One to three standardized cups with 40-mL espresso (i.e., 60 mg of caffeine, were given to the patient precataract surgery except for the control group and the contralateral eye). All patients received sedoanalgesia and were monitored for heart activity, blood pressure, and oxygen levels in the blood. Stand-by anesthesia was provided. To harvest the anterior lens capsule and adherent lens epithelial cells main incision and paracenteses were performed in a standardized way. Then, the anterior chamber was filled with ophthalmic viscosurgical device (OVD) and a capsulorhexis (aimed for 5.5 mm) was performed. Before continuing cataract surgery the lens capsule and adherent lens epithelial cells were taken with a forceps from the anterior chamber. Immediately after this procedure, the anterior lens capsule and adherent lens epithelial cells were transferred to sealed glass tubes and stored at 4°C prior to analysis. Each lens capsule and adherent lens epithelial cells were extracted with 0.25 mL of dichloromethane, evaporated to dryness, and dissolved in 0.05 mL of ethyl acetate. Four microliters were injected into a gas chromatography–mass spectrometry (GC–MS/MS) system, which consisted of a 7890B gas chromatograph coupled with a 7000C triple quad mass spectrometer (Agilent, Santa Clara, CA, USA). An autosampler AS 7693 was used for pulsed splitless injections onto a HP-5ms Ultra Inert capillary column (30 m, 0.25 mm internal diameter (ID), film thickness 0.5 μm; Agilent). The injector temperature was set to 280°C, the carrier gas was helium at a flow rate of 1.6 mL/min. The oven temperature was set to 160°C, held at this temperature for 2 minutes, heated at a rate of 30°C/min to 230°C, held for 2 minutes, followed by a rate of 20°C/min to 290°C, and held for 5.7 minutes. The transfer line temperature was set to 300°C. After electron impact (EI)-ionization the mass spectrometer was operated in multiple reaction monitoring (MRM)-mode with a transition 194.0 to 109.0 m/z as quantifier and two further transitions as qualifiers. The whole procedure could achieve a limit of detection of 0.1-ng caffeine per lens capsule/epithelium. The reference standard for caffeine in this study was purchased from Fluka-Honeywell International, Inc. (Morristown, NJ, USA).