Estimation of the mechanical properties of the eye through the study of its vibrational modes.

Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz-10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.

Cancer Incidence in Heart Transplant Recipients With Previous Neoplasia History.

Neoplasm history increases morbidity and mortality after solid organ transplantation and has disqualified patients from transplantation. Studies are needed to identify factors to be considered when deciding on the suitability of a patient with previous tumor for heart transplantation. A retrospective epidemiological study was conducted in heart transplant (HT) recipients (Spanish Post-Heart Transplant Tumor Registry) comparing the epidemiological data, immu-nosuppressive treatments and incidence of post-HT tumors between patients with previous malignant noncardiac tumor and with no previous tumor (NPT). The impact of previous tumor (PT) on overall survival (OS) was also assessed. A total of 4561 patients, 77 PT and 4484 NPT, were evaluated. The NPT group had a higher proportion of men than the PT group (p < 0.001). The incidence of post-HT tumors was 1.8 times greater in the PT group (95% confidence interval [CI] 1.2-2.6; p < 0.001), mainly due to the increased risk in patients with a previous hematologic tumor (rate ratio 2.3, 95% CI 1.3-4.0, p < 0.004). OS during the 10-year posttransplant period was significantly lower in the PT than the NPT group (p = 0.048) but similar when the analysis was conducted after a first post-HT tumor was diagnosed. In conclusion, a history of PT increases the incidence of post-HT tumors and should be taken into account when considering a patient for HT.

Optical power distribution of refractive and aspheric multifocal contact lenses: Effect of pupil size.

PURPOSE: To evaluate the power profile within the optic zone of different designs of multifocal contact lenses (CLs) and to analyze how the effect of pupil size could impact on their optical performance. METHODS: The optical power distribution within the optic zones of multifocal CLs was measured by the Nimo TR1504 (LAMBDA-X, Belgium). The multifocal CLs under study were the Acuvue Bifocal, the Acuvue Oasys for Presbyopia, the PureVision Multifocal and the PureVision 2 for Presbyopia. Each design was considered in all their available addition powers. All lenses had a nominal power of -3.0D. At the same time, three lenses of each model were considered and five consecutive readings of each lens were performed. RESULTS: The results show that the PureVision Multifocal and the PureVision 2 for Presbyopia have aspheric power profiles. Both designs showed aspheric center-near designs with a smoother progression of the optical power in the PureVision 2 for Presbyopia. The Acuvue Bifocal and the Acuvue Oasys for Presbyopia are shown to have concentric alternating near and far zones. Apart from the refractive rings, the Acuvue Oasys for Presbyopia showed an increase in negative (or less positive) values toward the periphery of the lens. CONCLUSIONS: Besides the refraction, the knowledge of the power profiles of multifocal CLs and the effect of pupil size on the optical distribution of these lenses could be crucial to understand the performance of these designs when they are fitted.

Type of tumour, gender and time since diagnosis affect differently health-related quality of life in adolescent survivors.

Research findings about health-related quality of life (HRQoL) of childhood cancer survivors are mixed and the features which could modulate these results have not been investigated rigorously. This research aims to improve the knowledge on these topics. Thus, HRQoL between central nervous system (CNST) and non-central nervous system (non-CNST) adolescent cancer survivors was compared. The influence of selected factors (gender and years since diagnosis) on HRQoL was also analysed. In a cross-sectional design, 78 survivors (12-20 years) who were ≥ 1 year free of oncological treatment answered the self-reported version of the KIDSCREEN-52. HRQoL mean scores of CNST survivors were lower in comparison with non-CNST in physical well-being and social support and peers dimensions. Furthermore, female gender was also related to lower HRQoL scores for both types of tumours in physical well-being and autonomy dimensions. Additionally, scores on psychological well-being, social support and peers, parent relations and home life and school environment dimensions decrease with length of time from diagnosis. Therefore, diagnosis of CNST and gender were related to lower HRQoL among survivors in some dimensions, whereas time from diagnosis was related to impaired HRQoL in other features. These results can help to design tailored interventions and psychosocial guidelines to follow-up survivors.

In vitro optical performance of a new aberration-free intraocular lens.

PURPOSE: To assess the optical performance of the new EnVista intraocular lens (IOL). MATERIALS AND METHODS: Four aspheric IOLs were evaluated; the new EnVista is one amoung them. This IOL, similarly to the Z-Flex HB and the Bi-Flex 1.8 667AB ones, has a neutral aspheric design, whereas the fourth IOL under test (AcrySof IQ IOL SN60WF) presents a negative spherical aberration (SA). The IOL's aberration patterns were measured in vitro, by setting them up on an optical bench. From these aberration-pattern data, the modulation transfer function (MTF), the average modulation values, and the points spread function (PSF) were calculated. Furthermore, in order to assess the potential optical quality that these IOLs would yield once they are implanted, an average corneal-aberration pattern was juxtaposed to the in-vitro profiles and the same parameters were calculated again. RESULTS: For the IOL-only scenario (ie, without including the corneal factor), it was the EnVista IOL, which is aberration-free that showed the higher MTF, PSF values. This was followed by the other two aberration-free IOL models. However, when the effect of an average corneal pattern was also taken into consideration, the AcrySof IQ IOL SN60WF always outperformed the other neutral-asphericity IOLs. CONCLUSIONS: The in-vitro optical performance of the EnVista IOL was good, but it decreases substantially in a whole-eye scenario, when the wavefront profile of an average cornea is added. Other designs with different degrees of SA should be considered for this IOL in order to surpass these results.

Use of mTOR inhibitors in chronic heart transplant recipients with renal failure: calcineurin-inhibitors conversion or minimization?

BACKGROUND: In the last decade, mTOR inhibitors (mTOR-is) have become the cornerstone of the calcineurin inhibitor (CNI)-reduced/free regimens aimed to the preservation of post-transplant renal function. We compared utility and safety of the total replacement of calcineurin inhibitors with a mTOR-i with a strategy based on calcineurin inhibitor minimization and concomitant use of m-TOR-i. METHODS: In a retrospective multi-center cohort of 394 maintenance cardiac recipients with renal failure (GFR<60 mL/min/1.73 m(2)), we compared 235 patients in whom CNI was replaced with a mTOR-i (sirolimus or everolimus) with 159 patients in whom mTOR-is were used to minimize CNIs. A propensity score analysis was carried out to balance between group differences. RESULTS: Overall, after a median time of 2 years from mTOR-i initiation, between group differences for the evolution of renal function were not observed. In a multivariate adjusted model, improvement of renal function was limited to patients with mTOR-i usage within 5years after transplantation, particularly with the conversion strategy, and in those patients who could maintain mTOR-i therapy. Significant differences between strategies were not found for mortality, infection and mTOR-i withdrawal due to drug-related adverse events. However, conversion group tended to have a higher acute rejection incidence than the minimization group (p=0.07). CONCLUSION: In terms of renal benefits, our results support an earlier use of mTOR-is, irrespective of the strategy. The selection of either a conversion or a CNI minimization protocol should be based on the clinical characteristics of the patients, particularly their rejection risk.

The posterior chamber phakic refractive lens (PRL): a review.

Implantation of phakic intraocular lenses (pIOLs) is a reversible refractive procedure, preserving the patient's accommodative function with minimal induction of higher order aberrations compared with corneal photoablative procedures. Despite this, as an intraocular procedure, it has potential risks such as cataracts, chronic uveitis, pupil ovalization, corneal endothelial cell loss, pigmentary dispersion syndrome, pupillary block glaucoma, astigmatism, or endophthalmitis. Currently, only two models of posterior chamber pIOLs are commercially available, the implantable collammer lens (STAAR Surgical Co.) and the phakic refractive lens (PRL; Zeiss Meditec). The number of published reports on the latter is very low, and some concerns still remain about its long-term safety. The present article reviews the published literature on the outcomes after PRL implantation in order to provide a general overview and evaluate its real potential as a surgical refractive option.

Risk factors associated with cytomegalovirus infection in heart transplant patients: a prospective, epidemiological study.

BACKGROUND: The objectives of this epidemiological, prospective study were to describe the characteristics of cytomegalovirus (CMV) infection in heart transplant (HT) recipients and to identify the variables that may influence the development of CMV viremia and CMV disease in these patients. METHODS: HT recipients ≥18 years of age (n=199) were included in the study. Variables studied included CMV serostatus, immunosuppressive treatment, and administration of anti-CMV prophylaxis. RESULTS: The mean age of the population was 52 years, and 84% were males. Immunosuppressive regimens were administered as induction therapy to 92.5% of patients; 88.5% of patients received calcineurin inhibitors as maintenance therapy. Anti-CMV treatment was given to 59% of 199 patients as prophylaxis (70%), preemptive therapy (10%), or to treat CMV infection (20%). Overall, 43% of patients had at least 1 positive viremia test. No patient with a high-risk serostatus (donor+/recipient-) receiving prophylaxis developed CMV syndrome, and only 2.5% of 199 patients developed CMV invasive disease. Multivariate analysis showed that having a positive donor CMV serostatus was associated with an increased risk of developing CMV viremia (P<0.012), while use of mammalian target of rapamycin (mTOR) inhibitors was associated with a decreased risk (P=0.005). CONCLUSIONS: In a population of HT recipients, the CMV infection rate was similar to that seen in previous studies, but the progression to overt CMV disease was very low. Having a CMV-positive donor was identified as an independent risk factor for developing CMV viremia, while the use of mTOR inhibitors was protective against viremia.

Incidence and risk factors for nonmelanoma skin cancer after heart transplantation.

INTRODUCTION: The incidence of skin cancer in heart transplant (HT) patients is higher than in the general population, reversing the proportion of cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) with a predominance of the former. The etiologic role of new immunosuppressants is not well known. We sought to ascertain the incidence of SCC and BCC in HT patients and the risk factors for its occurrence. PATIENTS AND METHODS: We report the incidence of all types of post-HT skin cancer, SCC, and BCC among adult HT patients in Spain (4089 subjects) as well as the influence of gender, age at heart transplant, immunosuppression, and sunlight exposure. RESULTS: The incidence rates of SCC and BCC, per 1000 persons/year, were 8.5 and 5.2, respectively. Males had a higher risk of SCC but not BCC. Induction therapy increased the risk of SCC and BCC. The relative risk of mycophenolate mofetil (MMF) was 0.3 (0.2-0.6; P<.0005) and azathioprine (AZA) 1.8 (1.2-2.7; P<.0032) for SCC, whereas tacrolimus and cyclosporine showed no difference. The relative risk of BCC was not affected by any immunosuppressant. CONCLUSION: Age at transplantation>45 years, induction therapy use, and high sunshine zone were risk factors for both SCC and BCC. Different immunosuppressive agents have different risks of nonmelanoma skin cancer, as AZA increases the risk of SCC and MMF is a protective factor. The relative risk of BCC was not affected by any immunosuppressor.

Steroid use in heart transplant patients in Spain in the current era: a multicenter survey.

OBJECTIVE: Steroid withdrawal (SW) from maintenance therapy in heart transplant patients is still a controversial subject. We designed a questionnaire to ascertain the attitudes and procedures of a number of Spanish heart transplant units (16) regarding the use/withdrawal of steroids as part of the immunosuppressive maintenance therapy. MATERIALS AND METHODS: We sent an 11-item questionnaire to the clinical director in charge of each unit. The questionnaire was completed and returned by 14 units. RESULTS: In 21.5% of the centers SW was performed in all patients, while 78.5% of the centers only performed SW in selected patients. In 57% of units SW was performed at 12 months posttransplantation and between 6 and 12 months in the rest. Fewer than 20% of patients were steroid-free in 46% of units while in 23% of units this proportion was >50%. In 11 units, the minimum prednisone dose administered was

Variables associated with diagnostic delay in immigrant groups with tuberculosis in Madrid.

OBJECTIVE: To identify variables associated with total diagnostic delay (TDD), patient delay (PD) and health service delay (HSD), among the tuberculous immigrant population in the Autonomous Community of Madrid (ACT). METHODOLOGY: Tuberculosis cases diagnosed in 15 hospitals in the ACT in 2003 were interviewed face-to-face and medical records were reviewed. A descriptive study was conducted, followed by univariate and multivariate analysis using non-conditional logistic regressions. 50th (p50) and 75th (p75) percentiles of the different diagnostic delay components were analysed as dependent variables. RESULTS: For the 296 cases included, the mean TDD was 40.5 days (IQR 16.0-90.0), the PD was 15 days (IQR 6.5-30.0), and the HSD was 5 days (IQR 0.0-30.0). TDD-p75 is associated with seeking primary health care (OR 2.87, 95%CI 1.47-5.58). PD-p75 is associated with identification of fever (OR 0.49, 95%CI 0.25-0.92) and non-identification of cough (OR 1.87, 95%CI 1.05-3.36) as symptoms resulting in health care being sought. The HSD-p75 is associated with primary health care being sought (OR 3.81, 95%CI 1.87-7.78), health cover (OR 15.07, 95%CI 1.96-115.68) and negative smear results at the time of diagnosis (OR 1.98, 95%CI 1.01-3.91). CONCLUSIONS: The HSD needs to be reduced, mainly when health care is sought through the primary care services and among patients with negative smear results.

A structural model of the relationships between perceived control and adaptation to illness in women with breast cancer.

OBJECTIVES: To examine whether perceived control produces better adaptation to illness in breast cancer patients in stages I or II. DESIGN: Longitudinal, 1-year following study. METHODS: One hundred and one women were assessed on five occasions: one week after surgery, and again 1, 3, 6 and 12 months later, using, among other measures, the Mental Adjustment to Cancer (MAC) and the Hospital Anxiety and Depression Scale (HADS). RESULTS: Structural equation models confirmed that patients with higher perceived control showed better adaptation to illness in all five assessments. CONCLUSIONS: These data fit well with previous research and suggest that psychological interventions which emphasize a sense of personal control would be effective in enhancing well-being in breast cancer patients at the early stages.

Contrast sensitivity function in children: normalized notation for the assessment and diagnosis of diseases.

The purpose of this article is to describe a normalized notation for the assessment of the contrast sensitivity in children. This notation is obtained dividing the log contrast sensitivity value found in a patient by the corresponding normative contrast sensitivity data. The ratio obtained describes the contrast sensitivity of a patient facilitating its understanding, assessment and consequently effective communications. This article shows the normalized notation developed for children aged from 3 to 7 years old. An evaluation of the contrast sensitivity in healthy and amblyopic patients has been shown in order to explain the procedure to follow. The use of normalized notation in clinical procedures will provide to the clinician a better understanding of the results and the changes over time as well by comparison in the assessment of an ocular disease.

Distribution of refractive errors in Spain.

The aim of this work was to characterise the refractive state of a Spanish population. Special attention to myopia prevalence was carried out. At this stage 7621 subjects, 3692 males and 3929 females, between 3 and 93 years were examined by means of static retinoscopy and subjective refraction. The most prevalent was emmetropia with a mean percentage of 43.2% and ranging from 60.6% (3-8 years) to 29.0% (66-93 years). The prevalence of hyperopia (35.6%) increased with age, from 36.9% (3-8 years) to 55.8% (66-93 years). Myopia appeared to be more prevalent in the 30-35 age group (30.1%), agreeing with the more near-work demanding age range. Mean refractive error obtained was +0.19 +/- 3.42 D, ranging from +0.05 +/- 3.18 D (20-35 years) to +0.96 +/- 2.42 (66-93 years). Reading addition value obtained was similar to respective values of age of other populations. The whole Spanish population evaluated was emmetrop. No differences in prevalence from other populations were found, obtaining greater values of myopia in groups with more near work and a greater percentage of hyperopia versus age.

Expression and molecular characterization of rat renal D-mannose transport in Xenopus oocytes.

Renal reabsorption appears to play a major role in d-mannose homeostasis. Here we show that in rat kidney, the transport of d-mannose by brush border membrane vesicles from tubular epithelial cells involves an uphill and rheogenic Na-dependent system, which is fully inhibited by d-mannose itself, incompletely inhibited by d-glucose, d-fructose, phloridzin, and phloretin, and noninhibited by l-mannose or disaccharides. In addition, this system exhibits both low capacity (112.9+/-15.6 pmol/mg/second) and high affinity (0.18+/-0.04 mm), with a 2:1 stoichiometry for the Na:d-mannose interaction, and low affinity for sodium (16.6+/-3.67 mm). We also show expression of d-mannose transport by Xenopus laevis oocytes injected with rat renal polyA(+) RNA. Kinetic analysis of the expressed transport was performed after RNA enrichment by fractionation through a sucrose density gradient and was shown to be identical to that measured in membrane vesicles. The RNA species encoding the expressed transport has a small mean size, 1 kb approximately, and shows no homology with the SGLT family of Na-dependent d-glucose transporters, as shown by low stringent RT-PCR and northern analysis. The expressed transport is specific for d-mannose, since in spite of a significant inhibition by d-glucose and d-fructose, neither of these two substrates was transported above the level of the water-injected oocytes.

The role of anxiety and adaptation to illness in the intensity of postchemotherapy nausea in cancer patients.

The aim of this work was to assess whether cancer patients presenting high anxiety levels or poor adaptation to cancer experience higher levels of postchemotherapy nausea, regardless of the emetogenicity of the chemotherapy schedule. Sixty-three patients were interviewed before receiving their chemotherapy schedule and some psychological variables were assessed. Nausea intensity was also assessed after treatment. The results showed that patients with relatively higher levels of nausea reported higher levels of anxiety prior to chemotherapy and lower levels of adaptation to cancer. Thus, evidence for a modulating effect of psychological factors in postchemotherapy emesis is suggested.

A solid-state NMR study of the molecular sieve VPI-5 synthesized in the presence of a CTABr surfactant.

Silicon-free and silicon-rich large-pore aluminophosphate VPI-5, synthesized with various contents of AIPO-H3 impurity, was studied by Bloch decay (BD) and cross polarization (CP) NMR under magic angle spinning (MAS). The 1H-->31P CP peaks were considerably stronger from AIPO-H3 than from VPI-5. A detailed examination of the CP kinetics and a careful comparison of the CP and BD spectra are prerequisites for the unequivocal interpretation of 1H-->31P CP in porous aluminophosphates.

Pretreatment with sedative-hypnotics, but not with nondepolarizing muscle relaxants, attenuates alfentanil-induced muscle rigidity.

STUDY OBJECTIVE: To evaluate and compare the efficacy of various pretreatment agents to attenuate or prevent opioid-induced muscle rigidity using a well-established, previously described clinical protocol. DESIGN: Prospective, controlled, single-blind, partially randomized study. SETTING: Large medical center. PATIENTS: ASA physical status I-III patients undergoing elective surgical procedures of at least 3 hours' duration. INTERVENTIONS: The effect of pretreatment with nondepolarizing muscle relaxants (atracurium 40 micrograms/kg or metocurine 50 micrograms/kg), benzodiazepine agonists (diazepam 5 mg or midazolam 2.5 mg), or thiopental sodium 1 mg/kg on the increased muscle tone produced by alfentanil 175 micrograms/kg was compared with a control group (given no pretreatment). MEASUREMENTS AND MAIN RESULTS: Rigidity was assessed quantitatively by measuring the electromyographic activity of five muscle groups (biceps, intercostals, abdominals, quadriceps, and gastrocnemius). Rigidity also was rated qualitatively by attempts to initiate and maintain mask ventilation, attempts to flex an extremity, and the occurrence of myoclonic movements. Pretreatment with the two nondepolarizing muscle relaxants had no effect on the severe muscle rigidity produced by high-dose alfentanil. Whereas thiopental was only mildly effective, the benzodiazepines midazolam and diazepam significantly attenuated alfentanil rigidity (p < 0.05). CONCLUSION: This study suggests that benzodiazepine pretreatment is frequently, but not always, effective in preventing opioid-induced muscle rigidity.

Anticipatory nausea and vomiting: are psychological factors adequately investigated?

Current research on chemotherapy-induced nausea and vomiting in cancer patients is reviewed, and some hypotheses to explain why anticipatory and post-chemotherapy nausea and vomiting appear are suggested. Methodological problems are also discussed. It is suggested that future research should focus on post-chemotherapy nausea and emesis, rather than anticipatory nausea and emesis, in order to achieve a deeper understanding of the psychological factors involved in the development of chemotherapy-induced nausea and vomiting.