Ординатура / Офтальмология / Английские материалы / Diagnosing and Treating Computer-Related Visual Problems_Sheedy, Shaw-McMinn_2003

104 Diagnosing and Treating Computer-Related Vision Problems

FIGURE 6-10. Tact (Hoya, Bethel, CT). Contour plots (0.25 diopter steps) of spherical equivalent (–0.25 to +2.00) and astigmatism (0.00–1.50). Measurements by COLTS Laboratory, Clearwater, FL.

FIGURE 6-11. Technica (American Optical, Southbridge, MA). Contour plots (0.25 diopter steps) of spherical equivalent (0.00 to +2.00) and astigmatism (0.00–1.25). Measurements by COLTS Laboratory, Clearwater, FL.

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computer working distance, is very narrow. This requires the patient to maintain a single fixed head position to see the screen clearly.

In some cases, the younger presbyope is able to successfully use PALs for computer work. Such a patient does not require the add for the intermediate viewing distance, something that can be determined in the demonstration process. The PAL can be successful in this case because the patient is able to use the distance portion of his or her lenses for work at the computer. The computer display should not be located too low on the patient’s desk in this situation. The intermittent short-term computer user is another patient for which PALs are acceptable. In this situation, the work period is short and poor posture can be tolerated.

Conclusion

In most of the cases above, the prescription and spectacle design that best meet the visual needs at the computer are different than those required to meet the patient’s other daily visual needs. This is likely to continue to be the case as long as we use computer monitors that are fixed to a desk surface and for which the users are required to orient themselves to the task rather than vice versa. Counseling is often necessary to demonstrate to patients that they require a separate pair of spectacles for their computer work.

Tints and Coatings

A pink tint can provide some symptom relief. Some patients who work in indoor environments, especially under fluorescent light, obtain increased comfort with light pink lenses. This obviously can apply to computer workers, because most offices are illuminated with fluorescent lights. The pink lenses serve to cut out some of the blue light emissions of the fluorescent lights, thereby decreasing the lights’ brightness and decreasing fluorescence within the eye.

There is no specific need for ultraviolet (UV) protection at a computer. There is almost no UV emission from the computer or display. UV protection is certainly warranted for anyone exposed to significant

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UV radiation, especially those who work in outdoor environments. However, there is no particular need for UV protection at a computer.

Antireflection coatings provide some benefit to those requiring spectacles at a computer workstation, as they similarly provide better vision in most environments. The antireflection coatings are on the surfaces of the spectacle lenses and significantly reduce reflections from the lenses. Light that is reflected from the back surface of the lens and then reflected again off the front surface ends up as improperly focused light that interferes with the primary image. For example, when looking into a dark café with a bright sky overhead, it is easier to see the detail in the dark café more clearly because light from the bright sky is not reflected inside the lens and hence on top of the image of the dark café. This can happen in a computer environment, especially one in which the screen has light characters on a dark background. Reflections from behind can be a source of annoying glare to a computer user, especially high myopes whose eyes are focused within 10 cm of the reflection. Antireflection coatings have increased value for patients with cataracts and macular degeneration who have decreased contrast sensitivity.

It is a common misperception that antireflection coatings on lenses reduce reflections off computer screens. This is because the reflections that occur on the video display terminal screen are well known, and, therefore, it is easy to assume that an antireflection coating on the spectacles improves the reflections in the screen. However, an antireflection coating on the spectacle lenses does not, in any way, reduce the reflection problems in the screen. Elimination of reflections off the computer screen are covered in Chapter 9.

Computer Glasses

Employers are increasingly finding it beneficial to provide computer glasses to their computer-using employees. This improves performance and comfort as well as employee morale. Very often the employee requires glasses for general wear and, for reimbursement purposes, it can be important to determine whether the glasses that are being prescribed are specifically for computer-viewing needs or if the glasses are essentially the same as those that the patient requires for general viewing needs.

108 Diagnosing and Treating Computer-Related Vision Problems

The American Optometric Association (1995) has established criteria to determine when a pair of glasses can be considered “computer glasses.” In general, glasses or other therapeutic eye care services are considered to be computer related if

•The person would not require the use of glasses or other treatment for a less visually demanding job.

•The glasses required for work at the computer are different in prescription power or design from those that would be required to meet the other general daily vision needs of the individual.

The American Optometric Association’s specific requirements for computer glasses depend on the diagnosis as follows.

Presbyopia

Glasses for the correction of presbyopia are considered to be computer related if they are of a prescription power or lens or frame design that is different from that required for everyday visual needs. In general, this includes

•Single vision lenses prescribed specifically for the computer working distance

•Intermediate or near bifocals prescribed for use at the computer workstation

•Other special multifocal lenses prescribed for use at the computer workstation

Computer-related glasses would not include general-purpose single vision or multifocal lenses prescribed for everyday wear or PALs, except those designed specifically for computer operators.

Hyperopia

Glasses for the correction of hyperopia (farsightedness) are considered to be computer related if the individual would not otherwise require correction of his or her hyperopia for everyday visual needs.

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lens designs are being developed to fit the specific needs of our presbyopic computer users. More and more organizations are recognizing the benefit of supporting the provision of computer-specific glasses for workers. Chapter 7 further discusses ocular pathology conditions that can affect computer vision comfort.

Action Items

1.Contact your laboratory and get information on the computerspecific lens designs that they carry.

2.Ask the laboratory for consumer materials such as brochures or fact sheets.

3.Train your staff about the lens designs you plan to prescribe (Appendix 6-1).

4.Prescribe the appropriate computer lens design for yourself and staff members to experience.

5.Train staff on demonstrating prescribed lens designs, materials, tints, and coatings.

6.Train staff on proper measurement and fitting of computer-specific lens designs.

7.Be prepared to identify when a pair of glasses meets the criteria to be computer-specific eyewear.

References

American Optometric Association. Criteria for Determining Whether the Need for Eyeglasses or Other Treatment Is Related to Computer Use. St. Louis, MO: AOA,1995.

Bachman WG. Computer-specific spectacle lens design preference of presbyopic operators. J Occup Med 1992;34(10):1023–1027.

Brischer C, Mebine B, Osias GA. Working with task-specific progressive lenses. Opt Prism March 1994;4–16.

Butzon SP, Eagels SR. Prescribing for the moderate-to-advanced ametropic presbyopic VDT user: a comparison of the Technica and Datalite CRT trifocal. J Am Optom Assoc 1997;68:495–502.

Hanks A, Kris M, Peachey G, Simon A. A clinical wearer study of the Sola Access lens. Clin Exp Optom 1996;79(2):67–73.

Appendix 6-1 111

Appendix 6-1

Staff Training Exercise

Explain the advantages and benefits of the following:

•Occupational progressive lenses

•Progressive addition lenses (PALs)

•Computer trifocals

•Large segment bifocals

•Single vision lenses

•Antireflection coatings

•Tints

What are the disadvantages of each?

How will you demonstrate the above lens characteristics?

Answer the question, “Why do I need a separate pair of glasses for working at my computer?”

What would you prescribe to the following patients?

1.A 50-year-old patient enters with a history of cataracts, diabetic

retinopathy affecting the macula, and glaucoma. His vision is 20/60 through +4.00 – 1.00 × 90 in each eye. He uses computers all day in his job as chief executive officer of an investment firm. Your examination supports the present medical treatment he is receiving. You can improve his distance vision to 20/40 through an increase of +0.75 diopter (D) in each eye. What may you prescribe for computer use?

2.A 60-year-old patient enters with the complaint of blurred vision at intermediate distances. The patient is presently wearing a

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straight top bifocal. You find no change in the patient’s prescription of +1.50 – 0.50 × 90 +2.50 add 20/20 OU. What may you prescribe for computer use?

3.A 42-year-old patient enters with no complaints; he works 4

hours per day at a computer. You find an increase in refractive error of –0.25 sphere OU from the patient’s habitual (PAL) of –2.00 – 1.25 × 90, +0.75 add, 20/20 OU. The patient wears the PAL all day at work. What will you prescribe for general wear and for wear at the computer?

4.A 48-year-old patient enters complaining of blurred vision across the room through her new single-vision glasses that she

received 3 months earlier from a competitor. You find the refractive error is +1.00 – 0.50 × 90 OU with a +1.75 add needed for 20/20 at 40 cm. The patient’s single-vision prescription is +2.75 spheres. Her computer is at 50 cm.

5.A 52-year-old patient works at a water treatment plant, transfer-

ring readings from gauges 3–4 ft away from his computer, which is at 50 cm. His refractive error is –2.50 – 0.75 × 180 20/20 OU with a +2.00 add to 20/20 at 40 cm. Occasionally, he must see a clock at 20 ft. He is presenting wearing PALs but complains of the narrow intermediate vision.

Answers to Appendix 6-1

1.His decreased visual acuity is going to require a closer working distance than normal on the computer. In all probability, he will not be required to see farther than 6–10 ft across the room from his computer, yet he will desire a large viewing area on the lens. In his position as a chief executive officer, he will be conscious of his image, which probably eliminates an executive bifocal or ST 35. He would likely benefit from occupational progressive lenses. These lenses provide a wider area and better focus for intermediate distances than typical progressive lenses, yet also allow the person to see far-intermediate distances through the top of the lenses. See Occupational Progressive Addition Lenses for examples.

2.This patient may benefit from occupational progressives, but, because the patient is currently wearing bifocals for general eye wear,

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the patient will most likely benefit from either intermediate-near bifocals or occupational trifocals. The intermediate-near bifocals will work best if the person performs dedicated work at the computer; the trifocals will be indicated if the person requires some distance vision while at the computer.

3.Prescribe the new glasses if the patient appreciates the improved distance vision. Because the patient is a beginning presbyope and has no complaints at the computer workstation, the patient will likely continue to successfully wear the PALs in the office.

4.Occupational progressive lenses will enable her to have good correction of intermediate and near distances and also allow her to see clearly at far-intermediate distances in the office. In the examination, determine how much plus she is able to accept when viewing at typical office distances—this is best done in free space. If, for example, she is satisfied with +0.50 add in the top of the lens, then you should select an occupational progressive with a power degression of 1.25 D (her near add is +1.75; 1.75 – 0.50 = 1.25).

5.An occupational progressive with a small area of distance power would work for this patient. The American Optical Technica is designed to provide this. An alternative would be to use another occupational progressive with a large degression—the largest alternative has a degression of 1.75 D. To use this as an alternative, determine whether the +0.25 of distance blur will be acceptable to the patient.