Intraocular pressure in keratoconus

Aims: To investigate IOP measurements with the dynamic contour tonometer (DCT) and non contact tonometer (NCT) in subjects with keratoconus. Methods: Twenty keratoconic subjects and 20 age-matched control subjects had IOP measurements taken using DCT and NCT instruments. Central and offcentre measures were taken with the DCT in order to highlight any systematic errors associated with corneal biomechanical factors. Measures of anterior and posterior corneal topography and thickness were also taken for each subject. Results: No significant difference was found between the central and off-centre DCT IOP readings for the keratoconics and age-matched controls (p>0.05). The average DCT IOP for the keratoconics was 14.2 ± 1.4 mmHg and for the agematched controls was 14.2 ± 1.6 mmHg. However, the average NCT readings differed significantly (p<0.001) between the keratoconics (9.2 ± 1.5 mmHg) and age-matched controls (12.9 ± 2.4 mmHg). DCT IOP showed no significant (p>0.05) correlation with the severity of keratoconus, as determined through measures of corneal topography and thickness. NCT IOP was correlated significantly with certain measures of corneal curvature and thickness in the keratoconic population. The difference between DCT and NCT IOP was strongly correlated with measures of corneal topography and thickness, with differences increasing for more advanced keratoconus. Conclusions: The measurements from the DCT do not appear to be dependent upon corneal factors, unlike the NCT. The presence or severity of keratoconus was not correlated with DCT IOP values.

Unilateral pseudogerontoxon

Peripheral corneal opacities are a common clinical finding. In this case report we describe the routine presentation of a young adult male patient with unilateral opacities in the peripheral cornea resembling a corneal arcus. These opacities were confined to the level of the anterior corneal stroma. The patient also exhibited bilateral signs of mild keratoconus and reported a history of vernal keratoconjunctivitis as a child. A diagnosis of unilateral pseudogerontoxon was made. Pseudogerontoxon is an opacity of the peripheral cornea resembling corneal arcus that typically occurs in patients with a history of allergic eye disease. The clinical features and differential diagnoses of this relatively uncommon cause of peripheral corneal opacity are discussed.

Changes in intraocular pressure and ocular pulse amplitude with accommodation

Aims: To investigate the change that occurs in intraocular pressure (IOP) and ocular pulse amplitude (OPA) with accommodation in young adult myopes and emmetropes. Methods: Fifteen progressing myopic and 17 emmetropic young adult subjects had their IOP and OPA measured using the Pascal dynamic contour tonometer. Measurements were taken initially with accommodation relaxed, and then following 2 min of near fixation (accommodative demand 3 D). Baseline measurements of axial length and corneal thickness were also collected prior to the IOP measures. Results: IOP significantly decreased with accommodation in both the myopic and emmetropic subjects (mean change 1.861.1 mm Hg, p<0.0001). There was no significant difference (p>0.05) between myopes and emmetropes in terms of baseline IOP or the magnitude of change in IOP with accommodation. OPA also decreased significantly with accommodation (mean change for all subjects 0.560.5, p<0.0001). The myopic subjects (baseline OPA 2.060.7 mm Hg) exhibited a significantly lower baseline OPA (p¼0.004) than the emmetropes (baseline OPA 3.261.3 mm Hg),and a significantly lower magnitude of change in OPA with accommodation. Conclusion: IOP decreases significantly with accommodation, and changes similarly in progressing myopic and emmetropic subjects. However, differences found between progressing myopes and emmetropes in the mean OPA levels and the decrease in OPA associated with accommodation suggested some changes in IOP dynamics associated with myopia.

Clustering of ad-hoc microphone arrays for robust blind beamforming

This paper proposes a clustered approach for blind beamfoming from ad-hoc microphone arrays. In such arrangements, microphone placement is arbitrary and the speaker may be close to one, all or a subset of microphones at a given time. Practical issues with such a configuration mean that some microphones might be better discarded due to poor input signal to noise ratio (SNR) or undesirable spatial aliasing effects from large inter-element spacings when beamforming. Large inter-microphone spacings may also lead to inaccuracies in delay estimation during blind beamforming. In such situations, using a cluster of microphones (ie, a sub-array), closely located both to each other and to the desired speech source, may provide more robust enhancement than the full array. This paper proposes a method for blind clustering of microphones based on the magnitude square coherence function, and evaluates the method on a database recorded using various ad-hoc microphone arrangements.

Identifying work related injuries : comparison of methods for interrogating text fields

Background: Work-related injuries in Australia are estimated to cost around $57.5 billion annually, however there are currently insufficient surveillance data available to support an evidence-based public health response. Emergency departments (ED) in Australia are a potential source of information on work-related injuries though most ED’s do not have an ‘Activity Code’ to identify work-related cases with information about the presenting problem recorded in a short free text field. This study compared methods for interrogating text fields for identifying work-related injuries presenting at emergency departments to inform approaches to surveillance of work-related injury.---------- Methods: Three approaches were used to interrogate an injury description text field to classify cases as work-related: keyword search, index search, and content analytic text mining. Sensitivity and specificity were examined by comparing cases flagged by each approach to cases coded with an Activity code during triage. Methods to improve the sensitivity and/or specificity of each approach were explored by adjusting the classification techniques within each broad approach.---------- Results: The basic keyword search detected 58% of cases (Specificity 0.99), an index search detected 62% of cases (Specificity 0.87), and the content analytic text mining (using adjusted probabilities) approach detected 77% of cases (Specificity 0.95).---------- Conclusions The findings of this study provide strong support for continued development of text searching methods to obtain information from routine emergency department data, to improve the capacity for comprehensive injury surveillance.

Technical note : modelling a complex micro-multileaf collimator using the standard BEAMnrc distribution

Purpose: The component modules in the standard BEAMnrc distribution may appear to be insufficient to model micro-multileaf collimators that have tri-faceted leaf ends and complex leaf profiles. This note indicates, however, that accurate Monte Carlo simulations of radiotherapy beams defined by a complex collimation device can be completed using BEAMnrc's standard VARMLC component module.---------- Methods: That this simple collimator model can produce spatially and dosimetrically accurate micro-collimated fields is illustrated using comparisons with ion chamber and film measurements of the dose deposited by square and irregular fields incident on planar, homogeneous water phantoms.---------- Results: Monte Carlo dose calculations for on- and off-axis fields are shown to produce good agreement with experimental values, even upon close examination of the penumbrae.--------- Conclusions: The use of a VARMLC model of the micro-multileaf collimator, along with a commissioned model of the associated linear accelerator, is therefore recommended as an alternative to the development or use of in-house or third-party component modules for simulating stereotactic radiotherapy and radiosurgery treatments. Simulation parameters for the VARMLC model are provided which should allow other researchers to adapt and use this model to study clinical stereotactic radiotherapy treatments.

Development and use of clinical guidelines

The purpose of this chapter is to provide an overview of the development and use of clinical guidelines as a tool for decision making in clinical practice. Nurses have always developed and used tools to guide clinical decision making related to interventions in practice. Since Florence Nightingale (Nightingale 1860) gave us ‘notes’ on nursing in the late 1800s, nurses have continued to use tools, such as standards, policies and procedures, protocols, algorithms, clinical pathways and clinical guidelines, to assist them in making appropriate decisions about patient care that eventuate in the best desired patient outcomes. Clinical guidelines have enjoyed growing popularity as a comprehensive tool for synthesising clinical evidence and information into user-friendly recommendations for practice. Historically, clinical guidelines were developed by individual experts or groups of experts by consensus, with no transparent process for the user to determine the validity and reliability of the recommendations. The acceptance of the evidence-based practice (EBP) movement as a paradigm for clinical decision making underscores the imperative for clinical guidelines to be systematically developed and based on the best available research evidence. Clinicians are faced with the dilemma of choosing from an abundance of guidelines of variable quality, or developing new guidelines. Where do you start? How do you find an existing guideline to fit your practice? How do you know if a guideline is evidence-based, valid and reliable? Should you apply an existing guideline in your practice or develop a new guideline? How do you get clinicians to use the guidelines? How do you know if using the guideline will make any difference in care delivery or patient outcomes? Whatever the choice, the challenge lies in choosing or developing a clinical guideline that is credible as a decision-making tool for the delivery of quality, efficient and effective care. This chapter will address the posed questions through an exploration of the ins and outs of clinical guidelines, from development to application to evaluation.