The Strange World of Invisible Bifocals
I can’t count the number of people I have seen over the years who were struggling with their blended/invisible/progressive “bifocals.” These of course are not bifocals, but complex, and very fussy multi-focal lenses; technically they are called progressive addition lenses (PALs). The idea is excellent - a single pair of glasses through which a person can theoretically see clearly at any distance, day or night, rain or shine. It’s a great idea whose implementation leaves a great deal to be desired in many cases, even after many years and many attempts by many clever people in many companies to iron out the bugs.
Some of the people who come to me for help are able to wear these lenses comfortably and successfully and others are not. Some had worn them with no apparent complaints until it was determined that using these lenses had contributed to rather significant disruption of their overall visual efficiency. Many successful wearers unconsciously adopt somewhat tortured head postures and head movements in order to use the lenses. Some had worn them uncomfortably for years, thinking they had no other choice or that there was something wrong with them. These people typically come in complaining of various things including eye fatigue, dry eyes, headaches, neck pain, queasiness, etc. Some assume it can’t be fixed, others insist that they want something else.
I have my reasons for disliking this technology. It’s important to know that every lens has a “sweet spot” (optical center) where the prescription is most accurate. This optical center is meant to be directly in front of the pupil in most cases. Optical centers are rarely in this position with PALs. Also, there are distortions essentially built into the lenses around the near lens corridor. These distortions often contribute to feeling off balance, or just off, while wearing PALs. The “bifocal” portion is a narrow corridor, nothing like the wide area afforded by a more traditional bifocal. The narrow corridor forces the wearer to move the head instead of just moving the eyes while reading. Many people have mentioned that they were told not to move their eyes when reading if they are wearing progressive addition lenses. This is the exact opposite of how we are meant to read and can cause all kinds of symptoms as demonstrated by the following case study. Just for the record, behavioral optometrists expect young children to learn to move their eyes independently of the head as an appropriate developmental milestone.
Progressive Addition Lens
N is one of my out-of-state patients, a 64 year old professional who began wearing glasses at an early age and has a long history of back problems causing her to work at stand-up desk because sitting for long periods is too painful. She had been wearing PALs for many years and was told to avoid moving her eyes while reading with them. Full disclosure: N is my cousin, but a first-time patient in 2011 who came in with complaints of increasing double vision, burning eyes and headaches related to sustained computer work, which is the majority of her workday…
July 9, 2011
Hey Dr Steve: -
I've been wearing the new glasses for the last few days in the office and it's really interesting! The hardest thing is getting used to that $#@*&! bifocal line, but that's a minor detail. The computer lens is terrific - noticeably less neck tension. The reading is a little harder - it seems to take a few minutes for my eyes to adjust, but I think that once they do that, I can read the small fonts with less straining.
July 23, 2011
Hey Dr. Steve:
The glasses just get better and better, at least for working in the office. Makes me think I need to get another pair to keep at home.
November 27, 2011
Dear Dr Steve,
I think that your suggestion of going to bifocals instead of progressives made a big difference, and it was apparent the first week. I almost immediately had less double vision, headaches and burning eyes. Much less pain in my neck at the end of each day!
The brain must adapt for any lenses to work, but it must adapt quite significantly to make use of progressive bifocals. Most of these adaptations, under any other circumstances, would be seen as undesirable. Imagine doing a workout regimen solely designed to improve the muscles you need to use crutches. Most doctors who regularly prescribe progressive bifocals are unaware of or unconcerned with the consequences of using these lenses. Sometimes these lenses can be very helpful, but it is not really a good idea for most people to rely on them as their only pair of glasses. I know it is hard to resist the convenience of such technology, but hopefully I have presented something to consider before attempting to take what only seems like the easy way out.
Please feel free to contact Dr. Gallop if you have any questions. Call 610-356-7425 and speak with Dr. Gallop personally.
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