PURPOSE: To determine and model the relationships between phacoemulsification conditions and viscoelastic agents that result in thermal wound injury. SETTING: Animal laboratory, Irvine, California, USA. METHODS: Mechanical and animal models, various wound sizes, phacoemulsification tips, and dispersive and cohesive viscoelastic agents were evaluated. Settings for phaco power, vacuum, and irrigation levels were controlled within a surgically relevant range. In the mechanical and animal models, incision temperature was assessed as a function of phacoemulsification parameters and time. In the animal model, wound damage was evaluated at the time of surgery. RESULTS: Induced time delays from the onset of phaco power to the onset of irrigation flow caused a thermal rise at the incision site. In these experiments, lack of irrigation and aspiration resulted in the greatest thermal rise and caused wound damage. Both the cohesive and dispersive viscoelastic agents were associated with a delay in the start of irrigation and aspiration, which resulted in similar maximum temperatures. Mathematical models were developed to estimate the maximum incision temperature from the phacoemulsification power, the duration (seconds) of occlusion, the tip gauge and type, and other phacoemulsification parameters. The models predict that under comparable conditions, occlusion with a viscoelastic agent will result in higher incision temperatures than occlusion with a balanced salt solution. CONCLUSION: Under comparable phacoemulsification conditions, both the cohesive and dispersive viscoelastic agents were associated with elevated temperatures that would be preventable by ensuring irrigation and aspiration flow before the onset of phacoemulsification power.
PURPOSE: To determine and model the relationships between phacoemulsification conditions and viscoelastic agents that result in thermal wound injury. SETTING: Animal laboratory, Irvine, California, USA. METHODS: Mechanical and animal models, various wound sizes, phacoemulsification tips, and dispersive and cohesive viscoelastic agents were evaluated. Settings for phaco power, vacuum, and irrigation levels were controlled within a surgically relevant range. In the mechanical and animal models, incision temperature was assessed as a function of phacoemulsification parameters and time. In the animal model, wound damage was evaluated at the time of surgery. RESULTS: Induced time delays from the onset of phaco power to the onset of irrigation flow caused a thermal rise at the incision site. In these experiments, lack of irrigation and aspiration resulted in the greatest thermal rise and caused wound damage. Both the cohesive and dispersive viscoelastic agents were associated with a delay in the start of irrigation and aspiration, which resulted in similar maximum temperatures. Mathematical models were developed to estimate the maximum incision temperature from the phacoemulsification power, the duration (seconds) of occlusion, the tip gauge and type, and other phacoemulsification parameters. The models predict that under comparable conditions, occlusion with a viscoelastic agent will result in higher incision temperatures than occlusion with a balanced salt solution. CONCLUSION: Under comparable phacoemulsification conditions, both the cohesive and dispersive viscoelastic agents were associated with elevated temperatures that would be preventable by ensuring irrigation and aspiration flow before the onset of phacoemulsification power.