Upper panel: average clinical score of hamster eyes injected with vehicle (control) or LPS from animals untreated (vehicle) or treated with melatonin (Mel 12 or Mel 24 h). At 24, 36, 48 and 72 h after the injection of LPS, the clinical score was significantly increased. Both treatments with melatonin (starting at 12 or 24 h post-injection) significantly decreased the clinical score at 36, 48 and 72 h (but not 24) post-LPS. Data are mean ± SEM (n = 14 eyes per group). **P < 0.01 versus vehicle-injected eyes; †P < 0.01 versus LPS-injected eyes, by Mann–Whitney U-test. Lower panel: representative photographs of clinical signs observed at 36 h after the intravitreal injections, in eyes submitted to the following treatments: control (A), LPS (B), LPS + Mel 12 h (C) and LPS + Mel 24 h (D). Note episcleral congestion (arrow), synechiae and cataract (*) in one eye injected with LPS from an animal untreated with melatonin. In eyes from animals treated with melatonin (Mel 12 h and Mel 24 h), the occurrence of inflammatory signs was lower. Note the miosis in the animal receiving Mel 12 or Mel 24 h.