1.56 Bifocal Lens Guide: Best Rx & Frame Sizes for Thin, Light Glasses

1.56 index plastic is the workhorse of everyday bifocals: light, shatter-resistant and easy on the wallet. It is not, however, a superhero. Past a certain prescription the lenses grow thick, heavy and stick out of the frame like ice-cream sandwiches. Here is the quick, non-techy guide to keep your glasses looking good and feeling light.

Safe power zone

Sphere (the main number): –3.00 to +3.00.
Add (the “reading boost”): up to +2.00.

Stay inside these lines and a 1.56 lens stays slim. Stray outside and the edges (for minus powers) or the middle (for plus powers) start to bulge; the glasses slide down your nose and the ring-around-the-lens look is real.

Frame size cheat-sheet

Bifocals need room for the little reading window. Pick a frame at least this tall and wide:

Flat-top “D” segment: 25 mm high × 45 mm wide
Round-top segment: 22 mm high × 40 mm wide
No-line progressive: 28 mm high × 48 mm wide

Smaller frames shrink the reading zone; bigger ones add weight, so stay close to these sweet spots.

Quick shopping tips

Choose a full-rim plastic or metal frame—its edge hides lens thickness.
Keep your PD (pupil distance) exact; off-center lenses thicken one edge.
Ask for factory “roll and polish” if you are at the high end of the safe zone; it tapers the edge for a cleaner profile.
If your script is stronger than –3.00/+3.00 or the add is above +2.00, jump to 1.60 high-index. The upgrade cost beats the daily tug-of-war with chunky glass.

Bottom line: Stay within ±3.00 sphere, +2.00 add, and pick a frame that meets the height and width numbers above. Do that and 1.56 index bifocals will stay light, sharp and almost invisible on your face—no ice-cream sandwiches, just easy reading and clear distance.

For assistance or if you have any questions, email us at info@fuzweb.com or call us at +1-778-860-5467.