"Rules For Ophthalmologists....only Diopters....."
Stand up straight, fix the target behind me against the wall, read the third letter from ..... during this exercise, which I remember, the college nurse, during the medical examination passed in front of the gaze these rules so that we could define where our reading comfort was....Pfff, I was 8 years old, no need, ;;;no need for glasses.... Today, I think that my answer would no longer be the same. Two ophthalmological rulers marked concave and convex, with lenses graduated from 0.5 to 4.5, in their original case (early 20th century). 
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