Comparison of the effect of torsional and microburst longitudinal ultrasound on clear corneal incisions during phacoemulsification

PURPOSE: To compare incision integrity after clear corneal microcoaxial phacoemulsification using longitudinal and torsional ultrasound (US). SETTING: Iladevi Cataract & IOL Research Centre, Ahmedabad, India. DESIGN: Prospective randomized experimental clinical trial. METHODS: Part 1 comprised an experimental study of rabbit eyes. Group 1 received longitudinal US. Group 2 received torsional US. The right eye of each rabbit served as a control. Samples were processed for histomorphology and collagen I denaturation by immunofluorescence. Part 2 comprised a clinical trial of patients. Group 1 received torsional US. Group 2 received longitudinal US. At the end of surgery, trypan blue 0.0125% was instilled. After 2 minutes, 0.1 mL of aqueous was aspirated and its optical density measured. RESULTS: In part 1, incision histomorphology was comparable in both modalities. Collagen denaturation tests (immunofluorescence, dot blot analysis) showed no irregularity in collagen arrangement in either group. In Group 2, Descemet membrane was detached and endothelial cells were minimal at the roof of the incision. In part 2, trypan blue ingress into the anterior chamber was significantly greater in Group 1 than in Group 2 (mean 3.40 + 0.6 log units versus and 3.77 + 0.82 log units) (P<.007). CONCLUSIONS: Incision histomorphology in the torsional group showed minimal Descemet membrane detachment and minimal endothelial cell loss at the roof of the incision. Minimal ingress of trypan blue into the anterior chamber was observed with torsional US, indicating better wound integrity than with longitudinal US.