To determine the effects of povidone iodine 5% (Betadine 5%) applied to the eye on visual function, corneal integrity, and subjective complaints. Ten subjects were chosen to participate in this study (average age 40.6 ± 19.6; age range 22-68). LogMAR acuity, contrast sensitivity, corneal fluorescein staining, and subjective complaints were measured before and after 60 μl of Betadine 5% or saline were applied to one eye (eligibility visit, baseline, 5, 30, and 60 minutes and 4 and 24 hours post-application). Contrast sensitivity at 14 cpd was determined with a spatial two-alternative, forced choice procedure (Beethoven software). The National Eye Institute (NEI) grid pattern was used to grade corneal staining with sodium fluorescein. To avoid the detrimental effects of sodium fluorescein administration on functional vision, the corneal staining baseline was measured at the eligibility visit. Subjective complaints were monitored using the Schein dry eye questionnaire. The data were analyzed with an ANOVA. Saline administration did not alter logMAR acuity, contrast sensitivity, corneal fluorescein staining, or subjective complaints at any visit. Betadine administration significantly reduced the logMAR acuity, compared to baseline and the saline data, at the 30- and 60-minute visits (all P values <.05). The contrast sensitivity was significantly reduced compared to the baseline and the saline results at 5, 30, and 60 minutes after Betadine application (all P values <.05). The Betadine significantly increased the Schein questionnaire score, compared both to baseline and the saline data, at the 1- and 4-hour visits (all P values <.05). Total corneal staining and the maximum NEI sector staining were significantly different from baseline and from the saline results at every visit (all P values <.05). Betadine 5% application significantly decreases epithelial integrity of the cornea, decreases functional vision, and increases subjective complaints.