Methods: Ozone (O₃) gas (200 mg/h) and 20-watt, 411 nm blue light were used in the study. A sealed, light- and air-tight box containing an ozone generator and blue light source was used. Petri dishes (r = 9 cm) were inoculated with E. coli ATCC 25922 at concentrations of 10⁷ CFU/mL and 10⁸ CFU/mL by diluting a 0.5 McFarland suspension 1:10, and applying it evenly with a swab. To observe physical effects, 1 cm² polymethyl methacrylate (PMMA) plates were also placed inside the box. Experiments were conducted using two bacterial densities (10⁷ and 10⁸ CFU/mL), with three ozone doses (1.335, 2.670, and 5.340 mg/L) and three blue light exposure times (8, 16, and 32 minutes). Each test was repeated twice.

Results: With 10⁷ CFU/mL bacteria, 1.335 mg/L ozone and 8 minutes of blue light reduced colonies by 98.2%; after 32 minutes, no colonies remained. At 10⁸ CFU/mL, 5.340 mg/L ozone and 32 minutes of light reduced colonies by 98.5%.

Conclusions: The combination of ozone and 411 nm blue light achieved dose-dependent disinfection even at high bacterial concentrations (10⁸ CFU/mL). This method appears to be effective under experimental conditions. Keywords : Goldmann tonometer, ozone, disinfection