A reliable corneal tomography system is still needed.
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Contraindications↗
Biomedical subjects
David Huang
Publications and source records attributed to David Huang.
Molecular biology and immunology.
OBJECTIVES: To review basic molecular biology and immunology concepts to provide a foundation for the understanding of current and developing biological treatments for cancer. DATA SOURCES: Published scientific papers, review articles, and book chapters. CONCLUSION: Research into the structure, functions of the human cell, and development of molecular biology techniques, has increased the understanding of cancer pathophysiology. This research has assisted scientists to develop new cancer treatments, collectively called biotherapies. IMPLICATIONS FOR NURSING PRACTICE: Oncology nurses are increasingly facing the administration of a variety of new biotherapies. Basic knowledge of molecular biology and immunology will assist the oncology nurse to understand the mechanisms of action of these therapies, leading to improved patient education and more vigilant surveillance of side effects during and after administration.
Adaptation, Physiological↗
The effect of isotope selection on the prostate-specific antigen response in patients treated with permanent prostate brachytherapy.
PURPOSE: To assess the difference in prostate-specific antigen (PSA) response kinetics in patients undergoing either (125)I or (103)Pd permanent prostate brachytherapy (PPB). METHODS AND MATERIALS: Between 1997 and 1999, 333 patients underwent PPB as monotherapy. Forty-eight patients received a (125)I implant, and 285 received a (103)Pd implant. Biochemical relapse-free survival was defined by the Kattan modification of the American Society for Therapeutic Radiology and Oncology consensus, based on three PSA increases. In addition, the time to reach a PSA threshold of <or=1.0 ng/ml was noted. Log-rank testing was performed, and multivariate analysis was used to evaluate those variables associated with biochemical freedom from recurrence. RESULTS: With a mean 36-month follow-up, the actuarial biochemical relapse-free survival at 4 years was 86.8%. No significant difference in biochemical relapse-free survival was noted between patients treated with (125)I and (103)Pd (p=0.417). Multivariate analysis failed to identify isotope as an independent variable to predict for biochemical relapse-free survival. The mean time for patients treated with (103)Pd to reach the threshold PSA value was 10.2 weeks, whereas it was 22 weeks for (125)I (p=0.014). When the median time to reach the PSA threshold of <or=1.0 ng/ml was used to calculate the percentage of delivered dose for each isotope relative to the prescribed dose, there was no significant difference noted between (125)I (84%) and (103)Pd (94%) (p=0.86). CONCLUSIONS: Isotope selection does not appear to influence biochemical relapse-free survival in patients treated with monotherapy PPB. There was a significant difference (p=0.014) in time to reach a PSA threshold of <or=1.0 ng/ml noted between (125)I and (103)Pd. However, the percentage of delivered dose relative to the time to reach the threshold was the same between (125)I and (103)Pd. This information is important for during patients their post-PPB period.
Adenocarcinoma↗
Toward a dynamic real-time intraoperative permanent prostate brachytherapy methodology.
PURPOSE: To evaluate dosimetry and source location relative to CT-based dosimetry when performing real-time dynamic permanent prostate brachytherapy (PPB) with inverse treatment planning. METHODS AND MATERIALS: A treatment algorithm for dynamic PPB was developed using inverse treatment planning. The technique utilizes real-time transrectal ultrasound prostate imaging connected to the treatment planning software. The implementation of the plan with the Mick interstitial gun is monitored with up-to-date dosimetry assessments based on the registration of each seed when placed. Real-time dose assessment is monitored and adjustments can be made during the case, if necessary. A final OR dosimetric (OR-D) assessment based on the registered seed locations is performed. Postoperative CT scans obtained at 3 weeks are used for traditional dosimetry analysis (CT-D). A matrix algorithm was developed to match the seed locations from the ultrasound registration to that of the CT-scan parameters. RESULTS: Twenty-six consecutive patients with clinically localized prostate cancer underwent PPB using the algorithm designed for dynamic real-time planning. The OR-D identified a mean D90 of 109% (range 100-118%) whereas the mean CT-D D90 at 3 weeks was 105% (range 89-122%) (p=0.894). Analysis of the OR-D V100 and V150 relative to the 3-week CT-dose V100 and V150 were also insignificant (p=0.112 and 0.167, respectively). Assessment of seed locations relative to the intraoperative ultrasound and postimplant CT identified a mean root-mean-square error of 4.6 mm (0-21 mm). The mean error for the x, y, and z coordinates were 2.01 mm, 2.24 mm, and 2.85 mm, respectively. CONCLUSIONS: This study reports the preliminary results of a new treatment algorithm for PPB that incorporates intraoperative inverse planning with dynamic dosimetry assessment during the case. Correlation was seen between the completed intraoperative, postimplant plan and the CT based plan at 3 weeks. Seed to seed deviations between the OR-D matched well with the CT-D. Additional study is necessary to assess whether this approach can assist in improving implant dosimetry and whether it appropriately documents the OR-dose without the need for postimplant dosimetry.
Adenosarcoma↗
Relationship between the axis and degree of high astigmatism and obliquity of palpebral fissure.
PURPOSE: To investigate a possible relationship between the slanting of palpebral fissures and the magnitude and axis of astigmatism in children with astigmatism. METHODS: Cross-sectional study at a referral center of 53 children with astigmatism of more than +1.50 D in at least 1 eye. Visual acuity testing, cycloplegic refraction, slit-lamp biomicroscopy, and ophthalmoscopy were done on every patient. Corneal topography was obtained in 40 cooperative patients. External photographs of the midface were taken in 45 children. The degree of slanting of the palpebral fissures was evaluated based on the photographs. The statistical analysis tool used was repeated measures analysis of variance. Patients in whom photographic analysis was not available were excluded from the part of the statistical analysis dealing with eyelid slant. RESULTS: Palpebral fissure slant (P =.013) and gender (P =.0005) were highly correlated with the obliquity of cylinder axis. There was a possible correlation between gender and eyelid slant (P =.0594), with females having slightly larger degrees of upward palpebral fissure slanting and male more downward slanting of their fissures compared to published angles in an age-matched population. We found a statistically significant correlation between the degree of total astigmatism and a larger abnormal slant (P =.0192) and between the axis and magnitude of corneal astigmatism and abnormal slant (P =.0092). Higher degrees of eyelid slant (> 8 degrees or < -4 degrees ) increased the risk of high cylinder magnitude (> 3.00 D) by an odds ratio of 4.17 (95% CI: 1.03, 19.95). CONCLUSIONS: Children with astigmatism with large degrees of slanting of their palpebral fissures are at higher risk for high astigmatism (> 3.00 D). The axis of the astigmatism is highly correlated with the slanting of the palpebral fissure.
Adolescent↗
Improving clinical trial design in acute lung injury.
If future trials of acute lung injury/acute respiratory distress syndrome are to be rigorous, informative, and successful, a number of key design issues need to be considered. First, appropriate sample size and entry criteria must be selected. The present definitions of acute lung injury/acute respiratory distress syndrome are arbitrary and select a broad, heterogeneous patient population in which treatment effects may often be small, requiring much larger sample sizes than those of previous trials. The alternative approach, selecting a subset of patients in whom a larger benefit is anticipated, is potentially hazardous because the subset selection criteria are unproven. Second, it must be ensured that the therapy is tested against current best methods of care. To ensure that a study is considered current at completion, investigators should anticipate that recent evidence at study commencement will be considered standard at study completion. Up-to-date evidence-based medicine should therefore be encouraged for all enrolled patients and, probably, protocolized in unblinded studies. Multiple novel therapies can also be tested, but care must be paid to the particular study design choice. Third, appropriate outcomes must be chosen. The traditional end point of 28-day mortality is too short and too crude to capture all relevant patient and societal outcomes. Thus, consideration of survival over a longer duration, coupled with assessment of quality of life, functional status, and morbidity, is essential. Fourth, the study must comply with new standards for the protection of human subjects. Protecting human subjects' rights and ensuring patient safety in subjects who are critically ill and who are rarely able to provide fully informed consent is a significant challenge. However, it is essential that new studies comply with required standards without becoming so burdensome that they cannot reasonably be completed.
Clinical Trials as Topic↗
Critical care training for emergency physicians.
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Critical Care↗
Priorities for lung transplantation among patients with cystic fibrosis.
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Cystic Fibrosis↗
Risk factors for intraoperative epithelial defect in laser in-situ keratomileusis.
PURPOSE: To report intraoperative epithelial defects (IED) in eyes undergoing laser in-situ keratomileusis (LASIK). DESIGN: Consecutive interventional case series. METHODS: Retrospective review of 247 eyes (133 patients) that underwent primary LASIK by a single surgeon at an academic institution using the Hansatome microkeratome. Patient characteristics and variations in preoperative and operative technique were analyzed. The main outcome measure was occurrence of IED (defined as loose epithelium that is > 1 mm or cannot be stably repositioned or absent epithelium). Multivariate logistic regression was performed. RESULTS: Intraoperative epithelial defects occurred in 24 (9.7%) of 247 eyes. Intraoperative epithelial defects significantly increased with older age (odds ratio [OR] 2.39/decade; 95% confidence interval [CI] 1.46-3.92), thicker preoperative corneal thickness (OR 2.30/50 microm; 95% CI 1.24-4.28), and maintenance of suction ring vacuum during the reverse pass of the microkeratome (OR 1.76; 95% CI 1.01-3.06). The preoperative and intraoperative eye-drop regimen (anesthetic, mydriatics, lubricants, and intraoperative tonometry) had a significant effect on IED risk (OR, 0.163 best vs worst regimen; 95% CI, 0.033-0.792). In patients undergoing bilateral LASIK, the incidence of IED is much higher in the second eye if the first eye developed an IED (57% vs 1%). CONCLUSIONS: Modifying the eyedrop regimen was the more effective technical approach to decrease the risk of IED. Age and corneal thickness are valuable patient characteristics for preoperative risk assessment. Intraoperative epithelial defects in the first eye is highly predictive of IED in the second eye of the same patient.
Adult↗
Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology.
OBJECTIVE: This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure. METHODS: A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies. RESULTS: The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience. CONCLUSIONS: For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.
Academies and Institutes↗
Spot size and quality of scanning laser correction of higher-order wavefront aberrations.
PURPOSE: To investigate the effect of laser spot size on the outcome of aberration correction with scanning laser corneal ablation. SETTING: Cleveland Clinic Foundation, Cleveland, Ohio, USA. METHODS: Corrections of wavefront aberrations of Zernike modes from the second to eighth order were simulated. Gaussian and top-hat beams of 0.6 to 2.0 mm full-width-half-maximum diameters were modeled. The fractional correction and secondary aberration (distortion) were evaluated. RESULTS: Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, a 2.0 mm or smaller beam was adequate for spherocylindrical correction (Zernike second order), a 1.0 mm or smaller beam was adequate for correction of up to fourth-order Zernike modes, and a 0.6 mm or smaller beam was adequate for correction of up to sixth-order Zernike modes. CONCLUSIONS: Since ocular aberrations above the Zernike fourth order are relatively insignificant in normal eyes, current scanning lasers with a beam diameter of 1.0 mm or less are theoretically capable of eliminating most higher-order aberrations.
Computer Simulation↗
Oxygen-mediated regulation of porphobilinogen formation in Rhodobacter capsulatus.
A Rhodobacter capsulatus hemC mutant has been isolated and used to show that oxygen regulates the intracellular levels of porphobilinogen. Experiments using a hemB-cat gene fusion demonstrated that oxygen does not transcriptionally regulate hemB transcription. Porphobilinogen synthase activity is not regulated by oxygen nor is the enzyme feedback inhibited by hemin or protoporphyrin IX. It was demonstrated that less than 20% of [(14)C]aminolevulinate was incorporated into bacteriochlorophyll, suggesting that the majority of the aminolevulinate is diverted from the common tetrapyrrole pathway. Porphobilinogen oxygenase activity was not observed in this organism; however, an NADPH-linked aminolevulinate dehydrogenase activity was demonstrated. The specific activity of this enzyme increased with increasing oxygen tension. The results presented here suggest that carbon flow over the common tetrapyrrole pathway is regulated by a combination of feedback inhibition of aminolevulinate synthase and diversion of aminolevulinate from the pathway by aminolevulinate dehydrogenase.
Aminolevulinic Acid↗
Cancer risk behaviors and screening rates among homeless adults in Los Angeles County.
The homeless encounter many barriers to health care and preventive services, while having an increased prevalence of most risk factors for cancer. A group of homeless adults (221) at nine different locations within Los Angeles County were surveyed during the summers of 1998 and 1999. A portion (71%) reported that they had had at least one rectal exam, 42% had a fecal occult blood test, 24% had a skin exam, and 23% had an endoscopy (flexible sigmoidoscopy or colonoscopy), and of the men aged 50+, only 19% had a prostate-specific antigen test in their lifetime. For women aged 40+, 55% had received a Pap smear, and 53% had a breast exam, but only 32% had a mammogram within the prior year. Among the sampled homeless population, 77% believed in the benefits of cancer screening, 79% were not fatalistic about cancer, 63% believed that early detection was efficacious, and 83% did not think it would be difficult to get screened. The majority of this population demonstrated accurate knowledge of cancer screening guidelines with the exception of endoscopy. Cancer screening rates of those surveyed were lower than the rates in California for endoscopy, prostate-specific antigen, mammography, and Pap smears. Given the lower cancer screening rates compounded by higher cancer risk factors, homeless populations need increased access to cancer screening tests, as well as education on the availability of free services. Additionally, facilities for the homeless and their staff should reinforce the purposes of cancer screening, provide more screening services, and implement institutional efforts, such as providing nutritious meals and sun protection products, to reduce high-risk behaviors and increase further access to cancer screening tests.
Adult↗
Laser in situ keratomileusus for mixed and simple myopic astigmatism with the Nidek EC-5000 Laser.
PURPOSE: To evaluate the visual and refractive results of laser in situ keratomileusis (LASIK) for mixed and simple myopic astigmatism using bitoric ablation. METHODS: A retrospective study was performed in 65 eyes of 38 consecutive patients to evaluate uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA) and cyclopegic and manifest refraction, before and 3 and 6 months after LASIK (Moria LSK-ONE microkeratome, Nidek EC-5000 excimer laser). RESULTS: At 3 and 6 months after LASIK, 40 eyes of 24 patients (64.5%) were available for follow-up examination. Mean age was 25.9 +/- 6.6 years (range 18 to 43 yr). Mean preoperative manifest spherical equivalent refraction was -1.40 +/- 0.80 D (range -3.80 to +0.50 D) mean preoperative cylinder was -3.30 +/- 1.30 D (range -1.00 to -6.00 D). At 6 months follow-up, mean manifest spherical equivalent refraction was +0.30 +/- 0.46 D (range -0.38 to +1.88 D), mean cylinder was -0.73 +/- 0.61 D (range -2.25 to 0 D). There was a 77.8% decrease in astigmatism magnitude. According to vector analysis, mean achieved vector magnitude was 80% of intended. Fifty percent (20 eyes) had a cylinder within +/- 0.50 D of emmetropia. Twenty-three eyes (57.5%) had a spherical component within +/- 0.50 D. Eighty-five percent (34 eyes) had postoperative UCVA of 20/40 or better. Ten percent (four eyes) lost two lines of Snellen BSCVA, whereas 35% (14 eyes) gained one or more lines. CONCLUSIONS: Bitoric LASIK with the Moria LSK-ONE microkeratome and Nidek EC-5000 excimer laser was effective and safe for the reduction of cylinder in mixed and simple myopic astigmatism. Moderate undercorrection of the cylinder was evident.
Adolescent↗
Predictors of two-year mortality in a prospective "UPBEAT" study of elderly veterans with comorbid medical and psychiatric symptoms.
Medical inpatients of nine VA medical centers (N=2,657) were screened for symptoms of depression, anxiety, and alcohol abuse and followed for 24 months. Survivors were compared with deceased subjects on the severity of symptoms of depression, anxiety, alcohol abuse, and self-rated health. Mortality was predicted by the length of hospitalization, as well as poor self-rated health at baseline. The severity of depressive symptoms and poor self-rated health measured at the time closest to the time of death also predicted mortality. Lack of improvement in symptoms of depression and anxiety at 6 months was associated with higher rates of mortality.
Chronic Disease↗