Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2000-05-31
2003-02-04
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
Reexamination Certificate
active
06513931
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and apparatus for use in optometric examinations of video display terminal users.
BACKGROUND OF THE INVENTION
An increasing number of people spend many hours a day looking at a video display terminal (VDT), such as a computer screen monitor. Whether used for business, entertainment, pleasure, research, or other reasons, prolonged time spent focusing on a VDT screen can lead to considerable eye strain. As the use of VDTs becomes even more widespread, so too does the number of ophthalmological afflictions caused by their use. These afflictions are often manifested as headaches, neck or shoulder pain, tired eyes, color fringes, blurred vision, double vision, changes in spectacle prescription over time, or loss of focus. The alphanumeric and graphic character images comprising VDT images are made up of pixels that do not have clearly defined borders. The eye muscles of accommodation constantly try to bring these images into focus, causing strain on the eyes.
VDT users typically maintain a constant distance of approximately 40-60 centimeters from a VDT. The constant distance forces prolonged use of the same eye muscles, resulting in significant amounts of stress and fatigue on the eyes. These characteristics of VDT use, aggravated by the many hours that VDT users spend looking at VDTs, cause peculiar eye problems requiring prescription spectacles specifically selected to treat and prevent the afflictions of VDT users.
To determine an effective prescription for VDT users, test equipment and procedures must be implemented to simulate actual use of a VDT. A prescription for reliable corrective lenses cannot accurately be determined without examining the eyes under conditions that accurately simulate those encountered by VDT users.
The traditional process used by medical practitioners to assess the need for corrective lenses involves placing an apparatus in front of the patient that enables the doctor to change lenses while simultaneously asking the patient to choose which lens performs the best. As the doctor changes lenses, the patient looks through the apparatus to focus on a test image. Through essentially a trial and error process, the doctor determines a combination of lenses and a prescription that provides the greatest relaxation for the eye muscles. However, if the image upon which the doctor has the patient focus does not accurately simulate the actual conditions the patient experiences, the prescription cannot be determined reliably. Traditional forms of testing equipment, including nearpoint cards and projections on walls, do not provide satisfactory simulation of actual conditions for VDT users. A doctor is reduced to essentially making an educated guess as to the prescription, letting the patient use the prescription spectacles to determine if they are satisfactory. If they are not satisfactory, the patient then has to return to the doctor and the process is repeated until a satisfactory prescription is achieved. This process is inefficient, wasting valuable time and energy.
An adequate vision test for VDT users should solve at least three main problems. The first problem is one of providing the doctor flexibility. A vision test must be sufficiently flexible to allow a doctor to examine patients with a wide variety of individual needs. The second problem is one of adequately simulating a VDT. The vision test should accurately simulate the actual work conditions of VDT users. Solving this second problem requires a testing apparatus that forces the patient's eyes to act as they would when focusing on a VDT. Solving the problem of accurate simulation is made possible if the patient is in the same relative position they would be in when using a VDT (i.e., the same distance from the screen, etc.), and if the test image accurately simulates a VDT display. The third problem that must be solved is the problem of accurate, objective evaluation. Solving this third problem is accomplished though retinoscopy. Retinoscopy involves using a retinoscope objectively to measure the refractive status of the eyes.
To be effective, retinoscopy requires reducing the off-axis angle during the examination. The term “off-axis angle” refers to the angle between the line segment from the patient's eye to the patient's focal point on the test image, and the line segment from the patient's eye to the doctor's retinoscope. This allows the doctor to examine the patient from a point substantially along the line of sight from the patient to the test image. In order to obtain an accurate, objective evaluation of the patient's eyes, the doctor's retinoscope should be within approximately one inch of the test image. Using the retinoscope at a location that provides a small off-axis angle is what allows for an objective evaluation of the patient's prescription needs. If the off-axis angle is too large, the doctor cannot use the retinoscope for an objectively accurate evaluation. The alternative is the subjective process of having the patient try test lenses and report which prescription functions the best. This subjective evaluation does not afford the same accurate results as the objective evaluation though proper use of a retinoscope at a reduced off-axis angle.
Vision testing systems currently available do not provide an economical, reliable, compact, or simple-to-use solution to all three of these problems. Even existing systems designed specifically for conducting optometric exams on VDT users do not completely solve the problem of adequate simulation. Although they do place the testing screen a distance from the patient that represents VDT use, they do not provide the most accurate simulation of a modern, high-resolution VDT display. Examples of such systems include those represented by U.S. Pat. Nos. 4,576,454; 4,998,820; 5,191,367; and 5,325,136.
One of the biggest limitations on previous eye-testing systems is that they provide little flexibility for doctors to meet patient needs. They are limited to one static, fixed image. Most VDT users are subject to continually changing images, constantly forcing the eye to refocus on new characters. Without being able to change an image, a doctor cannot accurately simulate actual VDT use. Using one static image also prevents efficient testing of VDT users who have special needs, such as children or others who do not read well, and people whose reading proficiency is in another language. To accommodate such users would require physically changing the actual apparatus and substituting it with another specialized apparatus specifically designed to accommodate that patient's needs. In addition to the time wasted physically switching apparatuses, a doctor would have to purchase, maintain, and store as many different types of apparatuses as necessary to meet the individual needs of patients. To do so, a doctor would incur significant expense and inconvenience.
While there are vision testing apparatuses that use computer screens (and therefore accurately represent the display of a VDT), those systems are not specifically designed to determine prescriptions for use with VDTs, and they do not simulate actual working conditions of a VDT user. One such system is the AcuityMax computer software program produced by Science20/20. That product is not cost effective because it requires a dedicated computer (or the manufacture will not guarantee support). Accordingly, a doctor is forced pay for an entire computer system for the sole purpose of testing vision. Also, that product is not designed to test VDT users for the purpose of determining a prescription for use with a VDT. AcuityMax is only used in acuity testing to take the place of a standard acuity projector. It is used at a distance of 8 to 24 feet from the patient, not at a distance representative of VDT use. Because the software allows a computer to replace an acuity projector, rather than using the computer to adequately simulate a VDT work environment, it is ineffective in solving the problems encountered in deriv
Squire David C.
Torrey Jonathan G.
Manuel George
PRIO Corporation
Stoel Rives LLP
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