Section III: Variable Focus Lenses

# 4 Choice - Variable Focus Near Lenses

Several versions are available


The best type will offer two or three power shifts


The design should have right and left versions to provide proper near decentration

More on Variable Focus Near Lenses

Plus power is reduced in the top portion of the lens by a set amount


Example of a 5 power shift version: -0.75D, -1.00D, -1.25D, -1.50D & -1.75D less than reading area


At the fitting cross, power will be 50% of the specified power shift amount


Lenses are decentered for right and left eyes

Beyond Computer Vision

The variable focus near lens provides sharp clear vision at 1.3 feet (40 cm)


Also at 2.6 feet (80 cm)


And up to 10 feet (3 meters) with some patients

Fitting Variable Focus lenses

Check total reading range (combined sum of sphere and add powers)


With selected frame on face, dot center of pupils

Do this exactly like fitting PALs

More on Fitting Variable Focus lenses

Determine monocular Distance PD with pupilometer


Be sure to take into consideration the lens depth of the frames (much like fitting PALs


Adjust height of pupil center to match monitor placement

Minimum fitting requirements

Frame should have minimum fitting position of 13mm from fitting cross to UPPER rim


Maintain minimum of 16mm from fitting cross to LOWER rim


The overall "B" measurement should be a minimum of 29mm or more


Many frames fall in this category so frame choice shouldn't be a problem

To continue, click on Section Four, Lesson Two in the left column