. Spectacles and eyeglasses, their forms, mounting, and proper adjustment . ndbending of wires, leave one to estimate what changes arerequired just as might have been done without their , the heavy parts and lost space in joints of trialframes may readily conceal an error of 2 mm., or even 3mm. in some measurements; the large, round eyes withheavy rims will not go under the brows, so that the in-outmeasurement of the bridge must frequently be guessed at;and the relation of the upper part of the eye wires to thebrows is not shown. In fact, they introduce, in my estima-tion, quite as
. Spectacles and eyeglasses, their forms, mounting, and proper adjustment . ndbending of wires, leave one to estimate what changes arerequired just as might have been done without their , the heavy parts and lost space in joints of trialframes may readily conceal an error of 2 mm., or even 3mm. in some measurements; the large, round eyes withheavy rims will not go under the brows, so that the in-outmeasurement of the bridge must frequently be guessed at;and the relation of the upper part of the eye wires to thebrows is not shown. In fact, they introduce, in my estima-tion, quite as many sources of error as they eliminate. Where the face is unsymmetrical no exact rules of pro- PRESCRIPTION OF FRAMES. 6l cedure can be given, and considerable ingenuity may berequired to fit a frame to such a face. If the nose is verypeculiar, or one side of its bridge markedly steeper thanthe other, it may be of advantage to take an outline of thebridge at the natural position by bending a piece of leadwire to fit accurately and marking, the outline of this upon ^ggn. B the prescription blank, or sending the wire itself to thespectacle maker. Sometimes the brows are overhangingand the eyes deep set; so that the glasses cannot be prop-erly centered before the eyes and placed close to themwithout the upper part of the rims burying themselves inthe brows. In such cases the glasses should be decenteredupward in their frames and the bridge made sufficiently 62 SPECTACLES AND EYEGLASSES. high to bring the optical centers opposite the the patient will then look through the upper partof his glasses, his field of vision will not be any more limitedthan is already the case because of the overhanging of Eyeglasses.—The dimensions which itis usual to furnish in prescribing eyeglass frames are theinterpupillary distance, of course, with the distance betweenthe two upper and the two lower ends of the nose-pieceswhen they are in place on the face (.4 to
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecteyeglasses, bookyear1
