Systematic and objective wet-lab testing of instruments for phacoemulsification: new Formalin Quadrant Model.

PURPOSE: To validate an improved wet-lab model for systematic and objective efficiency testing of instruments for phacoemulsification. SETTING: Institute of Medical Engineering, Lucerne University of Applied Sciences and Arts, Lucerne, Switzerland. DESIGN: Experimental study. METHODS: Porcine lenses were incubated for different time spans in formalin to simulate different cataract densities. Lenses were cut in quadrants and emulsified in a silicone test chamber. The use of ultrasound was restricted to full occlusion and the minimal power needed to promote emulsification. Equivalence to the surgical situation and cataract consistency were judged by an experienced surgeon. Efficiency was rated by effective phacoemulsification time, liquid consumption, and total surgery time. RESULTS: Formalin incubation times of 2 hours, 1.25 hours, and 0.5 hours were validated for hard, middle-hard, and soft cataracts, respectively. Systematic testing of different fluidics settings revealed the unique opportunities of the improved model: Experiments could be performed by laboratory staff without any surgical experience after a short training, and the model provided results in a fast and reproducible manner. Reduced effective phacoemulsification time, shorter total surgery time, and less liquid consumption were observed with higher fluidics settings, confirming and complementing earlier clinical findings. CONCLUSIONS: The Formalin Quadrant Model can be used to test new designs of instrumentation on different cataract densities or various instrument settings for efficiency. Using a validated cataract substitute, it closely represents the clinical situation and thus renders valid results in a short time. Instruments can be tested and improved profoundly before costly and elaborate clinical trials have to be applied.

Outcomes of coaxial microincision cataract surgery versus conventional coaxial cataract surgery.

PURPOSE: To compare the outcomes of coaxial microincision cataract surgery (MICS) with those of conventional coaxial cataract surgery. SETTING: University Eye Clinic, Geneva, Switzerland. METHODS: In a prospective study, 50 eyes of 50 patients with nuclear or corticonuclear cataract (grades 2 to 4 on the Lens Opacities Classification System III) were randomly selected to have cataract extraction through a temporal clear corneal incision using 1 of 2 techniques: coaxial MICS (25 eyes) or conventional coaxial cataract surgery (25 eyes). Coaxial MICS was performed through a 1.6 mm incision and conventional coaxial cataract surgery, through a 2.8 mm incision. In all cases, a flexible hydrophobic acrylic intraocular lens (Lentis L-303, WaveLight GmbH) was implanted. Intraoperative parameters were ultrasound time, surgical time, and total volume of balanced salt solution used. The best corrected visual acuity, corneal thickness, and endothelial cell count were evaluated preoperatively and postoperatively. RESULTS: There were no relevant clinical differences between groups or perioperative complications in either group. The only statistically significant differences between the 2 groups were ultrasound time (P = .0002) and surgical time (P = .005). CONCLUSIONS: Coaxial microincision cataract surgery was a safe and effective technique. Although ultrasound and surgical time were significantly higher with coaxial MICS than with conventional coaxial cataract surgery, the postoperative results in the 2 techniques were comparable.

Aspiration curette for anterior capsule polishing: laboratory and clinical evaluation.

Capsular fibrosis or fibrotic after-cataract results from transdifferation of anterior lens epithelial cells into myofibroblasts with consequent contraction and collagen deposition. To avoid possible complications, an instrument was designed for efficient and safe polishing of the anterior capsule leaf. The curette features an upward-facing slit with sharp-edged flanks and rounded turning points and an optional bypass hole. It is introduced through 3 equidistant 20-gauge paracentesis openings. In a laboratory test, vacuum rise time and vacuum levels under occlusion and the effect of adding a bypass hole were investigated for various pump settings. In a clinical pilot series, efficiency and safety of various designs were tested and vacuum and flow settings titrated for optimum performance; the clinical effect was determined in prospectively randomized bilateral studies. Optimum pump settings were 5 mL/min and 10 mm Hg with the nonventing curette and 7 to 10 mL/min and 50 mm Hg with the venting curette. A bypass hole delayed the vacuum rise and reduced the mean vacuum level on full occlusion. It also allowed fine-tuning the vacuum at the slit by varying the flow rate with the foot pedal. Anterior capsule polishing significantly decreased capsule fibrosis and is recommended when posterior capsulorhexis and optic buttonholing are combined.