Monitor position with trifocal lenses for far, intermediate and near vision (trifocal lens)

A trifocal lens is an extension of the bifocal lens explained before. Clear far vision is provided by the main lens (shown in blue) and clear reading is possible with the lower near vision inset lens (shown in red). Additionally, clear vision at the monitor is provided by a further segment (shown in green). The user has to look through the appropriate parts of the trifocal lens: by lowering the eyes and the head in the proper way, one can find the required optical power for far vision, computer vision and reading text documents, respectively. Today trifocals are not common since that part of the lensmeant to look through at the monitor is too small to work comfortable at a screen.

Quick Start Guide

The height of the monitor should be adjusted so that you can see the screen through the intermediate part of the trifocal lens (shown in green). But, at the same time your head should adopt a comfortable posture. You should always be able to look straight above the monitor beyond into the room.

Adjust the tilt of the monitor so that you are looking at right angles on to the monitor. The more you look downward , the screen will be the deeper, and the more you should tilt it backwards.

Shift the monitor back and forth until the text on the screen appears clear.

 

If you have any questions about your glasses, you can return to information in the SECOND STEP Trifocals for far vision, monitor vision and near vision

Detailed instruction: Monitor Position – Trifocals

Before you start, you should adopt an ergonomic sitting posture (FIRST STEP).

Use the following steps to adjust the height of the monitor so that the head tilt is not strenuous but feels comfortable.. However, always make sure that your look can still go straight above the monitor if you try to look behind it:

  1. Tilt your head with eyes closed significantly up and down. Find with decreasing head movements your individually comfortable head tilt, which you please retain for the next step .
  2. With the retained comfortable head tilt and closed eyes, move now only the eyes up and down . Start with distinct tendencies of the eyes up and down movement and you will find the pleasant eye inclination.
  3. If you now open your eyes and look through the monitor portion of your trifocals on the top third of your monitor, the height is correct . Otherwise, adjust the height position of the monitor accordingly.

Shift the monitor stepwise from a long viewing distance (about 100 cm) to a short viewing distance (about 50 cm) while you observe text characters on the screen with a size of about 3 mm that can easily be seen (a colleague may help you). You will notice that the clarity of the text changes and you can find out at which monitor position the text appears most clearly and vision is comfortable:

  1. If clear vision is found very near (at about 50 cm), then your computer lenses may be too strong: computer work at such a short viewing distance is stressful for the ocular muscles in the long run. Check with an optician / optometrist whether these glasses are suitable for working at a computer work place.
  2. If clear vision is found near 100 cm, this is often relaxing for the ocular muscles. But long viewing distances require larger text characters of about 5 mm that cannot always be achieved.
  3. If, in this range, you do not reach clear vision at the monitor, as you know it from distance vision, then your lenses may not be appropriate. Then, you better have your vision tested.

When you have worked with the chosen position for some days, you may experience whether the monitor position is really optimal for you. If not, you may change the monitor position again. For the fine adjustment, you may tilt the monitor in a way so that you look perpendicularly onto the screen surface: the more you look down, the more the monitor has to be tilted.

The height of the monitor position is very critical with trifocal lenses. Most important, the height of the monitor should allow seeing the screen through the intermediate part of the lens that includes the optical power for viewing the monitor. Further, the head posture should be comfortable for your neck and the vertical gaze direction should be comfortable for your eyes. If the monitor is placed too high, you have to raise you head to an uncomfortable posture. You should be able to look beyond the monitor into the room.

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