In most cases, chemical dilation is not required. However, a small percentage of patients (an estimated up to 15%) may require use of a mild dilating drop to temporarily increase pupil size. There are different concentrations of dilation drops, with the mildest concentration often being enough for this exam. The effect of mild dilation drops wears off relatively quickly. Once the drops are administered, the patient should remain in a darkened room for about ten minutes before the exam.