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Medical Forum / General / Vision / February 2006Unlined trifocal vs. progressive
Is there a difference between an unlined trifocal and a progressive lens? If so, what's the diffenence. thanks >Is there a difference between an unlined trifocal and a progressive >lens? >If so, what's the diffenence. thanks There's really no such thing as a no-line trifocal, although Bristol makes a blended (line is erased leaving a blur zone) trifocal. Trifocals have three distinct focal lengths- distance (beyond about four feet), intermediate (about 32") and near (about 16") with a line separating each zone. PALs (progressive addition lenses) have a smooth seamless change in focal length without lines. There are no "bifocal" or "trifocal" PALs. "Omnifocal" would probably describe their focus function the best, although the optical industry has settled on the more forward sounding "progressive". Hope this helps, Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr Thanks. Ok. My doctor said with my prescription I could get a single vision lens and take the glasses off to read OR get a bifocal (which I assume would be distant on the upper and near on the lower portion of the lens) OR that I could get a trifocal OR a progressive lens which would incorporate near, intermediate and distant. My intermediate vision - from about two feet out to six feet or so- seems to bother me the most. To cover this intermediate area I think I would have to get a trifocal or a progressive lens. Right? Some optical shops here advertise a no-line bifocal, but if I understand what you are saying, it is really just a progressive lens. >Thanks. Ok. My doctor said with my prescription I could get a single >vision lens and take the glasses off to read OR get a [quoted text clipped - 5 lines] >area I think I would have to get a trifocal or a progressive lens. >Right? No way to know for sure with the information provided. In general, if the add power is below +1.75, the vision at 32" should be clear through the distance portion of a multifocal lens, and blurred if the add is above +1.75. >Some optical shops here advertise a no-line bifocal, but if I >understand what you are saying, it is really just a progressive lens. Right. Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical robopt@execpc.com ~~~~~~~~~~~~~~~~~~ "An expert is a person who has made all the mistakes that can be made in a very narrow field." - Niels Bohr Thanks. Ok. My doctor said with my prescription I could get a single vision lens and take the glasses off to read OR get a bifocal (which I assume would be distant on the upper and near on the lower portion of the lens) OR that I could get a trifocal OR a progressive lens which would incorporate near, intermediate and distant. My intermediate vision - from about two feet out to six feet or so- seems to bother me the most. To cover this intermediate area I think I would have to get a trifocal or a progressive lens. Right? Some optical shops here advertise a no-line bifocal, but if I understand what you are saying, it is really just a progressive lens. |
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