Interaction of hybrid nanowire-nanoparticle structures with carbon monoxide.

A gas-phase sensor based on a GaN nanowire mat decorated with Au nanoparticles was studied both experimentally and theoretically. The sensor is responsive to CO and H(2) and could be used to study the water-gas-shift reaction, which involves combining CO and H(2)O to produce H(2). It was shown that for catalyzing this reaction using support Au nanoparticles, the sequence in which the reactants are exposed to the catalyst surface is critical. To quantitatively evaluate the sensor response to gas exposure a depletion model was developed that considered the Au nanoparticle-semiconductor interface as a nano-Schottky barrier where variation in the depletion region caused changes in the electrical conductivity of the nanowires.

Model independent bound on the unitarity triangle from CP violation in B-->pi(+)pi(-) and B-->psiK(S).

We derive model-independent lower bounds on the CKM parameters (1-rho) and eta as functions of the mixing-induced CP asymmetry S in B-->pi(+)pi(-) and sin(2 beta from B-->psiK(S). The bounds do not depend on specific results of theoretical calculations for the penguin contribution to B-->pi(+)pi(-). They require only the very conservative condition that a hadronic phase, which vanishes in the heavy-quark limit, does not exceed 90 degrees in magnitude. The bounds are effective if -sin(2 beta

Is asteroid hyalosis ocular gout?

In 76 cases of asteroid hyalosis, seven (9.2%) had gout, eight (10.5%) had close relatives with gout, and two (2.6%) were in both categories. Three of the gouty seven were receiving gout medications. Serum uric acid measurements were elevated in 28.3% of the 46 cases (60.5%) measured. In the 68 monocular cases (89.5%), whites (57 cases) showed no right/left predilection, but blacks (11 cases) had 100% left eye involvement (P less than .001). From a review of 49,000 records, prevalence rates were calculated for discrete age and sex groups. Females under age 60 had no asteroid hyalosis. After age 60 they had a constant prevalence rate of one case per 600 (0.15%). Males of all ages had a higher prevalence rate than females, increasing with age to one per 126 (0.79%) in the 80-or-older group. In all 76 patients, the male-to-female ratio was 1.45:1. Among whites it was, 1.74:1, and among blacks, 0.63:1.

Asteroid hyalosis affecting the choice of intraocular lens implant.

Asteroid hyalosis can create ultrasonic echoes capable of interfering with A-scan ultrasonic measurement of ocular length. Two cases are reported, one of which includes a measurement error necessitating a second implantation. Surgeons who entrust measurements to technicians should be aware of the measurement technique and should establish protocols that preclude such errors.

Ptosis following radial keratotomy. Performed using a rigid eyelid speculum.

Seven patients with acquired ptosis and normal levator function following anterior radial keratotomy are presented. Five of these patients then elected to undergo radial keratotomy of the opposite eye, and four had symmetrical lid fissures (mild bilateral ptosis) after bilateral surgery. Ptosis is a well-known complication of cataract extraction, but has not been reported following radial keratotomy. Unlike cataract extraction, radial keratotomy does not require anesthetic injections, bridle sutures, or conjunctival flaps. The rigid Knapp eyelid speculum used in these cases remains as the only apparent cause of eyelid trauma and subsequent ptosis. During radial keratotomy, the speculum was opened widely in order to provide good corneal exposure and avoid contact with the diamond knife. Contraction of the orbicularis oculi muscle against the rigid speculum may have traumatized the lid, resulting in a levator aponeurosis disinsertion and subsequent ptosis.

Ocular abnormalities in patients with gout.

We examined 69 patients with severe gout in a search for associated ocular diseases-particularly evidence of uveitis. None of the 69 patients had evidence of uveitis, past or present. Three patients had asteroid hyalopathy. The most common abnormality was bilateral ocular redness caused by hyperemia of the conjunctival and episcleral vessels. This was present in at least 43 of the 69 patients. Our findings support the evolving belief that in the past gout was assigned far too important a role as a causative factor in uveitis, and they confirm the well-described (but not generally recognized) clinical picture of red eyes in patients with gout. When evaluating a patient who is troubled by bilateral chronic conjunctival redness, the clinician should consider gout in the differential diagnosis.

Endothelial damage in monkeys after radial keratotomy performed with a diamond blade.

Anterior radial keratotomy was performed with a diamond blade in ten rhesus monkey eyes. Results were compared with those of a previous study in which a metal blade was used. Histologic assessment showed endothelial degeneration, but fewer edematous endothelial cells, than in the previous study. Specular microscopy demonstrated statistically significant endothelial cell losses (7.99%), when preoperative and three-month postoperative values were compared. Autoradiography showed little cell division in the endothelial cell layer. Cell loss seemed to be repaired mainly by the spreading of neighboring cells. Endothelial cell division is also limited in humans, and the cumulative loss of cells due to surgical trauma combined with continuous damage-related losses and later age-related reductions in cell numbers could produce corneal decompensation in some patients years after radial keratotomy.

Compensating for thermally caused dimensional changes in the cryolathe.

Dimensional changes in the Barraquer cryolathe , resulting from contraction due to refrigeration, can exert a considerable effect on the dimensions of the lathed lenticule . We have devised a simple technique for re- zeroing the cryolathe after freezing. This procedure negates the effects of the dimensional changes and thereby improves the accuracy of shaping the lenticules .

Corticosteroid therapy after anterior radial keratotomy in Primates.

Anterior radial keratotomy was performed on nine Green monkey eyes. Four of these eyes received subconjunctival corticosteroid injections immediately after surgery and three times thereafter at three-week intervals. Two eyes received subconjunctival physiologic salt solution injections on the same schedule. Three eyes received no injections after surgery. Although endothelial cell loss in the first week after surgery was reduced in the drug-treated eyes, there were no statistically significant differences in cell densities at nine months after surgery. Corticosteroid therapy after anterior radial keratotomy appeared to confer no long-range benefits in terms of the numbers of corneal endothelial cells in these primate eyes.

On-lay lamellar keratoplasty for the treatment of keratoconus.

On-lay lamellar keratoplasty was performed in 29 patients who had keratoconus. Twelve patients (greater than 1 year follow-up) showed an average decrease in keratometry of 9.13 +/- 2.02 (mean +/- SE) D; 6 patients (6-11 months follow-up) showed an average of 10.15 +/- 2.88 D. Visual acuity continued to improve for about one year after surgery. Six patients with best visual acuities of 20/20 before surgery showed an average visual acuity of 20/29 +/- 11 (mean +/- SD) 4 months after surgery; 4 with more than a year of follow-up achieved an average of 20/26 +/- 9. Four patients with 20/40 preoperatively achieved an average of 20/63 +/- 33 four months after surgery; 3 with more than a year of follow-up showed an average of 20/38 +/- 13. All patients with successful grafts can now tolerate contact lenses for daily wear.

Visual field testing with red targets.

Ten patients with partial temporal visual field defects were examined with a modified tangent screen projection perimeter (Auto-Plot). Defects demonstrated with an isopter for chromatic recognition of a 3-mm red stimulus could always be reproduced with an isopter for achromatic recognition of a dim, 3-mm white stimulus. The red-white intensity ratio producing equivalent fields remained constant for a given patient but varied from subject to subject (range, 3.0 to 7.5; mean, 5.7; SD, 1.8). Thus, red functioned as dim white, but no single fixed ratio of intensities was applicable to all subjects. Visual field testing with 1 foot-candle of tangent screen illumination permitted subjects to adapt to dark. As retinal sensitivities increased, the corresponding visual field steadily enlarged for 30 minutes. This effect was greater in the pathologic temporal fields, which increased relatively more than intact nasal fields. The result was poor visual field reproducibility with time.

Epikeratophakia: the surgical correction of aphakia. Update: 1982.

Sixty-five epikeratophakia procedures have been performed in 63 patients; visual acuity data have been tabulated on 31 patients with 4 to 30 months follow-up. Patients with more than a year of follow-up showed stable keratometry readings. Early patients achieved 70% of the predicted dioptric correction; more recent patients have achieved 87% with improvements in the lathing procedure, tissue handling, and surgical technique. Visual acuities improve with time. At any given time after surgery, acuities measured with a hard contact lens are better than those measured with spectacles; the decrease in spectacle acuity is probably a result of irregular refraction at the graft surface. The gap between contact lens and spectacle acuity decreases with time. A number of patients achieve postoperative visual acuities better than their preoperative acuities, and most achieve final spectacle acuities within a line or two of their preoperative acuities.

Update on keratophakia.

Visual results are reported for 23 cases of keratophakia for the correction of surgical aphakia followed from 12 to 48 months. Seventeen of the 23 patients had final visual acuities of 20/40 or better. The average residual visual overrefraction was 1.87 +/- 1.79 diopters (mean +/- SE), with an increase of postoperative astigmatism of 1.70 +/- 1.33 diopters. Complications included interface deposits and peripheral epithelial deposits that did not interfere with vision. One patient had an anterior chamber penetration and subsequent penetrating keratoplasty, and two patients had lenticules removed because of corneal edema secondary to increased intraocular pressure. The major disadvantages of keratophakia are the complexity of the procedure and the time required (4 to 6 months) to achieve best-corrected spectacle visual acuity. However, because this procedure is extraocular, it is a better choice than secondary intraocular lens implantation for patients who are unilaterally aphakic and for the young patient.

The cornea press: restoring donor corneas to normal dimensions and hydration before cryolathing.

The shaping of swollen, abnormally hydrated donor corneal tissue on the cryolathe for use in keratorefractive surgery yields lenticules of insufficiently predictable dioptric powers. The irregular nature of this abnormal hydration precludes the use of mathematical compensating factors. To improve control over the shape of the lenticule, we have developed a cornea press which restores normal hydration and dimensions to the donor tissue by mechanical dehydration.

A multipurpose low-vision aid.

We constructed a low-vision aid for a 61-year-old patient who had familial macular degeneration and a visual acuity of 20/300. The aid consisted of a spectacle lens incorporating his distance prescription as the carrier, a high-plus bifocal reading addition, and the high-minus ocular lens of a Galilean telescope of variable magnification. The objective lens of the telescope can be carried as a folding, dual-lens, hand magnifier.

Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study.

A five-year, multicenter, collaborative clinical trial of radial keratotomy for myopia is being carried out at nine clinical centers. The study, funded by the National Eye Institute, is recruiting approximately 500 patients aged 21 years or older with -2.00 to -8.00 diopters of physiologic myopia who also meet other clearly defined eligibility criteria. Surgeons use a diamond-bladed micrometer knife to make eight radial incisions in the anterior cornea. The diameter of the central clear zone is determined by the amount of myopia and the depth of the incisions by intraoperative ultrasonic pachymetry. Investigators other than the surgeon gather all pre- and post-operative data. Examinations include measurement of visual acuity with standardized charts, verification of refractions by a second observer, measurement of corneal curvature by keratometry and photokeratoscopy, quantitation of glare with a glare tester, and measurement of the size of individual endothelial cells from specular photomicrographs with a computerized digitizer. A formal psychometric questionnaire is used to evaluate the patients' subjective response. Physician monitors insure adherence to the protocol during site visits and members of the Data and Safety Monitoring Board oversee the progress of the study. Biostatisticians at the Coordinating Center insure complete data collection, process the data, and assist in the interpretation of results.