye function. The tears also help to maintain the proper oxygen balance of the external eye structures and to keep the optical properties of the visual system maintained. The normal tear layer is cleaned off and refreshed by the blinking action of the eyelids. The blink reflex is one of the fastest reflexes of the body, and is present at birth; however, our blink rate varies with different activities, faster when we are very active, and slower when we are still or concentrating. Research has shown that the blink rate of VDT workers drops significantly during work at a VDT, compared with work activities prior to, and following VDT work. Possible explanations for the decreased blink rate include concentration on a task or a relatively limited range of eye movements. The size of the eye opening is related to the direction of the gaze. As a person gazes higher, the eyes open wider and the amount of tear evaporation roughly relates to the extent of the eye opening. The higher the gaze angle when viewing a VDT screen, the greater the resulting tear loss. The higher gaze angle also results in a greater percentage of incomplete blinks. Since contact lenses float on tears, people that use them are especially vulnerable to discomfort resulting from the dryness and have been instructed by the professionals not to use them during computer work.
Human eyes are stimulated by light and are capable of controlling the amount of light entering the eye through the pupil. There are conditions existing today that are foreign to the natural lighting environment, and which can cause the eye to experience an adverse reaction to light. The largest single factor in the workplace is glare. Generally speaking, there are 2 kinds of glare. Direct glare occurs, for example, when an operator sits at their computer and a light shines directly into their eyes. Reflective glare is far less perceptible and is generated by light sources from behind, above or even next to the computer operator. Reflective glare bounces needless illumination onto the user's monitor or lenses of the eye glasses. Light from these unexpected sources is just as likely to result in CVS.
Discomfort from glare is caused primarily by great disparities in brightness in the field of view. It is much more desirable to eliminate bright sources of light from the field of view and to strive to obtain a relatively even distribution of luminaries. A person is at great risk of experiencing discomfort from glare when the source of light is brighter and closer to the point of attention. One of the primary reasons that discomfort glare is a problem for computer users is that light often leaves the overhead flourescent fixture in a wide angle, resulting in light directly entering the worker's eyes. This is particularly a problem for computer workers because they are generally looking horizontally into the screen. Bright, open windows pose the same risks as overhead light fixtures.
A multitude of solutions to control CVS have been offered. Some of these efforts have yielded limited benefits. Some of the solutions have been contradictory, for example, dimming lights to minimize glare, and yet maintaining light bright enough to see text on a document in order to prevent strain. Also, for many companies it is nearly impossible to implement environmental solutions when large numbers of individuals operating computers sit near windows which transmit ambient light that may need to be controlled. Some individuals may want the window shades open to provide sunlight and warmth, while other computer operators in close proximity may desire to have the windows closed to limit the amount of ambient and reflected light falling upon their computer screen.
The difficulty associated with controlling the multitude of environmental factors has been the major reason why all the solutions available have not eliminated CVS. New parabolic fixture
Basimah Khulusi MD, LLC
Lathrop & Gage LC
Mai Huy
LandOfFree
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