Calibration and Use of an Ocular Micrometer

Size is important in the differentiation of parasites and is most accurately determined with a calibrated ocular micrometer, thus, each laboratory performing diagnostic parasitology must have such a micrometer. 

An ocular micrometer is a disk on which is etched a scale in units from 0 to 50 or 100. To determine the micrometer value of each unit in a particular eyepiece and at a specific magnification, the unit must be calibrated with a stage micrometer. A stage micrometer has a scale 2 mm long ruled in fine intervals of 0.01 mm (10 finl). 

Insert the micrometer in the eyepiece so that the micrometer rests on the diaphragm, with the etched scale facing the eye. In many new microscopes, the micrometer can be dropped in and secured with a ring retainer. (It is helpful to have an extra ocular in which the micrometer may be left.) 

TABLE 1.3 LABORATORY EXAMINATIONS FOR VARIOUS TYPES OF FECAL SPECIMENS 

Type of specimen Direct wet mount Method Concen- tration Permanent stain 

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