Psychometric Evaluation of Glaucoma Quality of Life Item Banks (GlauCAT) and Initial Assessment Using Computerized Adaptive Testing.

Purpose: To evaluate the psychometric properties of glaucoma-specific quality of life (QoL) item banks (GlauCAT) and assess their performance using computerized adaptive testing (CAT) simulations. Methods: In this cross-sectional study, 293 participants with glaucoma (mean age ± SD, 70.7 ± 13.2 years; 45% female) answered 342 items in 12 QoL item banks (IBs): Activity Limitation (AL); Driving (DV); Convenience (CV); Economic (EC); Emotional (EM); General Symptoms (GS); Health Concerns (HC); Lighting (LT); Mobility (MB); Ocular Surface Symptoms (OS); Social (SC); and Visual Symptoms (VS). These IBs were assessed using Rasch analysis, and CAT simulations with 1000 simulated respondents were utilized to determine the average number of items to be administered to achieve moderate and high precision levels. Results: The AL, DV, EM, HC, LT, MB, EC, OS, SC, and VS IBs required relatively minor amendments to achieve satisfactory psychometric fit. To resolve multidimensionality, we split CV into Treatment Convenience (TCV) and General Convenience (GCV). Due to poor measurement precision, the GS IB was not pursued further. This resulted in 12 total IBs. In CAT simulations, an average of 3.7 and 7.3 items per IB were required to attain measurement at moderate and high precision, respectively. Conclusions: Following rigorous psychometric assessment, we developed 12 valid glaucoma-specific QoL domains that can obtain highly precise person measure estimates using a small number of items. Translational Relevance: GlauCAT will enable researchers and clinicians to quickly and comprehensively assess the impact of glaucoma and its associated interventions across a range of QoL domains.

Computerized Adaptive Tests: Efficient and Precise Assessment of the Patient-Centered Impact of Diabetic Retinopathy.

Purpose: Evaluate efficiency, precision, and validity of RetCAT, which comprises ten diabetic retinopathy (DR) quality of life (QoL) computerized adaptive tests (CATs). Methods: In this cross-sectional clinical study, 183 English and/or Mandarin-speaking participants with DR (mean age ± standard deviation [SD] 56.4 ± 11.9 years; 38% proliferative DR [worse eye]) were recruited from retinal clinics in Singapore. Participants answered the RetCAT tests (Symptoms, Activity Limitation, Mobility, Emotional, Health Concerns, Social, Convenience, Economic, Driving, and Lighting), which were capped at seven items each, and other questionnaires, and underwent eye tests. Our primary evaluation focused on RetCAT efficiency (i.e. standard error of measurement [SEM] ± SD achieved and time needed to complete each CAT). Secondary evaluations included an assessment of RetCAT's test precision and validity. Results: Mean SEM across all RetCAT tests was 0.351, ranging from 0.272 ± 0.130 for Economic to 0.484 ± 0.130 for Emotional. Four tests (Mobility, Social, Convenience, and Driving) had a high level of measurement error. The median time to take each RetCAT test was 1.79 minutes, ranging from 1.12 (IQR [interquartile range] 1.63) for Driving to 3.28 (IQR 2.52) for Activity Limitation. Test precision was highest for participants at the most impaired end of the spectrum. Most RetCAT tests displayed expected correlations with other scales (convergent/divergent validity) and were sensitive to DR and/or vision impairment severity levels (criterion validity). Conclusions: RetCAT can provide efficient, precise, and valid measurement of DR-related QoL impact. Future application of RetCAT will employ a stopping rule based on SE rather than number of items to ensure that all tests can detect meaningful differences in person abilities. Responsiveness of RetCAT to treatment interventions must also be determined. Translational Relevance: RetCAT may be useful for measuring the patient-centered impact of DR severity and disease progression and evaluating the effectiveness of new therapies.

Development and Psychometric Assessment of Novel Item Banks for Hereditary Retinal Diseases.

SIGNIFICANCE: This study develops psychometrically valid item banks across 10 areas of quality of life (QoL) specific to people with hereditary retinal diseases, which will enable clinicians and researchers to explore the impact of hereditary retinal diseases across all aspects of QoL. PURPOSE: The purpose of this study was to assess the psychometric properties of hereditary retinal disease QoL item banks using Rasch analysis and demonstrate the effectiveness of a computerized adaptive testing (CAT) system in obtaining precise measurement of QoL using only a few items. METHODS: The hereditary retinal disease item banks were answered by 233 participants (median age, 58 years; range, 18 to 94 years; female participants, 59%). The hereditary retinal disease item banks cover 10 QoL domains: activity limitation, mobility, emotional, social, convenience, economic, health concerns, visual symptoms, ocular comfort symptoms, and general symptoms. Rasch analysis assessed the psychometric properties of the 10 item banks and provided item calibrations for the development of CAT. Computerized adaptive testing simulations were performed to calculate the average number of items required to gain precise measurement of each QoL domain. RESULTS: The convenience, economic, visual symptoms, and the social domains formed unidimensional scales. However, the activity limitation and health concerns domains demonstrated multidimensionality and required major modifications to resolve this, which resulted in four new QoL domains, namely, reading, driving, lighting, and concerns about the disease progression. In total, 10 item banks underwent CAT simulation testing, which indicated that 8 to 12 items were required to gain precise measurement of each QoL domain. CONCLUSIONS: We have developed 10 psychometrically valid item banks to measure the QoL domains relevant to people with hereditary retinal diseases. On average, only 5 and 10 items were required to gain measurement at moderate and high precision, respectively.

Patient-reported Outcomes for Assessment of Quality of Life in Refractive Error: A Systematic Review.

SIGNIFICANCE: This review has identified the best existing patient-reported outcome (PRO) instruments in refractive error. The article highlights the limitations of the existing instruments and discusses the way forward. PURPOSE: A systematic review was conducted to identify the types of PROs used in refractive error, to determine the quality of the existing PRO instruments in terms of their psychometric properties, and to determine the limitations in the content of the existing PRO instruments. METHODS: Articles describing a PRO instrument measuring 1 or more domains of quality of life in people with refractive error were identified by electronic searches on the MEDLINE, PubMed, Scopus, Web of Science, and Cochrane databases. The information on content development, psychometric properties, validity, reliability, and responsiveness of those PRO instruments was extracted from the selected articles. The analysis was done based on a comprehensive set of assessment criteria. RESULTS: One hundred forty-eight articles describing 47 PRO instruments in refractive error were included in the review. Most of the articles (99 [66.9%]) used refractive error-specific PRO instruments. The PRO instruments comprised 19 refractive, 12 vision but nonrefractive, and 16 generic PRO instruments. Only 17 PRO instruments were validated in refractive error populations; six of them were developed using Rasch analysis. None of the PRO instruments has items across all domains of quality of life. The Quality of Life Impact of Refractive Correction, the Quality of Vision, and the Contact Lens Impact on Quality of Life have comparatively better quality with some limitations, compared with the other PRO instruments. CONCLUSIONS: This review describes the PRO instruments and informs the choice of an appropriate measure in refractive error. We identified need of a comprehensive and scientifically robust refractive error-specific PRO instrument. Item banking and computer-adaptive testing system can be the way to provide such an instrument.

The National Eye Survey of Trinidad and Tobago (NESTT): Rationale, Objectives and Methodology.

PURPOSE: This paper describes the rationale, study design and procedures of the National Eye Survey of Trinidad and Tobago (NESTT). The main objective of this survey is to obtain prevalence estimates of vision impairment and blindness for planning and policy development. METHODS: A population-based, cross-sectional survey was undertaken using random multistage cluster sampling, with probability-proportionate-to-size methods. Eligible participants aged 5 years and older were sampled from the non-institutional population in each of 120 cluster segments. Presenting distance and near visual acuity were screened in their communities. People aged 40 years and older, and selected younger people, were invited for comprehensive clinic assessment. The interview included information on potential risk factors for vision loss, associated costs and quality of life. The examination included measurement of anthropometrics, blood glucose, refraction, ocular biometry, corneal hysteresis, and detailed assessment of the anterior and posterior segments, with photography and optical coherence tomography imaging. Adult participants were invited to donate saliva samples for DNA extraction and storage. RESULTS: The fieldwork was conducted over 13 months in 2013-2014. A representative sample of 10,651 individuals in 3410 households within 120 cluster segments identified 9913 people who were eligible for recruitment. CONCLUSION: The study methodology was robust and adequate to provide the first population-based estimates of the prevalence and causes of visual impairment and blindness in Trinidad and Tobago. Information was also gathered on risk factors, costs and quality of life associated with vision loss, and on normal ocular parameters for the population aged 40 years and older.

Assessment of patient-reported outcomes in retinal diseases: a systematic review.

Advances in the understanding of the genetic, molecular, and cellular biology of retinal diseases have led to the development of new treatments. These expanding treatment options demand appropriate outcome measures for studies of treatment benefit including patient-reported outcomes (PROs). A plethora of PRO instruments assess impacts of retinal diseases from the patients' perspectives. We review all the studies that implemented PRO assessment in retinal diseases and also discuss quality assessment of the PRO instruments. We also include qualitative studies that explored quality of life impact on people with retinal diseases. Most studies used PRO instruments not specifically developed for retinal diseases (non-disease specific), nor have they undergone comprehensive validation in this disease group. A few retina-specific PRO instruments are available, but they suffer from limited content coverage of quality of life. Finally, we discuss the need for a new comprehensive and technologically advanced PRO instrument to assess quality of life impacts in retinal diseases.

Number of People Blind or Visually Impaired by Glaucoma Worldwide and in World Regions 1990 - 2010: A Meta-Analysis.

OBJECTIVE: To assess the number of individuals visually impaired or blind due to glaucoma and to examine regional differences and temporal changes in this parameter for the period from 1990 to 2012. METHODS: As part of the Global Burden of Diseases (GBD) Study 2010, we performed a systematic literature review for the period from 1980 to 2012. We primarily identified 14,908 relevant manuscripts, out of which 243 high-quality, population-based studies remained after review by an expert panel that involved application of selection criteria that dwelt on population representativeness and clarity of visual acuity methods used. Sixty-six specified the proportion attributable to glaucoma. The software tool DisMod-MR (Disease Modeling-Metaregression) of the GBD was used to calculate fraction of vision impairment due to glaucoma. RESULTS: In 2010, 2.1 million (95% Uncertainty Interval (UI):1.9,2.6) people were blind, and 4.2 (95% UI:3.7,5.8) million were visually impaired due to glaucoma. Glaucoma caused worldwide 6.6% (95% UI:5.9,7.9) of all blindness in 2010 and 2.2% (95% UI:2.0,2.8) of all moderate and severe visual impairment (MSVI). These figures were lower in regions with younger populations (<5% in South Asia) than in high-income regions with relatively old populations (>10%). From 1990 to 2010, the number of blind or visually impaired due to glaucoma increased by 0.8 million (95%UI:0.7, 1.1) or 62% and by 2.3 million (95%UI:2.1,3.5) or 83%, respectively. Percentage of global blindness caused by glaucoma increased between 1990 and 2010 from 4.4% (4.0,5.1) to 6.6%. Age-standardized prevalence of glaucoma related blindness and MSVI did not differ markedly between world regions nor between women. SIGNIFICANCE: By 2010, one out of 15 blind people was blind due to glaucoma, and one of 45 visually impaired people was visually impaired, highlighting the increasing global burden of glaucoma.

Assessment of Cataract Surgery Outcome Using the Modified Catquest Short-Form Instrument in China.

PURPOSE: To assess cataract surgery outcome using the Rasch scaled Chinese version of the Catquest short-form. METHODS: The Chinese translated and culturally adapted version of the Catquest-9SF was interviewer-administered to patients, pre and post cataract surgery. Rasch analysis was performed on the baseline data to revise the Catquest. For the surgical outcome assessment, we stacked pre- and post-surgical Catquest data to demonstrate improvement in visual function scores and responsiveness of the instrument to cataract surgery. RESULTS: A total of 247 cataract patients (median age, 70 yrs; male 51.0%) completed the Catquest 9SF at baseline.The Catquest-9SF possessed adequate measurement precision of 2.15. No disordering of response categories were observed and all the items perfectly fit to the Rasch model except item 7 (outfit >1.5). A slight reduction in precision was observed after removing misfitting item 7 (Catquest-8SF-CN), but the precision value was well above the acceptable value of 2.00. Notably, the instrument was well targeted (mean person location 0.30), demonstrated no evidence of multidimensionality and DIF. At 12 months post-surgery, 74 (30%) patients came for follow-up and completed the Catquest. There was a significant improvement in the Catquest scores post cataract surgery with a considerably large effect size. CONCLUSION: The Catquest-8SF-CN demonstrated promising Rasch based psychometric properties and was highly responsive to cataract surgery.

Global Estimates on the Number of People Blind or Visually Impaired by Diabetic Retinopathy: A Meta-analysis From 1990 to 2010.

OBJECTIVE: To estimate global and regional trends from 1990 to 2010 of the prevalence and number of persons visually impaired specifically by diabetic retinopathy (DR), as a complication of the precipitous trends in global diabetes, is fundamental for health planning purposes. RESEARCH DESIGN AND METHODS: The meta-analysis of published population studies from 1990 to 2012 for the Global Burden of Disease Study 2010 (GBD) yielded estimated global regional trends in DR among other causes of moderate and severe vision impairment (MSVI; presenting visual acuity <6/18, ≥3/60) and blindness (presenting visual acuity <3/60). RESULTS: Globally in 2010, out of overall 32.4 million blind and 191 million visually impaired people, 0.8 million were blind and 3.7 million were visually impaired because of DR, with an alarming increase of 27% and 64%, respectively, spanning the two decades from 1990 to 2010. DR accounted for 2.6% of all blindness in 2010 and 1.9% of all MSVI worldwide, increasing from 2.1% and 1.3%, respectively, in 1990. These figures were lower in regions with younger populations (<2% in East and Southeast Asia and Oceania) than in high-income regions (North America, Western Europe, and Australasia) with relatively aging populations (>4%). CONCLUSIONS: The number of persons with visual impairment due to DR worldwide is rising and represents an increasing proportion of all blindness/MSVI causes. Age-standardized prevalence of DR-related blindness/MSVI was higher in sub-Saharan Africa and South Asia. One out of 39 blind people had blindness due to DR, and 1 out of 52 visually impaired people had visual impairment due to DR.

Comparing the effectiveness of selective laser trabeculoplasty with topical medication as initial treatment (the Glaucoma Initial Treatment Study): study protocol for a randomised controlled trial.

BACKGROUND: Glaucoma is the leading cause of irreversible blindness in the world. Estimated to affect 60 million people worldwide, this figure is expected to rise to 80 million by 2020. Untreated, glaucoma leads to visual decay and eventually to blindness, and can significantly reduce quality of life. First-line treatment in patients with primary open-angle glaucoma and exfoliative glaucoma is topical medical therapy with ocular hypotensives as eye drops. However, eye drops have several disadvantages including cost, possible local and systemic side effects, and adherence and perseverance issues. Randomised controlled trials have demonstrated that selective laser trabeculoplasty is equally as effective in lowering intraocular pressure as eye drops. However, the impact of these two treatment modalities from the patient and economic perspectives has not been adequately determined. Thus, it remains unclear whether topical medical therapy or selective laser trabeculoplasty should be recommended as first-line treatment for glaucoma. METHODS/DESIGN: This protocol describes an international, multi-centre, randomised controlled trial to determine the optimum first-line therapy for people with primary open-angle glaucoma and exfoliative glaucoma. This study will compare the effect of selective laser trabeculoplasty and topical medication with respect to patients' generic and glaucoma-specific quality of life. The trial will also provide a detailed cost-effectiveness analysis and compare the clinical effectiveness with respect to the degree of intraocular pressure lowering and rates of treatment failure. Research coordinators in each centre will identify and recruit previously untreated patients with primary open-angle glaucoma and exfoliative glaucoma. Those who meet the eligibility criteria will be invited to enter a randomised controlled trial with either selective laser trabeculoplasty or topical ocular hypotensive therapy, according to a stepped regimen. Outcome assessment will be measured at 6 weeks and at 6, 12, and 24 months post-treatment. Regular clinic follow-ups will continue as clinically indicated between study outcome visits. DISCUSSION: The Glaucoma Initial Treatment Study is the first multi-centred RCT to determine the optimum first-line therapy for people with glaucoma. Our trial will have an unprecedented capacity to meaningfully transform the treatment and management of glaucoma in Australia and overseas. TRIAL REGISTRATION: ACTRN12611000720910; Date registered: 11 July 2011.

Prevalence and causes of vision loss in high-income countries and in Eastern and Central Europe: 1990-2010.

BACKGROUND: To assess prevalence and causes of blindness and vision impairment in high-income regions and in Central/Eastern Europe in 1990 and 2010. METHODS: Based on a systematic review of medical literature, prevalence of moderate and severe vision impairment (MSVI; presenting visual acuity <6/18 but ≥3/60 in the better eye) and blindness (presenting visual acuity <3/60) was estimated for 1990 and 2010. RESULTS: Age-standardised prevalence of blindness and MSVI decreased from 0.2% to 0.1% (3.314 million to 2.736 million people) and from 1.6% to 1.0% (25.362 million to 22.176 million), respectively. Women were generally more affected than men. Cataract was the most frequent cause of blindness in all subregions in 1990, but macular degeneration and uncorrected refractive error became the most frequent causes of blindness in 2010 in all high-income countries, except for Eastern/Central Europe, where cataract remained the leading cause. Glaucoma and diabetic retinopathy were fourth and fifth most common causes for blindness for all regions at both times. Uncorrected refractive error, followed by cataract, macular degeneration, glaucoma and diabetic retinopathy, was the most common cause for MSVI in 1990 and 2010. CONCLUSIONS: In highly developed countries, prevalence of blindness and MSVI has been reduced by 50% and 38%, respectively, and the number of blind people and people with MSVI decreased by 17.4% and 12.6%, respectively, even with the increasing number of older people in the population. In high-income countries, macular degeneration has become the most important cause of blindness, but uncorrected refractive errors continue to be the leading cause of MSVI.

Quality assessment of ophthalmic questionnaires: review and recommendations.

PURPOSE: The aim of this article was to systematically review all the available ophthalmic patient-reported outcome (PRO) instruments (questionnaires) that demonstrated interval measurement properties to identify the instruments with the highest psychometric quality for use in different eye diseases and conditions. METHODS: An extensive literature review was carried out to identify all existing ophthalmic PRO instruments. Instruments were then excluded if they did not have demonstrable interval measurement properties; the remaining instruments were reviewed. The quality of the following psychometric properties was assessed: content development (initial item development process), performance of the response scale, dimensionality (whether the instrument measures a single construct), measurement precision, validity (convergent, concurrent, discriminant, and known groups), reliability (test-retest), targeting (whether the items are appropriate [e.g., difficulty level] for the population), differential item functioning (whether subgroups of people respond differently to an item), and responsiveness. RESULTS: The search identified 48 PRO instruments that demonstrated interval measurement properties, and these were relevant to nine applications: glaucoma, dry eye, refractive errors, cataract, amblyopia and strabismus, macular diseases, adult low vision, children low vision, and others. These instruments were evaluated against the psychometric property quality criteria and were rated for quality based on the number of criteria met. CONCLUSIONS: This review provides a descriptive catalog of ophthalmic PRO instruments to inform researchers and clinicians on the choice of the highest-quality PRO instrument suitable for their purpose.

Comprehensive assessment of nuclear and cortical backscatter metrics derived from rotating Scheimpflug images.

PURPOSE: To quantify cataract in lens-backscatter metrics derived from Pentacam Scheimpflug photographs and determine the most predictive metrics for lens grading and visual performance measures. SETTING: Large tertiary referral hospital in South Australia. DESIGN: Evaluation of diagnostic test or technology. METHODS: In patients attending a cataract clinic between 2005 and 2008, standardized clinical assessments were performed and Scheimpflug photographs taken. Thirteen measures of cataract backscatter were drawn from the images of nuclear and cortical cataract, including new metrics for cortical cataract. The relationships between lens-scatter metrics, visual performance, and lens grades were determined with stepwise multiple linear regression. RESULTS: The study enrolled 342 eyes (177 patients). The Lens Opacities Classification System III (LOCS III) nuclear opalescence was best predicted by the average backscatter in the anterior half of the nucleus and the whole nucleus average (r(2) = 0.59). The LOCS III cortical grade was best predicted by the number of slices with significant cortical cataract (r(2) = 0.52), as was Pelli-Robson contrast sensitivity (r(2) = 0.16). Visual acuity was best predicted by the combined anterior half and whole nucleus averages (r(2) = 0.20). Pelli-Robson contrast sensitivity under glare was best predicted by a combination of the anterior half and whole nucleus averages and the calculated percentage of cortical cataract (r(2) = 0.16). CONCLUSIONS: Scheimpflug image-derived metrics of nuclear scatter were predictive of visual acuity and contrast sensitivity, whereas metrics of cortical cataract were predictive of visual performance under glare. Automated reporting of cataract severity from Scheimpflug images could be useful clinically and should include measurements of cortical cataract. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.

Subscale assessment of the NEI-RQL-42 questionnaire with Rasch analysis.

PURPOSE: To explore the psychometric properties of the 13 subscales of the NEI-RQL-42 questionnaire using Rasch analysis. METHODS: The NEI-RQL-42 is a refractive error-related quality of life (QoL) questionnaire with a complex design; its 13 subscales contain 42 questions, which include 16 different question/response category formats. It was completed by 100 laser refractive surgery subjects (spectacle and contact lens wearers) pre- and postoperatively. Rasch analysis was used to assess the use of response categories, success in measuring a single trait per subscale (unidimensionality), ability to discriminate persons (precision), and targeting of the questions to person QoL. RESULTS: Response categories were misused in four subscales (clarity of vision, diurnal fluctuation, symptoms, and appearance), which required repair before further analyses. Six subscales contained items that did not contribute to a single trait measurement (multidimensional). All subscales were found to be inadequate at distinguishing between persons (person separation >2.0), and targeting of the questions to QoL was poor for six subscales. CONCLUSIONS: The NEI-RQL-42 questionnaire is deficient for all psychometric properties tested. Clinicians or researchers wishing to measure QoL related to refractive error correction should consider other questionnaires that have been rigorously developed and meet standard psychometric properties.

Visual disability assessment: valid measurement of activity limitation and mobility in cataract patients.

AIM: The Visual Disability Assessment (VDA), a questionnaire for measuring the impact of cataract on visual functioning, was developed using classical test theory. Since this approach is limited, our aim was to further investigate the psychometric properties of the VDA using Rasch analysis. METHODS: 613 patients from the Flinders Medical Centre cataract surgery self-administered the VDA. Psychometric properties investigated for the overall VDA and each subscale included: measurement of a single construct (unidimensionality), item fit to the construct, reliable discrimination between strata of patient ability (person separation) and targeting of item difficulty to person ability. RESULTS: The VDA discriminated five strata of patient ability. However, seven mobility items constituted a second dimension and formed a valid separate scale. Sequestration of these items resulted in a unidimensional 11-item measure of activity limitation. Both the mobility and activity limitation scales had acceptable person separation and neither contained misfitting items. Targeting was suboptimal for mobility (-2.12 logits) but good for activity limitation (-0.72). The subscales also satisfied the requirements of the Rasch measurement model. CONCLUSIONS: The Rasch-scaled VDA effectively measures two separate constructs: mobility and activity limitation (with two subscales). Its good psychometric properties make it suitable for measuring cataract surgery outcomes.

Visual Activities Questionnaire: assessment of subscale validity for cataract surgery outcomes.

PURPOSE: To examine the psychometric properties of the Visual Activities Questionnaire (VAQ) and each of its subscales in a modern cataract population using Rasch analysis and if flawed, to revise the VAQ and create a valid measure that maximizes its measurement properties. SETTING: Flinders Eye Centre, Flinders Medical Centre, Adelaide, Australia. METHODS: Patients with cataract in 1 or both eyes drawn from the surgical waiting list were mailed the 33-item VAQ for self-administration. The following were examined for the entire questionnaire and each subscale: whether items measured a single construct (unidimensionality), the behavior of response categories, the ability to differentiate between patients' visual abilities (person separation), matching of item difficulty to participant ability (targeting), and whether items function similarly across subgroups of participants (differential item functioning [DIF]). RESULTS: The VAQ was completed by 561 patients. Response categories were used as intended. The VAQ discriminated the visual ability of the population (person separation, 4.88) but had suboptimum targeting, misfitting items, significant multidimensionality, DIF, and 4 dysfunctional subscales. Elimination of items causing multidimensionality resulted in a reduced 13-item VAQ that met all validity criteria for satisfactory instrument performance. Only 1 valid subscale (peripheral vision) could be preserved in the 13-item VAQ. CONCLUSIONS: The VAQ in its native form was multidimensional and contained subscales with poor psychometric properties. The revised unidimensional 13-item VAQ was more appropriate for application in cataract outcomes assessment. Ideally, more items should be included to improve the targeting of item difficulty to more able cataract patients.

Anterior segment biometry with the Pentacam: comprehensive assessment of repeatability of automated measurements.

PURPOSE: To comprehensively assess the reliability of automated Pentacam (Oculus, Inc.) measurements. SETTING: Flinders Eye Centre, Flinders Medical Centre, Bedford Park, South Australia, Australia. METHODS: Both eyes of 35 normal volunteers were tested twice on the same day by 2 different observers. All automated values were recorded, and manual analysis of topographic maps was performed only to overrule variance in corneal thickness due to pupil decentration altering the central reference point. Repeatability was determined with Bland-Altman limits of agreement and reported as the coefficient of repeatability (COR = +/-1.96 standard deviation of differences). Relative repeatability (RR) was calculated as a percentage of the ratio of COR to the mean. RESULTS: Overall, repeatability was good. Corneal curvature, reported in diopters, showed good repeatability anteriorly (simulated keratometry mean COR+/-0.28D; RR=0.64%) and posteriorly (COR+/-011D; RR=1.85%). Peripheral corneal curvature was more reliable when calculated by the sagittal (axial) method (RR=1.57%) than by the tangential (meridional) method (RR=2.38%). Keratometric power deviation was less reliable (RR=16.39%). Anterior chamber measurements showed good reliability (RR=3.07%-5.68%) except for anterior chamber angle (RR=14.41%). Pupil diameter showed poor reliability (RR=25.77%). Central corneal thickness was comparable at pupil center and corneal vertex, but peripheral repeatability was much better when centered on the corneal vertex (COR+/-16.00microm; RR=2.56%) than at pupil center (COR+/-26.28microm; RR=4.23%). CONCLUSIONS: Pentacam corneal curvature and anterior chamber parameters were highly repeatable, but pupil measurements had poor repeatability. Peripheral pachymetry readings were affected by pupil decentration and required manual analysis using the corneal vertex as the point of reference to achieve good repeatability.

The development, assessment, and selection of questionnaires.

Patient-reported outcome measurement has become accepted as an important component of comprehensive outcomes research. Researchers wishing to use a patient-reported measure must either develop their own questionnaire (called an instrument in the research literature) or choose from the myriad of instruments previously reported. This article summarizes how previously developed instruments are best assessed using a systematic process and we propose a system of quality assessment so that clinicians and researchers can determine whether there exists an appropriately developed and validated instrument that matches their particular needs. These quality assessment criteria may also be useful to guide new instrument development and refinement. We welcome debate over the appropriateness of these criteria as this will lead to the evolution of better quality assessment criteria and in turn better assessment of patient-reported outcomes.