Posted on February 19th, 2010 by eyeing (reprinted by permission)
Over-the-counter reading glasses, also known as readers, magnifiers or half-eyes are frequently used by people who need help magnifying the print they are reading. The magnification provided by these “readers” clears vision and/or reduces eyestrain. How do these readers differ from prescription eyewear?
Prescription eyewear is customized for your vision by providing a lens that matches the power in each eye. It is more often than not that the prescription between each eye is different, necessitating prescription eyewear that is different in one lens than the other. Over-the-counter readers cannot precisely meet the vision needs for most people for this reason. While they might make the print larger and easier to see, a prescription is likely to do an even better job.
Another factor is “astigmatism”. Astigmatism describes the way light is bent when it travels through parts of the eye that are not spherical. Most people have some small amounts of astigmatism, and no over the counter readers correct for it, so, once again, the readers might help but not as much as a full corrective prescription written by an eye doctor (optometrist or ophthalmologist).
Another factor that reduces the effectiveness of over-the-counter readers is based on the optical center of each lens. In a prescription pair of glasses, the optician is careful to measure the distance between the center of the pupil of each of your eyes, and make the lenses so that the center of the lens lies directly over the center of the pupil. Generic over-the-counter readers can’t do this. If the prescription of the over-the-counter reader is high enough and the lenses are off center significantly wearing them can lead to eyestrain.
In a worst case scenario, let’s assume many people have (1) unequal prescriptions, (2) slight astigmatism and (3) readers that don’t line up exactly over their pupillary line of sight in each eye. In this case, while they may report seeing better with over-the-counter readers than wearing nothing at all, a prescription pair of reading glasses would serve them much better. There is nothing wrong with wearing the over-the-counter readers in most cases, but be sure to ask your eye doctor.
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Copyright 2010 – Dr. Alan N. Glazier, Optometrist in Rockville, Maryland – all rights reserved
Alan N. Glazier, OD, FAAO