Readers or cheap reading glasses that you can buy anywhere without an optometrist or ophthalmologist taking a measurement do not cause lasting damage to the eyes in adults. However, Readers are not custom-made for the wearer. And that usually leads to prismatic side effects that can make vision strenuous over a long period of time.
The reason for this is that the eye muscles have to work unnecessarily hard with the readers. What can be compensated by an adult through effort is possibly harmful to the development of a child’s vision. For this reason, readers should only be used by adults. The lenses are positioned in the frame of the readers for the average pupillary distance between the eyes of adults.
Wearers with a very small interpupillary distance, of course, also have a harder time than people with an interpupillary distance of about 64mm.
Is It Bad to Wear Readers All the Time?
Wearing readers or reading glasses that are not individually made for you all the time can temporarily lead to visual fatigue, less perception of depth, and reduced visual acuity. Because the prescription of those reading glasses is the same for both eyes although slight differences are very common and the centration of the lenses is not optimal. The optical center of the reading lenses may be decentered.
These ready-made glasses should generally be put on only for short use, such as reading menus, city maps, etc. because for a short moment you get the necessary magnification, but they are not adjusted to the correct visual acuity or even anatomical requirements. Reading the daily newspaper, books or generally working in close proximity should be done with individually made reading glasses.
However, when your pupillary distance and your needed reading power match the specifications of the readers you may not notice any difference between a pair of individually made 300$ reading glasses and a pair of cheap 10$ readers.
What Is the Difference in Readers and Real Reading Glasses?
Individually made reading glasses consist of a frame and lenses that are custom-made for you. First, the customer’s visual acuity must be determined, because the diopters between the left and right eyes are almost never exactly the same. The frame must be selected and adjusted according to the shape of the head.
Before the lenses can be fitted, very specific parameters such as interpupillary distance, viewing height, corneal vertex distance, and visual habits must be recorded. All this data is needed to ensure that the glasses fit comfortably even when worn and read for long periods of time and actually relieve the strain on the eyes.
A reading aid (readers) is only made on the basis of average values of the population and is therefore never exactly fitted for one personally. Different values between left and right as well as corneal curvatures play just as much a role as the different distance between the eyes.
With eyeglasses, these values are prescribed precisely and strictly in tolerances that can sometimes be 0.5 millimeters or less. Some things are just missing that improve visual acuity for most people like astigmatism.
But those parameters and prescriptions are either produced for an average parameter set or just missing.
And it is precisely here that caution is called for in the case of children and adolescents, for whom poorly fitted glasses or even ready-made glasses can lead to far more serious consequences, as in, for example, strabismus.
For this already the wrong pupilary distance is enough, despite correct eyeglass strength. When the pupillary distance is not correct temporarily headaches suppression of one eye can be the result if the parameter set of the readers are way off from what you need.
There are even higher-end readers available that will cost you as much as individually made reading glasses. But when the centration is still off and the prescription does not fit you the visual experience will not be optimal either.
Who Are These Cheap Reading Glasses for Anyway?
These reading aids are only intended for people with deteriorating near vision. They should not be used by people under forty. It is only when presbyopia “develops” between the ages of 40 and 50 that near vision correction is needed here because the lens of the eye can no longer adjust sufficiently to near objects and writing.
The right time to try out such a reading aid is therefore when you notice that you need to hold the book further away to be able to see them more sharply. With readers, you can shorten the distance again and adopt a more comfortable position.
What Happens if You Wear Reading Glasses That Are Too Strong?
If the selected reading glasses are too strong you will have to hold the book unnaturally close. Typically, you use reading glasses to bring the sharp viewing area closer to you. When this is optimally chosen, you don’t have to stretch your arms as far away. The arms are then slightly bent and the distance between the book and your eyes is usually about 40-45 cm.
However, if the selected reading glasses are too strong, you will have to bend your arms unnaturally and you will feel that you have to hold the book too close to your eyes. This makes the position uncomfortable.
The eyes should only be supported by the glasses as much as necessary. They do not do lasting harm to the eyes if you wear reading glasses that are too strong but they do limit your comfort.
Since it is a focus area should be considered the activities you want to perform with the reading glasses. The older you get, the higher the support you need for reading and the narrower the sharp area in front of your eyes becomes. This means that if you are doing very fine work and need strong reading glasses, you may not be able to read a newspaper lying on the table. For this, the reading glasses that you use for very fine tasks would be individually too strong.