Trifocals for far vision, monitor vision and near vision
|Three optical powers in one trifocal lens: for far vision, monitor vision and near vision|
With trifocals you can see clearly at a distance, at the monitor distance and have near vision power for reading documents without a change of glasses. Due to the large distance portion no large head movements are necessary when looking into the distance. A slight downward inclination of gaze provides clear vision at the monitor and a larger gaze inclination provides clear near vision.
The visual field for monitor and near vision is smaller than with single vision lenses, but sufficient in most cases. Most important, the borders between the three parts may disturb vision since gradual clear vision at all distances is not possible. Recommended monitor position for trifocal lenses.
Trifocals are rarely worn nowadays. The visual field for monitor and near vision are very small and unfavorable for longer work in the near vision and in the monitor area. Trifocal glasses can be used when only the distance range is important for the task, and it must be seen clearly in the other areas. A better alternative are progressive lenses, which have no visible transition areas from the distance to near vision.Print