Making Use of Technology to Improve Stated Preference Studies

The interest in quantifying stated preferences for health and healthcare continues to grow, as does the technology available to support and improve health preference studies. Technological advancements in the last two decades have implications and opportunities for preference researchers designing, administering, analysing, interpreting and applying the results of stated preference surveys. In this paper, we summarise selected technologies and how these can benefit a preference study. We discuss empirical evaluations of the technology in preference research, with examples from health where possible. The technologies reviewed include serious games, virtual reality, eye tracking, innovative formats and decision aids with values clarification components. We conclude with a critical reflection on the benefits and limitations of implementing (often costly) technology alongside stated preference studies.

How to Present a Decision Object in Health Preference Research: Attributes and Levels, the Decision Model, and the Descriptive Framework

In health preference research (HPR) studies, data are generated by participants'/subjects' decisions. When developing an HPR study, it is therefore important to have a clear understanding of the components of a decision and how those components stimulate participant behavior. To obtain valid and reliable results, study designers must sufficiently describe the decision model and its components. HPR studies require a detailed examination of the decision criteria, detailed documentation of the descriptive framework, and specification of hypotheses. The objects that stimulate subjects' decisions in HPR studies are defined by attributes and attribute levels. Any limitations in the identification and presentation of attributes and levels can negatively affect preference elicitation, the quality of the HPR data, and study results. This practical guide shows how to link the HPR question to an underlying decision model. It covers how to (1) construct a descriptive framework that presents relevant characteristics of a decision object and (2) specify the research hypotheses. The paper outlines steps and available methods to achieve all this, including the methods' advantages and limitations.

Adolescent and caregiver preferences for juvenile idiopathic arthritis treatment: a discrete-choice experiment

BACKGROUND

This study aimed to elicit and quantify preferences for treatments for juvenile idiopathic arthritis (JIA).

METHODS

We conducted a discrete-choice experiment among adolescents with JIA in the United States (US) (n = 197) and United Kingdom (UK) (n = 100) and caregivers of children with JIA in the US (n = 207) and UK (n = 200). In a series of questions, respondents chose between experimentally designed profiles for hypothetical JIA treatments that varied in efficacy (symptom control; time until next flare-up), side effects (stomachache, nausea, and vomiting; headaches), mode and frequency of administration, and the need for combination therapy. Using a random-parameters logit model, we estimated preference weights for these attributes, from which we derived their conditional relative importance.

RESULTS

On average, respondents preferred greater symptom control; greater time until the next flare-up; less stomachache, nausea, and vomiting; and fewer headaches. However, adolescents and caregivers in the US were generally indifferent across varying modes and frequencies of administration. UK adolescents and caregivers preferred tablets, syrup, or injections to intravenous infusions. US and UK adolescents were indifferent between treatment with monotherapy or combination therapy; caregivers in the UK preferred treatment with combination therapy to monotherapy. Subgroup analysis showed preference heterogeneity across characteristics including gender, treatment experience, and symptom experience in both adolescents and caregivers.

CONCLUSIONS

Improved symptom control, prolonged time to next flare-up, and avoidance of adverse events such as headache, stomachache, nausea, and vomiting are desirable characteristics of treatment regimens for adolescents with JIA and their caregivers.

Heterogeneity in physician and patient preferences for the treatment of renal cell carcinoma: Evidence from latent class analysis

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Background: To inform shared decision-making, it is important to learn how patients or physicians trade off the features of adjuvant treatments and whether there is heterogeneity within preferences. Methods: An online discrete-choice experiment survey was administered to patients with physician-confirmed renal cell carcinoma (RCC) and physician-defined intermediate high/high risk of recurrence and physicians who treat such patients. Hypothetical treatment choices were defined by median disease-free survival (DFS); 5-year overall survival (OS) rate; mode and frequency of administration; need for concomitant daily pill; treatment duration; and the risks of severe diarrhea, fatigue, and dizziness. After making an adjuvant treatment choice, respondents were presented with the opportunity to opt out of treatment. Patient and physician choice data were analyzed separately using latent class (LC) models, which identify clusters within patients and physicians making similar choices. Each class’ preference weights were used to calculate the conditional relative attribute importance. Results: LC analysis identified three classes among the 250 patients (% respondents) that placed greater relative importance on: 1) 5-year OS and opting into treatment (37.5%), 2) median DFS and opting into treatment (26.9%), and 3) treatment duration and opting out of treatment (35.5%) (Table). Among the 250 physicians, the LC analysis identified three classes that placed greater relative importance on: 1) 5-year OS and recommending treatment (37.5%), 2) median DFS and recommending treatment (37.8%), and 3) not recommending treatment (24.7%). Additionally, each LC analysis showed that the other treatment attributes evaluated were less important, but the importance varied by LC (Table). Conclusions: Heterogeneity in physician and patient preferences for RCC adjuvant therapy was found, highlighting a need for shared decision-making. Discordance within patients and physicians in the propensity to opt out of adjuvant treatment suggests patient-physician dialogue is important. [Table: see text]

Patient and physician preferences for adjuvant treatment of renal cell carcinoma: A discrete-choice experiment

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Background: Although a handful of studies have elicited treatment preferences in renal cell carcinoma (RCC), most focused on advanced disease. This study elicited United States patients’ and physicians’ preferences for adjuvant treatment characteristics. Methods: Patients with physician-confirmed RCC and (physician-defined) intermediate high or high risk of recurrence and physicians who treat such patients completed online surveys in Q1-Q2 2022 with a discrete-choice experiment. Hypothetical treatments were described by median disease-free survival (DFS); 5-year overall survival (OS) rate; mode and frequency of administration; need for concomitant daily pill; treatment duration; and the risks of severe diarrhea, fatigue, and dizziness. Preference weight estimates from random parameter logit analysis were used to calculate the conditional relative importance of attributes and risk tolerance measures. Results: 250 patients (50% post-nephrectomy) and 250 physicians (64% oncologists; 36% urologists) completed the survey. OS was the most important attribute to both patients and physicians, but DFS was also important (Table). OS had a greater influence on physicians’ choices than on patients’ choices. On average, OS was 3.2 and 2.5 times as important as DFS and 5.8-9.1 and 2.4-3 times more important than the evaluated risks for physicians and patients, respectively. Further, DFS was 1.8-2.9 times more important to physicians than the evaluated risks, while the importance of DFS and risks were nearly equivalent for patients. The need for concomitant oral medication was the least important attribute to patients and physicians. Both groups were willing to accept more than a 25-percentage-point increase in the risks of severe diarrhea, fatigue, and dizziness for improvements (from 45% to 60% or 85%) in OS. Conclusions: While both patients and physicians weighted OS improvements more than the other treatment attributes, including risks, physicians tended to place lower importance on changes in risk and administration than patients. Physicians and patients should discuss potential benefits and harms when considering adjuvant RCC therapies. [Table: see text]

Current Practices for Accounting for Preference Heterogeneity in Health-Related Discrete Choice Experiments: A Systematic Review

BACKGROUND

Accounting for preference heterogeneity is a growing analytical practice in health-related discrete choice experiments (DCEs). As heterogeneity may be examined from different stakeholder perspectives with different methods, identifying the breadth of these methodological approaches and understanding the differences are major steps to provide guidance on good research practices.

OBJECTIVES

Our objective was to systematically summarize current practices that account for preference heterogeneity based on the published DCEs related to healthcare.

METHODS

This systematic review is part of the project led by the Professional Society for Health Economics and Outcomes Research (ISPOR) health preference research special interest group. The systematic review conducted systematic searches on the PubMed, OVID, and Web of Science databases, as well as on two recently published reviews, to identify articles. The review included health-related DCE articles published between 1 January 2000 and 30 March 2020. All the included articles also presented evidence on preference heterogeneity analysis based on either explained or unexplained factors or both.

RESULTS

Overall, 342 of the 2202 (16%) articles met the inclusion/exclusion criteria for extraction. The trend showed that analyses of preference heterogeneity increased substantially after 2010 and that such analyses mainly examined heterogeneity due to observable or unobservable factors in individual characteristics. Heterogeneity through observable differences (i.e., explained heterogeneity) is identified among 131 (40%) of the 342 articles and included one or more interactions between an attribute variable and an observable characteristic of the respondent. To capture unobserved heterogeneity (i.e., unexplained heterogeneity), the studies largely estimated either a mixed logit (n = 205, 60%) or a latent-class logit (n = 112, 32.7%) model. Few studies (n = 38, 11%) explored scale heterogeneity or heteroskedasticity.

CONCLUSIONS

Providing preference heterogeneity evidence in health-related DCEs has been found as an increasingly used practice among researchers. In recent studies, controlling for unexplained preference heterogeneity has been seen as a common practice rather than explained ones (e.g., interactions), yet a lack of providing methodological details has been observed in many studies that might impact the quality of analysis. As heterogeneity can be assessed from different stakeholder perspectives with different methods, researchers should become more technically pronounced to increase confidence in the results and improve the ability of decision makers to act on the preference evidence.

Accounting for Preference Heterogeneity in Discrete-Choice Experiments: An ISPOR Special Interest Group Report

OBJECTIVES

Discrete choice experiments (DCEs) are increasingly used to elicit preferences for health and healthcare. Although many applications assume preferences are homogenous, there is a growing portfolio of methods to understand both explained (because of observed factors) and unexplained (latent) heterogeneity. Nevertheless, the selection of analytical methods can be challenging and little guidance is available. This study aimed to determine the state of practice in accounting for preference heterogeneity in the analysis of health-related DCEs, including the views and experiences of health preference researchers and an overview of the tools that are commonly used to elicit preferences.

METHODS

An online survey was developed and distributed among health preference researchers and nonhealth method experts, and a systematic review of the DCE literature in health was undertaken to explore the analytical methods used and summarize trends.

RESULTS

Most respondents (n = 59 of 70, 84%) agreed that accounting for preference heterogeneity provides a richer understanding of the data. Nevertheless, there was disagreement on how to account for heterogeneity; most (n = 60, 85%) stated that more guidance was needed. Notably, the majority (n = 41, 58%) raised concern about the increasing complexity of analytical methods. Of the 342 studies included in the review, half (n = 175, 51%) used a mixed logit with continuous distributions for the parameters, and a third (n = 110, 32%) used a latent class model.

CONCLUSIONS

Although there is agreement about the importance of accounting for preference heterogeneity, there are noticeable disagreements and concerns about best practices, resulting in a clear need for further analytical guidance.

A General Public Study on Preferences and Welfare Impacts of Antimicrobial Resistance in the United Kingdom

BACKGROUND

Antibiotics have led to considerable increases in life expectancy. However, over time, antimicrobial resistance has accelerated and is now a significant global public health concern. Understanding societal preferences for the use of antibiotics as well as eliciting the willingness to pay for future research is crucial.

OBJECTIVE

To investigate preferences for different strategies to optimize antibiotic use and to understand the willingness to pay for future research in antimicrobial resistance and antimicrobial drug development.

METHODS

A discrete-choice experiment was administered to a sample of the UK general population. Respondents were asked to make nine choices, each offering three options-two hypothetical "doctor and antibiotics" and one "no doctor-no antibiotics"-defined by five attributes: treatment, days needed to recover, risk of bacterial infection that needs antibiotics, risk of common side effects, and risk of antimicrobial resistance by 2050. Data were analyzed using random parameters logit models. A double-bounded contingent valuation was also included in the survey to explore the willingness to pay for policies to contain antimicrobial resistance.

RESULTS

Among the 2579 respondents who completed the survey, 1151 always selected "no doctor-no antibiotics" and 57 never varied their choices; therefore, 1371 responses were used in the analysis. Risk of antimicrobial resistance by 2050 was the most important attribute and the "treatment" was the least important attribute, although this was sensitive to a higher risk of bacterial infection. The aggregate annual willingness to pay for containing antimicrobial resistance was approximately £8.35 billion (~£5-£10 billion).

CONCLUSIONS

The antimicrobial resistance risk is relevant and important to the general public. The high willingness to pay suggests that large investments in policies or interventions to combat antimicrobial resistance are justified.

Education, training, and experience in public health ethics and law within the UK public health workforce

BACKGROUND

Public health ethics and law (PHEL) is a core professional competency for the public health workforce. However, few data are available describing the extent to which UK public health workforce members experience ethical and legal issues or have sufficient educational and/or training background to adequately deal with such issues.

METHODS

An anonymous online survey was developed for dissemination via member mailing lists of the: Faculty of Public Health, Royal Society of Public Health, and UK Public Health Register. Public Health England also included a link to the survey in their newsletter. The survey included questions about education, training, and experience in relation to PHEL. The survey was deployed from October 2017 to January 2018.

RESULTS

The survey was completed by a diverse sample of five hundred and sixty-two individuals. The majority of respondents reported: (i) regularly encountering ethical issues, (ii) resolving ethical issues through personal reflection, (iii) having little or no education and training in PHEL, and (iv) questioning whether they have dealt with ethical issues encountered in practice in the best way.

CONCLUSIONS

The results suggest that there is a need to develop and support wider PHEL capacity within the UK public health workforce through the provision of PHEL education, training, guidance, and mentoring.

Opening the 'Black Box': An Overview of Methods to Investigate the Decision-Making Process in Choice-Based Surveys

The desire to understand the preferences of patients, healthcare professionals and the public continues to grow. Health valuation studies, often in the form of discrete choice experiments, a choice based survey approach, proliferate as a result. A variety of methods of pre-choice process analysis have been developed to investigate how and why people make their decisions in such experiments and surveys. These techniques have been developed to investigate how people acquire and process information and make choices. These techniques offer the potential to test and improve theories of choice and/or associated empirical models. This paper provides an overview of such methods, with the focus on their use in stated choice-based healthcare studies. The methods reviewed are eye tracking, mouse tracing, brain imaging, deliberation time analysis and think aloud. For each method, we summarise the rationale, implementation, type of results generated and associated challenges, along with a discussion of possible future developments.

Utilising Patient and Public Involvement in Stated Preference Research in Health: Learning from the Existing Literature and a Case Study

Publications reporting discrete choice experiments of healthcare interventions rarely discuss whether patient and public involvement (PPI) activities have been conducted. This paper presents examples from the existing literature and a detailed case study from the National Institute for Health Research-funded PATHWAY programme that comprehensively included PPI activities at multiple stages of preference research. Reflecting on these examples, as well as the wider PPI literature, we describe the different stages at which it is possible to effectively incorporate PPI across preference research, including the design, recruitment and dissemination of projects. Benefits of PPI activities include gaining practical insights from a wider perspective, which can positively impact experiment design as well as survey materials. Further benefits included advice around recruitment and reaching a greater audience with dissemination activities, amongst others. There are challenges associated with PPI activities; examples include time, cost and outlining expectations. Overall, although we acknowledge practical difficulties associated with PPI, this work highlights that it is possible for preference researchers to implement PPI across preference research. Further research systematically comparing methods related to PPI in preference research and their associated impact on the methods and results of studies would strengthen the literature.

Public preferences regarding data linkage for research: a discrete choice experiment comparing Scotland and Sweden

BACKGROUND

There are increasing examples of linking data on healthcare resource use and patient outcomes from different sectors of health and social care systems. Linked data are generally anonymised, meaning in most jurisdictions there are no legal restrictions to their use in research conducted by public or private organisations. Secondary use of anonymised linked data is contentious in some jurisdictions but other jurisdictions are known for their use of linked data. The publics' perceptions of the acceptability of using linked data is likely to depend on a number of factors. This study aimed to quantify the preferences of the public to understand the factors that affected views about types of linked data and its use in two jurisdictions.

METHOD

An online discrete choice experiment (DCE) previously conducted in Scotland was adapted and replicated in Sweden. The DCE was designed, comprising five attributes, to elicit the preferences from a representative sample of the public in both jurisdictions. The five attributes (number of levels) were: type of researcher using linked data (four); type of data being linked (four); purpose of the research (three); use of profit from using linked data (four); who oversees the research (four). Each DCE contained 6 choice-sets asking respondents to select their preferred option from two scenarios or state neither were acceptable. Background questions included socio-demographics. DCE data were analysed using conditional and heteroskedastic conditional logit models to create forecasts of acceptability.

RESULTS

The study sample comprised members of the public living in Scotland (n = 1004) and Sweden (n = 974). All five attributes were important in driving respondents' choices. Swedish and Scottish preferences were mostly homogenous with the exception of 'who oversees the research using linked data', which had relatively less impact on the choices observed from Scotland. For a defined 'typical' linked data scenario, the probability (on average) of acceptance was 85.7% in Sweden and 82.4% in Scotland.

CONCLUSION

This study suggests that the public living in Scotland and Sweden are open to using anonymised linked data in certain scenarios for research purposes but some caution is advisable if the anonymised linked data joins health to non-health data.

Frameworks and guidance to support ethical public health practice

This article reports and reflects on an element of a recent survey of UK public health professionals, specifically in relation to the Public Health Knowledge and Skills Framework (PHSKF) and the ethical requirements that underpin public health practice. Only 38.4% of respondents reported accessing the PHKSF and a mere 13.7% reported accessing the accompanying background paper on ethical public health practice. Given that ethical practice underpins the PHSKF, it is concerning that so few respondents are familiar with the PHSKF and one of the source documents. While issuing frameworks and guidance is one way to support public health practice, there is a further need for greater integration of skills and knowledge around ethical public health practice within education and training initiatives.

An Exploratory Application of Eye-Tracking Methods in a Discrete Choice Experiment

Background. Discrete choice experiments (DCEs) are increasingly used to elicit preferences for benefit-risk tradeoffs. The primary aim of this study was to explore how eye-tracking methods can be used to understand DCE respondents’ decision-making strategies. A secondary aim was to explore if the presentation and communication of risk affected respondents’ choices. Method. Two versions of a DCE were designed to understand the preferences of female members of the public for breast screening that varied in how risk attributes were presented. Risk was communicated as either 1) percentages or 2) icon arrays and percentages. Eye-tracking equipment recorded eye movements 1000 times a second. A debriefing survey collected sociodemographics and self-reported attribute nonattendance (ANA) data. A heteroskedastic conditional logit model analyzed DCE data. Eye-tracking data on pupil size, direction of motion, and total visual attention (dwell time) to predefined areas of interest were analyzed using ordinary least squares regressions. Results. Forty women completed the DCE with eye-tracking. There was no statistically significant difference in attention (fixations) to attributes between the risk communication formats. Respondents completing either version of the DCE with the alternatives presented in columns made more horizontal (left-right) saccades than vertical (up-down). Eye-tracking data confirmed self-reported ANA to the risk attributes with a 40% reduction in mean dwell time to the “probability of detecting a cancer” (P = 0.001) and a 25% reduction to the “risk of unnecessary follow-up” (P = 0.008). Conclusion. This study is one of the first to show how eye-tracking can be used to understand responses to a health care DCE and highlighted the potential impact of risk communication on respondents’ decision-making strategies. The results suggested self-reported ANA to cost attributes may not be reliable.

"I Was Trying to Do the Maths": Exploring the Impact of Risk Communication in Discrete Choice Experiments

BACKGROUND

Risk is increasingly used as an attribute in discrete choice experiments (DCEs). However, risk and probabilities are complex concepts that can be open to misinterpretation, potentially undermining the robustness of DCEs as a valuation method. This study aimed to understand how respondents made benefit-risk trade-offs in a DCE and if these were affected by the communication of the risk attributes.

METHODS

Female members of the public were recruited via local advertisements to participate in think-aloud interviews when completing a DCE eliciting their preferences for a hypothetical breast screening programme described by three attributes: probability of detecting a cancer; risk of unnecessary follow-up; and cost of screening. Women were randomised to receive risk information as either (1) percentages or (2) percentages and icon arrays. Interviews were digitally recorded then transcribed to generate qualitative data for thematic analysis.

RESULTS

Nineteen women completed the interviews (icon arrays n = 9; percentages n = 10). Analysis revealed four key themes where women made references to (1) the nature of the task; (2) their feelings; (3) their experiences, for instance making analogies to similar risks; and (4) economic phenomena such as opportunity costs and discounting.

CONCLUSION

Most women completed the DCE in line with economic theory; however, violations were identified. Women appeared to visualise risk whether they received icon arrays or percentages only. Providing clear instructions and graphics to aid interpretation of risk and qualitative piloting to verify understanding is recommended. Further investigation is required to determine if the process of verbalising thoughts changes the behaviour of respondents.

Discrete choice experiments of pharmacy services: a systematic review

Background Two previous systematic reviews have summarised the application of discrete choice experiments to value preferences for pharmacy services. These reviews identified a total of twelve studies and described how discrete choice experiments have been used to value pharmacy services but did not describe or discuss the application of methods used in the design or analysis. Aims (1) To update the most recent systematic review and critically appraise current discrete choice experiments of pharmacy services in line with published reporting criteria and; (2) To provide an overview of key methodological developments in the design and analysis of discrete choice experiments. Methods The review used a comprehensive strategy to identify eligible studies (published between 1990 and 2015) by searching electronic databases for key terms related to discrete choice and best-worst scaling (BWS) experiments. All healthcare choice experiments were then hand-searched for key terms relating to pharmacy. Data were extracted using a published checklist. Results A total of 17 discrete choice experiments eliciting preferences for pharmacy services were identified for inclusion in the review. No BWS studies were identified. The studies elicited preferences from a variety of populations (pharmacists, patients, students) for a range of pharmacy services. Most studies were from a United Kingdom setting, although examples from Europe, Australia and North America were also identified. Discrete choice experiments for pharmacy services tended to include more attributes than non-pharmacy choice experiments. Few studies reported the use of qualitative research methods in the design and interpretation of the experiments (n = 9) or use of new methods of analysis to identify and quantify preference and scale heterogeneity (n = 4). No studies reported the use of Bayesian methods in their experimental design. Conclusion Incorporating more sophisticated methods in the design of pharmacy-related discrete choice experiments could help researchers produce more efficient experiments which are better suited to valuing complex pharmacy services. Pharmacy-related discrete choice experiments could also benefit from more sophisticated analytical techniques such as investigations into scale and preference heterogeneity. Employing these sophisticated methods for both design and analysis could extend the usefulness of discrete choice experiments to inform health and pharmacy policy.

The Role of Qualitative Research Methods in Discrete Choice Experiments

Background. The use of qualitative research (QR) methods is recommended as good practice in discrete choice experiments (DCEs). This study investigated the use and reporting of QR to inform the design and/or interpretation of healthcare-related DCEs and explored the perceived usefulness of such methods. Methods. DCEs were identified from a systematic search of the MEDLINE database. Studies were classified by the quantity of QR reported (none, basic, or extensive). Authors (n = 91) of papers reporting the use of QR were invited to complete an online survey eliciting their views about using the methods. Results. A total of 254 healthcare DCEs were included in the review; of these, 111 (44%) did not report using any qualitative methods; 114 (45%) reported “basic” information; and 29 (11%) reported or cited “extensive” use of qualitative methods. Studies reporting the use of qualitative methods used them to select attributes and/or levels (n = 95; 66%) and/or pilot the DCE survey (n = 26; 18%). Popular qualitative methods included focus groups (n = 63; 44%) and interviews (n = 109; 76%). Forty-four studies (31%) reported the analytical approach, with content (n = 10; 7%) and framework analysis (n = 5; 4%) most commonly reported. The survey identified that all responding authors (n = 50; 100%) found that qualitative methods added value to their DCE study, but many (n = 22; 44%) reported that journals were uninterested in the reporting of QR results. Conclusions. Despite recommendations that QR methods be used alongside DCEs, the use of QR methods is not consistently reported. The lack of reporting risks the inference that QR methods are of little use in DCE research, contradicting practitioners’ assessments. Explicit guidelines would enable more clarity and consistency in reporting, and journals should facilitate such reporting via online supplementary materials.

Sub-wavelength ripples in fused silica after irradiation of the solid/liquid interface with ultrashort laser pulses

Laser-induced backside wet etching (LIBWE) is performed using ultrashort 248 nm laser pulses with a pulse duration of 600 fs to obtain sub-wavelength laser-induced periodic surface structures (LIPSS) on the back surface of fused silica which is in contact with a 0.5 mol l(-1) solution of pyrene in toluene. The LIPSS are strictly one-dimensional patterns, oriented parallel to the polarization of the laser radiation, and have a constant period of about 140 nm at all applied laser fluences (0.33-0.84 J cm(-2)) and pulse numbers (50-1000 pulses). The LIPSS amplitude varies due to the inhomogeneous fluence in the laser spot. The LIPSS are examined with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their power spectral density (PSD) distribution is analysed at a measured area of 10 µm × 10 µm. The good agreement of the measured and calculated LIPSS periods strongly supports a mechanism based on the interference of surface-scattered and incident waves.

Retinal nerve fiber layer birefringence evaluated with polarization sensitive spectral domain OCT and scanning laser polarimetry: a comparison

A polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) system is used to measure phase retardation and birefringence of the human retinal nerve fiber layer (RNFL) in vivo. The instrument records three parameters simultaneously: intensity, phase retardation and optic-axis orientation. 3D data sets are recorded in the optic nerve-head area of a healthy and a glaucomatous eye, and the results are presented in various ways: En-face phase-retardation maps of the RNFL are generated from the recorded 3D data and results are compared with scanning laser polarimetry (SLP). The depth information provided by OCT is used to segment the RNFL in the intensity image and measure the RNFL thickness. From the retardation and thickness data, 2D birefringence maps of the RNFL are derived. Circumpapillary plots of RNFL retardation and thickness obtained by PS-SD-OCT are quantitatively compared with those obtained by SLP.

Medical interventions for primary open angle glaucoma and ocular hypertension

BACKGROUND

Primary open angle glaucoma (POAG) is a progressive optic neuropathy with an elevated intraocular pressure (IOP), where the optic nerve head becomes pathologically excavated and the visual field (VF) is characteristically altered. Ocular hypertension (OHT) is a condition with elevated IOP but without discernible pathology of the optic nerve head or the VF. It is a major risk factor for development of POAG.

OBJECTIVES

To assess and compare the effectiveness of topical pharmacological treatment for POAG or OHT to prevent progression or onset of glaucomatous optic neuropathy.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE and EMBASE in May 2007. We searched the bibliographies of identified articles and contacted experts, investigators and pharmaceutical companies for additional published and unpublished studies.

SELECTION CRITERIA

Randomised controlled trials comparing topical pharmacological treatment to placebo, no treatment or other treatment for specified endpoints which included people with POAG or OHT, and with duration of treatment of at least one year.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality. Where appropriate, we summarised data using Peto odds ratio and mean difference after testing for heterogeneity between studies.

MAIN RESULTS

We included 26 trials, which randomised 4979 participants, in this review. Meta-analysis of 10 trials clearly demonstrated reduction of onset of VF defects in treated OHT (OR 0.62, 95% CI 0.47 to 0.81). No single drug showed a significant VF protection compared to placebo or untreated controls. We did identify some border line evidence for a positive influence of treatment on VF prognosis (OR 0.67, 95% CI 0.45 to 1.00) for the beta-blockers .

AUTHORS' CONCLUSIONS

The results of this review support the current practice of IOP lowering treatment of OHT. A visual field protective effect has been clearly demonstrated for medical IOP lowering treatment. Positive but weak evidence for a beneficial effect of the class of beta-blockers has been shown. Direct comparisons of prostaglandins or brimonidine to placebo are not available and the comparison of dorzolamide to placebo failed to demonstrate a protective effect. However, absence of data or failure to prove effectiveness should not be interpreted as proof of absence of any effect. The decision to treat a patient or not, as well as the decision regarding the drug with which to start treatment, should remain individualised, taking in to account the amount of damage, the level of IOP, age and other patient characteristics.

Effect of dorzolamide and timolol on ocular blood flow in patients with primary open angle glaucoma and ocular hypertension

BACKGROUND

There is evidence that perfusion abnormalities of the optic nerve head are involved in the pathogenesis of glaucoma. There is therefore considerable interest in the effects of topical antiglaucoma drugs on ocular blood flow. A study was undertaken to compare the ocular haemodynamic effects of dorzolamide and timolol in patients with primary open angle glaucoma (POAG) or ocular hypertension (OHT).

METHODS

One hundred and forty patients with POAG or OHT were included in a controlled, randomised, double blind study in two parallel groups; 70 were randomised to receive timolol and 70 to receive dorzolamide for a period of 6 months. Subjects whose intraocular pressure (IOP) did not respond to either of the two drugs were switched to the alternative treatment after 2 weeks. Scanning laser Doppler flowmetry was used to measure blood flow in the temporal neuroretinal rim and the cup of the optic nerve head. Pulsatile choroidal blood flow was assessed using laser interferometric measurement of fundus pulsation amplitude.

RESULTS

Five patients did not respond to timolol and were changed to the dorzolamide group, and 18 patients changed from dorzolamide treatment to timolol. The effects of both drugs on IOP and ocular perfusion pressure were comparable. Dorzolamide, but not timolol, increased blood flow in the temporal neuroretinal rim (8.5 (1.6)%, p<0.001 versus timolol) and the cup of the optic nerve head (13.5 (2.5)%, p<0.001 versus timolol), and fundus pulsation amplitude (8.9 (1.3)%, p<0.001 versus timolol).

CONCLUSIONS

This study indicates augmented blood flow in the optic nerve head and choroid after 6 months of treatment with dorzolamide, but not with timolol. It remains to be established whether this effect can help to reduce visual field loss in patients with glaucoma.

Effect of trabeculectomy on ocular blood flow

BACKGROUND/AIM

Current evidence suggests that vascular insufficiencies in the optic nerve head play an important part in the pathogenesis of glaucomatous optic neuropathy. Trabeculectomy is the most common operative procedure for the treatment of medically uncontrolled glaucoma. This study was conducted to investigate whether trabeculectomy may improve ocular haemodynamics.

METHODS

30 patients with primary open angle glaucoma about to undergo trabeculectomy were included in the study. Patients were evaluated before surgery and at 2 and 10 weeks after trabeculectomy. Optic nerve head blood flow (OnhBF) was assessed with scanning laser Doppler flowmetry. Fundus pulsation amplitude (FPA) measurements were obtained with laser interferometry.

RESULTS

Because of the decrease in intraocular pressure there was a significant increase in ocular perfusion pressure (OPP) following trabeculectomy (18.5% (SD 12.0%) and 19.0% (17.1%) at 2 and 10 weeks postoperatively; p <0.001). A significant increase in OnhBF was observed after trabeculectomy (11.6% (16.4%) and 16.2% (20.2%) for each postoperative visit, respectively; p <0.001). FPA was also significantly higher compared with baseline values (17.2% (17.3%) and 17.4% (16.3%), respectively; p <0.001). A significant association between the increase in OPP and the increase in OnhBF and FPA was observed 10 weeks after surgery (r = 0.47; p = 0.009, and r = 0.50; p = 0.005, respectively).

CONCLUSION

The results of this study suggest that trabeculectomy improves ocular blood flow in patients with chronic open angle glaucoma.

Effect of nimodipine on ocular blood flow and colour contrast sensitivity in patients with normal tension glaucoma

AIM

To investigate the effects of oral nimodipine on ocular haemodynamic parameters and colour contrast sensitivity in patients with normal tension glaucoma (NTG).

DESIGN

The study was performed in a randomised, placebo controlled, double masked, crossover design.

PARTICIPANTS

Nimodipine (60 mg) or placebo was administered to 14 consecutive NTG patients.

METHODS

The effects or oral nimodipine or placebo on ocular and systemic haemodynamic parameters and colour contrast sensitivity along the tritan axis were studied two hours after administration. Optic nerve head blood flow (ONHBF) and choroidal blood flow (CHBF) were assessed with laser Doppler flowmetry. Ocular fundus pulsation amplitude (FPA) was measured with laser interferometry. Colour contrast sensitivity (CCS) was determined along the tritan colour axis.

MAIN OUTCOME MEASURES

ONHBF, CHBF, FPA, intraocular pressure and CCS were assessed in patients with NTG.

RESULTS

Mean ocular FPA increased by 14% (SD 14%) (p = 0.0008), ONHBF by 18% (SD 16%) (p = 0.0031), and CHBF by 12% (SD 14%) (p<0.001) after administration of nimodipine. Nimodipine also decreased the threshold of colour contrast sensitivity along the tritan colour axis (-14% (SD 12%); p = 0.048). However, individual changes in FPA, ONHBF, or CHBF were not correlated with changes in threshold of CCS along the tritan colour axis.

CONCLUSIONS

The results indicate that nimodipine increases ONH and choroidal blood flow in NTG patients and improves CCS. The latter effect does not, however, seem to be a direct consequence of the blood flow improvement.

[Modern diagnostic methods for suspected glaucoma and glaucoma]

BACKGROUND

Diagnosis of early glaucomatous damage as well as the detection of glaucomatous change are still difficult tasks. During the last years numerous new diagnostic techniques have been investigated and some of them have been introduced to the market.

METHODS

This paper reviews the different aims of diagnostic technologies in the field of glaucoma. Methods appearing suitable for a large-scale use by ophthalmologists will be judged according to their suitability to meet the goals of early diagnosis, objective diagnosis, progression analysis and screening.

CONCLUSIONS

The new diagnostic techniques have not yet greatly influenced our diagnostic procedure. This is mainly due to the fact that, for the most difficult borderline cases of glaucoma, these methods are of limited value, or have not yet been sufficiently investigated. Nevertheless, the Heidelberg retina tomograph (HRT), the nerve fiber analyzer GDX, short wavelength perimetry (SWAP), and the frequency doubling test (FDT) may play a role in these cases. For follow-up, HRT and GDx have proven valuable, especially in early stages of the disease. The very short testing time of FDT together with good specificity qualifies this test for glaucoma screening.

Surgical strategies in patients with combined cataract and glaucoma

PURPOSE OF REVIEW

In the elderly population, the combined presence of cataract and glaucoma is a frequent condition. In this situation, several surgical options are possible: cataract surgery only and later maybe trabeculectomy, trabeculectomy only and later maybe cataract surgery, or combined cataract and glaucoma surgery. This review compares the different surgical options on the basis of their achievable postoperative intraocular pressure (IOP) level and success and complication rates.

RECENT FINDINGS

The impression of better IOP regulation with trabeculectomy than with phacotrabeculectomy has been recently confirmed by an evidence-based review. Contrary to this finding, the success of deep sclerectomy or trabeculotomy does not seem to be compromised by simultaneous phacoemulsification. In eyes with previous glaucoma-filtering surgery, cataract surgery with clear corneal incision has no effect on mean IOP but increases the 3-year failure probability. For phacotrabeculectomy, moderate evidence of a beneficial effect of MMC on IOP regulation and only weak evidence for separating the incisions has been recently reported by another evidence-based review.

SUMMARY

The choice of the preferred surgical method depends on the target pressure, the amount of glaucomatous damage, and the grade of visual disturbance caused by the cataract. Phacotrabeculectomy combined with mitomycin C achieves the best IOP lowering of all types of combined cataract and glaucoma surgery currently possible but is associated with potentially sight-threatening complications. In the absence of a low target pressure, phacotrabeculotomy or the combination of phacoemulsification with viscocanalostomy or deep sclerectomy may be the therapy of choice.

Interventions for normal tension glaucoma

BACKGROUND

Normal tension glaucoma is a clinical condition in which the optic nerve is pathologically excavated and the visual field is disturbed. Nevertheless it has been assumed that intraocular pressure plays a role in the progression of visual field defects in this disease, but other, mainly vascular factors, have been discussed as well.

OBJECTIVES

The objective of this review is to assess the effects of medical and surgical treatments for normal tension glaucoma.

SEARCH STRATEGY

Trials were identified from the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group trials register), MEDLINE, EMBASE and BIOSIS Previews. Bibliographies of identified trials were searched to find additional trials. In addition, investigators and pharmaceutical companies were contacted. Date of last search: January 2001.

SELECTION CRITERIA

This review includes randomised controlled trials in which medical or surgical interventions were compared to no treatment, placebo or other treatment in people with normal tension glaucoma. Two reviewers independently assessed the full text copies of the possibly relevant trials. Trial quality was assessed according to the methods set out in Section 6 of the Cochrane Reviewers' Handbook (Clarke 2000).

DATA COLLECTION AND ANALYSIS

Data were extracted by two reviewers and results were compared for differences. Discrepancies were resolved by discussion. The heterogeneity of interventions, follow-up periods and outcomes did not allow for statistical combinations of the study results.

MAIN RESULTS

According to the selection criteria on visual field loss, eight studies were included in this review. Only three studies focussed on patient relevant outcomes. In one trial a beneficial effect of lowering intraocular pressure was found, but only if data were corrected for cataract development. In two small studies a beneficial effect on visual field loss of brovincamine, a calcium antagonist was reported.

REVIEWER'S CONCLUSIONS

In one study the effect of intraocular pressure lowering on visual field outcome was only significant when data were corrected for cataract development. The results for calcium antagonists are promising, but larger trials have to be performed. Studies that focussed on reduction of intraocular pressure or haemodynamic variables are not necessarily relevant for the outcome in people with normal tension glaucoma.

Modifying subsceral fluid pressure in an experimental model of mitomycin-C diffusion

BACKGROUND

Episcleral application of mitomycin-C (MMC) during glaucoma filtration surgery hinders the post-operative wound healing. Diffusion through the sclera might result in a toxic effect on the ciliary body resulting in reduced aqueous humor production leading to post-operative hypotony. We developed an experimental model to investigate the influence of intraocular pressure on the diffusion of MMC through the sclera and in subscleral compartments.

METHODS

Scleral quadrants of 10 human donor eyes were mounted on PMMA tubes filled with saline imitating the intraocular volume. By height variation of a coupled infusion line different intraocular pressures were simulated (0, 8, 23 and 80 mmHg). Additionally the model included a subscleral sponge to mimic the compartment of the ciliary body. The episcleral sides of the scleral quadrants were exposed for 1 min to sponges soaked with 200 microg ml(-1) MMC. An 8-mm-diameter scleral disk was punched out with a trephine and horizontally dissected with a kryotome. The MMC concentrations of scleral layers, epi-and subscleral sponges and the fluid within the tubes were analysed by means of high-performance liquid chromatography.

RESULTS

The MMC concentration gradually declined from the episcleral sponge (165 microg ml(-1)) to the superficial (3.3 microg ml(-1)) and deep scleral layers (1.2 microg ml(-1)), and to the subscleral sponge (0.2 microg ml(-1)). We were able to detect very small concentrations of MMC in the fluid within the PMMA tubes (0.01 microg ml(-1)).

CONCLUSION

We developed a new experimental in vitro model for investigating transscleral MMC diffusion. The different simulated intraocular pressures had no effect on the concentration gradient through the investigated compartments of our model.

Activity of dissolved mitomycin C after different methods of long-term storage

PURPOSE

The cytostatic substance mitomycin C (MMC) is used in trabeculectomy to enhance the success rate in problematic cases and is usually dissolved immediately before application, but only approximately 1% of the substance is needed for treatment. The authors evaluated different methods of long-time storage of MMC for a period of 6 months.

METHODS

MMC in concentrations of 0.02, 0.05, 0.1, 0.2, and 0.4 mg/mL was prepared at the local pharmaceutical department and stored at +22 degrees C (room temperature), +4 degrees C (refrigerator), -20 degrees C (freezer compartment), and -196 degrees C (liquid N2). The activity of MMC was evaluated with a microagar diffusion method (bioassay) after 30 minutes, and 1, 3, 7, 14, 30, 90, and 180 days for the different concentrations and storage methods.

RESULTS

There was no difference in the long-term stability of the investigated MMC concentrations. Ninety percent of the initial activity was preserved after storage at +22 degrees C for 1 week, -20 degrees C for 1 month, or +4 degrees C for 3 months. At 6 months the activities were 16%, 48%, and 78% of the initial values, respectively. The activity of MMC stored at -196 degrees C is not reduced after storage for 6 months.

CONCLUSIONS

Dissolved MMC can be stored in the refrigerator for up to 3 months without significant loss of activity. Storage at room temperature is not recommended. Costs of trabeculectomy can be reduced by storage of reconstituted solutions rather than dissolving MMC before each glaucoma surgery.

A double masked placebo controlled study on the effect of nifedipine on optic nerve blood flow and visual field function in patients with open angle glaucoma

AIMS

To investigate whether nifedipine affects ocular perfusion or visual fields in open angle glaucoma patients.

METHODS

In a parallel group study nifedipine or placebo was administered for 3 months (n = 30). Ocular fundus pulsation amplitude (FPA), cup blood flow (Flowcup) and visual field mean deviation (MD) were measured.

RESULTS

Five patients receiving nifedipine discontinued due to adverse events. Nifedipine did not affect FPA [difference: 0.3 microm (95% CI -0.3,0.9); P = 0.70], Flowcup: [difference: -9 rel.units (95% CI -133,114); P = 0.99], or MD [difference: 0.2dB (95% CI -2.2,2.7); P = 0.51] vs placebo.

CONCLUSIONS

Systemic nifedipine is not well tolerated in glaucoma patients and exerts no effect on visual fields or ocular perfusion.

Tritan colour contrast sensitivity function in refractive multifocal intraocular lenses

AIMS

To compare tritan colour contrast sensitivity (CCS), without and with glare, in patients with refractive multifocal intraocular lenses (IOLs) and with monofocal intraocular lenses.

METHODS

Tritan CCS was determined (Moorfields Vision System, CH Electronics) in 15 eyes (14 patients, 75.7 (+/-6.6) years) with a refractive multifocal IOL (Allergan SA 40N) and in 11 eyes (10 patients, 73.7 (+/-6.4) years) with a monofocal IOL (Allergan SI 40 NB). Measurements were made monocularly under mesopic conditions at a distance of 2 metres from the monitor with best distance refraction plus 0.5 D at 0.5, 1, 3, 6, 11.4, and 22.8 cycles per degree (cpd). The test was then repeated for the multifocal IOLs, adding minus 2.5 D to the best distance refraction to force the patient to use the near focus. Both lenses were also investigated under glare conditions with the same set-up and using the brightness acuity tester (BAT).

RESULTS

The tritan CCS function without glare in multifocal lenses through the distance focus was nearly identical to that through the near focus. The following statistically significant differences were measured: the CCS function without glare for the multifocal lens was worse at 0.5 cpd and 1.0 cpd than that of the monofocal lens. In CCS testing of the multifocal group with glare at 6 cpd, the results through the distance focus were better than the results through the near focus. For the CCS function with glare, the values for the distance focus in the multifocal lens were worse than the values for the monofocal lens at 0.5 cpd and 1 cpd. In CCS testing with glare through the near focus and CCS testing through the monofocal lens, the monofocal lens performed better at 0.5 cpd, 1 cpd, 3 cpd, and 6 cpd.

CONCLUSION

Refractive multifocal intraocular lenses influence tritan CCS function compared to monofocal lenses.

[Adnexal torsion in childhood]

The authors report the case of a 10-year-old girl who was admitted with hypogastric complaints. Based on the examinations followed that, laparotomy was carried out, during which the torsion of the right-side adnexum was observed. During the case report special attention is put on the differential-diagnostic difficulties of adnexal torsion. The importance of the case is that we should think of this relatively rare disease even in childhood, because the early diagnosis and adequate therapy make possible to avoid the surgical amputation.

[Excimer laser versus diamond fraise: equal short-term outcome of corneal smoothing in pterygium operations]

BACKGROUND

The treatment of pterygia often results in irregular astigmatism. Corneal smoothing at the end of surgery plays a major role in the development of astigmatism. The aim of our study was to compare the efficiency of corneal smoothing performed by phototherapeutic keratectomy compared with the conventional method performed by a diamond fraise. The effect of postoperative excimer laser smoothing on refraction, visual acuity and irregular astigmatism was investigated.

PATIENTS AND METHODS

32 eyes underwent pterygium excision using a standardized surgical procedure. In addition 9 eyes underwent postoperative phototherapeutic keratectomy of the wound region with an excimer laser, 23 eyes were treated with a diamond fraise for corneal smoothing. The postoperative examination was performed 7, 14 and 30 days after surgery. Corneal topography was performed by a computer-assisted videokeratoscope (TMS-1). The results were evaluated by the Fourier transform analysis.

RESULTS

Both methods showed similar results concerning refraction and visual acuity postoperatively. Preoperatively all patients had an irregular flattening of the corneal topography in the area of the pterygium. Postoperatively a small irregular flattening was left in eyes treated with a diamond fraise. In the excimer laser treated group a steepening in the corneal topography could be observed.

CONCLUSIONS

The phototherapeutic keratectomy with excimer laser in the treatment of pterygia suggests to be a gentle alternative creating a smooth wound surface. Despite of this advantage the treatment with the excimer laser effects a remarkable increase in administration and expense.

Impact of Mitomycin-C application time on the scleral Mitomycin-C concentration

The aim of this study was to determine the effect of varying the application time of Mitomycin-C (MMC) on the scleral concentration of MMC. The sclerae of 14 human donor eyes were used for this study. The episcleral sides of the 4 scleral quadrants of each donor eye were exposed for 0.5, 1, 3 and 5 min to round, 8 mm-diameter sponges soaked with 50 microl of 0.2 mg/ml MMC. After 40-ml irrigation with saline, a central 8-mm diameter scleral disk was punched out, homogenized and analyzed with high performance liquid chromatography (HPLC). The scleral MMC concentrations (microg/g) after 0.5, 1, 3 and 5 min application times were 6.40 (+/-3.38), 9.02 (+/-2.40), 12.31 (+/-3.37), and 13.97 (+/-3.83). The differences of scleral MMC concentration in paired t-tests were statistically significant comparing 0.5 with 1 and 1 with 5 min application. However the effect was relatively small within the range of usual application times (1 to 5 min), and 64% of the MMC was delivered to the sclera within the first min.

In vitro diffusion of mitomycin-C into human sclera after episcleral application: impact of diffusion time

The purpose of this study was to investigate the impact of different diffusion times of mitomycin-C (MMC) on the intrascleral concentration vs depth profile of MMC in an experimental model. Scleral quadrants of eight human donor eyes were exposed to sponges soaked with MMC for an application time of 1 min. After irrigation with 40 ml saline, we allowed further diffusion of MMC in the sclera for 1, 5, 14 and 29 min until the specimens were further processed. A central 8 mm diameter scleral disk was horizontally dissected with a kryotome at -20 degrees C. MMC concentrations of six layers of 140 microm thickness were analysed by means of high-performance liquid chromatography. The MMC concentrations (microg g(-1)) of layer 1 were: 13.45+/- 5.9 (mean +/- S.D. at 2 min diffusion time), 7.6+/-2.5 (6 min diffusion), 5.6+/-3.1 (15 min diffusion) and 3.6+/-1.7 (30 min diffusion). The corresponding MMC concentrations of layer 6 were: 0.61+/-0.48, 1.47 +/-0.66, 1.83+/-0.42 and 2.98+/-0.97 microg g(-1). The superficial concentration of intrascleral MMC decreased with increasing diffusion time, the deep concentrations increased. After 30 min of diffusion time, equal concentrations of MMC were found in all layers. Even with current low-dose application regimens of MMC the concentrations in the inner side of the sclera rapidly increase beyond the limits of the therapeutic range. Owing to this fast diffusion of MMC, the only means of reducing ciliary body concentrations of MMC is to reduce the dose.

Assessment of optic disk blood flow in patients with open-angle glaucoma

PURPOSE

To characterize optic disk blood flow in patients with open-angle glaucoma compared with age-matched healthy control subjects.

METHODS

In this prospective cross-sectional study, 90 eyes of 90 patients with open-angle glaucoma and 61 eyes of 61 age-matched healthy control subjects were evaluated. Flow in the optic disk cup and the neuroretinal rim were assessed with scanning laser Doppler flowmetry. Fundus pulsation amplitude in the cup and the macula were assessed with laser interferometry. Visual field mean deviation was measured with the Humphrey 30 to 2 program.

RESULTS

Flow in the neuroretinal rim (-18%, P =.002), and in the cup (-46%, P <.001) and fundus pulsation amplitude in the cup (-33%, P <.001) and in the macula (-24%, P <.001) were significantly lower in patients with open-angle glaucoma compared with healthy control subjects. A significant association between blood flow measurements in the cup and fundus pulsation amplitudes in the cup was observed in both study cohorts. A significant association was also observed between the mean defect from visual field testing and ocular hemodynamic parameters.

CONCLUSIONS

Reduced optic disk perfusion in patients with open-angle glaucoma is evidenced from two independent methods in the present study. Moreover, our data indicate that reduced ocular blood flow in these patients is linked to visual field changes. It remains to be established whether compromised optic disk and choroidal blood flow contributes to optic disk damage in glaucomatous eyes or is a secondary functional phenomenon.

Phacotrabeculectomy with a small-optic PMMA implant: two-year functional and morphological results

PURPOSE

Previous studies have documented good pressure control with combined cataract and filtering surgery. However, relatively high incidences of iridocapsular synechiae (ICS) and cell precipitates on the optic (CPO) were found. Corneal valve incisions preclude intraoperative chamber flattening and iris injury or prolapse. Rigid one-piece PMMA lenses with a small optic maintain a pronounced optic-iris clearance. In a prospective series, the effect of this approach was studied with special regard to the morphological results.

METHODS

A temporary corneal lip was created in the clear cornea beneath the scleral flap to serve as a temporary valve during cataract extraction. The lip was then widened and a rigid one-piece 5-mm PMMA lens implanted. Lip and trabeculum were finally excised en bloc at a width of 3 mm. Two years' functional and morphological results were evaluated.

RESULTS

Fifty-four eyes were available for evaluation. After the mean follow-up of 21 months, mean IOP had dropped from 21.6+/-3 mm Hg preoperatively to 13.9+/-2.4 mm Hg, with a mean pressure reduction of 7.7+/-3.4 mm Hg. IOP was 18 mm Hg or less in all cases. The mean medication index dropped from 2.7 to 1.0. Eyes with a preoperative IOP of 21 mm Hg or more showed a significantly greater IOP reduction than eyes with an IOP of 20 mm Hg or less (-9.2+/-3.0 vs. -6.1+/-2.9 mm Hg, p = 0.0003). Intraoperatively, the temporary valve effectively prevented chamber flattening and iris injury or prolapse. Postoperatively, 9 eyes or 6% showed hyphemas, 1 undergoing lavage. Two eyes developed a capsular hematoma, 1 requiring YAG capsulotomy. Ten eyes or 19% developed mild and 2 eyes severe but transient fibrin exudation following hypotony or iridoplasty. One eye showed grade I anterior chamber flattening, 1 developed a ciliolenticular block requiring surgery. Postoperative pressure spikes of 30-35 mm Hg were noted in 4 eyes. Three eyes showed prolonged hypotony associated with transient choroidal effusion. A pronounced optic-iris clearance was found in 87% of the eyes. Iris-optic touch developed in 1 eye with prolonged postoperative anterior chamber flattening and in 3 of the 4 eyes that had undergone intraoperative iridoplasty. Three of the latter developed extensive ICS followed by CPO. The mean optic-iris distance was 1.2 mm and the anterior chamber depth 4.2 mm.

CONCLUSION

Apart from effectively lowering IOP, the surgical approach used significantly reduced the incidence of ICS and CPO.

Astigmatism correction with a foldable toric intraocular lens in cataract patients

PURPOSE

To determine the efficacy and rotational stability of a toric posterior chamber silicone intraocular lens (IOL) to correct preoperative astigmatism in cataract patients.

SETTING

Department of Ophthalmology, University Hospital of Vienna, Vienna Austria.

METHODS

Between 1993 and 1998, foldable toric single-piece plate-haptic silicone IOLs were implanted in 37 eyes (30 patients). The cylindrical IOL power was 2.00 diopters (D) (n = 29), 3.50 D (n = 7), or 4.00 D (n = 1). Phacoemulsification was performed through a scleral or a corneal sutureless self-sealing incision. Outcomes of Snellen visual acuity (without, with spherical, and with best correction), refractive and keratometric astigmatism, and IOL rotation after early postoperative (mean 15.9 days +/- 10.1 [SD]) and long-term (mean 20.3 +/- 16.6 months) follow-ups were evaluated.

RESULTS

At last follow-up, 31 eyes (83.8%) had a spherically corrected and 34 (91.9%) a best corrected visual acuity of 0.5 (20/40) or better. Mean preoperative refractive and keratometric astigmatism was 2.68 and 2.70 D, respectively. At the last postoperative follow-up, mean refractive astigmatism was reduced to 0.84 D; keratometric astigmatism was 2.30 D. In 7 eyes (18.9%), the IOL axis was rotated a maximum of 25 degrees. In all 37 eyes, the axis of the toric IOL remained within 30 degrees of rotation.

CONCLUSIONS

Early postoperative and long-term follow-ups showed effective and stable correction of astigmatism after implantation of a foldable toric posterior chamber silicone IOL.

The capsular tension ring: designs, applications, and techniques

Originally, the open poly(methyl methacrylate) (PMMA) capsular tension ring (CTR) was designed to compensate for zonular defects or to stretch the posterior capsule in highly myopic eyes not receiving an intraocular lens (IOL). We address the variety of subsequent designs, applications, and techniques that have evolved. With pre-existing or intraoperative zonular defects, a standard CTR may be inserted before or at any time during cataract removal to maintain or re-establish an extended capsular diaphragm. For profound zonular dialysis or weakness, a CTR was designed for scleral fixation. Capsular tension rings with integrated tinted sector shields have been developed to compensate for sector iris colobomas or aniridia. The CTR has also been used as a measuring gauge for in vivo quantification of capsule dimensions and postoperative capsular shrinkage. The CTR has improved control during primary posterior capsulorhexis and prevented oval distortion along the lens axis postoperatively. During combined cataract and vitreous surgery, a CTR prevents capsule damage and provides undisturbed peripheral visualization before IOL implantation. Capsular tension rings may also influence capsule opacification formation. A special band-shaped CTR with sharp edges was developed to inhibit lens epithelial cell migration and avoid capsulorhexis-optic contact.