chocolate can improve blood flow, mood, and cognition in the short term, but little is known about the possible effects of dark chocolate on visual performance.OBJECTIVE To compare the short-term effects of consumption of dark chocolate with those of milk chocolate on visual acuity and large-and small-letter contrast sensitivity.DESIGN A randomized, single-masked crossover design was used to assess short-term visual performance after consumption of a dark or a milk chocolate bar. Thirty participants without pathologic eye disease each consumed dark and milk chocolate in separate sessions, and within-participant paired comparisons were used to assess outcomes. Testing was conducted at the Rosenberg School of Optometry from June 25 to August 15, 2017. MAIN OUTCOMES AND MEASURESVisual acuity (in logMAR units) and large-and small-letter contrast sensitivity (in the log of the inverse of the minimum detectable contrast [logCS units]) were measured 1.75 hours after consumption of dark and milk chocolate bars. RESULTS Among the 30 participants (9 men and 21 women; mean [SD] age, 26 [5] years), small-letter contrast sensitivity was significantly higher after consumption of dark chocolate (mean [SE], 1.45 [0.04] logCS) vs milk chocolate (mean [SE], 1.30 [0.05] logCS; mean improvement, 0.15 logCS [95% CI, 0.08-0.22 logCS]; P < .001). Large-letter contrast sensitivity was slightly higher after consumption of dark chocolate (mean [SE], 2.05 [0.02] logCS) vs milk chocolate (mean [SE], 2.00 [0.02] logCS; mean improvement, 0.05 logCS [95% CI, 0.00-0.10 logCS]; P = .07). Visual acuity improved slightly after consumption of dark chocolate (mean [SE], −0.22 [0.01] logMAR; visual acuity, approximately 20/12) and milk chocolate (mean [SE], −0.18 [0.01] logMAR; visual acuity, approximately 20/15; mean improvement, 0.04 logMAR [95% CI, 0.02-0.06 logMAR]; P = .05). Composite scores combining results from all tests showed significant improvement after consumption of dark compared with milk chocolate (mean improvement, 0.20 log U [95% CI, 0.10-0.30 log U]; P < .001).CONCLUSIONS AND RELEVANCE Contrast sensitivity and visual acuity were significantly higher 2 hours after consumption of a dark chocolate bar compared with a milk chocolate bar, but the duration of these effects and their influence in real-world performance await further testing.TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT03326934

de Toledo et al 6 suggested the dragging of recipient epithelial cells through the peripheral incisions as the most feasible cause, in this case, the donor origin could be proven. Because storage time was normal (18 days), an association with a long organ culture entailing corneal epithelial cells growing around the scleral rim of the corneoscleral button is unlikely. No precut tissue was used, so fibrosis or epithelial ingrowth at the rim is improbable. Implantation of epithelial cells from the donor, which were attached to the Descemet membrane after preparation, seems most likely.