Computer Vision Syndrome
Presbyopia and Dry Eye

Where is the computer and other near work located?

It is clinically useful if computer-using patients measure the distance from their eyes to the computer screen and to reference documents, note the height of these tasks relative to their eyes and bring this information with them to their eye examination. This information is useful to either determine the correct prescription or lens design, or to enable counseling about workstation arrangement or changes. The viewing distance and height of the computer screen can be obtained by sending an advance questionnaire to the patient.

Viewing distances and angles that are out of recommended and normal range (20-28 inches, 10-20 degrees downward gaze) should be investigated for cause.

If specific information about the computer location is not available, it is best to design the prescription and/or lenses for a 60 cm (24 inch) viewing distance and a screen center located 15 cm (6 inch) below eye level. This assumption has a greater likelihood of being valid if the person is working at a fairly standard computer workstation for word processing. However, many workstations have visual requirements that are significantly different from this arrangement.

Although the computer visual needs are at the intermediate distance, nearly all computer users also have viewing requirements at 40 cm. Distance visual needs are usually less important and can often be compromised in the interests of best meeting the intermediate and near needs. The prescription that is written depends upon the lens design selected for the patient.

It is not always prudent to prescribe for the viewing distance and angle of the patient�s current computer location. For example, the patient may have an unusually long distance because of an uncorrected presbyopia � in which case the correction should be designed for a �normal� location. In many cases an unusual screen height should be managed by suggesting a workstation alteration. If the current screen location is appropriate or if it cannot be altered, then this information can be used for prescribing. If not, then the prescription should be designed for the altered location of the computer screen.