BACKGROUND This study was designed to evaluate the effect of Paremyd, a combination of 1.0 percent hydroxyamphetamine hydrobromide and 0.25 percent tropicamide, on pupil size during binocular indirect ophthalmoscopy (BIO) upon 164 subjects of various skin pigmentation, iris color, and age. METHODS Pupillary dilation and ease of performing BIO were measured after 30 minutes following instillation of a single drop of either Paremyd or tropicamide (1.0 or 0.5 percent) to an eye. Subjects were assigned to one of three groups; either Paremyd OU, or Paremyd OS and tropicamide (either 0.5 or 1.0 percent) OD, or Paremyd OD and tropicamide OS. Pupillary dilation was measured during BIO performed at a set illumination using a near point card. RESULTS Results indicate that Paremyd is a significantly more effective dilator than either concentration of tropicamide alone. BIO was rated good to excellent for all dilating agents. As could be expected (based upon data from previous experiments), there was a small, but significant, negative correlation between dilation and age, skin pigmentation, and iris pigmentation. CONCLUSIONS Paremyd, because of its superior effect upon dilation without side effects, can be the preferred agent used for routine single-drop dilation in all patients, independent of age, iris color, or skin color.