August 12, 2010 
Ready-prescription glasses can be found today in various shopping malls, drug stores and pharmacies. Unfortunately, it is not very well known that such glasses can not replace individually well-made glasses, with the recipe from optometrist or ophthalmologist…
How many people have an equal dioptra in both eyes? How many people have the proper pupil gap that fits to lenses of almost all glasses? How many people do not have astigmatism? Still, some experts classify finished prescription eyeglasses in ideal correction aids, especially in developing countries. Correction with spheric lenses in these countries is satisfactory because it is used particularly in the areas where individual adjustment is difficult to access. Experts estimate that in these difficult circumstances, final correction glasses are used by up to two thirds of the population. The question remains, how great harm these glasses with incorrect correction can cause?
Doctors have tried to answer this question. Emetropists (people with normal vision) were randomly given one of nine test glasses with plan prismatic lenses. Glasses had a horizontal or vertical difference between right and left eye, stimulating a very bad centration in ready-made glasses. The consequences of intolerance to prismatic excessive loads were at least very uncomfortable: faint, blurry vision, nausea, vomiting, pain in the eyes, difficulty in concentrating, etc.
Famous ophthalmologists and optometrists warned that recently number of people who use ready-made prescription glasses when driving motor vehicles is increasing. They are mostly emetrops, whom the years brought hipermetropisations, aged farsightedness. These people have concluded that with ready-made reading glasses they can see better while driving, so these drivers need to hear an important warning, for the safety of themselves and other participants in traffic.
Taken from: www.optometrija.net