Which of the following microscopic procedures requires high contrast and lower light?
a. Examining unstained objects (e.g., urine sediments)
b. Evaluating red cell morphology
c. Manual differentials
d. Platelet estimates
ANS: A
Urine sediments are generally unstained. To improve the contrast, and thus the ability to identify the elements, requires high contrast and lower light. All the other items use a Wright-stained blood film for evaluation. The stain allows for contrast between the various cell components; these are all performed using an oil immersion lens, thus requiring a large amount of light.
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