Methodological approaches to measuring mental health in a cost-of-living crisis: A rapid review

BACKGROUND

Cost-of-living crises are damaging to population mental health and require a public health response. It is important to assess whether public health interventions are effective. We aimed to identify population-level methods and measures and the appropriateness of the measures for vulnerable populations.

METHODS

A rapid evidence review was undertaken. Nineteen databases, including grey literature, were searched for evidence published between 1970 and April 2023.

RESULTS

Seven reviews, nine primary studies and two reports from grey literature were identified. Methods consisted of analyses of existing data from national or regional cohort studies, household panel surveys, repeated cross-sectional surveys, routine medical data, or data on suicide death rates. Twelve brief validated mental health measurement tools, embedded in population-level surveys, were identified. Two quasi-experimental studies used data from a UK household panel survey to examine the impact of the introduction of specific welfare policies on mental health. Studies identified socio-economic vulnerabilities, but it was not possible to determine whether data were effectively captured from people from minority ethnic groups.

CONCLUSION

Population-level surveys can be used in quasi-experimental studies to measure the effects of a public health initiative with specific roll out dates to tackle cost-of-living impacts. It is unclear as to whether the identified methods and tools are suitable for use with people from minority ethnic groups.

''I felt marvellous e-cycling. If I had long hair I would have flicked it": a qualitative investigation of the factors associated with e-cycling engagement among adults with type 2 diabetes

Background

Physical activity (PA) is a key component in the management of type 2 diabetes. However, this population have low rates of PA engagement. Electrically assisted cycling has been identified as a means through which to increase PA by incorporating activity into daily life, while overcoming some of the barriers to conventional cycling. The determinants of e-cycling among people living with chronic disease are largely unknown. The aim of this research was to explore the determinants of e-cycling among individuals with type 2 diabetes using the Theoretical Domains Framework (TDF) and the Capability, Opportunity and Motivation for Behaviour change model (COM-B). This information is important for determining the suitability of future e-cycling initiatives and, if appropriate, inform future e-cycling interventions.

Method

One-to-one semi structured interviews were conducted with 16 participants from the e-cycling arm of a pilot randomised controlled trial between September 2019 and April 2020. The TDF was used to develop the interview guide. The framework method of analysis was used, incorporating both deductive and inductive reasoning. A conceptual model of the factors that influence e-cycling in this population was created.

Results

The most commonly reported TDF domains were skills, knowledge, belief about capabilities, belief about consequences and environmental context and resources. Specifically, e-bike training facilitated e-cycling engagement by providing participants with the skills, knowledge, and confidence needed to ride the e-bike and ride on the road. In addition, the enjoyment of e-cycling was a key facilitator to engagement. Participants engaged in e-cycling to improve their health rather than for environmental reasons. Most barriers to e-cycling related to the natural or physical environment.

Conclusion

This study provides insight into the personal, social, and environmental factors associated with e-cycling in this population. The findings of this study can be used to develop a more refined e-cycling intervention targeting the factors identified as influencing e-cycling engagement. In addition, this information will help in the selection of mechanistic outcome measures for evaluation.

Prehabilitation for frail patients undergoing total hip or knee replacement: protocol for the Joint PREP feasibility randomised controlled trial

BACKGROUND

Approximately, 8% of community-based adults aged ≥ 50 years in England are frail. Frailty has been found to be associated with poorer outcomes after joint replacement. Targeting frailty preoperatively via exercise and protein supplementation has the potential to improve outcomes for people undergoing joint replacement. Prior to proceeding with a randomised controlled trial (RCT), a feasibility study is necessary to address key uncertainties and explore how to optimise trial design and delivery.

METHODS

The Joint PRehabilitation with Exercise and Protein (Joint PREP) study is a feasibility study for a multicentre, two-arm, parallel group, pragmatic, RCT to evaluate the clinical and cost-effectiveness of prehabilitation for frail patients undergoing total hip or knee replacement. Sixty people who are ≥ 65 years of age, frail according to the self-reported Groningen Frailty Indicator, and scheduled to undergo total hip or knee replacement at 2-3 hospitals in England and Wales will be recruited and randomly allocated on a 1:1 ratio to the intervention or usual care group. The usual care group will receive the standard care at their hospital. The intervention group will be given a daily protein supplement and will be asked to follow a home-based, tailored daily exercise programme for 12 weeks before their operation, in addition to usual care. Participants will be supported through six follow-up calls from a physiotherapist during the 12-week intervention period. Study questionnaires will be administered at baseline and 12 weeks after randomisation. Embedded qualitative research with patients will explore their experiences of participating, reasons for nonparticipation, and/or reasons for withdrawal or treatment discontinuation. Primary feasibility outcomes will be eligibility and recruitment rates, adherence to the intervention, and acceptability of the trial and the intervention.

DISCUSSION

This study will generate important data regarding the feasibility of a RCT to evaluate a prehabilitation intervention for frail patients undergoing total hip and knee replacement. A future phase-3 RCT will determine if preoperative exercise and protein supplementation improve the recovery of frail patients after primary joint replacement.

TRIAL REGISTRATION

ISRCTN11121506, registered 29 September 2022.

Diet After Ileostomy Study: an observational study describing dietary intake and stoma-related symptoms in people with an ileostomy

BACKGROUND

People with ileostomy are frequently advised to avoid specific foods and food groups, making it plausible that they are at risk of a range of nutrition-related adverse health consequences. Despite this there has been no recent study in the United Kingdom describing dietary intake, symptoms and food avoidance in people with ileostomy or post-reversal.

METHODS

A cross-sectional study was conducted at different time points in people with ileostomy and reversal. Participants were recruited at 6-10 weeks post-formation (n = 17) and ≥12 months with established ileostomy (n = 16) and with reversal (n = 20). In all participants, ileostomy/bowel-related symptoms in the previous week were assessed using a study-specific questionnaire. Dietary intake was assessed using three online diet recalls or 3-day dietary records. Food avoidance and reasons for food avoidance were assessed. Data were summarised using descriptive statistics.

RESULTS

Participants reported a few ileostomy/bowel-related symptoms in the previous week. However, over 85% of participants reported avoiding foods, particularly fruits and vegetables. At 6-10 weeks the most common reason was being advised to do so (71%), although 53% avoided foods due to gas. At ≥12 months the most common reasons were foods visible in the bag (60%) or advised to do so (60%). Reported intakes of most nutrients were comparable to population medians, apart from lower fibre in people with ileostomy. Intakes of free sugars and saturated fats were above recommended levels in all groups, due to high consumption of cakes and biscuits and sugar-sweetened drinks.

CONCLUSION

After the initial healing period, foods should not be automatically excluded unless found to be problematic after reintroduction. There may be a need for healthy eating advice for people with established ileostomies and post-reversal, targeting discretionary high-fat, high-sugar foods.

Electrically assisted cycling for individuals with type 2 diabetes mellitus: a pilot randomized controlled trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) and its associated complications puts considerable strain on healthcare systems. With the global incidence of T2DM increasing, effective disease management is essential. Physical activity (PA) is a key component of T2DM management; however, rates of PA engagement are low in this population. Developing effective and sustainable interventions that encourage PA is a high priority. Electrically assisted bicycles are becoming increasingly popular and may increase PA in healthy adults. This study aimed to provide evidence of the feasibility of conducting a randomized controlled trial to evaluate the efficacy of an e-cycling intervention to increase PA and improve health in individuals with T2DM.

METHODS

A parallel-group two-arm randomized, waitlist-controlled pilot study was conducted. Individuals were randomized to either an e-bike intervention or standard care. The intervention incorporated two one-to-one e-bike skills training and behavioural counselling sessions delivered by a community-based cycling charity, followed by a 12-week e-bike loan with two further sessions with the instructors. Feasibility was assessed via measures related to recruitment, retention and intervention implementation. Post-intervention interviews with instructors and participants explored the acceptability of the study procedures and intervention. Clinical, physiological and behavioural outcomes were collected at baseline and post-intervention to evaluate the intervention's potential.

RESULTS

Forty participants (M_age = 57) were randomized, of which 34 were recruited from primary care practices. Thirty-five participants were retained in the trial. The intervention was conducted with high fidelity (> 80% content delivered). E-bike training provided participants with the skills, knowledge and confidence needed to e-bike independently. Instructors reported being more confident delivering the skills training than behavioural counselling, despite acknowledging its importance. The study procedures were found to be acceptable to participants. Between-group differences in change during the intervention were indicative of the interventions potential for improving glucose control, health-related quality of life and cardiorespiratory fitness. Increases in overall device measured moderate-to-vigorous PA behaviour following the intervention were found, and there was evidence that this population self-selected to e-cycle at a moderate intensity.

CONCLUSIONS

The study's recruitment, retention, acceptability and potential efficacy support the development of a definitive trial subject to identified refinements.

TRIAL REGISTRATION

ISRCTN, ISRCTN67421464 . Registered 17/12/2018.

Healthcare professionals' perspectives on dietary advice provided to people with an ileostomy

BACKGROUND

Diet is a common concern amongst people with an ileostomy as it can be associated with serious and burdensome complications, e.g., dehydration and obstruction, and dietary advice is often unsatisfactory. In this study, we explored healthcare professionals' (HCPs) perspectives on dietary advice for ileostomy management.

METHODS

Semi-structured interviews were conducted with HCPs, from multiple professions, who provide dietary advice to patients with an ileostomy. A Framework approach to thematic analysis was used to understand and compare HCPs experiences, beliefs, and attitudes that influence how dietary advice is provided and effectiveness of dietary management.

RESULTS

Findings from interviews with 21 HCPs, across three hospitals, related to seven key themes: tailoring of dietary advice to the patient, patient autonomy and communication, HCP knowledge and understanding, patient pathway, mixed messages, access to formal and social support, and patient understanding and relationship with dietary advice. Profession was a strong determinator of what and how dietary advice is provided; however, closer team working increased consistency of dietary advice. Lack of scientific research and consensus contribute to mixed messages and reduce confidence in dietary advice for people with an ileostomy. Due to individual differences between patients, experiential learning with diet is key to self-management and is encouraged in a controlled way by HCPs; however, a lack of 'one size fits all' guidance can be difficult for some.

CONCLUSION

The study findings should inform HCPs caring for patients with an ileostomy, and researchers designing and evaluating interventions, to improve how patients receive dietary advice for ileostomy management. This article is protected by copyright. All rights reserved.

Impact of low iodine diets on ablation success in differentiated thyroid cancer: A mixed-methods systematic review and meta-analysis

BACKGROUND

Debate remains regarding whether to recommend a low iodine diet (LID) before radioactive-iodine treatment and its duration and stringency. This mixed-methods review aimed to determine if iodine status affects treatment success, the most effective diet to reduce iodine status, and how LID impacts wellbeing.

METHODS

Five electronic databases were searched until February 2021. An effectiveness synthesis (quantitative studies) and views synthesis (qualitative, survey, and experience-based evidence) were conducted individually and then integrated. Quality assessment was undertaken.

RESULTS

Fifty-six quantitative and three qualitative studies were identified. There was greater ablation success for those with an iodine status of <50 mcg/L (or mcg/gCr) compared with ≥250 (odds ratio [OR] = 2.63, 95% confidence interval [CI], 1.18-5.86, n = 283, GRADE certainty of evidence very low). One study compared <50 mcg/L (or mcg/gCr) to 100-199 and showed similar rates of ablation success (OR = 1.59, 95% CI, 0.48-6.15, n = 113; moderate risk of bias). People following a stricter LID before ablation had similar rates of success to a less-strict diet (OR = 0.67, 95% CI, 0.26-1.73, n = 256, GRADE certainty of evidence very low). A stricter LID reduced iodine status more than a less strict (SMD = -0.40, 95% CI, -0.56 to -0.24, n = 816), and reduction was seen after 1 and 2 weeks. The main challenges were a negative impact on psychological health, over restriction, confusion, and difficulty for sub-groups.

CONCLUSIONS

Although a LID of 1-2 weeks reduces iodine status, it remains unclear whether iodine status affects treatment success as only a few low-quality studies have examined this. LIDs are challenging for patients. Higher-quality studies are needed to confirm whether a LID is necessary.

Is glycaemic control associated with dietary patterns independent of weight change in people newly diagnosed with type 2 diabetes? Prospective analysis of the Early-ACTivity-In-Diabetes trial

BACKGROUND

It is unclear whether diet affects glycaemic control in type 2 diabetes (T2D), over and above its effects on bodyweight. We aimed to assess whether changes in dietary patterns altered glycaemic control independently of effects on bodyweight in newly diagnosed T2D.

METHODS

We used data from 4-day food diaries, HbA1c and potential confounders in participants of the Early-ACTivity-In-Diabetes trial measured at 0, 6 and 12 months. At baseline, a 'carb/fat balance' dietary pattern and an 'obesogenic' dietary pattern were derived using reduced-rank regression, based on hypothesised nutrient-mediated mechanisms linking dietary intake to glycaemia directly or via obesity. Relationships between 0 and 6 month change in dietary pattern scores and baseline-adjusted HbA1c at 6 months (n = 242; primary outcome) were assessed using multivariable linear regression. Models were repeated for periods 6-12 months and 0-12 months (n = 194 and n = 214 respectively; secondary outcomes).

RESULTS

Reductions over 0-6 months were observed in mean bodyweight (- 2.3 (95% CI: - 2.7, - 1.8) kg), body mass index (- 0.8 (- 0.9, - 0.6) kg/m²), energy intake (- 788 (- 953, - 624) kJ/day), and HbA1c (- 1.6 (- 2.6, -0.6) mmol/mol). Weight loss strongly associated with lower HbA1c at 0-6 months (β = - 0.70 [95% CI - 0.95, - 0.45] mmol/mol/kg lost). Average fat and carbohydrate intakes changed to be more in-line with UK healthy eating guidelines between 0 and 6 months. Dietary patterns shifting carbohydrate intakes higher and fat intakes lower were characterised by greater consumption of fresh fruit, low-fat milk and boiled/baked potatoes and eating less of higher-fat processed meats, butter/animal fats and red meat. Increases in standardised 'carb/fat balance' dietary pattern score associated with improvements in HbA1c at 6 months independent of weight loss (β = - 1.54 [- 2.96, - 0.13] mmol/mol/SD). No evidence of association with HbA1c was found for this dietary pattern at other time-periods. Decreases in 'obesogenic' dietary pattern score were associated with weight loss (β = - 0.77 [- 1.31, - 0.23] kg/SD) but not independently with HbA1c during any period.

CONCLUSIONS

Promoting weight loss should remain the primary nutritional strategy for improving glycaemic control in early T2D. However, improving dietary patterns to bring carbohydrate and fat intakes closer to UK guidelines may provide small, additional improvements in glycaemic control.

TRIAL REGISTRATION

ISRCTN92162869 . Retrospectively registered on 25 July 2005.

Pre-admission interventions (prehabilitation) to improve outcome after major elective surgery: a systematic review and meta-analysis

OBJECTIVE

To determine the benefits and harms of pre-admission interventions (prehabilitation) on postoperative outcomes in patients undergoing major elective surgery.

DESIGN

Systematic review and meta-analysis of randomised controlled trials (RCTs) (published or unpublished). We searched Medline, Embase, CENTRAL, DARE, HTA and NHS EED, The Cochrane Library, CINAHL, PsychINFO and ISI Web of Science (June 2020).

SETTING

Secondary care.

PARTICIPANTS

Patients (≥18 years) undergoing major elective surgery (curative or palliative).

INTERVENTIONS

Any intervention administered in the preoperative period with the aim of improving postoperative outcomes.

OUTCOMES AND MEASURES

Primary outcomes were 30-day mortality, hospital length of stay (LoS) and postoperative complications. Secondary outcomes included LoS in intensive care unit or high dependency unit, perioperative morbidity, hospital readmission, postoperative pain, heath-related quality of life, outcomes specific to the intervention, intervention-specific adverse events and resource use.

REVIEW METHODS

Two authors independently extracted data from eligible RCTs and assessed risk of bias and the certainty of evidence using Grading of Recommendations, Assessment, Development and Evaluation. Random-effects meta-analyses were used to pool data across trials.

RESULTS

178 RCTs including eight types of intervention were included. Inspiratory muscle training (IMT), immunonutrition and multimodal interventions reduced hospital LoS (mean difference vs usual care: -1.81 days, 95% CI -2.31 to -1.31; -2.11 days, 95% CI -3.07 to -1.15; -1.67 days, 95% CI -2.31 to -1.03, respectively). Immunonutrition reduced infective complications (risk ratio (RR) 0.64 95% CI 0.40 to 1.01) and IMT, and exercise reduced postoperative pulmonary complications (RR 0.55, 95% CI 0.38 to 0.80, and RR 0.54, 95% CI 0.39 to 0.75, respectively). Smoking cessation interventions reduced wound infections (RR 0.28, 95% CI 0.12 to 0.64).

CONCLUSIONS

Some prehabilitation interventions may reduce postoperative LoS and complications but the quality of the evidence was low.

PROSPERO REGISTRATION NUMBER

CRD42015019191.

Dietary management for people with an ileostomy: a scoping review

OBJECTIVE

The objective of this review was to identify and map the evidence for oral dietary management of ileostomies.

INTRODUCTION

Dietary advice is commonly provided for ileostomy management but can be inconsistent, conflicting, and inadequate. There is a lack of high-quality research investigating dietary management of ileostomies. This scoping review highlights gaps in the literature that need addressing to inform practice, and identifies dietary strategies and outcomes to be investigated in future studies.

INCLUSION CRITERIA

Evidence relating to the use of oral dietary strategies to manage complications and nutritional consequences associated with having an ileostomy was included. Evidence included all types of original research (ie, quantitative and qualitative methodologies, expert opinion articles, and consensus guidelines).

METHODS

This review followed JBI methodology for scoping reviews. A pre-determined search of 13 databases, including MEDLINE, Embase, and Web of Science, was conducted in August 2019. The search was not limited by date, but during screening, expert opinion evidence was limited to 2008 onward. Data extraction was carried out by two reviewers for each study/article using a database tool designed specifically for this review. Results are presented using a combination of tabular summaries and narrative reports.

RESULTS

Thirty-one research studies were included: 11 experimental (including four crossover randomized controlled trials), three pre-post design, 13 observational (12 cross-sectional, one longitudinal), and four qualitative. Forty-four expert opinion articles/guidelines were also included. In experimental studies, nine nutrient modifications and 34 individual foods/drinks were investigated. In pre-post studies, 10 nutrient modifications, 80 foods/drinks, and 11 eating-related behaviors were investigated. In observational studies, eight nutrient modifications, 94 foods/drinks, and five eating-related behaviors were reported. In qualitative studies, two nutrient modifications, 17 foods/drinks, and one eating-related behavior were reported. In expert opinion articles/guidelines, recommendations relating to 51 nutrient modifications, 339 foods/drinks, and 23 eating-related behaviors were reported. Although large numbers of individual foods and drinks were suggested to be associated with outcomes relating to ileostomy management, findings from observational studies showed these were generally reported by <50% of people with an ileostomy. The most common nutrients reported in association with outcomes related to ileostomy management were fiber, fat, and alcohol. Across most outcomes and studies/expert opinion, low fiber and low fat were suggested to be beneficial, while alcohol was detrimental. Other nutrient associations frequently reported in expert opinion (but with minimal attention in research studies) included negative consequences of caffeinated drinks and positive effects of white starchy carbohydrates on stoma output. Output volume and consistency were the most commonly reported outcomes relating to ileostomy management across all study types. Flatulence and odor were also common outcomes in observational studies.

CONCLUSIONS

This review found an abundance of literature, particularly expert opinion, reporting on dietary management for people with an ileostomy. However, this literature was highly heterogeneous in terms of dietary strategies and outcomes reported. It is likely that most dietary advice provided in practice is based on expert opinion with some supported by limited research. High-quality research investigating the effect of the dietary strategies identified in this review on commonly associated outcomes relating to ileostomy management is needed to improve evidence-based advice.

Exploring dietitians' practice and views of giving advice on dietary patterns to patients with type 2 diabetes mellitus: A qualitative study

BACKGROUND

Dietary guidelines for type 2 diabetes mellitus (T2DM) emphasise weight management and individualised total carbohydrate intake. Evidence on the most effective dietary patterns (DPs) for T2DM management is mixed, potentially leading to variations in the advice that dietitians provide. The present study aimed to explore dietitians' practice of DP advice provision to adults with T2DM, as well as understand their views when advising their patients on the DPs deemed effective for glycaemic management or recommended by current guidelines.

METHODS

Semi-structured interviews were conducted with 12 UK-registered dietitians, with experience in consulting adults with T2DM. Dietitians were asked for their views on five DPs recommended for glycaemic management of T2DM. Interview transcripts were analysed using deductive and inductive thematic analysis.

RESULTS

Nine themes were identified that draw attention to DP advice provision practices, the five DPs (low-carbohydrate, low-fat, low-glycaemic index, Mediterranean diet and Dietary Approaches to Stop Hypertension diet), other DPs, the barriers and facilitators to DP advice provision and following this advice, and the factors affecting the provision of DP advice. Participants' current practice of DP advice provision to patients with T2DM was perceived to be individualised and patient-centred. Participants discussed their current practice and perceptions of available evidence and how patients respond to advice on the DPs shown to be effective for glycaemic management. Several barriers to providing advice on specific DPs, including safety and compliance challenges, were identified. Participants also highlighted factors that would facilitate the provision of advice on specific DPs and would help patients to follow this advice, including social support, educational resources and more robust scientific evidence.

CONCLUSIONS

The findings of the present study provide important insights regarding dietitians' views of promoting whole DPs to patients with T2DM. Emerged barriers and facilitators should be considered when developing future guidance for dietetic practice to support patients with following whole DPs for T2DM management.

Exploring support needs of people living with diabetes during the coronavirus COVID-19 pandemic: insights from a UK survey

INTRODUCTION

The coronavirus COVID-19 pandemic has radically compromised healthcare for people living with chronic conditions such as diabetes. Government-imposed restrictions to contain the spread of the virus have forced people to suddenly adjust their lifestyle. This study aimed to capture the impact of the pandemic on people living with diabetes and the views of these individuals on ways in which the information, advice and support they are receiving could be improved.

RESEARCH DESIGN AND METHODS

An online anonymous survey was distributed across the UK during the first lockdown and initial easing. The survey comprised questions about confidence in diabetes self-management, resources used to obtain information, advice and support, and opinions on how these could be improved. Open-ended questions captured subjective experiences.

RESULTS

The survey was completed by 773 adults with diabetes (69.2% type 1, 28.5% type 2). There was notable variability in the impact of the pandemic on confidence in self-management, with confidence having deteriorated most commonly in the ability to take care of own mental well-being (37.0% respondents) and improved most commonly in maintaining a healthy weight (21.1% respondents). 41.2% of respondents living alone reported not receiving any outside support. The quality of information, advice and support received from the healthcare team was rated poorly by 37.2%. Respondents sought greater communication and tailored advice from their care team, clear and consistent information from the government and news channels, and improved understanding of diabetes and its challenges from their personal networks and employers.

CONCLUSION

Adjusting to the COVID-19 pandemic has strained the mental health and well-being of people living with diabetes. Diabetes care teams must receive assistance to support these individuals without risking further inequalities in access to healthcare. Equipping personal networks and employers with knowledge on diabetes and skills to support self-management may reduce the burden on the National Health Service.

Provision of dietary advice for people with an ileostomy: a survey in the UK and Ireland

AIM

The aim was to explore whether people with an ileostomy in the UK and Ireland receive the dietary advice they require.

METHOD

An online survey with multiple-choice questions asked people with an ileostomy about the dietary advice they received and would have preferred to receive. Participants were recruited via websites of the Ileostomy and Internal Pouch Association and Crohn's and Colitis UK and via social media. People with a current ileostomy, age 16 years or over, and living in the UK or Ireland were eligible for inclusion. Responses were analysed using descriptive statistics.

RESULTS

In all, 291 eligible responses were received and included in the analysis; 201 (69%) received advice on diet for their ileostomy from a healthcare professional or the internet. Of the 90 who did not receive dietary advice, 82 (91%) would have liked advice. Stoma nurses were the most common source of dietary advice (55%), but many other sources were frequently reported. Most (62%) felt that at least some dietary advice they received was conflicting. Over half (55%) felt anxious about managing their diet with a new ileostomy, 39% were confused, and 31% frustrated. Of 291 respondents, 29% received advice from a dietitian compared to 60% who would have preferred advice from a dietitian.

CONCLUSION

Many people undergoing ileostomy surgery do not receive the dietary advice and support they require. Healthcare professionals working with people with an ileostomy should be mindful they are often anxious about their diet and require clear and consistent dietary advice and support.

The impact of e-cycling on travel behaviour: A scoping review

INTRODUCTION

Electrically assisted bicycles (e-bikes) have become increasingly popular in the past decade. This review aimed to scope the literature to identify what is known about the frequency and duration of e-bike use, their impact on travel behaviour, the purposes for which e-bikes are used and factors associated with e-bike use. In addition, the review aimed to identify gaps in the literature and highlight future research priorities.

METHODS

A scoping review of published and unpublished literature in any language. Relevant articles were identified through searching six databases, two grey literature platforms and reference lists. Searches were conducted until August 2019. Data were extracted using a standardised extraction form and descriptive and narrative results are provided.

RESULTS

Seventy-six studies met the inclusion criteria. The volume of research has increased since 2017 and primarily examines personal e-bike use, as opposed to e-bike share/rental schemes or organizational e-bike initiatives. The use of e-bikes increased the frequency and duration of cycling compared to conventional cycling and may help overcome barriers associated with conventional cycling. The uptake in e-cycling largely substitutes for conventional cycling or private car journeys, though the degree of substitution depends on the primary transport mode prior to e-bike acquisition. E-bikes are primarily used for utilitarian reasons, though older adults also engage in recreational e-cycling. Research priorities include quantitatively examining e-bike use, their impact on overall transport behaviour and identifying determinants of e-cycling to inform intervention and policy.

CONCLUSIONS

This review suggests that the personal use of e-bikes is associated with a reduction in motorized vehicle use, which has potential positive impacts on the environment and health. The impacts of e-bike share schemes and workplace initiatives are less well understood. Evidence describing the purposes for which e-bikes are used, and the factors associated with usage, are useful to inform e-cycling promotion policy.

Weight maintenance interventions for people with type 2 diabetes mellitus: a systematic review protocol

BACKGROUND

Weight loss maintenance is a challenge for people with type 2 diabetes mellitus (T2DM), which attenuates the long-term benefits of weight loss for diabetes management. Medication, specific dietary requirements and the psychosocial burden of T2DM signify that weight loss maintenance designed for obesity may not suit people with T2DM. The primary objective of this review is to comprehensively evaluate existing weight maintenance interventions for people with or at high risk of T2DM.

METHODS

We registered a protocol for the systematic review and meta-analysis of randomised and non-randomised weight maintenance interventions for T2DM. Studies included will have been carried out in adults with clinical diagnosis of T2DM or pre-diabetes. All intervention types will be accepted (e.g. behavioural/lifestyle change and pharmacological). The primary outcomes will be weight control, glycaemic control and adverse effects. Secondary outcomes will include cardiovascular risk factors (e.g. total cholesterol, LDL-cholesterol, blood pressure control), psychological wellbeing (including health-related quality of life), change in glucose medication and waist circumference. Multiple electronic databases will be searched such as MEDLINE, EMBASE, Web of Science, PsychINFO and international registers (e.g. Cochrane Central Register of Controlled Trials, WHO ICTRP). OpenGrey will be searched for grey literature. Two researchers will screen all citations and abstracts. This process will also be conducted by an additional researcher using a semi-automated tool to reduce human error. Full-text articles will be further examined by the researchers to select a final set for further analysis, and a narrative synthesis of the evidence will be presented. Potential sources of heterogeneity will be assessed, and a meta-analysis will be conducted if feasible. Risk of bias will be evaluated using the Cochrane risk of bias tool and the certainty of evidence using the GRADE (grading of recommendations, assessment, development and evaluation) approach.

DISCUSSION

This review will critically appraise existing weight maintenance interventions targeting T2DM. Findings will inform future intervention development to support people with T2DM delay weight regain and prolong successful diabetes management.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020168032.

Electrically assisted cycling for individuals with type 2 diabetes mellitus: protocol for a pilot randomized controlled trial

Background

The global incidence of type 2 diabetes mellitus (T2DM) is increasing. Given the many complications associated with T2DM, effective management of the disease is crucial. Physical activity is considered to be a key component of T2DM management. However, people with T2DM are generally less physically active than individuals without T2DM and adherence to physical activity is often poor following completion of lifestyle interventions. As such, developing interventions that foster sustainable physical activity is of high priority. Electrically assisted bicycles (e-bikes) have been highlighted as a potential strategy for promoting physical activity in this population. E-bikes provide electrical assistance to the rider only when pedalling and could overcome commonly reported barriers to regular cycling. This paper describes the protocol of the PEDAL-2 pilot randomized controlled trial, an e-cycling intervention aimed at increasing physical activity in individuals with T2DM.

Methods

A parallel-group two-arm randomized waitlist-controlled pilot trial will be conducted. Forty individuals with T2DM will be randomly assigned, in a 1:1 allocation ratio, to an e-cycling intervention or waitlist control. Recruitment and screening will close once 20 participants have been randomized to each study arm. The intervention will involve e-bike training with a certified cycle instructor and provision of an e-bike for 12 weeks. Data will be collected at baseline, during the intervention and immediately post-intervention using both quantitative and qualitative methods. In this trial, the primary interests are determination of effective recruitment strategies, recruitment and consent rates, adherence and retention and delivery and receipt of the intervention. The potential impact of the intervention on a range of clinical, physiological and behaviour outcomes will be assessed to examine intervention promise. Data analyses will be descriptive.

Discussion

This paper describes the protocol for the PEDAL-2 pilot randomized controlled trial. Results from this trial will provide information on trial feasibility and identify the promise of e-cycling as a strategy to positively impact the health and behaviour of individuals with T2DM. If appropriate, this information can be used to design and deliver a fully powered definitive trial.

Trial registration

ISRCTN, ISRCTN67421464. Registered 03/01/2019.

Health benefits of electrically-assisted cycling: a systematic review

BACKGROUND

Electrically assisted bicycles (e-bikes) have been highlighted as a method of active travel that could overcome some of the commonly reported barriers to cycle commuting. The objective of this systematic review was to assess the health benefits associated with e-cycling.

METHOD

A systematic literature review of studies examining physical activity, cardiorespiratory, metabolic and psychological outcomes associated with e-cycling. Where possible these outcomes were compared to those from conventional cycling and walking. Seven electronic databases, clinical trial registers, grey literature and reference lists were searched up to November 2017. Hand searching occurred until June 2018. Experimental or observational studies examining the impact of e-cycling on physical activity and/or health outcomes of interest were included. E-bikes used must have pedals and require pedalling for electric assistance to be provided.

RESULTS

Seventeen studies (11 acute experiments, 6 longitudinal interventions) were identified involving a total of 300 participants. There was moderate evidence that e-cycling provided physical activity of at least moderate intensity, which was lower than the intensity elicited during conventional cycling, but higher than that during walking. There was also moderate evidence that e-cycling can improve cardiorespiratory fitness in physically inactive individuals. Evidence of the impact of e-cycling on metabolic and psychological health outcomes was inconclusive. Longitudinal evidence was compromised by weak study design and quality.

CONCLUSION

E-cycling can contribute to meeting physical activity recommendations and increasing physical fitness. As such, e-bikes offer a potential alternative to conventional cycling. Future research should examine the long-term health impacts of e-cycling using rigorous research designs.

Blood Flow Stasis Induced by cw-Nd: YAG Laser Irradiation: Comparative Morphology of Mesenteric and Choroidal Vessels in Pigmented Rabbits

cw-Nd: YAG laser radiation was effective in producing blood flow stasis within arteries (35 – 40 μm in diameter) of pigmented rabbit mesentery (beam spot size: 80 μm; fluence :2 × 104 J cm−2) and choroid (beam spot size : 200 μm; fluence: 6 × 102 J cm−2) However, the mechanism by which this was achieved differed in each case, and depended upon the energy absorbing structures present in the irradiated tissue. In non-pigmented tissue, such as the mesentaty, haemoglobin represents the primary absorption centre, and the temperature attained within the vessel lumen (as inferred from morphological changes) is sufficient to denature plasma proteins, in particular fibrinogen, which consequently occlude the vessel lumen and arrest bleeding. In pigmented tissue, such as the choroid, melanocyte granules represent the primary absorption centre, which is thus shifted from the vessel lumen to the stroma. The temperature rise achieved within the vessel lumen is consequently loweq as evidenced by the absence of plasma protein denaturation. Blood flow stasis nonetheless occurs, but is triggered according to the normal haemostatic mechanism.

Potential of electric bicycles to improve the health of people with Type 2 diabetes: a feasibility study

AIM

To explore in a feasibility study whether 'e-cycling' was acceptable to, and could potentially improve the health of, people with Type 2 diabetes.

METHODS

Twenty people with Type 2 diabetes were recruited and provided with an electric bicycle for 20 weeks. Participants completed a submaximal fitness test at baseline and follow-up to measure predicted maximal aerobic power, and semi-structured interviews were conducted to assess the acceptability of using an electric bicycle. Participants wore a heart rate monitor and a Global Positioning System (GPS) receiver in the first week of electric bicycle use to measure their heart-rate during e-cycling.

RESULTS

Eighteen participants completed the study, cycling a median (interquartile range) of 21.4 (5.5-37.7) km per week. Predicted maximal aerobic power increased by 10.9%. Heart rate during electric bicycle journeys was 74.7% of maximum, compared with 64.3% of maximum when walking. Participants used the electric bicycles for commuting, shopping and recreation, and expressed how the electric bicycle helped them to overcome barriers to active travel/cycling, such as hills. Fourteen participants purchased an electric bicycle on study completion.

CONCLUSIONS

There was evidence that e-cycling was acceptable, could increase fitness and elicited a heart rate that may lead to improvements in cardiometabolic risk factors in this population. Electric bicycles have potential as a health-improving intervention in people with Type 2 diabetes.

Oculoplastic Surgery with a Contact Nd:YAG Laser Silica Scalpel. A Case Report

Baso-cellular carcinomas involving the medial canthal regions of both eyes were resected using a 10 W cw-Nd: YAG laser scalpel.

The wound bed was repaired one side by a free, split-thickness graft and on the other by a frontal pedicle flap. Surgery was, for the most part, virtually bloodless. Since laser radiation immediately seals both capillaries and lymphatics, the incidence of postoperative hemorrhage and edema was significantly less than after cold scalpel surgery. Healing was uneventful. The advantages of laser-assisted surgery are worthy of consideration: not only is the operation time markedly curtailed, but the wound healing response is excellent, with only a minimal inflammatory reaction.

Validation of the English Version of the 14-Item Mediterranean Diet Adherence Screener of the PREDIMED Study, in People at High Cardiovascular Risk in the UK

The aim of this study was to examine the validity of the English version of the PREvencion con DIetaMEDiterranea (PREDIMED) 14-item Mediterranean Diet Adherence Screener (MEDAS), a brief questionnaire assessing adherence to the Mediterranean diet (MedDiet), which was used in the PREDIMED trial for assessment and immediate feedback. This instrument (MEDAS) was administered to 96 adults with a high cardiovascular risk (66% women, mean age 68.3 ± 6.0 years), recruited from general practices in Bristol, UK. Participants then completed a 3-day estimated food record, and the MEDAS was administered again one month later. A MedDiet score (range = 0-14) was calculated from the MEDAS' administrations and food record to assess concurrent validity and test-retest reliability. Predictive validity was assessed by examining the association of the MEDAS-derived score with cardiometabolic risk factors and dietary intakes derived from the food records. The MEDAS-derived MedDiet score was higher by 1.47 points compared to food records (5.47 vs.4.00, p < 0.001), correlated moderately with the record-derived score (r = 0.50, p < 0.001; ICC = 0.53, p < 0.001) and there was borderline fair agreement between the two methods (κ = 0.19, 95% CI 0.07-0.31, p = 0.002; 95% limits of agreement -2.2, 5.1). Exact agreement within score categories and gross misclassificationwere 45.8% and 21.9%, respectively. The distribution of dietary intakes, reported on the food records by the MEDAS-derived total MedDiet score, was in the expected direction, but no association was observed with cardiometabolic risk factors. The two administrations of the MEDAS produced similar mean total MedDiet scores (5.5 vs. 5.4, p = 0.706), which were correlated (r and ICC = 0.69, p < 0.001) and agreed fairly (κ = 0.38, 95% CI 0.24-0.52, p < 0.001; 95% limits of agreement -3.1, 3.2). The English version of the MEDAS has acceptable accuracy and reliability for assessing MedDiet adherence among individuals with a high cardiovascular risk, in the UK, and can be used to rank individuals according to MedDiet adherence in research and practice.

Transconjunctival application of mitomycin C in combination with laser sclerostomy ab interno: a long-term morphological study of the postoperative healing process

The precise mechanism whereby mitomycin C enhances IOP reduction in glaucoma filtering surgery still eludes us. Ten rabbits received full-thickness Nd:YAG laser sclerostomy ab interno and adjunctive intraoperative treatment with mitomycin C (MMC) applied topically over the intact conjunctiva (0.5 mg ml-1 for 5 min). A systematic ultrastructural analysis of the fistulas and surrounding tissue was then conducted in conjunction with clinical observations, over the ensuing 10 weeks. In order to investigate also the extent to which MMC impedes fistula occlusion in the absence of percolating aqueous humour, we created non-perforating ('half-thickness') sclerostomies ab interno in three additional rabbits, one with and two without MMC therapy. Transconjunctival MMC application resulted in no serious complications. Eight of the ten full-thickness fistulas remained patent throughout the study, maintaining significant IOP reduction; the other two sclerostomies were compromised by iris incarceration. The MMC-treated, half-thickness canal remained as a tissue-free cul de sac; the two non-treated ones became completely occluded within one week without having recourse to extraocular cell populations. MMC suppressed the migration and proliferation of fibroblasts, macrophages and clump cells from the episclera, sclera, ciliary body and iris root. Repolymerization of heat-damaged collagen was abortive; neosynthesis was not observed. Myofibroblasts were encountered in the vicinity of the sclerostomy canals, and, after the fifth week, these cells were also found to be deployed as a canal-lining layer, delimiting the lumen from the surrounding stroma along most of the fistula length. Towards the external ostium, this layer of myofibroblasts was incomplete or absent. Near the internal ostium, lining cells were derived from the corneal endothelium. The transconjunctival mode of applying MMC appears to be efficient. This antifibrotic drug exerts its inhibitory influence by suppressing not only cell migration and proliferation, but also phagocytic and synthetic activities. However, exposed tissues are not acellular, and amongst the populations present, myofibroblasts are found to dominate the scene. The canal-delimiting cellular lining may play a role in maintaining fistula patency in MMC-treated eyes.

Morphological changes elicited in skeletal muscle by a Nd:YAG laser scalpel and electrocautery during surgical reduction of the human tongue

A Nd:YAG laser scalpel was used for the surgical reduction of a human hyperplastic tongue. This instrument combines a fine cutting precision with haemostatic properties, whereby loss of blood is minimized and the surgeon's field of view unimpeded by flooding from the damaged capillary bed. The coagulative properties of Nd:YAG laser light are, however, insufficient to effect blood flow stasis in larger calibre vessels (arteries > 2 mm; veins > 3-5 mm), such as those located at the base of the tongue. For this purpose, bipolar diathermy (electrocautery) was employed. The ultrastructural changes incurred by skeletal muscle fibres using these two "heat" sources were compared. The damage profile elicited using each modality was similar: coagulation of myofilamentous proteins leads to destruction of fibrillar architecture with concomitant loss of periodic banding; on moving away from the wound margin, characteristic features are gradually restored. As the severity of these heat-induced effects decreases, there is a corresponding increase in superimposed dislocation and tearing phenomena induced by post-treatment swelling.

Spontaneous and Pharmacologically-Modulated Wound Healing after Nd: Yag Laser Sclerostomy Ab Interno in Rabbits

The course of tissue repair evoked by Nd:YAG laser sclerostomy ab interno and the effect of mitomycin-C on same were investigated ultrastructurally in 15 rabbits. In ten of them, the dynamics of the spontaneous postoperative healing response (i.e. in the absence of medication) was analyzed at two-day intervals by light- and electron microscopy. In two, fibroblast activity was assessed autoradiographically. In the last three rabbits, the sclerostomy site was exposed transconjunctivally to mitomycin-C (0.5 mg/ml; 5 minutes) before surgery, and morphological analysis was done on postoperative days 6 and 12.

RESULTS

In the spontaneously healing group, blebs disappeared within five days of surgery. This corresponded to a massive invasion of macrophages and fibroblasts from the episclera and iris root. The sheath of coagulated tissue around the fistula appeared to act as a barrier to cell migration from the sclera itself at this stage. By days 8 to 12, the canal had become occluded by a network of cells and capillaries, and collagen fibrils in the coagulation sheath had undergone repolymerization. In the mitomycin-C group, large filtering blebs and patent, cell-free fistulas were observed over the entire period. Although applied transconjunctivally, the drug penetrated the whole scleral depth, as the iris root and ciliary body cell reaction was inhibited. Repolymerization of heat-damaged collagen was also hindered. The overall findings provide information on the sequence of repair events following laser sclerostomy. Local, non-invasive application of mitomycin-C delays the onset of this process, not only by inhibition of cell proliferation but also by suppressing the collagen recovery.

A new laser scalpel--a brief report

One may consider the clad silica fibre cutting probe as a cheap alternative of the popular sapphire probe, sharing some of its properties. Made of silica, the scalpels have a fair heat tolerance and may be used without cooling by liquids or gas as is necessary with sapphire blades. The laser scalpel described here is driven (powered) with a 10 W cw Nd:YAG laser energy source (1064 nm) and possesses good cutting and haemostatic properties. It may also be used with lasers emitting other wavelengths. One may assume that a diode laser emitting in the near infrared (800-810 nm) may have very similar, although no analogous cutting properties when used with the described scalpel.

The repair response following Nd:YAG laser sclerostomy ab interno in rabbits

This study was undertaken to examine ultrastructurally the course of tissue regeneration after thermally-induced laser sclerostomy and compare it with the post-operative clinical events in a rabbit model. Applying a continuous wave neodymium:YAG (Nd:YAG) laser, two sclerostomies were created ab interno on one eye in each of ten pigmented rabbits using a 200-microns-diameter quartz optical fiber; the unoperated fellow-eyes served as controls. Intraocular pressure (IOP) was measured daily before and after surgery. Animals were observed post-operatively for up to 16 days. Well-defined filtering blebs and a low complication rate demonstrated the success of the procedure. IOP was significantly lowered during the entire course of the observation period but after the fifth day, the conjunctival blebs had disappeared. The morphology of the changes in the sclerostomy fistulas were analysed at 2-day intervals by light and electron microscopy. Immediately after surgery, the canal was ensheathed by an approximately 100-microns-thick layer of coagulated collagenous tissue in which two zones could be distinguished according to the intensity of damage. Within 5 days, the inner and outer canal openings were invaded by macrophages and fibroblasts originating from the iris root and episclera, respectively. The former cells were engaged in the phagocytosis of disintegrated collagen adjacent to the lumen. More distally located fibrils which had incurred less severe damage, had retained their fibrillar structure but had lost banding periodicity. After thermal stress had faded, they appeared to undergo a process of repolymerisation. By day 10, the lumen had become occluded by a loose meshwork of phagocytes, fibroblasts and proliferating capillaries. These new vessels and the loose nature of the canal-occluding framework and of the surrounding regenerating collagenous tissue could have further permitted percolation and transport of aqueous humor, since IOP remained low, despite the disappearance of filtering blebs. Although the time course of repair is more rapid in rabbits than in humans, the data gleaned nonetheless yield valid information respecting the sequence of events following thermally-induced scleral fistula.

Irradiation of rabbit retina with diode and Nd:YAG lasers

AIMS

This study was carried out to compare the effects of continuous wave infrared laser radiation on pigmented and albino rabbit retinas at two wavelengths: 810 nm (diode) and 1064 nm (Nd:YAG).

METHODS

Transpupillary laser pulses were applied with a spot size of 200 microns and durations of 200 ms (pigmented rabbits) and 0.5-1 s (albino rabbits). Light and electron microscopic analyses were performed immediately after exposure.

RESULTS

In pigmented rabbits, threshold lesions were induced using a power of 100 mW with the diode and 200 mW with the Nd:YAG lasers. Damage was incurred by the retinal pigment epithelium with extension into the superficial and mid choroid posteriorly and into the outer retina anteriorly. In albino rabbits, lesions of comparable anteroposterior extension were identified using a power of 10 W with the Nd:YAG laser. Using diode laser irradiation, a maximum power output of 1.2 W failed to produce discernible lesions.

CONCLUSIONS

The observed patterns of morphological damage are produced by complex tissue radiation interactions. In pigmented animals, this was primarily related to absorption of radiant energy by melanin within the retinal pigment epithelium and the choroidal melanocytes. In albino rabbits, laser induced effects occurred as a consequence of multiple scattering, together with absorption within haemoglobin and possibly also within tissue water. The data obtained provide further insight into the biological mechanisms arising from retinal photocoagulation with near infrared lasers.

Sclerostomy ab interno using long-wave laser modalities: acute morphological effects

Sclerostomy fistulas were created ab interno in cadaver porcine eyes by an active contact method using a 200-microns-diameter silica optical fiber in conjunction with either Ho:YAG-, Nd:YAG-, or diode-laser light, and a qualitative comparison of the degree of collateral thermal damage induced in each case was undertaken at the light and electron microscopic levels. The apparent breadth of coagulated tissue observed in association with cross-sectioned fistula profiles exhibited considerable local variation, irrespective of the radiation source employed; no intrinsic difference in either the intensity or the extent of the thermal insult incurred was noted between the three laser modalities.

[Sclerostomy using various laser modalities. Ultrastructure of acute effects]

The effects of Ho:YAG- (free-running mode), Nd:YAG- (continuous wave mode) and diode- (continuous wave mode) laser radiation on the degree of collateral thermal damage realized during the creation of sclerostomy canals ab interno (by an active contact method) were compared morphologically: Both the nature and extent of coagulation occurred by scleral collagen fibrils were found to be independent of the laser modality employed.

[The current status of sclerostomy procedures in treatment of open angle glaucoma]

METHODS

A number of ab interno and ab externo sclerostomy procedures have been described in recent years.

CONCLUSION

At the present time, there is no clear indication that such interventions are superior to the classical fistulizing glaucoma operations, such as trabeculectomy.

[Surgery with the laser scalpel. Physical principles and clinical effectiveness]

BACKGROUND

The conventional surgical method for cutting vascularized tissue with scalpel and scissors may now be improved by use of the laser scalpel. In particular, the frequent interruption necessitated and the poor visibility caused by bleeding may be mitigated owing to the haemostatic properties of laser light. This instrument may be of particular value for tasks involving extrabulbar structures, such as extraocular muscles and lacrimal tissue, as well as for facial surgery.

MATERIALS AND METHODS

The mode of action and physical properties of a new laser scalpel are described and its characteristics compared with those of other instruments on the market. The probe consists of a clad, sculptured silica fibre with a core diameter of 0.6 mm and a conical 0.15 mm-diameter cutting tip. Radiation generated by a low cw-Nd:YAG laser module is fed into the probe, at the exit point of which a maximal power density of 57 kW/cm2 is attained. Radiated laser energy penetrates the tissue as an incision is made, thereby inducing an efficient blood flow stasis which is amplified by thermal energy diffusing from the immediate surroundings of the scalpel tip.

RESULTS

In this report, the laser scalpel is implemented for the excision of a vascularized, amelanotic, facial naevus. Both the cutting and haemostatic effects were found to be excellent, occurrence of the latter phenomenon being supported by ultrastructural findings. The healing response was comparable to that observed after conventional surgery.

CONCLUSION

The new laser scalpel represents an inexpensive and effective cutting and haemostatic tool powered by a standard cw Nd:YAG laser module, with a wide spectrum of potential applications.

Versatility of the cw-Nd:YAG and diode lasers in ocular surgery

The effectiveness of cw-Nd:YAG and diode laser light in performing transscleral chorioretinal coagulation is demonstrated in cadaver porcine eyes using a new contact probe that facilitates irradiation of these layers. Both radiation sources also may be viable alternatives to argon laser light in effecting chorioretinal and cycloendocoagulation.

Optical principles related to optimizing sclerostomy procedures

A simple probe, consisting of a 200-micrometer uncladded silica optical fiber, advanced from a protecting 22-gauge hypodermic needle, was used to create sclerostomy fistulas both ab interno and ab externo by means of a combined radiation/mechanical effect. Perforation was achieved by exerting gentle forward pressure on the fiber in synchrony with the delivery of radiation pulses. An irradiation protocol suitable for producing such canals in cadaver porcine eyes was delineated using Ho:YAG, Nd:YAG, and diode laser energy sources. Despite significant differences in the pulse energy required for perforation (0.25, 7, and 8 J for the Ho:YAG, diode, and Nd:YAG lasers, respectively), the extent of collateral damage was comparable for each type of laser. The physical mechanisms underlying these findings are discussed.

Induction of vascular haemostasis by Nd:YAG laser light in melanin-rich and melanin-free tissue

Haemostasis was effected in vessels of melanin-rich (MR: choroid) and melanin-free (MF: mesentery) rabbit tissue irradiated with a cw-Nd:YAG laser. The following parameters were employed: - pulse duration: 200 ms (MR) and 100 ms (MF); focal spot diameter: 200 microns (MR) and 80 microns (MF); pulse energies: 100-250 mJ (MR) and 0.5-1 J (MF); irradiances: 1.6-4.0 kW cm-2 (MR) and 1-2 x 10(2) kW cm-2 (MF). In melanin-rich tissue, laser energy is absorbed principally by melanin granules contained within the stromal melanocytes. The heat generated in these structures radiates into the surrounding tissue where it is dissipated. The damage thus incurred by the endothelium of blood vessels encompassed within this field triggers the haemostatic mechanism whereby blood flow is arrested. This effect is realized by the formation of an occluding plug of platelets, which is stabilized by the deposition of fibrin, particularly in capillaries, and to a lesser degree in larger vessels of the vascular lamina. In melanin-free tissue, haemoglobin serves as the primary site of energy absorption, which is thus shifted from the stroma to the vessel lumen. Irradiation of vessels in such tissue leads to thermocoagulation of plasma proteins and consequent stasis of blood flow.

A new instrument for controlling pressure exerted on the sclera during contact Nd:YAG laser cyclodestruction

We tested the device described by Rol et al in their article in this issue, designed to define and precisely control the pressure applied to the sclera during contact cyclodestruction with a cw-Nd:YAG laser. Since scleral transparency, and hence transmission of laser energy, depends on the pressure applied, control of this parameter represents an important advance toward the goal of standardizing the cyclodestructive procedure. In eight of nine cadaver pig eyes, pressure was exerted on the sclera using the pressure-controlling device, with a setting of 0.25 N for two of these eyes, and one of 0.4 N for the other six. In the remaining eye, pressure was controlled intuitively by an experienced surgeon. Applying forces of 0.25 or 0.4 N yielded similar success rates, although these fluctuated greatly even under constant pressure conditions (from 17% to 50% at 0.25 N; from 27% to 42% at 0.4 N). The highest success rate (55%) was achieved by the intuitively controlled pressure irradiations of the experienced surgeon. The variation in coagulation intensity that occurred despite constant pressure suggests that additional factors contribute to the results achieved. Nonetheless, this pressure-controlling probe represents an important achievement. It will permit not only the novice but even experienced operators to adhere unambiguously to a protocol of quantitative, reproducible parameters, and will also help researchers to better understand the relationship between energy delivered and intraocular pressure reduction achieved in contact cyclophotocoagulation.

[Hemostatic effect of the Nd:YAG laser in cw function]

The Nd:YAG laser may be effectively employed to induce blood flow stasis and vessel closure in rabbits. The mechanism by which these effects are achieved depends upon the nature of the primary absorbing structures in the irradiated tissue, as well as upon the energy level of radiation. Vascular wall damage occasioned in consequence of energy absorption in melanin granules triggers blood flow stasis according to the classic clotting cascade, defects in the endothelial cell wall being closed by aggregated platelets. In tissue lacking melanin pigmentation, energy is absorbed primarily by the haemoglobin of erythrocytes, and blood flow is arrested by coagulation of plasma proteins, platelets being absent from the impact centre. The portent of these different haemostatic mechanisms upon repair of the endothelial cell wall and neovascularization have yet to be determined.

Blood flow stasis induced by cw-Nd:YAG laser irradiation: comparative morphology of mesenteric and choroidal vessels in pigmented rabbits

cw-Nd:YAG laser radiation was effective in producing blood flow stasis within arteries (35-40 microns in diameter) of pigmented rabbit mesentery (beam spot size: 80 microns; fluence: 2 x 10(4) J cm-2) and choroid (beam spot size: 200 microns; fluence: 6 x 10(2) J cm-2). However, the mechanism by which this was achieved differed in each case, and depended upon the energy absorbing structures present in the irradiated tissue. In non-pigmented tissue, such as the mesentery, haemoglobin represents the primary absorption centre, and the temperature attained within the vessel lumen (as inferred from morphological changes) is sufficient to denature plasma proteins, in particular fibrinogen, which consequently occlude the vessel lumen and arrest bleeding. In pigmented tissue, such as the choroid, melanocyte granules represent the primary absorption centre, which is thus shifted from the vessel lumen to the stroma. The temperature rise achieved within the vessel lumen is consequently lower, as evidenced by the absence of plasma protein denaturation. Blood flow stasis nonetheless occurs, but is triggered according to the normal haemostatic mechanism.

Transpupillary irradiation of the rabbit retina with the cw-Nd:YAG laser. I. Acute morphologic effects produced using two different pulse forms

The retinas of six pigmented rabbits (12 eyes) were irradiated with a cw-Nd:YAG laser using two different pulse forms, in conjunction with a constant pulse duration of 200 msec and a retinal focus diameter of 200 microns. The first pulse form (a) was characterized by an initial transient, lasting 15-20 msec, with a peak power twice that of the ensuing plateau phase of 180-185 msec. The second pulse form (b) was almost rectangular in shape. Although the average energies (and powers) for each pulse form were identical, almost 20% of this entity was delivered within the first 20 msec for the first pulse form. Impact lesions were examined at the biomicroscopic, light, and electron microscopic levels, and the characteristic morphologic features described for the cw-mode in general. Comparison of the effects produced using each pulse form revealed a number of differences. At low pulse energies (less than 150 mJ) the rectangular pulse form produced a photocoagulation reaction within the outer sensory retina, but when using the pulse form with the initial transient, this effect was superimposed by a degree of mechanical disruption. Ruptures produced within the elastic component of Bruch's membrane first appeared at lower pulse energies (ie, at 75 mJ, as opposed to 150 mJ for the rectangular pulse form) and were more frequent, and choroidal macrohemorrhaging (observed at pulse energies greater than or equal to 200 mJ) occurred only, when this latter pulse form was employed. Each of these phenomena may be attributed to the higher power and energy densities attained during the initial transient, which has disruptive properties. In order to avoid the risk of severe bleeding, these irradiation parameters should be maintained below approximately 6.4 X 10(3) W/cm2 and approximately 0.13 X 10(3) J/cm2.

The effect of transscleral laser cyclophotocoagulation on rabbit ciliary body vascularization

Long-term changes in the vascular network of rabbit ciliary processes induced by Nd:YAG laser cyclophotocoagulation were examined both from a morphological viewpoint and with respect to three-dimensional organization (in vascular casts). Relative changes in intraocular pressure (IOP), monitored within eyes irradiated across one-quarter, one-half, three-quarters, or all of the ciliary body circumference, are discussed in relation to morphological changes. The clinical implications of these findings are considered.

Cyclophotocoagulation in glaucoma therapy

In a morphological study, the long-term effects of transscleral cyclophotocoagulation on rabbits using the free-running Nd:YAG laser with either a contact or a non-contact delivery system are described. A marked atrophy of the irradiated ciliary processes may be observed. Regeneration of the ciliary epithelial layers is incomplete at least up to 8 months after treatment. The vascular network is also atrophic, and shows a small regenerative capacity only.

Diffusion barriers impeding the flow of solutes to the ciliary body epithelium during immersion fixation of rabbit eyes. Assessment of ultrastructural preservation quality by examination of mitochondrial profiles in the electron microscope

Various manipulations of rabbit anterior eye segments were carried out during the initial stages of glutaraldehyde fixation in order to assess the contribution made by particular tissues in restricting the flow of solutes to the ciliary body epithelium. Ultrastructural preservation quality was monitored by inspection of mitochondrial profiles. These organelles are structurally extremely sensitive to environmental disturbances, and hence changes in their morphological appearance may be used as an early indication of such adverse conditions. The results indicate that the principal barriers to diffusion are represented by the vitreous, posteriorly, and by the cornea at the anterior face. Since the cortical vitreous is strongly attached to the inner basement membrane of the ciliary epithelium, its removal may cause damage to this layer. A simpler and equally effective means of improving flow of fixative to the ciliary epithelium is to remove the cornea.