Applying multilevel item response theory to vision-related quality of life in Dutch visually impaired elderly.

PURPOSE: Instead of applying the usual longitudinal methods to assess the outcome of low-vision rehabilitation services in terms of vision-related quality of life, a three-level Item Response Theory (IRT) method was proposed. METHODS: The translated Vision-Related Quality of Life Core Measure (VCM1) and Low Vision Quality Of Life (LVQOL) questionnaires were used in a nonrandomized follow-up study among elderly patients (n = 296) referred to two different low-vision rehabilitation services in the Netherlands. Factor analysis was performed on the matrix of polychoric correlations to investigate (uni-)dimensionality and to prepare both questionnaires for the multilevel IRT analyses. A statistical model, which was characterized by a graded response model for rating scales, was developed. Threshold and item difficulty parameters and group by time-specific mean fixed effects were estimated. Random individual effects were predicted. Measurement invariance across occasions was tested. RESULTS: The VCM1 and the LVQOL "reading and fine work" dimension showed item parameter drift. In the multidisciplinary rehabilitation center patients, deterioration was found on the "mobility" dimension after 1 year and improvement was found on "adjustment" and "visual (motor) skills" after 5 months (p < 0.05). Patients in both low-vision services showed improvement on the "reading small print" subscale at both follow-up time points (p < 0.05). CONCLUSIONS: Except for improvement in "reading small print," low-vision rehabilitation services did not seem to contribute substantially to any other dimensions of vision-related quality of life. The results showed a change in only a limited number of individual patients. However, with regard to the field of low-vision rehabilitation, the proposed IRT method seemed to be successful in the follow-up of individuals. IRT specific software was unnecessary. The data did not have to be complete and the use of cumulative logits made the proposed IRT method an economical and efficient approach. Because of item parameter drift, the VCM1 was difficult to interpret. The use of multilevel IRT models with longitudinal data and dependent observations is recommended.     

Changes in spherical aberration after lens refilling with a silicone oil

PURPOSE: It may be possible to restore accommodation to presbyopic human eyes by refilling the lens capsular bag with a soft polymer. In the present study, optical changes were measured that occurred in a pig eye model after the refilling of the capsular bag. METHODS: The optical power and spherical aberration in 10 isolated pig lenses were measured under different conditions. They were first determined by using a scanning laser ray-tracing technique over an effective pupil size of 6 mm. Second, the contours of the anterior and posterior lens surface were photographed, and a mathematical ray-tracing was performed by using a polynomial fit through the digitized surface contours, to determine optical power and spherical aberration. Third, the lenses were refilled with a silicone oil until their preoperative lens thickness was reached, and scanning laser ray-tracing, contour photography, and mathematical ray-tracing were repeated. Comparisons between the measurements were made to determine how the change from a gradient refractive index to a homogeneous refractive index influenced spherical aberration. The influence of the change in lens contour on spherical aberration after lens refilling was also studied. RESULTS: The natural lenses had a higher lens power than the refilled lenses (49.9 +/- 1.5 D vs. 36.8 +/- 1.5 D; P < 0.001). Moreover, there was a change in sign from negative spherical aberration before lens refilling (-3.6 D) to positive spherical aberration after lens refilling (7.9 D; P < 0.001). The comparison between scanning laser ray-tracing of the natural lens and mathematical ray-tracing of the photographed surface contours of the natural lens to determine the effect of refractive index substitution (i.e., replacement of a gradient refractive index by a homogeneous refractive index) showed a significant change in spherical aberration from -3.6 +/- 2.0 to 11.0 +/- 2.1 D (P < 0.001). The change in lens contour did not result in a significant change in spherical aberration (P = 0.08) before and after lens refilling with an equal refractive index. CONCLUSIONS: The lower lens power of refilled pig lenses compared to natural lenses was due to the lower refractive index of the refill material. Refilling pig lenses with the silicone oil used in this study resulted in an increase in spherical aberration. This increase was mainly caused by the change from a gradient refractive index to a homogeneous refractive index. The change in lens curvature after lens refilling did not result in an increase in spherical aberration. The influence of lens refilling on spherical aberration of human lenses must be determined in similar experiments in human eyes.     

Monitoring accommodative ciliary muscle function using three-dimensional ultrasound

BACKGROUND: Our objective was to develop a three-dimensional high-resolution ultrasonic imaging technique to be utilized for in-vivo characterization of the ciliary body and the posterior iris. The benefit of this imaging in enhancing the quantification of the configurational changes in the ciliary body during accommodation is demonstrated. METHODS: Sequential ultrasound biomicroscopic images of the ciliary body region were obtained with a computer-controlled scanning device designed for use with a standard ultrasound biomicroscope for 3D imaging. Custom-made software allows online data collection, data analysis and 3D reconstruction in conjunction with commercially available VoxelView software. RESULTS: The three-dimensional presentation allows a close approximation of the ciliary muscle inside the ciliary body in vivo. We are able to distinguish and to analyze the changes in the muscle contour in different accommodation states. During accommodation a shift in the ciliary muscle center of gravity in a range of 0.04-0.26 mm (mean 0.13+/-0.06 mm) in the direction of the lens equator, with an interindividual variation and a small decrease with age, was observed. CONCLUSIONS: High-resolution ultrasound is a well established technique for in-vivo investigation of the anterior segment. Three-dimensional ultrasound biomicroscopy allows an assessment of the individual ciliary muscle activity in consideration of the ciliary processes. In combination with a contour analysis tool we improved the muscle contour determination during different accommodation states. The investigation showed an activity of the ciliary muscle in young volunteers as well as those of presbyopic age.     

Measurement Properties of Visual Analogue Scale,Numeric Rating Scale,and Pain Severity Subscale of the Brief Pain Inventory in Patients With Low Back Pain: A Systematic Review

The Visual Analogue Scale (VAS), Numeric Rating Scale (NRS), and Pain Severity subscale of the Brief Pain Inventory (BPI-PS) are the most frequently used instruments to measure pain intensity in low back pain. However, their measurement properties in this population have not been reviewed systematically. The goal of this study was to provide such systematic evidence synthesis. Six electronic sources (MEDLINE, EMBASE, CINAHL, PsycINFO, SportDiscus, Google Scholar) were searched (July 2017). Studies assessing any measurement property in patients with nonspecific low back pain were included. Two reviewers independently screened articles and assessed risk of bias using the COSMIN checklist. For each measurement property, evidence quality was rated as high, moderate, low, or very low (GRADE approach) and results were classified as sufficient, insufficient, or inconsistent. Ten studies assessed the VAS, 13 the NRS, 4 the BPI-PS. The 3 instruments displayed low or very low quality evidence for content validity. High-quality evidence was only available for NRS insufficient measurement error. Moderate evidence was available for NRS inconsistent responsiveness, BPI-PS sufficient structural validity and internal consistency, and BPI-PS inconsistent construct validity. All VAS measurement properties were underpinned by no, low, or very low quality evidence; likewise, the other measurement properties of NRS and BPI-PS.

Testing the psychometric properties of the Participation Scale in Eastern Nepal

Purpose

To test the psychometric properties of the Participation Scale (P-scale) among people with various disabling conditions in Eastern Nepal.

Methods

A sample of 153 individuals with disabling conditions was selected through systematic random sampling. The following psychometric properties were tested: structural validity (explanatory and confirmatory factor analyses), internal consistency, inter-tester reliability, construct validity and floor and ceiling effects.

Results

The explanatory factor analysis indicated a two-factor structure (‘work-related participation’ and ‘general participation’). The confirmatory factor analysis suggested good model fit. The internal consistency measured with Cronbach’s alpha was 0.93 for the whole scale and 0.78 and 0.93 for the subscales. The inter-tester reliability coefficient was 0.90. All hypothesized correlations were as expected confirming the construct validity of the scale. No floor or ceiling effects were identified for the whole scale; only the subscale ‘work-related participation’ showed a ceiling effect.

Conclusion

The results of the analyses suggest that the psychometric properties of the P-scale are sufficient in the context of Eastern Nepal. Use of the P-scale will require (re-) confirmation of its validity in each new cultural context.     

Dutch–Flemish translation of nine pediatric item banks from the Patient-Reported Outcomes Measurement Information System (PROMIS)®

Quality of Life Research - The Patient-Reported Outcomes Measurement Information System (PROMIS®) is a new, state-of-the-art assessment system for measuring patient-reported health and...     

Evaluation of measurement properties of self-administered PROMs aimed at patients with non-specific shoulder pain and “activity limitations”: a systematic review

Objective

To critically appraise and compare the measurement properties of self-administered patient-reported outcome measures (PROMs) focussing on the shoulder, assessing “activity limitations.”

Study design

Systematic review. The study population had to consist of patients with shoulder pain. We excluded postoperative patients or patients with generic diseases. The methodological quality of the selected studies and the results of the measurement properties were critically appraised and rated using the COSMIN checklist.

Results

Out of a total of 3427 unique hits, 31 articles, evaluating 7 different questionnaires, were included. The SPADI is the most frequently evaluated PROM and its measurement properties seem adequate apart from a lack of information regarding its measurement error and content validity.

Conclusion

For English, Norwegian and Turkish users, we recommend to use the SPADI. Dutch users could use either the SDQ or the SST. In German, we recommend the DASH. In Tamil, Slovene, Spanish and the Danish languages, the evaluated PROMs were not yet of acceptable validity. None of these PROMs showed strong positive evidence for all measurement properties. We propose to develop a new shoulder PROM focused on activity limitations, taking new knowledge and techniques into account.