. Refraction and motility of the eye, with chapters on color blindness and the field of vision . been carriedback to the retina, while the ver-tical ones are behind it. In otherwords, the astigmatism is now asimple hyperopic of 2 D. with which a young, person mayhave a vision of 20/30. Evidently the glass would improvevision, but would cause strain. The best way is to beginwith the cylinder, gradually increasing the strength, andsearching for the axis which gives the best vision, andwhen increase of strength no longer causes improvement invision, to add concave spheres of gradually increasings
. Refraction and motility of the eye, with chapters on color blindness and the field of vision . been carriedback to the retina, while the ver-tical ones are behind it. In otherwords, the astigmatism is now asimple hyperopic of 2 D. with which a young, person mayhave a vision of 20/30. Evidently the glass would improvevision, but would cause strain. The best way is to beginwith the cylinder, gradually increasing the strength, andsearching for the axis which gives the best vision, andwhen increase of strength no longer causes improvement invision, to add concave spheres of gradually increasingstrength. If the combination of lenses which gives thebest distant vision nearly coincides with the result of theobjective tests, it may be prescribed, but such is rarely thecase, since the patient almost invariably obtains themaximum vision with an over-correction which allows himto accommodate. A moderate over-correction of thespherical element does probably no harm in many cases,but the same cannot be said of the cylindrical which shouldbe as exact as possible. In myopic astigmatism, as in. ASTIGMATISM. 191 simple myopia, the rule is to find the weakest glass whichwill give the best vision. For this reason the greatmajority of myopes should be examined under contradistinction to the hyperope, who always sees poorlyunder a tropin, the myope whose vision is best with accom-modation relaxed not infrequently sees better and so sub-mits more gracefully to the necessity. Under theseconditions the subjective and objective tests should cor-respond within a fraction of a dioptre, and it only remainsto decide on the glass to be prescribed. In low and moderate errors it is certainly best toorder the full correction for constant use and it is bestput on while the patient is still under cyeloplegia. Invery high myopia and especially when the patient hasnever worn glasses, it is sometimes advisable to under-correct for a time and even prescribe a weaker glass fornear work. T
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Keywords: ., boo, bookcentury1900, bookdecade1920, booksubjecteye, bookyear1920
