Verifying the prescription of a computer/task specific lens style.

For computer/task specific lens styles, all designs have you verify the prescription in the reading circle/arc (or however the manufacturer identifies their NRP- Near Reference Point) for the full reading power. Checking power anywhere else will not tell you very much because they all vary on the manufacture’s degression designs. If the circle/arc location is reading the full reading prescription then the prescription is correct.

Note 1: The full reading prescription will be:

Distance power in the 90˚ meridian + the Add power = Full Reading power at the reading Near Reference Point.

3 Examples, same powers with 3 different axes:

Rx: -2.00 -2.00 x 090 Add +2.50 … Near Reference Point =  +0.50D

Rx: -2.00 -2.00 x 045 Add +2.50 … Near Reference Point =  -0.50D

Rx: -2.00 -2.00 x 180 Add +2.50 … Near Reference Point =  -1.50D

Note 2: If the lenses do not have the factory markings on them, you will have to use a re-marking card to redraw the markings (just like re-marking a progressive).

Expert’s own computer/task specific lens is the Expert Tween. Depending on which MFH style is chosen will determine the Near Reference Point location.

Robert Hughbanks ABOC, HOAA- Manager of Training and Development