Perimeters are admitted by all practitioners of ophthalmology to be a necessity. But they are so heavy and unwieldy that they have been looked upon as a nuisance in the office, hardly to be tolerated. A perimeter that best meets all the demands for which they are used, is light, neat, and of moderate price, will commend itself to all. These conditions I have tried to meet, with what result I leave my professional brethren to judge. I do not claim great originality; I have simply utilized principles already existing.
The base, A, is of cast iron, japanned, and with the legs, BB, forms a tripod. The quadrant C, of brass, japanned black on the upper side, is cut out by a lathe and is absolutely correct. It has a radius of twelve and one-half inches; a smaller radius I consider useless for testing a presbyopic eye. The chinrest, E,
DIBBLE LS. A NEW PERIMETER.. JAMA. 1886;VII(21):572. doi:10.1001/jama.1886.04250110068006
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