Thermal evaluation of two phacoemulsification systems.

OBJECTIVE: To compare thermal profiles of new transversal ultrasound power modulation to torsional ultrasound in an artificial chamber and cadaver eye. DESIGN: Laboratory investigation. METHODS: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Temperature increase after 30 seconds was measured at the needle midshaft in an artificial chamber and at maximal friction point in a cadaver eye. Ellips FX (transverse) was tested at 100% power, as was Signature with micropulse settings (6 milliseconds on and off). OZil (torsional only) was tested at 100% power in the artificial chamber and cadaver eye. Runs were completed with aspiration blocked. Temperature was continuously measured on the phacoemulsification sleeve using a microthermistor probe connected to the BAT-10 multipurpose thermometer, with an accuracy of ±0.1°C. RESULTS: Transversal FX had a greater temperature increase than micropulse (p < 0.001) and torsional (p < 0.001). Micropulse had a greater temperature increase than torsional (p < 0.001). The cadaver eye had a greater temperature increase than the artificial chamber for torsional (p < 0.001). CONCLUSIONS: Higher heat accumulation and potential for incisional burn occurred with the cadaver model than with the artificial chamber, suggesting the need for caution when using 100% torsional ultrasound with aspiration blocked. Transversal FX generated more heat than was reported originally. Further study is needed to determine the incidence of incisional burn with varied power settings for this new model. Micropulse generated more heat than previous reports, but the increased efficiency is likely to negate potentially increased incisional burn risk.

Effect of pulsing ultrasound on phacoemulsification efficiency.

PURPOSE: To evaluate pulse type technology used to remove lens fragments during phacoemulsification. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Lens nuclei soaked in 10 mL of 10% neutral buffered formalin for 2 hours were placed in 10 mL of balanced salt solution. Lenses were cut into 2 mm × 2 mm cubes; no more than 36 hours later, cubes were randomly selected for testing. Two aspiration and 2 vacuum settings were assessed at moderate- and high-flow and vacuum (30 mL/min and 300 mm/Hg, low-flow vacuum; 50 mL/min and 500 mm/Hg, high-flow vacuum), with continuous 50 milliseconds on and off (long pulse) and 6 milliseconds on and off (micropulse) ultrasound. RESULTS: There was a significant difference in efficiency favoring micropulse compared with combined long pulse and continuous pulse in high-flow vacuum at 80% power (P = .018) and between combined long pulse and continuous pulse versus micropulse in high-flow vacuum at 20% power (P = .019). Low-flow vacuum micropulse was more efficient than continuous (19.7%) (P < .0001) and long pulse (22.7%) (P < .0001). Continuous and long pulses were not significantly different from one other. There was a significant difference in chatter rates between high-flow vacuum and low-flow vacuum when all results were compared (P < .0001), with no additional significant differences found. CONCLUSION: Micropulse technology was better than continuous and long pulse at moderate but not high-flow and vacuum settings. At the higher setting, chatter was observed less often, with all modalities more efficient than the lower setting.

Evaluation of stability and capsular bag opacification with a foldable intraocular lens coupled with a protective membrane in the rabbit model.

PURPOSE: To evaluate the stability and capsular bag opacification of a smooth or a patterned silicone protective membrane implanted in the bag with secondary placement of an intraocular lens (IOL). SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Twelve New Zealand rabbits had bilateral implantation of a protective membrane and an IOL or an IOL alone. Three groups of 8 eyes each received the IOL and the smooth protective membrane, the IOL and the patterned membrane, or the IOL alone. Slitlamp examination was performed weekly for 4 weeks. The rabbits were then humanely killed and their globes enucleated. Capsular bag opacification was scored based on the Miyake-Apple view, and the eyes underwent histopathology. RESULTS: At 4 weeks, the mean central posterior capsule opacification (PCO) score was 0.28 ± 0.32 (SD) in all eyes with a protective membrane and 2.08 ± 1.28 in eyes with the IOL alone (P < .00001, Student t test). Peripheral PCO and Soemmerring ring formation were also significantly less in eyes with the protective membrane. Histopathologically, the posterior capsules were relatively clear in most IOLs with the protective membrane. The smooth and patterned protective membranes showed a significant difference in overall capsular bag opacification formation compared with the IOLs without the membrane. CONCLUSIONS: The circular geometry of the protective membrane led to expansion of the capsular bag and appeared to prevent capsular bag opacification. Further studies are warranted to assess whether the pattern on the device's posterior surface further enhances this effect. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Bent versus straight tips in micropulsed longitudinal phacoemulsification.

OBJECTIVE: The aim of this study was to evaluate bent and straight phacoemulsification tips to determine which tip is more efficient in removal of lens fragments, using micropulsed longitudinal ultrasound in phacoemulsification. DESIGN: In vitro laboratory study. METHODS: The John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Pig lenses hardened in a manner comparable with dense human cataracts were cut into 2-mm cubes and removed with micropulsed longitudinal ultrasound using settings previously shown to be optimally efficient (6 milliseconds on and 6 milliseconds off for a bent tip). To verify this time as most efficient for a straight tip, we also tested times of 5, 6, and 7 milliseconds time on and off. The tips were either straight or with a 20-degree bend. Twenty cubes were used for each comparative run. RESULTS: For the straight tip, 6 milliseconds on (1.56 ± 0.815 seconds) was significantly more efficient than 7 milliseconds on (2.45 ± 1.56 seconds, p = 0.001) and not significantly more efficient than 5 milliseconds on (1.69 ± 0.86 seconds, p = 0.43). Five milliseconds off time (1.45 ± 0.76s) was more efficient than 6 milliseconds (2.06 ± 1.37 seconds, p = 0.004) and 7 milliseconds off (2.18 ± 1.24s, p = 0.001). The straight tip was more efficient than the bent tip (1.38 ± 0.83 versus 2.93 ± 2.14 seconds, p = 0.006). CONCLUSIONS: Results are contrary to accepted common belief. Micropulsed longitudinal phacoemulsification is more efficient with a straight rather than a bent tip.

Evaluation of uveal and capsule biocompatibility of a single-piece hydrophobic acrylic intraocular lens with ultraviolet-ozone treatment on the posterior surface.

PURPOSE: To evaluate a single-piece hydrophobic acrylic intraocular lens (IOL) with ultraviolet-ozone (UV-O3) treatment on the posterior surface and compare it with an identical untreated IOL in a rabbit model. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Study IOLs were implanted in the right eyes and control IOLs in the left eyes of 10 New Zealand rabbits. Slitlamp examinations were performed 1 to 6 weeks postoperatively. Neodymium:YAG (Nd:YAG) posterior capsulotomy was performed in both eyes of 5 rabbits after the 4-week slitlamp examination. At 6 weeks, the rabbits were killed humanely and their globes were enucleated. Capsular bag opacification was scored from the posterior aspect (Miyake-Apple view), and the eyes were processed for histopathology. RESULTS: At 4 weeks, the mean posterior capsule opacification (PCO) scores were 0.88 ± 0.33 (SD) in the study eyes and 2.55 ± 1.13 in the control eyes (P=.003, 2-tailed paired t test). Performance of Nd:YAG posterior capsulotomy was similar in both groups. Gross postmortem examination also showed statistically less peripheral PCO in eyes with the study IOLs than in control eyes. There was no difference in histopathologic findings between study eyes and control eyes and no signs of untoward inflammation or toxicity in any eye evaluated. CONCLUSIONS: Treatment of the posterior surface of a single-piece hydrophobic acrylic IOL with UV-O3 appears to prevent PCO, likely by increasing adhesion between the posterior capsule and the IOL while retaining uveal biocompatibility. Performance of Nd:YAG posterior capsulotomy was similar between treated IOLs and untreated IOLs.

Evaluation of stability and capsular bag opacification of a new foldable adjustable intraocular lens.

BACKGROUND: Incorrect lens power remains one of the most common reasons for intraocular lens explantation/exchange. We evaluated stability and effect on capsular bag opacification of a new foldable modular lens system, with a base component and an optic component in rabbit eyes. METHODS: Bilateral phacoemulsification was performed on six rabbits; one eye received the test lens (Harmoni Modular Lens, ClarVista Medical), whereas the other received a single-piece hydrophobic acrylic control lens (SA60AT, Alcon). Slit-lamp examinations were performed at postoperative weeks 1, 2, 3, 4 and 6. All rabbits were sacrificed at week 6. After enucleation, the eyes were examined grossly from the Miyake-Apple view. Following, all globes were sectioned and processed for histopathological examination. RESULTS: The modular lens was stable in all six rabbits. Uveal biocompatibility was similar to or better in the test eyes when compared with control eyes up to 6 weeks postoperatively. Overall, capsular bag opacification was found to be significantly lower in the test eyes when compared with control eyes. At the 6-week gross examination, central posterior capsule opacification was scored as 0.58 ± 0.73 in the test group, and as 3.00 ± 1.26 in the control group (paired two samples for means t-test; two-tail P = 0.005). CONCLUSIONS: The Harmoni Modular system remains stable within the capsular bag after implantation. Due to the design of the base component featuring long loops, along with peripheral anterior and posterior square edges, the lens appeared to prevent overall capsular bag opacification in the rabbit model.

Effect of increased vacuum and aspiration rates on phacoemulsification efficiency.

PURPOSE: To evaluate the effect of vacuum and aspiration rates on phacoemulsification efficiency. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Formalin-soaked porcine lenses were divided into 2.0 mm cubes, and 0.9 mm 30-degree beveled 20-degree bent tips were used with micropulse ultrasound (US) (6 milliseconds on and 6 milliseconds off) and a peristaltic flow system. Vacuum levels were tested at 200, 300, 400, and 500 mm Hg, and aspiration rates were tested at 20, 35, and 50 mL/min. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined. RESULTS: Increasing vacuum increased efficiency only when going from 200 mm Hg to higher vacuum levels. Increasing aspiration increased efficiency at all points measured (25 mL/min versus 35 mL/min, P < .0001; 35 mL/min versus 50 mL/min, P = .012; 25 mL/min versus 50 mL/min, P < .0001). Chatter was highest at 200 mm Hg and decreased when vacuum was increased from 200 mm Hg to 300 mm Hg and up. Chatter decreased with increasing flow. CONCLUSIONS: Vacuum improved efficiency only up to 300 mm Hg and was more dependent on increasing flow. Similarly, chatter correlated with 200 mm Hg vacuum only and was more correlated with flow. Limitations of this study include use of only 1 US power modulation and hard nuclear material. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Comparison of venturi and peristaltic vacuum in phacoemulsification.

PURPOSE: To evaluate the efficiency of peristaltic-based and venturi-based vacuums. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine lenses were hardened with formalin and cut into 2.0 mm cubes. Time to fragment removal (efficiency) and fragment bounces off the tip (chatter) were measured using a Signature machine with the ability to switch between peristaltic-based and venturi-based vacuum. Micropulse longitudinal and transversal ultrasound motions were tested. RESULTS: Venturi-based vacuum had increased efficiency and decreased chatter compared with peristaltic-based vacuum at lower vacuum levels. CONCLUSION: Use of a venturi-based vacuum, when available, may result in reduced clearance time of lens material and mitigate chatter even under noisy conditions. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Long-term uveal and capsular biocompatibility of a new accommodating intraocular lens.

PURPOSE: To evaluate long-term uveal and capsular biocompatibility of a new accommodating intraocular lens (IOL). SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Bilateral phacoemulsification was performed in 14 rabbits; 1 eye received the accommodating IOL (Fluidvision) and the other received a hydrophobic acrylic control IOL. Slitlamp examinations were performed at postoperative weeks 1 to 4 and months 2, 3, 4, and 6. Six rabbits were humanely killed at 2 months and 8 rabbits at 6 months. After gross examination with the Miyake-Apple view, selected IOLs were removed for implant cytology. All globes were then sectioned and processed for histopathologic examination. RESULTS: Uveal biocompatibility of study and control IOLs was similar in clinical and pathologic examinations up to 6 months postoperatively. In the study group, anterior capsule opacification appeared absent and posterior capsule opacification (PCO) was significantly less than in the control group. At the gross examination at 6 months, central PCO was 0.8 ± 0.5 (SD) in the study IOLs and 3.7 ± 0.4 in the control IOLs (P < .0001, 2-tailed paired t test). Histopathologic examination confirmed the relative lack of capsule opacification in study eyes compared with controls and the absence of untoward inflammatory reaction or toxicity in all eyes. CONCLUSIONS: The accommodating IOL maintained an expanded capsular bag secondary to the large size of the haptic elements without significant contact with the anterior capsule. This appeared to prevent overall capsular bag opacification and to retain uveal and capsular biocompatibility.

Cell-based reporter gene assay for therapy-induced neutralizing antibodies to interferon-beta in multiple sclerosis.

Patients with therapy-induced neutralizing antibodies (NAbs) to interferon-beta (IFN-ß) have reduced responses to IFN-ß treatment, resulting in higher relapse rates, increased magnetic resonance imaging activity, and a higher risk of disease progression. A functional assay was employed for both screening and titering of IFN-ß NAbs utilizing a human cell line transfected with a luciferase reporter gene responsive to IFN-ß. This assay demonstrated 100% sensitivity and specificity compared with the traditional cytopathic effect (CPE) assay and normal donor specimens. Additionally, 183 patients with multiple sclerosis (MS) undergoing therapy with IFN-ß were tested in the reporter gene assay. Percent positivity for NAbs to the IFN-ß was as follows: Avonex (1α) 26.5%, Rebif (1α) 34.1%, and Betaseron (1ß) 31.8%. The IFN-ß reporter gene assay showed excellent correlation with the well-established CPE assay offering clear advantages. The 50% false-positivity rate typically seen in enzyme-linked immunosorbent assays could be eliminated by using a functional assay for both screening and titering. Results can be reported within 20 h, and the cell line is cryopreserved, eliminating the need to maintain live viral and cell cultures. The use of this functional assay should be a valuable tool for detecting and monitoring the presence of NAbs in IFN-ß-treated patients with MS.