Purpose: To evaluate the ultrastructural effect of trypan blue 0.1% staining for capsulorhexis on lens epithelial cells (LECs) and capsules.Setting: Division of Ophthalmology, University of São Paulo, São Paulo, Brazil. Methods: Before capsulorhexis, patients were randomly assigned to 1 of 2 groups. Trypan blue 0.1% staining was performed in the treatment group. No trypan blue was used in the control group. Samples of capsules with LECs were fixed and analyzed with routine optical microscopy techniques, immunohistochemistry for beclin-1 expression (a marker of autophagy), terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling to detect apoptosis, and transmission electron microscopy (TEM). Morphometric analyses were performed, and the 2 sets of data were compared.Results: Each group comprised 15 patients. Cell death by autophagy and apoptosis was observed in the treatment group but not in the control group. The TEM images of subcapsular epithelium cells showed mitochondrial rupture, dilation of the cisterns of the endoplasmic reticulum, increased cytoplasmic and nuclear electron density, and abnormalities in the nuclear profile of trypan blue-stained cells. Morphometric analysis showed statistically significant differences between the 2 groups in the longest nuclear axes and the ratio between the total nuclear perimeter and the cell area (P = .03). The difference in capsule thickness between groups was not significant.Conclusion: Trypan blue caused LEC death, which supports the hypothesis that staining with trypan blue 0.1% can help reduce the incidence of posterior capsule opacification after cataract surgery.Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.