It has been quite awhile since I wrote Part 1, nearly two years in fact. I tend to write about what I’ve learned from following up with my own patients. Occasionally, however I’ll see patients who have been Rx-ed elsewhere and a departure from the dictum of “Less is More” is evident. To be fair, regarding other eyecare practitioners, we tend to see only one another’s dropouts or failures. Patients who respond well to what a colleague is prescribing generally stay with that colleague.
My purpose here is not to point out relative successes or failures. It’s the challenge parents face when their child doesn’t respond well to what has been prescribed. Whether it is prism, bifocals, and/or vision therapy, they’re likely to think: Well, we tried that, and …
Of course we know that there isn’t any “one size fits all” approach that works 100% of the time. But there are predictable pitfalls, and I’ll share one of them with you here. It falls within the “less is more” category, and may even reflect a bias or insecurity on the part of the doctor early in her or his career, or who is relatively new to prescribing bifocals or prism. The dictum to follow is that it is always best to start with relatively low power that can be increased if needed, rather than higher amounts of power that creates side effects worse than the original symptoms or performance problems.
I’ve written about this elsewhere as it pertains to prism. But it also holds true as it relates to bifocal power for children. Regarding plus lens acceptance at near, many of us learn the hard way that just because a little bit of plus is good doesn’t mean more is better. Yet the temptation to give more because the patient will perceive the change seems hard to overcome. So … I’ll see patients who have been given 2^ BI each eye, for example, and reject it even though measurements seem to support it. Or a particular doctor who prescribes 1^ BI each eye for every patient empirically. The full power measured, or empirical approaches without adequate measures, fail more often than they succeed.
Aside from the amount of plus being too high, there are practitioners who insist that the seg height bisects the pupil. That is the standard approach for young children with accommodative esotropia. If the child is older, the seg height might be specified as being to the lower edge of pupil. Here is an example of an 8 year-old I just saw who who refused to wear her glasses:
The obvious problem is that the line is incredibly annoying to most school-aged children when it is within the line of sight looking straight ahead. But there is another problem when a flat top is set with a seg height that high on a child with an average size frame for someone age 8. Notice that there is a gap between the bottom edge of the seg and the bezel of the frame. That means that when the child looks downward, she is just as likely to be looking through the carrier as she is through the add.
You can see what has happened here. A one-sizes-fits-all instruction to set the seg height to bisect the pupil is given anticipating that it will insure the bifocal portion is being used for near. However, the school-aged child is likely to reject it because neither distance or near is as comfortable or as clear compared to removing the glasses or looking over the top. Perhaps the thinking by the prescriber is that children’s glasses often slide down the nose a bit anyway, so a very high seg height is likely to be just right. But typically setting the seg height just 2 or 3 millimeters above the lower lid works just fine. And even better for school-aged children, I might add, than the bifocal bisecting the pupil. With seg height, as with add power, often times less is more.