Marginal corneal infiltrates as an ocular manifestation of acute generalized exanthematous pustulosis

Purpose

To report a case of keratoconjunctivitis with marginal corneal infiltrates in a patient with acute generalized exanthematous pustulosis (AGEP) secondary to trimethoprim-sulfamethoxazole.

Observations

A 63-year-old female presented with a diffuse pustular skin rash and bilateral keratoconjunctivitis with marginal corneal infiltrates. Skin biopsy led to the diagnosis of AGEP secondary to trimethoprim-sulfamethoxazole use. Treatment of the ocular findings with topical corticosteroids and lubrication led to near-full resolution after two weeks.

Conclusions and Importance

To the best of our knowledge, this is the first reported association between AGEP and keratoconjunctivitis with marginal corneal infiltrates. A hypersensitivity reaction to a foreign antigen is implicated in the pathogenesis of both AGEP and sterile marginal infiltrates, and we suggest that the patient's underlying hypersensitivity process associated with AGEP accounted for the ocular findings.

POSITION OF IN-THE-BAG POSTERIOR CHAMBER INTRAOCULAR LENSES RELATIVE TO THE LIMBUS: Applications to Scleral-Sutured Lenses

PURPOSE

To characterize the true position of in-the-bag intraocular lenses (IOLs) relative to the limbus using ultrasound biomicroscopy and estimate scleral-sutured IOL positioning.

METHODS

This prospective single-center study included 70 eyes of 41 patients with in-the-bag posterior chamber IOLs. Four vertical ultrasound biomicroscopy captures were performed in each eye in the superior, inferior, nasal, and temporal quadrants. Postoperative biometric data were collected. The primary outcome was the vertical distance of the in-the-bag IOL from the sclerocorneal limbus. Secondary outcomes included anterior shift and refractive change of a theoretical scleral-sutured IOL using sclerotomies at 2.5 mm and 3 mm posterior to the limbus.

RESULTS

A total of 265 ultrasound biomicroscopy images were analyzed, including 64 superior, 69 inferior, 66 nasal, and 66 temporal. The true in-the-bag IOL position measured as distance posterior to the sclerocorneal limbus was 4.23 ± 0.56 mm superiorly, 4.22 ± 0.46 mm inferiorly, 3.95 ± 0.48 mm nasally, and 3.86 ± 0.52 mm temporally. The anterior shift of a theoretical scleral-sutured IOL was 0.60 mm for a 3-mm sclerotomy and 0.93 mm for a 2.5-mm sclerotomy, resulting in a theoretical myopic shift of 0.45 diopter (D) and 0.79 D, respectively, assuming a 15-D IOL. Larger biometric measurements correlated with a more posterior in-the-bag position.

CONCLUSION

True in-the-bag IOL position was found to be more posterior than estimates of scleral-sutured IOLs. Additional corrections in scleral-sutured IOL calculations may improve refractive outcomes.

Salzmann's nodular degeneration

Salzmann nodular corneal degeneration is a non-inflammatory, progressive corneal degeneration characterized by bluish-white nodules of varying shapes classically located in the mid-peripheral cornea. It was first described by Maximilian Salzmann in 1925 and was noted at that time to be associated with "eczematous keratoconjunctivitis". Since then, significant progress has been made to understand environmental and genetic risk factors associated with SND. However, etiopathogenesis remains poorly understood. A review of the literature was performed to highlight our recent understanding of SND and its management.

The Effect of Mass Azithromycin Distribution on Childhood Mortality: Beliefs and Estimates of Efficacy

A cluster-randomized trial demonstrated that mass oral azithromycin distribution reduced childhood mortality 49.6% (Trachoma Amelioration in Northern Amhara [TANA]). The relative risk of childhood mortality was then estimated using two approaches: an expert survey and a Bayesian analysis. The survey asked public health experts to estimate the true effect of mass azithromycin distribution on childhood mortality. The Bayesian estimation used the TANA study's results and prior estimates of the efficacy of other effective population-level interventions. The experts believed mass azithromycin reduces childhood mortality (relative risk = 0.83, 95% credible intervals [CrI] = 0.70-1.00). The Bayesian analysis estimated a relative risk of 0.71 (95% CrI = 0.39-0.93). Both estimates suggest that azithromycin may have a true mortality benefit, though of a smaller magnitude than found in the single available trial. Prior information about nonantibiotic, population-level interventions may have informed the expert's opinions. Additional trials are needed to confirm a mortality benefit from mass azithromycin.

Prior elicitation and Bayesian analysis of the Steroids for Corneal Ulcers Trial

PURPOSE

To elicit expert opinion on the use of adjunctive corticosteroid therapy in bacterial corneal ulcers. To perform a Bayesian analysis of the Steroids for Corneal Ulcers Trial (SCUT), using expert opinion as a prior probability.

METHODS

The SCUT was a placebo-controlled trial assessing visual outcomes in patients receiving topical corticosteroids or placebo as adjunctive therapy for bacterial keratitis. Questionnaires were conducted at scientific meetings in India and North America to gauge expert consensus on the perceived benefit of corticosteroids as adjunct treatment. Bayesian analysis, using the questionnaire data as a prior probability and the primary outcome of SCUT as a likelihood, was performed. For comparison, an additional Bayesian analysis was performed using the results of the SCUT pilot study as a prior distribution.

RESULTS

Indian respondents believed there to be a 1.21 Snellen line improvement, and North American respondents believed there to be a 1.24 line improvement with corticosteroid therapy. The SCUT primary outcome found a non-significant 0.09 Snellen line benefit with corticosteroid treatment. The results of the Bayesian analysis estimated a slightly greater benefit than did the SCUT primary analysis (0.19 lines verses 0.09 lines).

CONCLUSION

Indian and North American experts had similar expectations on the effectiveness of corticosteroids in bacterial corneal ulcers; that corticosteroids would markedly improve visual outcomes. Bayesian analysis produced results very similar to those produced by the SCUT primary analysis. The similarity in result is likely due to the large sample size of SCUT and helps validate the results of SCUT.

Diagnostic characteristics of tests for ocular Chlamydia after mass azithromycin distributions

PURPOSE

Although trachoma control programs frequently use the World Health Organization (WHO) simplified grading system for trachoma to monitor the clinical response after repeated mass azithromycin treatments, the programmatic relevance of this evaluation after multiple rounds of antibiotic treatments is unclear.

METHODS

Three rounds of annual mass azithromycin were distributed to 12 villages in Ethiopia. Twelve months after the third treatment, children were assessed for follicular trachomatous inflammation (TF) and intense trachomatous inflammation (TI) using the WHO simplified grading system and for ocular chlamydial infection using DNA-based and RNA-based tests. Test characteristics for predicting chlamydial infection were computed assuming a chlamydial RNA-based gold standard. As a secondary analysis, test characteristics were also assessed using a latent class analysis.

RESULTS

The prevalence of RNA evidence of ocular chlamydia was 7.1% (95% confidence interval [CI], 2.7-17.4). A DNA-based test and TF had sensitivities of 61.0% (95% CI, 47.1-73.3) and 65.9% (95% CI, 41.6-83.9), specificities of 100% (95% CI, 99.3-100) and 67.5% (95% CI, 61.0-73.5), and positive predictive values of 100% (95% CI, 86.3-100) and 13.4% (95% CI, 5.5-29.3) compared with an RNA-based gold standard. The latent class analysis confirmed that the RNA-based test was a reasonable choice for a gold standard, with a sensitivity of 100% (95% CI, 67.1-100) and specificity of 99.6% (95% CI, 98.1-100).

CONCLUSIONS

Basing treatment decisions after mass azithromycin distributions on the WHO simplified grading system will maximize the treatment of infected persons compared with a DNA-based test but will also result in more uninfected persons being treated. The RNA-based test was considerably more sensitive, and almost equivalently specific, compared with a DNA-based test. (ClinicalTrials.gov number, NCT00322972.).

Reliability of measurements performed by community-drawn anthropometrists from rural Ethiopia

BACKGROUND

Undernutrition is an important risk factor for childhood mortality, and remains a major problem facing many developing countries. Millennium Development Goal 1 calls for a reduction in underweight children, implemented through a variety of interventions. To adequately judge the impact of these interventions, it is important to know the reproducibility of the main indicators for undernutrition. In this study, we trained individuals from rural communities in Ethiopia in anthropometry techniques and measured intra- and inter-observer reliability.

METHODS AND FINDINGS

We trained 6 individuals without prior anthropometry experience to perform weight, height, and middle upper arm circumference (MUAC) measurements. Two anthropometry teams were dispatched to 18 communities in rural Ethiopia and measurements performed on all consenting pre-school children. Anthropometry teams performed a second independent measurement on a convenience sample of children in order to assess intra-anthropometrist reliability. Both teams measured the same children in 2 villages to assess inter-anthropometrist reliability. We calculated several metrics of measurement reproducibility, including the technical error of measurement (TEM) and relative TEM. In total, anthropometry teams performed measurements on 606 pre-school children, 84 of which had repeat measurements performed by the same team, and 89 of which had measurements performed by both teams. Intra-anthropometrist TEM (and relative TEM) were 0.35 cm (0.35%) for height, 0.05 kg (0.39%) for weight, and 0.18 cm (1.27%) for MUAC. Corresponding values for inter-anthropometrist reliability were 0.67 cm (0.75%) for height, 0.09 kg (0.79%) for weight, and 0.22 kg (1.53%) for MUAC. Inter-anthropometrist measurement error was greater for smaller children than for larger children.

CONCLUSION

Measurements of height and weight were more reproducible than measurements of MUAC and measurements of larger children were more reliable than those for smaller children. Community-drawn anthropometrists can provide reliable measurements that could be used to assess the impact of interventions for childhood undernutrition.

How reliable are tests for trachoma?--a latent class approach

PURPOSE

Tests for ocular Chlamydia trachomatis have not been well characterized, because there is no gold standard test. Latent class analysis (LCA) was performed to estimate the sensitivity and specificity of laboratory and clinical tests for trachoma in the absence of a gold standard.

METHODS

Individual data from pretreatment, hyperendemic areas in Ethiopia were used. A clustered LCA was performed for three diagnostic tests: PCR and WHO simplified criteria grades of follicular trachoma (TF) and intense trachomatous inflammation (TI).

RESULTS

Data from 2111 subjects in 40 villages were available. TF was estimated to be 87.3% (95% CI, 83.3-90.1) sensitive and 36.6% (95% CI, 23.6-40.3) specific; TI was estimated to be 53.6% (95% CI, 46.1-88.0) sensitive and 88.3% (95% CI, 83.3-92.0) specific, and PCR was estimated to be 87.5% (95% CI, 79.9-97.2) sensitive and 100% (95% CI 69.3-100) specific.

CONCLUSIONS

LCA allows for an estimate of test characteristics without prior assumption of their performance. TF and TI were found to act in a complementary manner: TF is a sensitive test and TI is a specific test. PCR is highly specific but lacks sensitivity. The performance of these tests may be due to the time course of ocular chlamydial infection, and for this reason, results may differ in areas of low prevalence or recent mass treatment (ClinicalTrials.gov number, NCT00221364).

The epidemiological dynamics of infectious trachoma may facilitate elimination

INTRODUCTION

Trachoma programs use mass distributions of oral azithromycin to treat the ocular strains of Chlamydia trachomatis that cause the disease. There is debate whether infection can be eradicated or only controlled. Mass antibiotic administrations clearly reduce the prevalence of chlamydia in endemic communities. However, perfect coverage is unattainable, and the World Health Organization's goal is to control infection to a level where resulting blindness is not a public health concern. Here, we use mathematical models to assess whether more ambitious goals such as local elimination or even global eradication are possible.

METHODS

We fit a class of non-linear, stochastic, susceptible-infectious-susceptible (SIS) models which allow positive or negative feedback, to data from a recent community-randomized trial in Ethiopia, and make predictions using model averaging.

RESULTS

The models predict that reintroduced infection may not repopulate the community, or may do so sufficiently slowly that surveillance might be effective. The preferred model exhibits positive feedback, allowing a form of stochastic hysteresis in which infection returns slowly after mass treatment, if it returns at all. Results for regions of different endemicity suggest that elimination may be more feasible than earlier models had predicted.

DISCUSSION

If trachoma can be eradicated with repeated mass antibiotic distributions, it would encourage similar strategies against other bacterial diseases whose only host is humans and for which effective vaccines are not available.

Double-grating-structured light microscopy using plasmonic nanoparticle arrays

Structured illumination increases the spatial bandwidth of optical microscopes. We demonstrate bandwidth extension using a physical grating placed close to the sample. This comprises an array of elongated nanoparticles, whose localized surface plasmon resonance is polarization dependent. By arranging the particle orientation to vary with position the grating can be moved by changing the input polarization. A projected optical grating provides an additional independent mechanism for bandwidth extension. Experimental results showing bandwidth improvement in one direction are presented, and the measures necessary to extend the technique for routine imaging are discussed.

Imaging of the cell surface interface using objective coupled widefield surface plasmon microscopy

We report on the development and on the first use of the widefield surface plasmon (WSPR) microscope in the examination of the cell surface interface at submicron lateral resolutions. The microscope is Kohler illuminated and uses either a 1.45 numerical aperture (NA) oil immersion lens, or a 1.65 NA oil immersion lens to excite surface plasmons at the interface between a thin gold layer and a glass or sapphire cover slip. Like all surface plasmon microscope systems the WSPR has been proven in previous studies to also be capable of nanometric z-scale resolutions. In this study we used the system to image the interface between HaCaT cells and the gold layer. Imaging was performed in air using fixed samples and the 1.45 NA objective based system and also using live cells in culture media using the 1.65 NA based system. Imaging in air enabled the visualisation of high resolution and high-contrast submicron features identified by vinculin immunostaining as component of focal contacts and focal adhesions. In comparison, imaging in fluid enabled cell surface interfacial interactions to be tracked by time-lapse video WSPR microscopy. Our results indicate that the cell surface interface and thus cell signalling mechanisms may be readily interrogated in live cells without the use of labelling techniques.

Imaging performance of widefield solid immersion lens microscopy

We investigate the performance of a widefield imaging system employing an aplanatic solid immersion lens. Off-axis imaging quality is examined theoretically at different radii and thicknesses of the aplanatic solid immersion lens. It is found that field curvature is the major aberration affecting the imaging quality. Aberrations are measured experimentally, and the results are in very good agreement with those obtained from simulations and demonstrate the situations where high quality images can be obtained with the aplanatic solid immersion lens.

Two-photon fluorescence surface wave microscopy

This paper demonstrates the principle of two-photon surface wave microscopy with a view to applications on biological samples. We describe a modified scanning optical microscope, which uses specially prepared coverslips. These coverslips are designed to support the propagation of surface waves capable of large field enhancements. We also discuss the beam conditioning necessary to ensure efficient use of the available illumination. Two-photon surface wave fluorescent excitation is demonstrated on fluorescent nanospheres, demonstrating a point spread function width of approximately 220 nm at an illumination wavelength of 925 nm. The potential of non-linear surface wave excitation for both fluorescence and harmonic imaging microscopy is discussed.

High-resolution wide-field surface plasmon microscopy

This paper describes the application of a Köhler illuminated high-resolution wide-field microscope using surface plasmons to provide the image contrast. The response of the microscope to a grating structure in both the Fourier and the image planes is presented to demonstrate image formation by surface waves. The effect of spatial filtering in the back focal (Fourier) plane to enhance image contrast is described. We also discuss how the surface wave contrast mechanism affects the imaging performance of the microscope and discuss factors that can be expected to lead to even greater improvements in lateral resolution and sensitivity.

Quantitative optical microscope with enhanced resolution using a pixelated liquid crystal spatial light modulator

This paper presents a brief account of a novel optical microscope, which combines the advantages of two well-known techniques, namely phase contrast and phase stepping, to provide high contrast imaging and precision measurements. The inclusion of a programmable liquid crystal spatial light modulator provides for the phase stepping required, while also allowing flexibility for future improvements. The results shown reveal an important aspect of the system to facilitate quantitative sample measurements, with an enhancement of optical resolution compared with conventional optical imaging systems.

Subpixel microscopic deformation analysis using correlation and artificial neural networks

Microscopic deformation analysis has been performed using digital image correlation and artificial neural networks (ANNs). Cross-correlations of small image regions before and after deformation contain a peak, the position of which indicates the displacement to pixel accuracy. Subpixel resolution has been achieved here by nonintegral pixel shifting and by training ANNs to estimate the fractional part of the displacement. Results from displaced and thermally stressed microelectronic devices indicate these techniques can achieve comparable accuracies to other subpixel techniques and that the use of ANNs can facilitate very fast analysis without knowledge of the analytical form of the image correlation function.

High-resolution scanning surface-plasmon microscopy

Surface plasmons (SP's) are electromagnetic surface waves that propagate along the interface between conductors and dielectrics. The k vector of these waves is larger than the free-space wave vector. The importance of SP's lies in the fact that they are extremely sensitive to small changes in the dielectric properties of substances that are in contact with the conductors. This property means that SP's have many sensor applications; however, when they are used in microscopic applications the lateral resolution is limited to several micrometers. We discuss how this limit can be overcome by use of defocused high-numerical-aperture liquid-immersion objectives. We also present SP images that demonstrate a resolution comparable with that expected from high-numerical-aperture optical microscopes. Finally, we discuss how ultrahigh-numerical-aperture objectives with numerical apertures greater than 1.5 can be expected to have considerable influence on biological imaging.

Optical V(z) for high-resolution 2pi surface plasmon microscopy

Surface plasmons are electromagnetic surface waves whose k vectors are greater than that of free-space radiation. We excite surface plasmons by using an oil-immersion lens, which forms one arm of an interferometer. We demonstrate the way in which the characteristic output variation with defocus is determined by the propagation properties of the surface plasmons, which leads to diffraction-limited surface plasmon microscopy in the far field.

Resolution beyond the rayleigh limit using beam displacement

Two fluorescence microscope systems which claim to achieve resolution beyond the Rayleigh limit have recently been described. These systems operate using two displaced beams focused on the sample and produce the image from the region of overlap. We describe an analogous system, which performs in a similar manner but does not rely on fluorescence. The imaging performance of these systems is analysed and we show that they all give improved resolution although, crucially, the optical bandwidth is not increased. These systems merely attenuate the lower spatial frequencies and, although such systems can be useful and operate in a manner analogous to pupil plane filters, it is important to appreciate that they do not offer true superresolution, contrary to the impression given in previous papers.

Ultrastable absolute-phase common-path optical profiler based on computer-generated holography

A new scanning common-path interferometric profiler capable of absolute-phase measurement is described. The key element is a computer-generated hologram, which acts as the beam-splitting element. Unlike most absolute phase systems, it can be made entirely common path with respect to piston microphonics and is thus exceptionally stable. In addition to operating in scanning mode, the optical configuration permits simultaneous operation as a single-shot phase measuring interferometer and is thus capable of simultaneous form and texture measurements. The operation and stability of the scanning profiler are demonstrated experimentally.

Single-probe-beam differential amplitude and phase-scanning interferometer

We describe a common path differential amplitude and phase interferometer capable of measuring differential amplitude and phase responses simultaneously. The system uses a single probe beam that is imaged onto the detector plane; differentiation in any direction can be performed by the alteration of the position of the detectors. Experimental and theoretical results, which show excellent agreement, are presented to demonstrate how the transfer function of the system can be controlled to suit different application areas.

Scanning optical microellipsometer for pure surface profiling

We describe a scanning optical interferometer that can simultaneously perform ellipsometry measurements and thus provides a true surface profile. This is accomplished by projecting the back focal plane of the objective lens onto a CCD array. The measured phase differences between the p- and s-polarization components are converted, by using a specially developed algorithm, to optical phase changes caused by material variations. The compensation process is then applied to extract the true profile of the object surface. Experimental results obtained with the system are shown.

Differential amplitude scanning optical microscope: theory and applications

A differential amplitude scanning optical microscope is described. The operation of the system depends on the sinusoidal interrogation of the sample, at any scan coordinate, by moving the beam through a fraction of the focal spot on the object surface. The technique is capable of detecting variations in sample reflectivity down to 3 x10(-7) in a 10-Hz bandwidth. The image formation mechanism of the microscope is presented and applied to a number of important structures. Experimental results on grain structure of metals, surface integrity of polished diamond, and doped silicon wafers are presented. The microscope is well suited to the accurate measurement of linewidths. Theoretical and experimental results are presented to demonstrate this capability. It is further shown that the main limitations in providing accurate linewidth measurements are due to the accuracy of the scan coordinates rather than the optical aspects of the system.

Scanning differential phase contrast optical microscope: application to surface studies

The characteristics and theory of operation of a new scanning differential phase contrast optical microscope are described, and a number of results are presented. High-contrast micrographs of a polished stainless steel sample are included, showing clearly the grain boundaries as well as some fine structure within the grains. Micrographs are also presented of natural diamonds both in polished and unpolished forms. In the former many polishing lines are visible, and in the latter one can clearly see a large number of stacking faults. Results on the study of monolayers of Langmuir-Blodgett films are also presented. The micrographs clearly show the boundaries as well as nonuniformities within the films. The ability of our system to image objects showing refractive-index variation is demonstrated by producing micrographs of an exposed but undeveloped photoresist film and a partially doped Si sample. In each case a qualitative comparison is made with the differential interference (Nomarski) micrograph of the same field of view.

Design and operation of a differentially pumped environmental chamber for the HVEM

A differentially pumped environmental chamber, or DIFPEC, has been developed for the AEI EM7 1.2 MV HVEM. The chamber is suitable for imaging and diffraction studies and is capable of operation at pressures approaching one atmosphere. Any mixture of gases can be used including water vapor supplied from an internal reservoir. Correct operation is demonstrated by measurements of temperature, pressure, and water consumption. High resolution (0.2 nm) diffraction patterns were recorded from unfixed, unstained, fully hydrated catalase crystals. This is good functional test of DIFPEC operation and specimen preparation because catalase disorders irreversibly of exposed to less than 95% relative humidity. High- and low-angle diffraction patterns were recorded from unfixed, unstained, fully hydrated rat hemoglobin crystals. All patterns were recorded using 10-4 C/cm2. Whole cell mounts prepared in different ways were imaged and show that 5.3 kPa of nitrogen gas has no detrimental effect on image contrast or resolution. The column vacuum and differentially pumped volume pressure were measured for a number of pumping configuration, as well as for several gases and pressures in the specimen volume. The pressure in the high vacuum portion of the objective lens gap is conductance-limited when the DIFPEC is in place.