Jill Carlton

Determinants of health related quality of life and health state utility in patients with age related macular degeneration: the association of contrast sensitivity and visual acuity

BackgroundThere has been increasing interest in the use of measures of health related quality of life (HRQoL) and health state utility values in Age Related Macular Degeneration (ARMD). Visual acuity has been found to be an important determinant of such measures in previous studies. More recently, another measure of visual impairment, contrast sensitivity has received considerable attention. We designed a study to examine whether the contribution of contrast sensitivity in explaining HRQoL and health utilities over and above that of visual acuity.Methods209 patients with unilateral or bilateral ARMD were recruited into a cross-sectional study of patients from a large teaching hospital. Patients underwent visual tests (near and distant visual acuity, contrast sensitivity) and completed a vision function questionnaire, the VF-14, HUI3, and time trade-off.ResultsUsing multivariate regression analysis, the study revealed that contrast sensitivity remained a statistically significant predictor of all outcome measures even when visual acuity was included. This result was supported by the correlation coefficients between measures.ConclusionsThe measurement of contrast sensitivity appears to be better related to a person’s HRQoL and health utility. Future studies should consider incorporating contrast sensitivity in addition to visual acuity. Studies, in particular economic evaluations, may underestimate the effect of treatment unless contrast sensitivity is considered.

Amblyopia and quality of life: a systematic review

Amblyopia is a common condition, which can affect up to 5% of the general population. Health-related quality-of-life (HRQoL) implications of amblyopia and/or its treatment have been explored in the literature. A systematic literature search was undertaken during the period of 7–14 May 2010 to identify the HRQoL implications of amblyopia and/or its treatment. A total of 35 papers were included in the literature review. The HRQoL implications of amblyopia related specifically to amblyopia treatment, rather than to the condition itself. These included impact on family life, social interactions, difficulties in undertaking daily activities, as well as feelings and behaviour. The identified studies adopted a number of methodologies. The study populations included children with the condition, parents of children with amblyopia, and adults who had undertaken amblyopia treatment as a child. Some studies developed their own measures of HRQoL, and others determined HRQoL through proxy measures. The reported findings of the HRQoL implications are of importance when considering the management of cases of amblyopia. The issues identified in the literature review are discussed with respect to how HRQoL is measured (treatment compliance vs proxy measures), and whether HRQoL is taken from a childs or a parents perspective. Changing societal views over glasses and occlusion therapy are also discussed. Further research is required to assess the immediate and long-term effects of amblyopia and/or its treatment on HRQoL using a more standardised approach.

Health-related quality of life measures (HRQoL) in patients with amblyopia and strabismus: a systematic review

Background/aims Health-related quality of life (HRQoL) measures are used in healthcare to help inform clinical decision-making and policy-making decisions. A number of disease-specific or condition-specific measures have been developed and applied in ophthalmology; however, their use in the specific fields of amblyopia and strabismus are not as established. The purpose of this study is to identify and discuss specific HRQoL instruments that may be used in the investigation and management of patients with amblyopia and/or strabismus. Methods A systematic literature review was undertaken in November 2009. The electronic databases of AMED (Allied and Complementary Medicine: 1985 to November 2009), the British Nursing Index and Archive (1985 to October 2009), Ovid Medline In-Process and Other Non-Indexed Citations and Ovid Medline (1950 to present) and PsycINFO (1806 to November Week 1 2009) were searched. No language restrictions were applied to the search. Results Four instruments were identified: the Amblyopia and Strabismus Questionnaire (A&SQ), the Amblyopia Treatment Index (ATI), the Adult Strabismus Questionnaire (AS-20) and the Intermittent Exotropia Questionnaire (IXTQ). Conclusion The use of HRQoL measures in patients with amblyopia and/or strabismus is a developing area. Further research is necessary to determine the impact of issues such as diplopia and poor cosmesis upon patient groups, and to determine the influence of ethnicity and parental reporting in these patients.

Valuing condition specific health states using simulation contact lenses

OBJECTIVE This article reports on a study that used contact lenses to simulate the effects of a visual impairment caused by age-related macular degeneration (ARMD). The primary objective was to examine the feasibility of using this method of simulation. A secondary objective was to compare the results from this experiment with those obtained from ARMD patients (n = 209) using generic preference-based measures (Health Utilities Index 3 (HUI3) and EUROQOL 5 Dimensions (EQ-5D) and patient time trade-off (TTO). METHODS Utility values were elicited from healthy participants (n = 108) for three ARMD states simulated using contact lenses. RESULTS A significant relationship was found between visual acuity and TTO values elicited from our sample population (n = 108). It was stronger than that found for HUI3, EQ-5D, and own TTO values from patients (n = 209). Our sample values informed by the experience of simulation were found to be significantly different from values from patient TTO and generic preference-based measures obtained from patients for the same level of visual impairment. Sociodemographic characteristics did not significantly affect results, although baseline TTO utility values were positively associated with TTO values for simulated states. Nevertheless, the patient population was significantly older than the sample population. CONCLUSIONS ARMD has a major impact on our sample values TTO health state values. Differences across four visual health severity groups appear larger than those found for a generic preference-based measure and patient TTO values. For conditions that are difficult to describe and imagine, simulation methods may offer an additional tool when combined with usual methods of description for obtaining better informed general population preferences.

Informing disinvestment through cost-effectiveness modelling

The mandatory nature of recommendations made by the National Institute for Health and Clinical Excellence (NICE) in the UK has highlighted inherent difficulties in the process of disinvestment in existing technologies to fund NICE-approved technologies. A lack of evidence on candidate technologies means that the process of disinvestment is subject to greater uncertainty than the investment process, and inefficiencies may occur as a result of the inverse evidence law.This article describes a potential disinvestment scenario and the options for the decision maker, including the conduct of value of information analyses. To illustrate the scenario, an economic evaluation of a disinvestment candidate (screening for amblyopia and strabismus) is presented. Only very limited data were available. The reference case analysis found that screening is not cost effective at currently accepted values of a QALY. However, a small utility decrement due to unilateral vision loss reduced the incremental cost per QALY gained, with screening expected to be extremely cost effective.The discussion highlights the specific options to be considered by decision makers in light of the model-based evaluation. It is shown that the evaluation provides useful information to guide the disinvestment decision, providing a range of focused options with respect to the decision and the decision-making process.A combination of explicit model-based evaluation, and pragmatic and generalizable approaches to interpreting uncertainty in the decision-making process is proposed, which should enable informed decisions around the disinvestment of technologies with weak evidence bases.

Inventory of current EU paediatric vision and hearing screening programmes

Objective To examine the diversity in paediatric vision and hearing screening programmes in Europe. Methods Themes for comparison of screening programmes derived from literature were used to compile three questionnaires on vision, hearing, and public health screening. Tests used, professions involved, age, and frequency of testing seem to influence sensitivity, specificity, and costs most. Questionnaires were sent to ophthalmologists, orthoptists, otolaryngologists, and audiologists involved in paediatric screening in all EU full-member, candidate, and associate states. Answers were cross-checked. Results Thirty-nine countries participated; 35 have a vision screening programme, 33 a nation-wide neonatal hearing screening programme. Visual acuity (VA) is measured in 35 countries, in 71% of these more than once. First measurement of VA varies from three to seven years of age, but is usually before age five. At age three and four, picture charts, including Lea Hyvarinen, are used most; in children over four, Tumbling-E and Snellen. As first hearing screening test, otoacoustic emission is used most in healthy neonates, and auditory brainstem response in premature newborns. The majority of hearing testing programmes are staged; children are referred after 1–4 abnormal tests. Vision screening is performed mostly by paediatricians, ophthalmologists, or nurses. Funding is mostly by health insurance or state. Coverage was reported as >95% in half of countries, but reporting was often not first-hand. Conclusion Largest differences were found in VA charts used (12), professions involved in vision screening (10), number of hearing screening tests before referral (1–4), and funding sources (8).

Estimating quality-adjusted life years from patient-reported visual functioning

PurposeGlaucoma is an important disease, the impacts of which on vision have been shown to have implications for patients’ health-related quality of life (HRQoL). The primary aim of this study is to estimate a mapping algorithm to predict EQ-5D and SF-6D utility values based on the vision-specific measure, the 25-item Visual Functioning Questionnaire (VFQ-25), as well as the clinical measures of visual function, that is, integrated visual field, visual acuity, and contrast sensitivity.MethodsOrdinary least squares (OLS), Tobit, and censored least absolute deviations were compared using data taken from the Moorfields Eye Hospital in London, to assess mapping functions to predict the EQ-5D and SF-6D from the VFQ-25, and tests of visual function. These models were compared using root mean square error (RMSE), R2, and mean absolute error (MAE).ResultsOLS was the best-performing model of the three compared, as this produced the lowest RMSE and MAE, and the highest R2.ConclusionsThe models provided initial algorithms to convert the VFQ-25 to the EQ-5D and SF-6D. Further analysis would be needed to validate the models or algorithms.

Identifying potential themes for the Child Amblyopia Treatment Questionnaire.

Purpose Patient-reported outcome (PRO) instruments are increasingly common in both clinical practice and research. The data obtained from these instruments can be used to help inform decision making and policy-making decisions. The methodological approaches undertaken in developing PROs is not frequently reported. Literature on the development of the descriptive systems for PROs is sparse in comparison with that on the assessment of the psychometric properties of such instruments. The purpose of this study is to describe the results of qualitative interviews conducted to identify potential themes for the Child Amblyopia Treatment Questionnaire (CAT-QoL), a pediatric disease-specific health-related quality of life instrument for amblyopia designed for children aged 4 to 7 years. Methods Semistructured interviews were undertaken with 59 children (aged 3 years 9 months to 9 years 11 months; average, 6 years 3 months) with amblyopia. The interviews were transcribed verbatim and imported into QSR NVivo 8. Interview transcripts were analyzed to identify potential items to be included in the descriptive system. Thematic content analysis was undertaken using Framework. Results Eleven potential themes were identified for inclusion in the CAT-QoL instrument, namely, physical sensation of the treatment, pain, being able to play with other children, how other children have treated them, ability to undertake schoolwork, ability to undertake other tasks, sad or unhappy, cross, worried, frustrated, and feelings toward family members. Conclusions Children are able to identify their thoughts and opinions of their own health and to describe what impact their amblyopia treatment has had on their daily lives. Themes for the draft descriptive system for a pediatric self-reported amblyopia QoL instrument have been identified. A draft version of the CAT-QoL instrument has been developed. Further research is required to refine and assess the psychometric properties of the instrument.

Health state utilities in patients with diabetic retinopathy, diabetic macular oedema and age-related macular degeneration: a systematic review

BackgroundHealth state utility values (HSUVs) are important in the assessment of the cost effectiveness of new interventions. In the case of visual conditions, models generally tend have tended to be built around a set of health states defined by visual acuity (VA). The aim of this review was to assess the impact of VA on HSUVs in patients with diabetic retinopathy, diabetic macular oedema or age-related macular degeneration.MethodsA systematic literature search was undertaken in major bibliographic databases to identify articles reporting on the relationship between HSUVs and vision. Data were extracted for population characteristics, visual levels and estimated utilities. Evidence from reported statistical models, where available, was considered in the evaluation of vision in the better-seeing eye and the worse-seeing eye. Due to the heterogeneity of included studies, a narrative synthesis was undertaken.ResultsOf the 17 relevant studies, 9 studies had data that could be used in the analysis of the impact of vision on HSUVs. Visual loss was associated with a marked impact on health utilities. However, the relationship was not comparable between conditions or by measure of HSUVs. Key results included the finding that overall, self-rated time-trade off estimates were more likely to discriminate between different VA levels than EQ-5D values. Additionally, a stronger correlation was observed between HSUVs and better-seeing eye VA compared to worse-seeing eye VA.ConclusionsVisual acuity has a significant impact on HSUVs. Nevertheless, care must be taken in the interpretation and use of estimates in cost-effectiveness models due to differences in measures and population diversity.

The nuclear propulsion of merchant ships: Aspects of engineering, science and technology

This paper first considers the underlying nuclear physics and then explores the potential application of that science to the propulsion of merchant ships. It then examines the options for the exploitation of nuclear technology and considers some of the engineering implications of deploying the technology. Consideration is then given to the application of nuclear propulsion to a series of ship types, including tankers, container ships and cruise vessels. In each case two sizes of ship are chosen, one of fairly conventional size and the other much larger.