Accurate measurement from the line of insertion of any rectus muscle to the point on the sclera where it is desired to recede or advance that muscle is necessary. For this purpose a number of calipers have been designed. I have not been satisfied with any so far placed on the market. One type, designed on the principle of a slide rule, measures accurately the desired distance, but the projecting bars are dull and do not give an opportunity to indicate by a delicate scratch mark the position on the sclera for the insertion of the sutures. Another type is a small caliper with dull points neither of which serves the particular purpose desired.
I have had an instrument maker construct a caliper one shank of which carries a thin shaft of steel which terminates in a very fine sharp point. This point cannot penetrate the sclera, as it is
Green J. A NEW CALIPER. Arch Ophthalmol. 1937;18(3):430–431. doi:10.1001/archopht.1937.00850090098012
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