We may find marks on the progressive glasses purchased, and some even think that are the defects of the lenses. Theses marks appears as circles, letters, and numbers as shown in the picture below.

1. Bifocals help you get far and near vision only, and will generate image jumps when you look near after you see distance. 2. You will get continuous vision at distant, middle, and near focal ranges with progressive lens, and with no lines, no annoying image jumps. 3. progressive lens will be more expensive than bifocals. But the extra price is worthy of its value.

Bifocals are dual-version glasses, you can see two different fields of vision through one pair of bifocal glasses. Bifocals are designed with two prescirptions on the lenses, so you can see far through the top part of the lenses, and reading book or use computer through the bottom part of the lenses.

Progressives provide a smooth transition from distance through intermediate to near, with all the in-between corrections included as well. You can look up to see anything in the distance, look ahead to view your computer in the intermediate zone, and drop your gaze downward to read and do fine work comfortably in the close zone. That’s to say, progressive lenses are the closest to how natural vision is that you can get in a pair of prescription eyeglasses.