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Biomedical subjects

D E Singer

Publications and source records attributed to D E Singer.

31 records · Page 2Linked to original sources
PubMed1987

Corneal topography in myopic patients undergoing epikeratophakia.

We analyzed the corneal topography of eight eyes in seven patients who had undergone myopic epikeratophakia, using a 1.5-mm graft/host disparity. Topographic maps of corneal power generated by computer analysis of keratoscope photographs disclosed a central spherical optical zone smaller in diameter than was predicted by the preoperative lathing measurements. Outside this optical zone, the dioptric power of the graft surface increased steadily, indicating a progressive steepening of the corneal slope as the graft/host interface is approached. This pattern occurred in patients with accurate and inaccurate refractive results. The center of the graft was noted in some cases to be decentered from the patient's visual axis. The corneal topography analysis system has made clear the need to maximize the diameter of the effective optical zone.

Cornea↗
PubMed1987

Graphic presentation of computer-analyzed keratoscope photographs.

We describe a corneal topography analysis system that creates accurate high-resolution graphics of corneal surface power from computer analysis of keratoscope photographs, and we present several examples of corneal shape analyses. The major improvement in the updated version presented here is the development of a contour map of corneal surface power. Improvements in computer algorithms used to analyze the raw data obtained from the keratoscope photographs have also been made, resulting in increased accuracy. This system allows the ophthalmologist to see the patterns of power distribution on the corneal surface more easily than is possible by visual inspection of keratoscope photographs. Improved corneal topography analysis should find wide clinical application in the study of refractive corneal surgery techniques and in the study of corneal disorders that cause irregular astigmatism.

Adult↗
PubMed1986

Non-insulin-dependent diabetes in older patients. Complications and risk factors.

Non-insulin-dependent diabetes mellitus is predominantly a disease of aging, with more than 70 percent of non-insulin-dependent (type II) diabetic patients older than 55 years of age. The prevalence of macrovascular, microvascular, and neurologic complications in outpatients with type II diabetes between the ages of 55 and 74 was compared with that in a similarly aged nondiabetic group of patients. The association between duration of diabetes, hypertension, age, and other putative risk factors that are prevalent in this elderly diabetic population and the occurrence of complications was explored. This cross-sectional survey confirmed a significant increase in retinopathy, neuropathy, impotence, and macrovascular complications in patients with type II diabetes. Within the diabetic population, duration of disease was associated with the occurrence of retinopathy and neuropathy, but not associated with such macrovascular complications as coronary artery disease. Gender, type of therapy, and previously identified risk factors for vascular disease such as hypertension had little impact on the prevalence of complications in this population. The notion that type II diabetes in the elderly represents "mild" diabetes with regard to complications must be discarded. Further identification of risk factors within this diabetic population may suggest therapeutic approaches that will prevent or ameliorate the development of complications.

Age Factors↗
PubMed1986

Diagnosing liver metastases: a Bayesian analysis.

Clinicians frequently perform tests to determine whether patients have liver metastases. Optimal use of a laboratory test requires that the clinician know the test's operating characteristics (its sensitivity and specificity) and have an estimate of the pretest probability that disease is present. We have surveyed studies that examined the value of four biochemical and three imaging tests in establishing a diagnosis of hepatic metastases in patients who underwent an invasive procedure to establish the presence or absence of disease. We have pooled the data from these studies to arrive at values for the sensitivity and specificity of each of these tests, and calculated the predictive values for these tests over a wide range of pretest probabilities of disease. Several examples illustrate how this information may be used clinically. We provide a framework for the optimal interpretation of these commonly ordered tests and indicate the data needed for their complete analysis.

Bayes Theorem↗
PubMed1986

Retinopathy in older type II diabetics. Association with glucose control.

Non-insulin-dependent (type II) diabetics over the age of 55 comprise most of the diabetic population and are at considerable risk for the development of both macrovascular and microvascular complications. We studied the prevalence of retinopathy and its association with putative risk factors for its development in an elderly (55- to 75-yr-old) population of type II diabetics. Our cross-sectional analysis revealed that duration of diabetes and hemoglobin A1c (HbA1c) concentration were the two major predictors of the presence of retinopathy. Duration effect was seen after 10 yr of diabetes, whereas HbA1c effect was linear over its entire range. Hypertension, which has been reported to be a risk factor for microvascular disease in younger diabetic patients, was not associated with retinopathy in the older type II population. Multiple logistic regression analysis revealed that both the duration of diabetes and HbA1c remained significant independent determinants of retinopathy even after taking age and blood pressure into account. Our results support an etiologic role for metabolic control in the development of retinopathy in the elderly type II population.

Aged↗
PubMed1986

Single-chamber and dual-chamber cardiac pacemakers. A formal cost comparison.

Dual-chamber pacemakers, more sophisticated and costly than single-chamber pacemakers, are being used with increasing frequency, often with unclear indications. Proponents of dual-chamber devices have focused on initial differences in cost without considering additional induced costs. We examined the incremental cost of dual-versus single-chamber pacemakers over the expected lifetime of a pacemaker recipient. In addition to initial costs, we included the costs of pacemaker malfunction, reimplantation, generator replacement, and follow-up. Expected differences in cumulative costs per patient were calculated over a 12-year period. Dual-chamber pacing is $2500 more costly at implantation. The difference in cumulative cost increases to $5100 by year 12, reflecting shorter functional life for dual-chamber pacemaker generators and increased cost of follow-up. The incremental cost of dual-chamber pacemaking is neither short-term nor trivial. Dual-chamber pacemakers should be reserved for those who clearly benefit from its advanced technology.

Costs and Cost Analysis↗
PubMed1985

Complications after overdose with tricyclic antidepressants.

We reviewed 72 consecutive cases of tricyclic antidepressant (TCA) overdose (OD) admitted from the emergency ward (EW) to the ICU between 1977 and 1982. Most patients were seriously ill before ICU admission: 70% were comatose; 68% were intubated, including 61% in need of mechanical ventilation; and 30% were hypothermic. One patient died after ICU admission. ECG abnormalities were present in 37 (51%) patients in the EW. These abnormalities were associated with higher TCA plasma levels, but not with either acidosis or hypoxemia. Of 14 patients without ECG abnormalities or the need for intubation in the EW, none developed new ECG abnormalities or required ventilatory support. No patient had a late complication after transfer from the ICU, after a mean stay of 2.1 days. Late, unexpected complications in TCA OD are very rare. Our study suggests that TCA OD patients who do not have an abnormal ECG and do not require ventilatory support at the time of initial evaluation may not need ICU admission simply for intensive observation.

Adolescent↗
PubMedDate not supplied

The triage decision in pulmonary edema.

The authors studied the clinical courses of 216 prospectively selected patients with cardiogenic pulmonary edema presenting to an emergency ward (EW) to identify which patients should be triaged to the intensive care unit (ICU). The first four hours were considered the EW or pre-triage phase of hospitalization. During the EW phase, 108 patients remained stable; 33 of them developed cardiopulmonary complications over the next two days. Logistic regression identified four significant independent features that distinguished these 33 patients from the remaining patients: four-hour diuresis less than 1L, history of prior pulmonary edema, T-wave abnormalities, and jugular venous distention. A model containing the four variables predicted hospital complications with a sensitivity of 81% and a specificity of 65%. In comparison, the sensitivity of physicians in admitting to the ICU patients who would go on to have complications was 70%, with a specificity of 63%. In a model containing a term for the physicians' actual triage decision, all four independent predictors remained significant, producing an overall sensitivity of 81% and an overall specificity of 69%.

Aged↗
PubMedDate not supplied

The limited clinical value of home urine testing by diabetic patients.

To investigate the value of home urine glucose testing in assessing chronic diabetic glucose control, the authors compared patients' glycosuria patterns with their mean blood glucose (MBG) levels calculated from glycosylated hemoglobin (Hb Alc). One hundred and twenty-one patients who regularly checked their urines reported on the frequencies of glycosuria over the preceding ten weeks. There was substantial overlap in the glycosuria patterns of patients at different levels of MBG. Glycosuria was not detectable in only 44% of patients with good control (MBG less than or equal to 150 mg/dl). The probability of such good control given no glycosuria was only 26%. Similarly, frequent glycosuria was reported by only 27% of patients with poor control (MGB greater than 250 mg/dl). The probability of such poor control given frequent glycosuria was only 34%. Because home urine testing cannot reliably identify good or poor control, it has a very limited role in assessing patients' chronic glucose control.

Adolescent↗
PubMedDate not supplied

Smoking cessation following admission to a coronary care unit.

OBJECTIVE: To determine the impact of an episode of serious cardiovascular disease on smoking behavior and to identify factors associated with smoking cessation in this setting. DESIGN: Prospective observational study in which smokers admitted to a coronary care unit (CCU) were followed for one year after hospital discharge to determine subsequent smoking behavior. SETTING: Coronary care unit of a teaching hospital. PATIENTS: Preadmission smoking status was assessed in all 828 patients admitted to the CCU during one year. The 310 smokers surviving to hospital discharge were followed and their smoking behaviors assessed by self-report at six and 12 months. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: Six months after discharge, 32% of survivors were not smoking; the rate of sustained cessation at one year was 25%. Smokers with a new diagnosis of coronary heart disease (CHD) made during hospitalization had the highest cessation rate (53% vs. 31%, p = 0.01). On multivariate analysis, smoking cessation was more likely if patients were discharged with a diagnosis of CHD, had no prior history of CHD, were lighter smokers (less than 1 pack/day), and had congestive heart failure during hospitalization. Among smokers admitted because of suspected myocardial infarction (MI), cessation was more likely if the diagnosis was CHD than if it was noncoronary (37% vs. 19%, p less than 0.05), but a diagnosis of MI led to no more smoking cessation than did coronary insufficiency. CONCLUSION: Hospitalization in a CCU is a stimulus to long-term smoking cessation, especially for lighter smokers and those with a new diagnosis of CHD. Admission to a CCU may represent a time when smoking habits are particularly susceptible to intervention. Smoking cessation in this setting should improve patient outcomes because cessation reduces cardiovascular mortality, even when quitting occurs after the onset of CHD.

Analysis of Variance↗
PubMedDate not supplied

Noninvasive testing of asymptomatic bilateral hilar adenopathy.

The diagnostic strategy for asymptomatic patients with persistent bilateral bilar adenopathy often involves invasive procedures. The authors used Bayesian analysis to: 1) estimate the relative prevalences of diseases causing bilateral bilar adenopathy; 2) assess changes in the prevalence of disease by race, the presence of other clinical symptoms, and geography; and 3) determine the value of relevant noninvasive tests, including the angiotensin-converting enzyme (ACE) assay, gallium scan, and purified protein derivative (PPD), in order to assess when a strategy of watchful waiting is appropriate. The analysis indicated that the ACE assay, particularly when paired with the PPD, can identify many patients who might safely be managed without immediate invasive biopsy. Patients who are ACE+ and PPD- have an estimated probability of sarcoidosis of 0.95 or greater; patients who are ACE- and PPD+ have a probability of tuberculosis of 0.86 if black, 0.79 if white. In contrast, gallium scanning has no diagnostic role in this clinical situation. Bronchoscopic or mediastinoscopic biopsy has a limited role for patients who are ACE+ PPD- or ACE- PPD+ because of limited sensitivity. Patients who are both ACE- and PPD-, particularly if white, may have a high enough risk of lymphoma to consider invasive biopsy.

Bayes Theorem↗