How do Varilux lenses reduce vertical head and eye movement?

November 27th, 2006 by Aakash Shah

How do Varilux lenses reduce vertical head and eye movement?
A Unique Power Progression. The higher location of the near vision zone of Varilux lenses results from a unique power progression profile consisting of three parts (See the figure below for an example of a lens with +2.00 D addition, the amount of magnification needed to increase near vision).

Part 1 (from the optical center to 8mm below): A quick increase in power up to 85 percent of the addition. At this point, the near vision zone is considered to start since 85% of the full addition power is sufficient to read the top part of a document that is naturally held further away from the eyes than the bottom part. The physiological length of progression of Varilux is thus 12mm compared with an average 14 to 15mm for other progressives.

Part 2 (from 12 to 18mm below the fitting cross): A slow increase in power up to the full add power at the center of the near-vision circle. The shape of the power progression, in this part, follows the variation in proximity of the document to the eyes as the gaze lowers, thus creating a truly physiological near-vision zone.

Part 3 (below the vision center): A stabilization of the power progression and then a slight power decrease in the very bottom of the lens below normal reach of the gaze.

Be Sociable, Share!