Difference Between No-Line Bifocals, Progressive Bifocals, and Trifocals
JAN 16, 2013
Can you explain the difference between no-line bifocals, progressive bifocals, and trifocals? I was told at a discount eyewear store that there was no difference and that all three of these glasses were essentially trifocals.
Generally, we think of vision in three distinct distance ranges: near for reading, intermediate for computer, card playing, etc. and distance-as in driving. A bifocal provides clear vision in any two of these ranges of vision, whether it has a line or not. A trifocal has lines and provides vision in all three ranges, but there is often blurring of vision between these three focal distances. Think of each focal range as a step in a stairs. A progressive lens provides good vision in all three ranges like a trifocal, but has no lines and provides clear vision in the spaces between the three steps of a trifocal. A progressive lens is more like a ramp than it is individual steps. I suggest you ask your ophthalmologist to go over this with you.