Clinical comparison of optimum and large diameter soft contact lenses.

PURPOSE: To compare the clinical performance of large diameter lenses with optimally fit lenses in the same material and monocurve back surface design. METHOD: In a four-visit, randomised, bilateral, crossover, study, 25 myopic subjects wore optimum diameter lenses (control) and large diameter lenses (test) in random succession for 1 week each. Both study lenses were made of methafilcon A and of an identical design. Trial fittings with Frequency 55 (Coopervision) lenses modified with a design algorithm were used to determine the appropriate custom-made study lenses. RESULTS: The least squares mean scores (±SE) for overall comfort and end-of-day comfort (0-10 scale) were 7.57 ±â€¯0.33 vs. 7.42 ±â€¯0.33 (P = 0.59) and 7.00 ±â€¯0.31 vs. 7.27 ±â€¯0.32 (P > 0.05) for the optimum and large diameter lenses, respectively. There were no significant differences in mean (±SE) gradings for limbal hyperaemia (1.23 ±â€¯0.11 vs. 1.19 ±â€¯0.11, 0-4 scale, P = 0.60) and corneal staining (1.79 ±â€¯0.25 vs. 2.04 ±â€¯0.25, P = 0.39). Conjunctival staining was greater for the optimum lens: 1.80 ±â€¯0.28 vs. 0.93 ±â€¯0.28 (0-4 scale, P = 0.001). With regard to lens fit, the large diameter lenses showed significantly less post-blink movement (0.22 ±â€¯0.01 vs. 0.16 ±â€¯0.01 mm, P = 0.004), and greater total decentration (0.15 ±â€¯0.02 vs. 0.21 ±â€¯0.02 mm, P = 0.010). However, there was no significant difference in the key fit variable of tightness on push-up (46 ±â€¯0.69% vs. 48 ±â€¯0.69%, 0-100 scale, P = 0.12). DISCUSSION: The findings suggest that larger than optimal soft lenses may be worn without detriment to either comfort or ocular physiology, provided an optimal fit is otherwise maintained.

Inter-relationship of Soft Contact Lens Diameter, Base Curve Radius, and Fit.

PURPOSE: To evaluate the inter-relationship of soft contact lens base curve radius (BC), diameter, and lens fit using a mathematical model. METHODS: A spreadsheet mathematical model was used to evaluate theoretical fitting characteristics for various combinations of soft lens BC and diameter. The designs were evaluated using ocular topography data collected from 163 UK subjects. The model evaluated lens tightness (edge strain) and on-eye diameter (horizontal corneal overlap) and assumed that acceptable values fell within the range 0 to 6% and 0.2 to 1.2 mm, respectively. Analyses were undertaken of various trends relating to soft lens fit, including (1) the effect of BC and diameter on fitting success; (2) the effect of lens asphericity, BC, and sag on lens diameter on the eye; and (3) the effect of lens diameter on lens tightness. RESULTS: The highest overall success rate (90.2%) was achieved with an 8.60/14.2 mm (BC/diameter) design. Using this design on the sample population, the median edge strain value was 3.2% (IQR: 2.1%) whereas median corneal overlap was 0.62 mm (IQR: 0.35). There was a positive correlation (r = 0.37, P < .0001) between edge strain and corneal overlap. Edge strain showed significant correlations with each of the ocular topography variables, most notably corneal asphericity (-0.62, P < .0001). Corneal overlap showed significant correlations with corneal asphericity (r = -0.42, P < .0001) and corneal diameter (r = 0.92, P < .0001). For a 0.4 mm change in BC, it is necessary to change diameter by 0.2 mm to maintain similar on-eye diameter (arclength). When changing lens diameter, a change in BC of 0.2 mm is required to maintain similar tightness of fit. CONCLUSIONS: Mathematical modeling is a useful technique for large-scale evaluation of the interactions of soft contact lens design and fit. The study has given useful insights into the general performance of soft lens designs.

The influence of end of day silicone hydrogel daily disposable contact lens fit on ocular comfort, physiology and lens wettability.

PURPOSE: To quantify the end-of-day silicone-hydrogel daily disposable contact lens fit and its influence of on ocular comfort, physiology and lens wettability. METHODS: Thirty-nine subjects (22.1±3.5 years) were randomised to wear each of 3 silicone-hydrogel daily-disposable contact lenses (narafilcon A, delefilcon A and filcon II 3), bilaterally, for one week. Lens fit was assessed objectively using a digital video slit-lamp at 8, 12 and 16h after lens insertion. Hyperaemia, non-invasive tear break-up time, tear meniscus height and comfort were also evaluated at these timepoints, while corneal and conjunctival staining were assessed on lens removal. RESULTS: Lens fit assessments were not different between brands (P>0.05), with the exception of the movement at blink where narafilcon A was more mobile. Overall, lag reduced but push-up speed increased from 8 to 12h (P<0.05), but remained stable from 12 to 16h (P>0.05). Movement-on-blink was unaffected by wear-time (F=0.403, P=0.670). A more mobile lens fit with one brand did not indicate that person would have a more mobile fit with another brand (r=-0.06 to 0.63). Lens fit was not correlated with comfort, ocular physiology or lens wettability (P>0.01). CONCLUSIONS: Among the lenses tested, objective lens fit changed between 8h and 12h of lens wear. The weak correlation in individual lens fit between brands indicates that fit is dependent on more than ocular shape. Consequently, substitution of a different lens brand with similar parameters will not necessarily provide comparable lens fit.

Objective analysis of contact lens fit.

PURPOSE: To assess the validity and repeatability of objective compared to subjective contact lens fit analysis. METHODS: Thirty-five subjects (aged 22.0±3.0 years) wore two different soft contact lens designs. Four lens fit variables: centration, horizontal lag, post-blink movement in up-gaze and push-up recovery speed were assessed subjectively (four observers) and objectively from slit-lamp biomicroscopy captured images and video. The analysis was repeated a week later. RESULTS: The average of the four experienced observers was compared to objective measures, but centration, movement on blink, lag and push-up recovery speed all varied significantly between them (p<0.001). Horizontal lens centration was on average close to central as assessed both objectively and subjectively (p>0.05). The 95% confidence interval of subjective repeatability was better than objective assessment (±0.128 mm versus ±0.168 mm, p=0.417), but utilised only 78% of the objective range. Vertical centration assessed objectively showed a slight inferior decentration (0.371±0.381 mm) with good inter- and intrasession repeatability (p>0.05). Movement-on-blink was lower estimated subjectively than measured objectively (0.269±0.179 mm versus 0.352±0.355 mm; p=0.035), but had better repeatability (±0.124 mm versus ±0.314 mm 95% confidence interval) unless correcting for the smaller range (47%). Horizontal lag was lower estimated subjectively (0.562±0.259 mm) than measured objectively (0.708±0.374 mm, p<0.001), had poorer repeatability (±0.132 mm versus ±0.089 mm 95% confidence interval) and had a smaller range (63%). Subjective categorisation of push-up speed of recovery showed reasonable differentiation relative to objective measurement (p<0.001). CONCLUSIONS: The objective image analysis allows an accurate, reliable and repeatable assessment of soft contact lens fit characteristics, being a useful tool for research and optimisation of lens fit in clinical practice.

Exploring the optimum step size for defocus curves.

PURPOSE: To evaluate the effect of reducing the number of visual acuity measurements made in a defocus curve on the quality of data quantified. SETTING: Midland Eye, Solihull, United Kingdom. DESIGN: Evaluation of a technique. METHODS: Defocus curves were constructed by measuring visual acuity on a distance logMAR letter chart, randomizing the test letters between lens presentations. The lens powers evaluated ranged between +1.50 diopters (D) and -5.00 D in 0.50 D steps, which were also presented in a randomized order. Defocus curves were measured binocularly with the Tecnis diffractive, Rezoom refractive, Lentis rotationally asymmetric segmented (+3.00 D addition [add]), and Finevision trifocal multifocal intraocular lenses (IOLs) implanted bilaterally, and also for the diffractive IOL and refractive or rotationally asymmetric segmented (+3.00 D and +1.50 D adds) multifocal IOLs implanted contralaterally. Relative and absolute range of clear-focus metrics and area metrics were calculated for curves fitted using 0.50 D, 1.00 D, and 1.50 D steps and a near add-specific profile (ie, distance, half the near add, and the full near-add powers). RESULTS: A significant difference in simulated results was found in at least 1 of the relative or absolute range of clear-focus or area metrics for each of the multifocal designs examined when the defocus-curve step size was increased (P<.05). CONCLUSION: Faster methods of capturing defocus curves from multifocal IOL designs appear to distort the metric results and are therefore not valid. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Factors affecting corneoscleral topography.

PURPOSE: To evaluate factors affecting corneoscleral profile (CSP) using anterior segment optical coherence tomography (AS-OCT) in combination with conventional videokeratoscopy. METHODS: OCT DATA WERE COLLECTED FROM 204 SUBJECTS OF MEAN AGE 34.9 YEARS (SD: ±15.2 years, range 18-65) using the Zeiss Visante AS-OCT and Medmont M300 corneal topographer. Measurements of corneal diameter (CD), corneal sagittal height (CS), iris diameter (ID), corneoscleral junction angle (CSJ), and scleral radius (SR) were extracted from multiple OCT images. Horizontal visible iris diameter (HVID) and vertical palpebral aperture (PA) were measured using a slit lamp graticule. Subject body height was also measured. Associations were then sought between CSP variables and age, height, ethnicity, sex, and refractive error. RESULTS: Significant correlations were found between age and ocular topography variables of HVID, PA, CSJ, SR, and ID (P < 0.0001), while height correlated with HVID, CD, and ID, and power vector terms with vertical plane keratometry, CD, and CS. Significant differences were noted between ethnicities with respect to CD (P = 0.0046), horizontal and vertical CS (P = 0.0068 and P = 0.0095), and horizontal ID (P = 0.0010). The same variables, with the exception of vertical CS, also varied with sex; horizontal CD (P = 0.0018), horizontal CS (P = 0.0018), and ID (P = 0.0012). Age accounted for the greatest variance in topography variables (36%). CONCLUSIONS: Age is the main factor influencing CSP; this should be taken into consideration in contact lens design, IOL selection, and in the optimization of surgical procedures. Ocular topography also varied with height, sex, ethnicity, and refractive error.

Endovascular treatment of a congenital thoracic aortic aneurysm in a premature newborn.

Congenital aortic aneurysms are a rare, life-threatening disorder that present complex treatment challenges. The authors describe a congenital thoracic aortic aneurysm treated by endovascular means with stent-assisted coil deployment. Because of rapid in utero aneurysm growth and cardiac dysfunction, a 2.6-kg male was delivered expeditiously by Cesarean section at 35(2)/(7) weeks' gestation. On day of life 1, bilateral femoral arterial access was used to deliver a balloon-expandable stent across the wide-necked aneurysm. Microcoil embolization of the aneurysm via a prepositioned microcatheter was then performed. The child had an uncomplicated hospital course and is asymptomatic 5 months later, with complete aneurysm thrombosis.

The influence of corneoscleral topography on soft contact lens fit.

PURPOSE: To evaluate the influence of peripheral ocular topography, as evaluated by optical coherence tomography (OCT), compared with traditional measures of corneal profile using keratometry and videokeratoscopy, on soft contact lens fit. METHODS: Ocular surface topography was analyzed in 50 subjects aged 22.8 years (SD ±5.0) using videokeratoscopy (central keratometry, corneal height, and shape factor) and OCT to give both full sagittal cross-sections of the cornea and cross-sections of the corneoscleral junctions. Corneoscleral junction angle, corneal diameter, corneal sagittal height, and scleral radius were analyzed from the images. Horizontal visible iris diameter and vertical palpebral aperture were analyzed from digital slit lamp images. Lens fit was graded after 30 minutes wear of a -2.50 D commercially available standard hydrogel (etafilcon A, modulus 0.30 MPa) and silicone hydrogel (galyfilcon A, 0.43 MPa) design of similar geometries (8.30-mm base curve, 14.0-mm diameter). RESULTS: The mean horizontal corneal diameter was 13.39 mm (SD ±0.44). In many cases, there was a tangential transition at the corneoscleral junction. The corneoscleral shape profile analyzed from cross-sectional OCT images contributed significantly (P < 0.001) to the prediction of soft contact lens fit compared with keratometry and videokeratoscopy, accounting for up to 24% of the variance in lens movement. The fit of the stiffer material silicone hydrogel lens was better able to be predicted and was more varied than the hydrogel contact lens. CONCLUSIONS: The extra peripheral corneoscleral data gained from OCT characterization of ocular surface architecture provide valuable insight into soft contact lens fit dynamics.

Sign Change of Poisson's Ratio for Carbon Nanotube Sheets.

Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in-plane Poisson's ratio of carbon nanotube sheets (buckypaper) can be tuned from positive to negative by mixing single-walled and multiwalled nanotubes. Density-normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in-plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet-derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.

Intentional retrieval of viabil stent-grafts from the biliary system.

The present report describes the intentional retrieval of six Viabil stent-grafts from the biliary system. The six stent-grafts were successfully removed from five patients with a mean time from placement to retrieval of 38 days. Successful retrieval was independent of underlying disease etiology and included strictures associated with benign disease, malignant disease, disease of unknown etiology, and stent-graft misplacement. There were no complications resulting from stent-graft retrieval. Intentional removal of Viabil stent-grafts is technically feasible. Further study is necessary to establish its potential role in the management of biliary disease.

Fuel-powered artificial muscles.

Artificial muscles and electric motors found in autonomous robots and prosthetic limbs are typically battery-powered, which severely restricts the duration of their performance and can necessitate long inactivity during battery recharge. To help solve these problems, we demonstrated two types of artificial muscles that convert the chemical energy of high-energy-density fuels to mechanical energy. The first type stores electrical charge and uses changes in stored charge for mechanical actuation. In contrast with electrically powered electrochemical muscles, only half of the actuator cycle is electrochemical. The second type of fuel-powered muscle provides a demonstrated actuator stroke and power density comparable to those of natural skeletal muscle and generated stresses that are over a hundred times higher.

Placement of the Essure permanent birth control device with fluoroscopic guidance: a novel method for tubal sterilization.

An effective transcervical method for fluoroscopically guided fallopian tube occlusion has long been sought for female sterilization. The Essure permanent birth control device was approved by the Food and Drug Administration in November 2002 and is currently indicated for hysteroscopic placement. In a series of eight patients, bilateral Essure microcoils were placed with fluoroscopic guidance in seven patients for a success rate of 87.5%. One patient described peri- and postprocedure pelvic pain, otherwise no complications were identified. All patients returned to normal activities within 24 hours. Fluoroscopically guided transcervical tubal sterilization with the Essure microcoil device (Conceptus, San Carlos, CA) is a viable outpatient procedure.

A palette of desired leadership competencies: painting the picture for successful regionalization.

Regionalization is occurring across the country in an attempt to improve accessibility and services to populations with increased expectations and significant budget pressures. A successful reorganization requires strong and effective leadership, equipped with an array of knowledge, skills and abilities known as competencies. The model of leadership competencies presented in this article will become an essential tool for organizations in their pursuit of leaders to implement and drive successful change. This leadership competency model, discussed within a framework of change management process, will ensure that essential steps of change are followed and provide organizations with a blueprint for success. Is your organization ready?

Two-center clinical evaluation of a new automated fluorometric immunoassay for the quantitative analysis of total betaeta-human chorionic gonadotropin.

OBJECTIVES: This study evaluated the quantitative total betahCG assay on the Stratus CS point-of-care instrument at two medical centers. DESIGN AND METHODS: Analytical sensitivity, linearity, within-run and total imprecision, interferences, dilution recovery, method comparison (Dimension RxL), comparison of matched heparinized whole blood and plasma samples, and determination of the normal reference interval were studied. RESULTS: Analytical sensitivity was <0.5 IU/L. The assay's linear range was 0 to 1250 IU/L; the clinical reportable range was up to 50,000 IU/L. Within-run imprecision (CV) at both low (<20 IU/L) and elevated (760 IU/L) betahCG concentrations were <4%. Total imprecision for three QC levels and two pools were <4%. Method comparison showed Stratus CS betahCG = 0.98 +/- 0.01* Dimension RxL hCG -0.11 +/- 2.69 (n = 136; r = 0.996; Sy/x = 27.7). Matched heparinized whole blood/plasma sample-comparison showed: whole blood = 1.05*Plasma + 0.37 +/- 1.29 (n = 41; r = 1.000; Sy/x = 7.57). Mean dilution recovery was 99% (range: 95% to 103%). None of the 52 drugs tested, lipemia, icterus, hemolysis, LH, FSH, TSH, hGH or prolactin represented a significant interference with the assay. Reference intervals were <0.5 IU/L for males (n = 123) and <3.0 IU/L for nonpregnant females (n = 120). CONCLUSIONS: The Stratus CS betahCG test offers the advantage of quantitative measurement of total betahCG in whole blood at the point of care and is suitable for clinical use.

Vascular Thoracic Outlet Syndrome.

Vascular thoracic outlet syndrome generally affects young, active, otherwise healthy patients. The diagnosis is suspected by clinical presentation, and can be confirmed with angiography or venography. Conservative management has been associated with significant morbidity and long-term residual disability. We have used a multimodal treatment protocol that includes thrombolysis, anticoagulation, surgical decompression, and interventional procedures. Catheter-directed recombinant tissue-type plasminogen activator and intravenous heparin infusion are instituted at the time of diagnosis to promote recanalization and prevent propagation of thrombus. Surgical decompression of the thoracic outlet can be readily achieved by first rib resection during the same hospitalization. Postoperative venograms are obtained in all patients. Residual stenoses can be managed with angioplasty alone in some patients but more commonly require stent placement. We believe thrombolysis, anticoagulation, surgical decompression, and percutaneous interventions act synergistically to improve results of therapy in patients with vascular thoracic outlet syndrome.