American Board of Opticianry (ABO) Practice Test

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Prepare for the ABO (American Board of Opticianry) Test with interactive flashcards and hundreds of multiple choice questions. Updated for 2024 to help you excel on exam day

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If the pupillary distance is ground too narrow for a minus prescription, what type of prism base is likely to result?

In and In
Out and Out
In and Out
Up and Up

The correct answer is: Out and Out

If the pupillary distance (PD) is ground too narrow for a minus prescription, it means that the lenses are closer together than they should be based on the individual's PD. This causes the eyes to over-converge, which can lead to visual discomfort and strain. To correct this, prism is added to the lenses. In this case, because the lenses are too close together, the prism base would need to be placed towards the outer sides of the lenses, resulting in Out and Out prism. In and In prism, as well as Up and Up prism, would not be helpful in correcting for the negative effects of a narrow PD. In and Out prism could potentially be used, but it may not fully correct the issue and could lead to visual discomfort as well. Therefore, the most likely result would be Out and Out prism.