I need your support.

**Chul** · 08-10-2006, 10:42 PM

Hi everyone.

I'm a korean optician. I have studyed an article written by Mo Jalie.

Unfortunately, I can't understand some part of the article due to my poor english. The part is as below.

The drawbacks of trifocals are much the same as with bifocal lenses. They have zones of fixed power, which provide the wearer with a limited focusing range through each zone, there is jump at the dividing lines unless visible, no-jump designs are used, and the presence of the segment dividing lines detracts from the appearance of the lenses. These drawbacks are eliminated by dispensing progressive power lenses, the use of which has expanded rapidly in the last few years. Without doubt, progressive lenses have become the first choice of multifocal design for the correction of presbyopia.

I can't understand above sentence with red. I'd like you to allow me to understand easily.

Regards,

**GOS_Queen** · 08-10-2006, 10:55 PM

You know how a bifocal has 2 sections of power and a trifocal has 3 sections of power? Going from one section of power to the next section of power provides a very sudden change of the power (jump = sudden change of the power). Some people find the "jump" very distracting.

A progressive lens has a very smooth change of power up and down the lens (without the jump) ~ it seems more natural (almost like how the eye worked before needing a multifocal).

I hope that answers your question. :)

**HarryChiling** · 08-11-2006, 09:21 AM

Think of the segment as a circle with the top chopped off. The optical center is not directly in your line of sight when looking down through the lenses. This creates prism which is associated with the term jump. If you were to use the franklin style bifoal their is no jump due to the fact that the optical center for the reading is bisected. Hope this helps.

**Chul** · 08-11-2006, 11:43 AM

Thanks a lor GOS Queen and Harry Chiling.

As a matter of fact, I have written teaching matrerial. sometime, I used to meet difficult matter relared to translation. I think understanding is different with teaching. Anyway, I really appreciated your kind help.