Improvement in retinal image quality with dynamic correction of the eye's aberrations.

We measured the improvement in retinal image quality provided by correcting the temporal variation in the eye's wave aberration with a closed-loop adaptive optics system. This system samples the eye's wave aberration at rates up to 30 Hz. Correction of the eye's aberrations can be completed in 0.25-0.5 seconds, resulting in residual rms wave-front errors as low as 0.1 microns for 6.8 mm pupils. Real-time wave-front measurements were used to determine how effectively the spatial and temporal components of the eye's wave aberration were corrected. The system provides dynamic correction of fluctuations in Zernike modes up to 5 th order with temporal frequency components up to 0.8 Hz. Temporal performance is in good agreement with predictions based on theory. Correction of the temporal variation in the eye's wave aberration increases the Strehl ratio of the point spread function nearly 3 times, and increases the contrast of images of cone photoreceptors by 33% compared with images taken with only static correction of the eye's higher order aberrations.

Visual benefit of correcting higher order aberrations of the eye.

There is currently considerable debate concerning the visual impact of correcting the higher order aberrations of the eye. We describe new measurements of a large population of human eyes and compute the visual benefit of correcting higher order aberrations. We also describe the increase in contrast sensitivity when higher order aberrations are corrected with an adaptive optics system. All these results suggest that many, though not all, observers with normal vision would receive worthwhile improvements in spatial vision from customized vision correction, at least over a range of viewing distances and particularly when the pupils are large. Keratoconic patients or patients suffering from spherical aberration as a result of laser refractive surgery as it is presently performed would especially benefit. These results encourage the development of methods to correct higher order aberrations.

Wave-front design algorithm for shaping a quasi-far-field pattern.

To design a fully continuous wave-front distribution suitable for focused beam shaping by a deformable mirror, we modify the phase-retrieval algorithm by employing a uniformly distributed phase as a starting phase screen and spatial filtering for the near-field phase retrieved during the iteration process. A special phase unwrapping algorithm is not required to obtain a continuous phase distribution from the retrieved phase since the boundary of the 2pi-phase-jumped region in the designed phase distribution is perfectly closed. From the computational result producing a uniform square beam transformation from a circular defocused beam, this algorithm has provided a fully continuous wave-front distribution with a lower spatial frequency for a deformable mirror. The transformed square beam has a normalized intensity nonuniformity of varsigma(rms) = 0.14 with respect to a desired flat-topped square beam pattern. This beam-shaping method also provides a high energy-concentration rate of more than 98%.

High-aspect-ratio line focus for an x-ray laser by a deformable mirror.

A high-aspect-ratio line focus is required on a plane target in x-ray laser experiments for obtaining a high gain-length product. Inherent wave-front aberrations in line-focusing optics, which consist of a cylindrical lens and a spherical lens, are discussed with respect to beam diameter. The nonuniformity of the linewidth that is due to the aberrations is also calculated by the ABCD matrix method. A deformable mirror of a continuous plate type with a diameter of 185 mm provides an adequate wave-front distribution for compensating for the wave-front aberration. The wave-front control by the deformable mirror realizes a fine linewidth of 25 microm and 18.2 mm long, corresponding to the aspect ratio of 728. The linewidth is three times the diffraction limit. The intensity distribution along the line focus is also improved.

Shack Hartmann wave-front measurement with a large F-number plastic microlens array.

A new plastic microlens array, consisting of 900 lenslets, has been developed for the Shack Hartmann wave-front sensor.The individual lens is 300 µm × 300µm and has a focal length of 10 mm, which provides the same focal size, 60 µm in diameter, with a constant peak intensity. One can improve thewave-front measurement accuracy by reducing the spot centroiding error by averaging a few frame memories of an image processor. A deformable mirror for testing the wave-front sensor gives anappropriate defocus and astigmatism, and the laser wave front is measured with a Shack Hartmann wave-front sensor. The measurement accuracy and reproducibility of our wave-front sensor are better than λ/20 and λ/50 (λ = 632.8 nm),respectively, in rms.

Diagnosis, transport, and outcome in fetuses with left ventricular outflow tract obstruction.

Between March 1986 and April 1990, 22 consecutive fetuses (at gestational ages of 21 to 38 weeks) with a suspected diagnosis of critical (ductus-dependent) left ventricular outflow tract obstruction on fetal echocardiogram were referred to our center for delivery and surgical treatment. Diagnoses were hypoplastic left heart syndrome (n = 16), valvular aortic stenosis (n = 2), common atrioventricular canal with subaortic stenosis (n = 3), and single ventricle with subaortic stenosis (n = 1). Postnatal echocardiography revealed that fetal echocardiography was correct in predicting left ventricular outflow tract obstruction to be critical in all but one patient, for a positive predictive value of 96%. Of the 21 patients with true, critical left ventricular outflow tract obstruction, 17 patients underwent cardiac surgery as neonates (birth to 6 days of age, median 2 days); 13 (or 77%) survived and were discharged from the hospital. In addition, one patient underwent successful balloon aortic valvotomy for critical valvular aortic stenosis but later died of sepsis. Lethal chromosomal and congenital abnormalities should be sought and are contraindications for this approach. In utero transport of fetuses with suspected critical left ventricular outflow tract obstruction to a neonatal cardiac surgical center can result in improved neonatal condition and may improve overall survival.

Acute fetal ductal occlusion in lambs.

To assess fetal right ventricular and hemodynamic responses to acute occlusion of the ductus arteriosus, the pulmonary pressure, right and left ventricular output, and right ventricular dimensions of five fetal lambs were measured with simultaneous echocardiographic monitoring. Ductal occlusion resulted in a rise in pulmonary arterial pressure, a decrease in right ventricular output of 68%, an increase in left ventricular output of 18%, and a fall in combined cardiac output of 34%. The right ventricular systolic dimension increased, and the shortening fraction decreased from 0.41 to 0.14. Tricuspid regurgitation started within two heartbeats after ductal occlusion and resolved as soon as the occlusion was released. Acute fetal ductal occlusion imposes a marked increase in the right ventricular afterload, resulting in reversible triscuspid regurgitation.

Changes in fetal hemodynamics with terbutaline treatment and premature labor.

The aim of this study was to examine the fetal hemodynamic effects of terbutaline treatment and premature labor. Image-directed pulsed and continuous wave Doppler ultrasound studies, using 3.3-MHz and 5-MHz transducers (GE PASII and ATL echocardiographic machines), were used to assess fetal cardiac blood velocities in three groups of pregnancies matched for menstrual age (MA). Group 1: 13 normal pregnancies, mean MA 31 weeks. Group 2: 7 women in premature labor prior to tocolytic therapy, mean MA 32 weeks. Group 3: 8 women treated with terbutaline, average dose 18.8 mg daily, for previous premature labor, mean MA 31 weeks. Heart rate averaged 150 bpm, 135 bpm, and 127 bpm in the terbutaline, premature labor, and normal groups, respectively, and each were significantly different from each other. Products of time velocity interval and heart rate at the aortic valves were 1603 cm +/- 140 cm, 1413 cm +/- 190 cm and 1238 cm +/- 200 cm, and at the mitral valves 1102 cm +/- 170 cm, 812 cm +/- 110 cm, and 878 cm +/- 150 cm in the terbutaline, premature labor, and the normal groups, respectively. Aortic and mitral blood velocity products of time velocity integrals and heart rates were significantly higher (p = 0.01) in the terbutaline group relative to the normal group. In addition, the terbutaline group was significantly higher than the labor group at the mitral valve (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular mortality trends in Harris County, Texas: 1980 to 1986.

Cardiovascular diseases are the leading causes of death in Texas and in the United States. This study determines the trend in mortality rates attributed to cardiovascular diseases in Harris County from 1980 to 1986. The region of the county that does not include the City of Houston was specifically studied. Mortality of cardiovascular diseases in these two areas follow patterns similar to that of the United States in the same time period. Both the entire county and Harris County excluding Houston show declines in cardiovascular mortality rates in the 7-year period. The populations were divided into four ethnic categories (white, black, Hispanic and "other"), and each ethnic group reported significant declines in overall cardiovascular mortality except in the "other" population, which showed an increase in the male group. Significant downward trends were noticed in the white and Hispanic population in the two major subcategories of cardiovascular diseases: diseases of the heart and cerebrovascular diseases. The black population in each geographic area studied was consistently higher in cardiovascular mortality than the other three ethnic groups observed (white, Hispanic and "other"). Knowledge of cardiovascular disease mortality rates by ethnicity, sex, and age as well as temporal changes in mortality rates within Harris County are important for health planners in continuing and implementing programs aimed at awareness, prevention, and treatment of cardiovascular diseases.

Two-dimensional echocardiographic determination of ventricular septal defect size: correlation with autopsy.

The presence of a large ventricular septal defect (VSD) may affect the surgical treatment of congenital heart defects. VSD size and shape by two-dimensional echocardiography (2DE) and at autopsy were compared in 18 patients, average age 6 months, who had 2DE studies shortly prior to death. Six had isolated VSD and the other 12 had additional cardiac anomalies. The maximal diameter of the VSD was measured in long- and short-axis views and the VSD area was calculated assuming an elliptical shape. A large VSD was present in 11 of 18 (61%) and was correctly detected by 2DE in 10 of 11 (91%, no false positives). 2DE-predicted area of VSDs correlated with autopsy measurements (r = 0.94). The shape and orientation of the VSD were correctly predicted by 2DE (16 of 18); it was elliptical in 13 and circular in five, with the major axis of the elliptical VSDs aligned with the short axis of the heart in eight and with the long axis in five. The diameters of the VSD ranged from 3 to 25 mm (r = 0.93). Diameters measured from the long-axis and short-axis views correlated with autopsy (r = 0.98 and 0.89, respectively). Thus: (1) 2DE was useful in distinguishing large VSDs from smaller defects, and in measuring their diameters and areas. (2) The shape and orientation of the VSD were well predicted by 2DE.

Results of balloon valvuloplasty in typical and dysplastic pulmonary valve stenosis: Doppler echocardiographic follow-up.

To assess the usefulness of balloon valvuloplasty in patients with a dysplastic pulmonary valve, the files of 36 patients (aged 1 day to 18.5 years) who had two-dimensional echocardiography before and continuous wave Doppler echocardiography late after balloon valvuloplasty (balloon diameter greater than or equal to 20% anulus diameter) were reviewed. Results of relief of pulmonary stenosis were graded by catheter gradient in the catheterization laboratory and compared with Doppler echocardiographic findings at follow-up. There were 32 patients with typical pulmonary stenosis and 4 with a dysplastic valve. In the 32 patients with typical pulmonary stenosis, transvalvular gradient changed from a mean of 67 +/- 32 to 20 +/- 20 mm Hg (p less than 0.0001, mean reduction 72.6%). The gradients at follow-up by Doppler echocardiography averaged 20 mm Hg including 15 that increased, 3 that were unchanged and 14 that decreased. Only 3 (9%) of 32 patients had a gradient greater than 25 mm Hg at follow-up and only one gradient was greater than 35 mm Hg. All four patients with a dysplastic valve had a gradient that decreased with valvuloplasty from a mean of 85 +/- 33 to 33 +/- 20 mm Hg (p less than 0.05); gradient reduction in this group ranged from 40 to 85% (mean 57.5%). The gradient at follow-up increased in three of these four patients and decreased in one (the only late gradient less than 25 mm Hg). Late gradient was less than 35 mm Hg in two of the four patients and was reduced by 43 and 57%, respectively, in the other two.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgery without angiography for neonates with aortic arch obstruction.

Traditional diagnostic assessment of the neonate and infant with congenital abnormalities of the aorta causing left ventricular outflow tract obstruction has required catheterization and angiography. However, these patients frequently present critically ill and invasive diagnostic procedures may be associated with significant risks. Two-dimensional echocardiography has been used for aiding diagnosis of aortic arch abnormalities, but there has been little information concerning its use as the definitive imaging technique for preoperative assessment. We reviewed neonates who required urgent surgery for congenital obstruction of the aorta. The diagnosis was made using two-dimensional echocardiographic imaging and Doppler techniques for hemodynamic assessment in lieu of catheterization and angiography in all. Anatomic detail provided by the noninvasive approach was both sensitive and specific in guiding surgery in all but one case. We conclude that echocardiography eliminates the need for invasive preoperative diagnostic procedures in selected neonates with congenital aortic arch obstruction.