Day 2.4 - Lens Types

Lens Types

Single Vision:  SV 

These lenses have only one prescription throughout the entire lens.  No matter where you look through the lens the prescription will be the same as it is in the middle.

Bifocal:  FT28

FT stands for flat top because these bifocals have a straight flat top.  These lenses have two prescription points in the lens.  The top portion is typically for their distance prescription and the segment window at the bottom of the lenses is for reading.  When measuring where the bifocal should be placed, it is important to try to match the placement of their prior pair of lenses.  If this is their first pair you should place the segment 2mm below the bottom of their eyelid.

Trifocal:  7x28

These lenses have three different prescriptions in the lens.  The top is the distance prescription, the middle is the intermediate prescription and the bottom is the reading area.  The intermediate area is typically used for “finger tip” distance such as computer screens and vehicle dashboards.  These lenses are mostly for people that use their intermediate area throughout the day such as computer work, truck drivers, piano players, etc.   When measuring the placement of a trifocal, you must try to match the placement of their prior pair.  If this is their first pair, then you should place the segment 1mm below their pupil.  Trifocals must be higher than bifocals so the customer can utilize the intermediate area without having to raise their head too much.

No-line/Progressive: 

“No-Line Bifocals,” Amplitude Mini, Shoreview Mini, Easy View:  These lenses work much like a trifocal lens.  No-line lenses have a top portion for the distance prescription, a middle portion for the intermediate, and a bottom portion for reading.  The biggest difference is there is no defining line showing on the lenses.  These lenses accomplish the different prescriptions with different front curves throughout the lens.  The prescription in the lens slowly progresses from the distance on the top to the reading on the bottom.  So no matter what distance you are looking at, there is a place in the lens that will allow you to see clearly.  When measuring the placement of the no-line lens you must place the segment height directly below the pupil.  Because of the numerous benefits this lens provides, it is recommended for first-time bifocal wearers.  

In order to have the best customer service, look at or ask the customer what they have worn before and if they were satisfied with the lenses.  This will help you determine which style is best for them.  If they have worn a no-line before, or if they had problems with their lined bifocal, no-lines are a great route to take.  If they have worn lined bifocals/trifocals before and were happy with them, then a lined bifocal/trifocal is probably the best lens for them.  Some careers may require a lined bifocal such as truck drivers, so getting an idea of what the person does for a living can help in choosing the best lens option.