|
Section IV: Fitting Requirements
Minimum fitting requirements
- Many frames will fall in this size category
- Frame selection is not overly restrictive for variable focus near lenses
- There are certain minimum fitting requirements that dispensers should keep in mind
Minimum fitting requirements
The differences
- Using a computer prescription based on a Gaussian type eye exam, a near variable focus lens will produce broad distortion-free vision
Lens description
- Plus power is reduced in top portion by one of five power shift amounts
- 0.75D, 1.00D, 1.25D, 1.50D, 1.75D
- At fitting cross, power will be 50% of specified power shift amount
- Lens comes right and left for near decentration
Fitting Variable Focus lenses
- Total reading range: -6.00D to +6.50D (combined sum of sphere and add powers)
- With selected frame on face, dot center of pupils (exactly like fitting PALs)
- Determine monocular PD with electronic pupilometer
Minimum fitting heights
- Frame should have minimum fitting height of 13mm from fitting cross to UPPER rim
- Minimum of 16mm from fitting cross to LOWER rim
- Overall "B" measurement should be 29mm or more
Ordering the lens
Provide the lab with:
Patient's distance Rx
40cm reading add
Computer add power
If computer tester add not available, provide normal reading add
Lab will choose correct power shift
Verifying lenses from lab
- Check reading prescription in the circle (see diagram)
- If reading Rx is correct, power shift will automatically place the proper computer Rx at the center of the lens
To continue, click on Section Five, Lesson Two in the left column
|
|
