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I have found that when light is directed through the speculum now in common use, which is shaped similarly to that shown on the left in figure 1, the illumination on the objective is not uniform, spots of increased intensity of light resulting, probably due to reflection of the light rays back and forth on the curved, conical inner surface of the speculum which causes convergence of the light rays at certain spots.
A means is therefore provided to obviate this difficulty and for producing a substantially uniform light on the objective through the speculum. To this end the outer, or tip, end of the speculum is formed with a great many relatively small perforations, these being relatively close together and extending substantially half the distance from one end of the speculum to the other, or forming the entire wall. I have found that with such construction a substantially uniform
PITMAN LK. A GLARELESS EAR SPECULUM. Arch Otolaryngol. 1937;25(2):210–211. doi:10.1001/archotol.1937.00650010232010
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