Cheap prescription glasses may offer a huge price advantage over customized glasses purchased after an eye exam, but this same “one-size-fits-all” approach is also their biggest disadvantage. If cost is the most important consideration for the wearer, then cheap glasses might work just as well as customized ones, but if the wearer’s eyesight is especially poor, then the cheap glasses might cause more problems, including increased cost in future.
Cheap glasses bought off the rack or at a drugstore have lenses of the same power. Also, the optical center of both lenses are fixed, farther away from the center of the pupils than they need to be and not customized for each wearer. In reality, most people have different prescriptions in each eye, and therefore require lenses with different power for clear, strain-free vision.
Also, astigmatism is a very common problem among the general population, and it requires a cylinder power lens in addition to the spherical lens power that is required to correct near- or far-sightedness. Cheap glasses do not provide for this astigmatism correction, causing the wearer to strain his eyes. This may lead to headaches, eye pain, and in severe cases, even nausea.
Cheap glasses are usually mass produced and therefore their fit may not suit everyone. Some types cause strain on the wearer’s face and neck muscles, which may lead to other health problems. The quality of the lenses may also be less than 100 percent, which may cause further eye problems for the wearer.