Gareth L. Gardiner

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

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.

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.

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.

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. Financial Disclosure Dr. Werner is a member of the Scientific Advisory Board of Powervision, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

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.

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.

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-β) have reduced responses to IFN-β 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-β NAbs utilizing a human cell line transfected with a luciferase reporter gene responsive to IFN-β. 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-β were tested in the reporter gene assay. Percent positivity for NAbs to the IFN-β was as follows: Avonex (1α) 26.5%, Rebif (1α) 34.1%, and Betaseron (1β) 31.8%. The IFN-β 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-β-treated patients with MS.

The impact of tip bevel angulation on phacoemulsification efficiency and chatter

Primary objective: To evaluate the effect of tip bevel angulation on phacoemulsification efficiency and chatter. Research design: In vitro laboratory study. Methods and procedures: Formalin-soaked porcine lenses were divided into 2 mm cubes. 0.9 mm straight 0, 15, 30, 45 beveled degree tips were used with micropulse ultrasound (6 ms on and 6 ms off ). Power was set at 100%, vacuum levels were set at 500 mmHg; and aspiration rates were set at 50 mL/min. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined. Main outcomes and results: Changing the bevel angulation on a straight 0.9 mm phacoemulsification tip had no significant effect on efficiency. A 45 degree bevel was the most efficient tip overall. Chatter was seen to be significantly higher with a 15 degree tip (ANOVA, P=.0046). Conclusions: Tip bevel angulation has little effect on phacoemulsification efficiency and chatter, especially when optimized parameters are used. Limitations of this study include use of only one ultrasound power modulation and hard nuclear material.