Biomedical subjects

W J Feuer

Publications and source records attributed to W J Feuer.

17 recordsLinked to original sources

PubMed1992

Effectiveness of a gentamicin dosing protocol based on postconceptional age: comparison to published neonatal guidelines.

OBJECTIVE: To evaluate the effectiveness of a gentamicin dosing protocol based on postconceptional age in producing therapeutic serum concentrations and to compare the protocol with commonly used gentamicin dosing guidelines. DESIGN: During the initial three months of this study infants were dosed according to physician discretion (group I). In the subsequent three-month period patients were dosed according to a postconceptional age dosing schedule (group II). SETTING: Infants were enrolled after being admitted to the Newborn Intensive Care Unit at the University of Miami/Jackson Memorial Medical Center. PATIENTS: Infants less than 37 weeks gestational age with normal renal function, not receiving indomethacin, and requiring gentamicin treatment were enrolled. Fifty-nine infants were enrolled into group I (median weight 1300 g [range 720-3300]), postconceptional age 29 weeks [26-37]); and 68 infants were enrolled into group II (weight 970 g [530-3000], postconceptional age 29 weeks [24-36]). INTERVENTION: Patients in group II were dosed according to the following protocol: postconceptional age less than 30 weeks, 3.0 mg/kg q24h, and postconceptional age 30-37 weeks, 2.5 mg/kg q18h. Peak and trough serum gentamicin concentrations were obtained in all study patients. Pharmacokinetic parameters were calculated from measured serum concentrations. Using the calculated pharmacokinetic data, peak and trough serum concentrations were simulated for five published neonatal dosing guidelines and the proposed postconceptional age protocol. MAIN OUTCOME MEASURES: The number of therapeutic serum gentamicin concentrations resulting from the dosing guidelines studied were compared. RESULTS: Measured trough concentrations differed significantly between the two groups with 35 percent of patients in group I and 90 percent of patients in group II having trough values less than 2 mg/L (p less than 0.001). There was no significant difference in measured peak concentrations between groups. Simulated trough concentrations were significantly different when postconceptional age dosing was compared with commonly used protocols (p less than 0.0001) with the highest percentage of concentrations less than 2 mg/L (89 percent) resulting from the proposed postconceptional age guidelines. CONCLUSIONS: These data suggest that the proposed postconceptional age protocol is reproducible and reliable in achieving therapeutic gentamicin serum concentrations in neonates.

Drug Administration Schedule↗

PubMed1992

Effects of pentoxifylline on the cardiovascular manifestations of group B streptococcal sepsis in the piglet.

Pentoxifylline (PTXF) is a methylxanthine that modifies leukocyte function and inhibits cytokine release. To evaluate its effects on the cardiovascular manifestations of sepsis secondary to group B streptococci, 14 anesthetized, mechanically ventilated piglets were studied over a 240-min period. Animals were randomly assigned to a treatment group that received a PTXF bolus (20 mg/kg) followed by a continuous infusion of 5 mg/kg/h before and during group B streptococci (1 x 10(8) colony forming units/kg/min) administration and a control group that received saline as a placebo. Comparison of the hemodynamic measurements and arterial blood gases during the first 90 min of PTXF treatment with those of the control group resulted in the following 90 min values: systemic arterial blood pressure was significantly higher in the PTXF group (89 +/- 10 versus 56 +/- 30 mm Hg; p less than 0.005) as was cardiac output (0.18 +/- 0.04 versus 0.10 +/- 0.07 L/kg/min; p less than 0.005). Pulmonary vascular resistance remained lower in the PTXF-treated animals (135 +/- 117 versus 248 +/- 119 mm Hg/L/min/kg; p less than 0.001), and these animals were less acidotic as measured by pH (7.07 +/- 0.2 versus 7.31 +/- 0.1; p less than 0.05) and base deficit (-15 +/- 9 versus -5 +/- 2 mmol/L; p less than 0.05). Median survival time was significantly longer in the PTXF group (210 versus 90 min; p less than 0.002). These data demonstrate that PTXF can ameliorate some of the deleterious hemodynamic manifestations of group B streptococci sepsis and result in improved survival in a young animal model.

Acid-Base Equilibrium↗

PubMed1991

Statpac 2 glaucoma change probability.

We compared the traditional intuitive criterion (fixed at 5 dB) with the variable Statpac 2 criterion of the Humphrey Field Analyzer for identifying visual deterioration at individual points within a visual field. The separation of depressed from stable points in 123 follow-up fields of 17 patients, when all points within a field were considered, was reasonably equivalent between the two methods (kappa = 0.55 +/- 0.027 [+/- SE]). Centrally located points within the field demonstrated a stronger agreement (kappa = 0.68 +/- 0.028), because the fixed criterion more often labeled the edge points as having progressed than did the Statpac 2 algorithm. The glaucoma change probability printout is more simply obtained than the manual comparison required for intuitive interpretation with a fixed criterion, and it is potentially more accurate because of its reliance on a database that permits a variable criterion to be applied.

Aged↗

PubMed1991

Beta-adrenergic responsiveness of choroidal vasculature.

Using in vitro binding methods and autoradiographs, the authors showed that choroidal vessels specifically bind iodine 125 cyanopindolol, a nonselective blocker of beta-adrenergic receptors, in albino rabbits. In humans, the presence of beta-adrenergic receptors in choroidal vessels was confirmed by showing an increased choroidal vascular tone after systemic administration of timolol maleate, a nonselective beta-adrenergic blocker. Topically administered timolol maleate lowered the intraocular pressure but did not reach the choroidal receptors in sufficient quantity to produce a measurable effect on vascular tone.

Administration, Topical↗

PubMed1991

Pseudo-loss of fixation in automated perimetry.

During automated perimetry with the Humphrey Visual Field Analyzer, field examinations are labeled unreliable whenever the reported rate of fixation loss is 20% or more. The reported rate of fixation loss results in part from times when the patient's gaze drifts from the fixation point during the examination, but also in part from technical artifacts such as faulty initial localization of the blind spot or false-positive responses by the patient. It was found that technical artifacts caused nearly half of the instances in which a field examination had a reported fixation loss rate of greater than 20%. It was also found that the perimetrist can prevent the artifacts, with the result that the frequency of field examinations labeled as having excessive fixation loss fell from 26% to 14%.

Automation↗

PubMed1991

Nd:YAG cyclophotocoagulation: outcome of treatment for uncontrolled glaucoma.

We reviewed the records of 35 patients (35 eyes) treated with Nd:YAG cyclophotocoagulation for uncontrolled glaucoma and followed for 6 to 36 months or until treatment was declared a failure (loss of light perception, or intraocular pressure (IOP) greater than 21 mm Hg). The mean pretreatment intraocular pressure was 37.9 mm Hg (range, 20 to 61 mm Hg). The total energy in the initial treatment session ranged from 50.4 to 372.4 J (191.7 +/- 66.3 J). After the treatment, the mean IOP was 21.2 mm Hg (range, 0 to 53 mm Hg). The Kaplan Meier survival analysis demonstrated that failures occurred throughout the follow-up period and that the majority of patients required further intervention or lost all vision if followed long enough. Visual outcome was not correlated with energy used. Eleven eyes (31%) lost two or more lines of acuity or lost all light perception. These findings suggest that Nd:YAG cyclophotocoagulation may control IOP but cannot always save vision.

Adolescent↗

PubMed1990

Contact B-scan echography in the assessment of optic nerve cupping.

We determined the reliability of high-resolution contact B-scan echography for estimating the optic cup size in 56 eyes of 28 patients with glaucoma or ocular hypertension. Two trained observers independently evaluated horizontal and vertical cup/disk ratios in stereophotographs, and two skilled echographers independently estimated optic cup size in photoechograms in a masked fashion. The reliability of echographic interpretation varied (kappa 0.29 to 0.71), but it always exceeded that expected by chance alone, even for cups of 0.3 disk diameter or less. Subtly saucer-shaped cups (three of 50 eyes) and deep cups with intact neuroretinal rims (two of 50 eyes) were misinterpreted echographically. High-resolution contact B-scan echography may provide a useful and reliable estimate of the optic cup size in eyes with opaque media.

Fundus Oculi↗

PubMed1989

The influence of decreased retinal illumination on automated perimetric threshold measurements.

Decreased retinal illumination (such as can be caused by pupillary constriction or light absorption by ocular media opacities) was simulated with a randomly ordered series of neutral density filters in front of the right eyes of five subjects with dilated pupils. Threshold measurements were performed on Humphrey and Octopus perimeters at 0, 5, 10, 15, 20, and 25 degrees nasally along the 180-degree meridian. A 0.6-log unit neutral density filter, which reduces retinal illumination the equivalent of halving the pupillary diameter, decreased the mean Humphrey thresholds by 1.1 +/- 0.8 decibels (dB) (mean +/- standard deviation) and the mean Octopus thresholds by 1.7 +/- 1.4 dB. Statistically significant (P less than or equal to .05, Dunnett's test) threshold depressions were observed at all eccentricities with a 1.5-log unit neutral density filter on the Humphrey perimeter (-4.5 +/- 0.7 dB) and with a 1.0-log unit neutral density filter on the Octopus perimeter (-3.5 +/- 1.0 dB).

Adult↗

PubMed1989

Threshold equivalence between perimeters.

To determine equivalence between perimeters, 49 eyes of 35 subjects underwent static threshold testing of the central 30 degrees twice on each of three automated perimeters and twice by manual kinetic threshold testing with the Goldmann perimeter. The Octopus-Humphrey difference was 3.3 dB (2.3 dB in the upper two rows for programs 32 and 30-2). The Dicon-Octopus difference was 3.5 dB and the Dicon-Humphrey, 6.5 dB. The I4e stimulus of the Goldmann perimeter was equivalent to 17.1 dB, 13.6 dB, and 10.8 dB on the Humphrey, Octopus, and Dicon perimeters, respectively. The III4e stimulus of the Goldmann perimeter, used for visual impairment determination, was roughly equivalent to 7 to 10 dB, 4 to 7 dB, and 0 to 6 dB on the Humphrey, Octopus, and Dicon perimeters, respectively. The prediction when converting from one instrument to another was only 10% less reliable than the ability of a perimeter to predict the values on a second examination with the same perimeter. Validity of the conversion formulas was confirmed by the age-corrected normal values available for the Octopus, Humphrey, and Goldmann perimeters.

Adult↗

PubMed1989

Evaluation of phototoxic retinal damage after argon laser iridotomy.

We performed several visual function tests in 17 eyes (ten patients) before and after argon laser iridotomy in an effort to detect diffuse photochemical damage to photoreceptors caused by exposure to the intense, blue-green light that is transmitted into the posterior segment as the iridotomy is created and enlarged. No change was detected in static threshold sensitivity in the central 30 degrees of the field (Octopus perimeter), color sensitivity (Farnsworth-Munsell 100-Hue test), or visual acuity. Contrast sensitivity showed a small increase at low spatial frequencies and a small decrease at high spatial frequencies. The latter change was small and not necessarily laser related, but precautions to limit laser exposure of the posterior pole are prudent.

Argon↗

PubMed1989

Interocular asymmetry of visual function in heterozygotes of X-linked retinitis pigmentosa.

Heterozygotes of X-linked retinitis pigmentosa were studied with full field rod and cone electroretinography and light adapted kinetic perimetry. Twelve parameters from the electroretinograms (ERGs) and two parameters from the kinetic visual fields of both eyes of 22 heterozygotes were measured and statistical comparisons made with results from female control subjects. Rod and cone ERG amplitude parameters were significantly lower and cone timing delayed in the heterozygotes. Most of the ERG parameters that were abnormal in measured value also showed significantly greater interocular differences compared with controls. Kinetic visual fields with both V-4e and I-4e test targets were smaller in heterozygotes than in controls. Only with the I-4e target, however, were interocular differences significantly larger in the heterozygotes. For the I-4e target and many of the ERG parameters, using the interocular difference in conjunction with the measured parameter value from a single eye significantly increased the efficacy of discrimination between heterozygotes and controls; for some ERG parameters, the interocular difference alone provided the best separation of the two groups.

Adolescent↗

PubMed1989

Static threshold asymmetry in early glaucomatous visual field loss.

Ten normal subjects underwent static threshold visual field testing of both eyes with the Humphrey perimeter, with one eye tested twice. The mean sensitivity of the field seemed virtually identical in the two eyes, with the average difference between the right and left eyes (0.65 decibels [dB]) being no greater than the testing error as reflected in the difference between the same eye tested twice (0.7 dB). The authors provide the mathematical basis for recognizing that a right eye-left eye difference in mean sensitivity might be abnormal. Additional information is needed about the variance of the right eye-left eye difference in the population at large, but present information suggests that a 2-dB difference may be meaningful on a single examination. A 1.5-dB difference is statistically significant if confirmed on a second test, and a difference as small as 1 dB may be meaningful if shown consistently in a series of four examinations. In all cases, nonglaucomatous causes of field abnormality needs to be ruled out, and the generalized asymmetry is most meaningful if it is consistent with asymmetry of cupping or intraocular pressure. Several cases are reported in which a mild (1 dB) generalized depression of the visual field is the only recognizable abnormality in the visual field in eyes with early glaucoma.

Adult↗

PubMed1989

Possibly reduced prevalence of peripapillary crescents in ocular hypertension.

We studied optic disc photographs from 137 healthy subjects and 195 subjects with ocular hypertension. The prevalence of peripapillary crescents was lower among hyperopes than among myopes (p less than 0.05). Moreover, the ocular hypertensive subjects had a statistically significant tendency toward a hyperopic median refraction (p less than 0.01). In keeping with this, we observed a lower prevalence rate of crescents in the ocular hypertensive group (35%) than among the healthy subjects (41%). This difference is in the expected direction and magnitude if the absence of a crescent decreases the risk of glaucomatous damage from elevated intraocular pressure, but the number of subjects was too small to obtain statistical significance; however, the evidence is suggestive. Further study, such as in a large population survey or by comparison of two groups with matched genetic heritage, is needed to substantiate the relation between the presence of a crescent and increased risk of glaucomatous damage.

Female↗

PubMed1988

The influence of simulated light scattering on automated perimetric threshold measurements.

The effect of light scattering by ocular media opacities on OCTOPUS and Humphrey perimeter threshold measurements was simulated with randomly ordered sequences of six ground-glass diffusers in the right eyes of five subjects. Threshold measurements were performed at 0 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees nasally along the 180 degrees meridian with the F4 program on an OCTOPUS perimeter, and with twice-repeated profiles on a Humphrey perimeter. The reduction in differential light sensitivity correlated well with the 2.7-dB to 16.7-dB reduction in stimulus intensity caused by the 46% to 98% scattering of incident light by the diffusers. Contrast sensitivity in the presence of a glare source (Miller-Nadler glare test) was also affected by the diffusers, such that a 75% contrast target was not visible through the strongest diffuser whereas a 5% contrast target was visible without a diffuser. Conversely, the diffusers had very little effect on visual acuity measurements that were performed with projected high-contrast targets in a darkened room. Our data suggest that even minimal light scattering, such as might be caused by a cataract that has a relatively insignificant effect on visual acuity, may influence threshold measurements.

Adult↗

PubMed1987

The influence of refraction accuracy on automated perimetric threshold measurements.

The effect of refraction accuracy on the differential light threshold of a Goldmann size III (0.43 degrees diameter) stimulus was evaluated in the right eyes of five normal subjects with randomly ordered sequence of plano, +1.00-, +2.00-, +3.00-, +4.00-, +5.00-, and +6.00-diopter (D) spherical overcorrections. Threshold measurements were performed at 0 degree, 5 degrees, 10 degrees, 15 degrees, 20 degrees, and 25 degrees eccentricity nasally along the 180 degrees meridian with the F4 program on the Octopus 201 perimeter. The +1.00- through +6.00-D overcorrections decreased the threshold values by an average of 1.4, 2.9, 4.2, 5.6, 6.7, and 7.6 dB, respectively, compared with the plano overcorrection. The depression of the differential light threshold was of similar magnitude at all eccentricities within the central 25 degrees.

Adult↗

PubMed1987

Accommodation of an endocapsular silicone lens (Phaco-Ersatz) in the nonhuman primate.

In owl monkeys, as a model of endocapsular cataract extraction, the lens material was removed through a small hole in the capsule and was replaced with a silicone polymeric gel. The ability of this endocapsular implant (Phaco-Ersatz) to accommodate was documented when pilocarpine produced an increase in the curvature of the lens surface and a decrease in the anterior chamber depth, just as occurs with the untouched natural lens. Refinements of the surgical technique are required to achieve a controlled degree of filling of the capsular bag and inhibit postoperative epithelial proliferation on the inner capsular surface.

Accommodation, Ocular↗

PubMed1986

Rebleeding after traumatic hyphema.

We reviewed the medical records of 175 patients who were admitted between 1977 and 1984 with a diagnosis of traumatic hyphema to define the incidence of operative intervention for the treatment of complications related to rebleeding. Of the 156 patients admitted with primary hyphemas, 25 (16%) rebled during hospitalization. Seven of these 25 in-hospital rebleeds required surgical intervention. Nineteen other patients were admitted with ocular histories and examinations strongly suggestive of rebleeding prior to admission (secondary hyphema--presumed preadmission rebleed). Seven of these 19 eyes underwent surgery. Of the 175 eyes studied, only one eye that did not rebleed underwent surgery during the initial hospitalization. Fourteen (32%) of 44 eyes that rebled underwent operative intervention. Nine of these 14 patients were operated on under general anesthesia. Potential benefits of newer hyphema treatments, such as epsilon-aminocaproic acid, designed to prevent rebleeding should be weighed against not only the ocular risks of rebleeding but also the risks of general anesthesia.

Adolescent↗