Comparative effectiveness between two types of head-mounted magnification modes using a smartphone-based virtual display

SIGNIFICANCE

This work shows the benefits of using two different magnification strategies to improve the reading ability of low-vision patients using a head-mounted technology.

PURPOSE

The aim of this study was to conduct a comparative clinical trial evaluating the effectiveness of two magnification strategies in a head-mounted virtual reality display.

METHODS

Eighty-eight eligible low-vision subjects were randomized into two arms: (1) the full-field magnification display or (2) the virtual bioptic telescope mode. Subjects completed baseline testing and received training on how to use the device properly and then took the device home for a 2- to 4-week intervention period. An adaptive rating scale questionnaire (Activity Inventory) was administered before and after the intervention (home trial) period to measure the effect of the system. A Simulator Sickness Questionnaire was also administered. Baseline and follow-up results were analyzed using Rasch analysis to assess overall effectiveness of each magnification mode for various functional domain categories.

RESULTS

Both magnification modes showed a positive effect for reading, visual information, and the overall goals functional domain categories, with only reading reaching statistical significance after correction for multiple comparisons. However, there were no significant between-group differences between the two modes. The results of the Simulator Sickness Questionnaire showed that the magnification modes of the head-mounted display device were overall well tolerated among low-vision users.

CONCLUSIONS

Both the full-field and virtual bioptic magnification strategies were effective in significantly improving functional vision outcomes for self-reported reading ability.

Application of Rasch Analysis to Timed Instrumental Activities of Daily Living in Low Vision: A Validation Study

SIGNIFICANCE

This work validates Rasch analysis of a performance-based low vision outcome measure evaluated in patients' own homes to ensure real-world relevance. Inclusion of sources of variance from the patient's home environment in functional outcome measures introduced nonuniform variance in measurements but did not preclude estimation of valid measures.

PURPOSE

This study aimed to validate Rasch analysis of a performance-based outcome measure with real-world relevance.

METHODS

Low vision patients (N = 161) receiving services from an occupational therapist performed Timed Instrumental Activity of Daily Living (TIADL) tasks in their homes. Rasch analysis was applied to error count and performance time data. Internal validity was assessed with evaluations of the accuracy and precision of estimated measures. External validity was assessed by comparing TIADL measures with measures estimated from the Activity Inventory (i.e., from self-reported difficulty ratings).

RESULTS

Task measures were well targeted to person measures estimated from task performance time but were poorly targeted for measures estimated from task performance errors, for which most task trials (72%) were performed without error at baseline. Error-based person measures had larger standard errors with a smaller pseudo- R2 than time-based person or task measures and error-based task measures. Person measure infits for time- and error-based estimates conformed to expected values. The linear regressions between time-based person and task measures and corresponding error-based estimates had slopes of approximately 0.5, an observation consistent with larger estimation error variance for error-based measures than for time-based measures. Time-based TIADL person measures ( x ) and Activity Inventory person measures (estimated from all items, y ) were colinear but weakly correlated ( R = 0.19).

CONCLUSIONS

Functional ability measures estimated from performance times of instrumental activity of daily living tasks in patients' homes demonstrate good internal and external validity. The ceiling effect from the infrequency of task performance errors in our data set limits use of TIADL error data to measure rehabilitation outcomes.

The NEI VFQ-25C: Calibrating Items in the National Eye Institute Visual Function Questionnaire-25 to Enable Comparison of Outcome Measures

Purpose

To improve the usefulness of the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25) by enabling estimation of measures on an invariant scale and comparisons between patients and across studies.

Methods

Datasets of baseline NEI VFQ-25 responses from nine studies (seven retina randomized trials, n = 2770; two low vision studies, n = 572) were combined. The method of successive dichotomizations was applied to patient ratings of the main NEI VFQ-25 and six supplemental items to estimate Rasch model parameters using the R package 'msd.' Calibrated item measures and rating category thresholds were estimated for the NEI VFQ-25, as well as for two domain-specific versions: the NEI VFQ-VF that includes only visual function items and the NEI VFQ-SE that includes only socioemotional items.

Results

Calibrated item measures were estimated from study participants (n = 3342) ranging in age from 19 to 103 years, with mean (SD) age of 69.3 (11) years and a mean logMAR visual acuity of 0.30 (Snellen 20/40). Item measure estimates had high precision (standard error range, 0.026-0.085 logit), but person measure estimates had lower precision (standard error range, 0.108-0.499 logit). Items were well targeted to most persons, but not to those with higher levels of function.

Conclusions

Calibrated item measures and rating category thresholds enable researchers and clinicians to estimate visual, socioemotional, and combined measures on an invariant scale using the NEI VFQ-25.

Translational Relevance

Applying NEI VFQ 25C calibrated item measures (software provided) to the NEI VFQ-25, users can estimate overall, visual, and socioemotional function measures for individual patients.

Patient-Reported Measures of the Effects of Vision Impairments and Low Vision Rehabilitation on Functioning in Daily Life

The quantification of vision impairments dates to the mid-nineteenth century with standardization of visual acuity and visual field measures in the eye clinic. Attempts to quantify the impact of vision impairments on patients' lives did not receive clinical attention until the close of the twentieth century. Although formal psychometric theories and measurement instruments were well developed and commonplace in educational testing, as well as in various areas in psychology and rehabilitation medicine, the late start applying them to clinical vision research created a vacuum that invited poorly developed and poorly functioning instruments and analytic methods. Although this research is still burdened with legacy instruments, mandates by regulatory agencies to include the patients' perspectives and preferences in the evaluation of clinical outcomes have stimulated the development and validation of self-report instruments grounded in modern psychometric theory and methods. Here I review the progress and accomplishments of applying modern psychometrics to clinical vision research. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Evaluation of photography using head-mounted display technology (ICAPS) for district Trachoma surveys

Background

As the prevalence of trachoma declines worldwide, it is becoming increasingly expensive and challenging to standardize graders in the field for surveys to document elimination. Photography of the tarsal conjunctiva and remote interpretation may help alleviate these challenges. The purpose of this study was to develop, and field test an Image Capture and Processing System (ICAPS) to acquire hands-free images of the tarsal conjunctiva for upload to a virtual reading center for remote grading.

Methodology/Principal findings

This observational study was conducted during a district-level prevalence survey for trachomatous inflammation—follicular (TF) in Chamwino, Tanzania. The ICAPS was developed using a Samsung Galaxy S8 smartphone, a Samsung Gear VR headset, a foot pedal trigger and customized software allowing for hands-free photography. After a one-day training course, three trachoma graders used the ICAPS to collect images from 1305 children ages 1–9 years, which were expert-graded remotely for comparison with field grades. In our experience, the ICAPS was successful at scanning and assigning barcodes to images, focusing on the everted eyelid with adequate examiner hand visualization, and capturing images with sufficient detail to grade TF. The percentage of children with TF by photos and by field grade was 5%. Agreement between grading of the images compared to the field grades at the child level was kappa = 0.53 (95%CI = 0.40–0.66). There were ungradable images for at least one eye in 199 children (9.1%), with more occurring in children ages 1–3 (18.5%) than older children ages 4–9 (4.2%) (χ² = 145.3, p<0.001).

Conclusions/Significance

The prototype ICAPS device was robust, able to image 1305 children in a district level survey and transmit images from rural Tanzania to an online grading platform. More work is needed to improve the percentage of ungradable images and to better understand the causes of disagreement between field and photo grading.

Trachoma is the leading infectious cause of blindness worldwide, caused by the bacterium Chlamydia trachomatis. Programs targeting trachoma elimination in endemic regions largely rely on periodic prevalence surveys to monitor progress, but training field graders requires active cases, which is becoming challenging as prevalence declines. Photography of the tarsal conjunctiva with remote interpretation via telemedicine may serve as a more auditable, effective, and cost-efficient method for surveys. We developed and evaluated the Image Capture and Processing System (ICAPS), a smartphone-based, hands-free, head-mounted camera system (Samsung Galaxy S8 with custom app, Samsung Gear VR headset, and a Bluetooth-linked foot pedal trigger). The ICAPS was easy to use in challenging field conditions, was able to upload images from Tanzania and link images to field data. The percentage of TF was 5% by both field grade and photo grade, with agreement kappa = 0.53. Additional field training and enhanced certification of photographers may help reduce the proportion of ungradable images; further research on reasons for mismatch of grades between field and photo is needed.

Topical Review: Understanding Vision Impairment and Sports Performance through a Look at Paralympic Classification

SIGNIFICANCE

To provide meaningful competition that is equitable for Paralympic athletes, classification systems are vital to determine which athletes are eligible to compete in adapted forms of sports and to group athletes for competition. Our discussion has important implications to inform how we should approach visual function assessment in sports performance. Sport participation positively benefits individuals with low vision. In particular, adapted sports exist to provide people with visual disabilities an avenue for participating in recreational activity. High-performance low-vision athletes can participate in Paralympic sports but need to be properly classified based on the severity of their vision impairment. The model for Paralympic classification was initiated by Sir Ludwig Guttmann in 1952 in a rehabilitation clinic for soldiers with spinal cord injuries. Today, the International Paralympic Committee mandates that international sports federations develop evidence-based sport-specific classification systems to ensure that eligible disabled athletes have an opportunity for meaningful competition. With the current classification system, only visual acuity and visual field measures are considered to determine an athlete's eligibility to compete, leaving room to expand our understanding of visual function requirements for individual sports. In this topical review, we discuss the origins of Paralympic sports, limitations of current classification methods, and requirements toward achieving evidence-based sport-specific evaluation systems.

Vision-related quality of life in adults with severe peripheral vision loss: a qualitative interview study

Background

Existing patient-reported outcome (PRO) measures may not be relevant to the full range of functional and vision-related quality of life (VR-QOL) concerns of individuals with vision impairment due to severe peripheral field loss (PFL). Measurement of VR-QOL in severe PFL is important in order to determine the effectiveness of vision rehabilitation interventions for this population. The purpose of this study was to characterize the impact of severe PFL due to retinitis pigmentosa (RP) and glaucoma on VR-QOL as the initial phase in the development of a novel PRO measure.

Methods

Individuals with severe PFL due to RP or glaucoma were recruited from the Kellogg Eye Center and the Association for the Blind and Visually Impaired. Participants completed semi-structured qualitative interviews, the Impact of Vision Impairment (IVI) questionnaire and the RAND 36-Item Health Survey. Interviews were analyzed by two coders using thematic analysis. A matrix analysis was conducted to compare VR-QOL by cause of severe PFL. Sample size was determined by thematic saturation.

Results

The study included 37 participants (19 RP, 18 glaucoma). Median best-corrected visual acuity for those with RP and glaucoma was 20/40 and 20/27.5, while Pelli-Robson contrast sensitivity was 1.2 log contrast sensitivity (logCS) and 1.1 logCS, respectively. Median domain scores on the IVI (reading, mobility, well-being) ranged from a low of − 0.2 to a high of 0.7 logits in those with RP and from 0.5 to 1.2 logits in those with glaucoma. Qualitative interviews identified six VR-QOL themes relevant across participants with both RP and glaucoma, including activity limitations, driving, emotional well-being, reading, mobility, and social function. VR-QOL concerns were largely consistent among those with severe PFL due to RP and glaucoma. These overarching themes contained content relevant to specific challenges related to severe PFL.

Conclusions

There are commonly occurring VR-QOL concerns among individuals with severe PFL due to RP and glaucoma. The outlined themes will serve as the basis for development of the Low Vision Severely Constricted Peripheral Eyesight (LV-SCOPE) Questionnaire.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41687-020-00281-y.

Estimating measures of latent variables from m-alternative forced choice responses

Signal Detection Theory is the standard method used in psychophysics to estimate person ability in m-alternative forced choice tasks where stimuli are typically generated with known physical properties (e.g., size, frequency, contrast, etc …) and lie at known locations on a physical measurement axis. In contrast, variants of Item Response Theory are preferred in fields such as medical research and educational testing where the axis locations of items on questionnaires or multiple choice tests are not defined by any observable physical property and are instead defined by a latent (or unobservable) variable. We provide an extension of Signal Detection Theory to latent variables that employs the same strategy used in Item Response Theory and demonstrate the practical utility of our method by applying it to a set of clinically relevant face perception tasks with visually impaired individuals as subjects. A key advantage of our approach is that Signal Detection Theory explicitly models the m-alternative forced choice task while Item Response Theory does not. We show that Item Response Theory is inconsistent with key assumptions of the m-alternative forced choice task and is not a valid model for this paradigm. However, the simplest Item Response Theory model–the dichotomous Rasch model–is found to be a special case of SDT and provides a good approximation as long as the number of response alternatives m is small and remains fixed for all items.

Economic Evaluation of Low-Vision Rehabilitation for Veterans With Macular Diseases in the US Department of Veterans Affairs

Importance

Examining costs and consequences of different low-vision (LV) programs provides important information about resources needed to expand treatment options efficiently.

Objective

To examine the costs and consequences of LV rehabilitation or basic LV services.

Design, Setting, and Participants

The US Department of Veterans Affairs (VA) Low Vision Intervention Trial (LOVIT) II was conducted from September 27, 2010, to July 31, 2014, at 9 VA facilities and included 323 veterans with macular diseases and a best-corrected distance visual acuity of 20/50 to 20/200. Veterans were randomized to receive basic LV services that provided LV devices without therapy, or LV rehabilitation that added a therapist to LV services who provided instruction and homework on using LV devices, eccentric viewing, and environmental modification. We compared costs and consequences between these groups.

Interventions

Low-vision devices without therapy and LV devices with therapy.

Main Outcomes and Measures

Costs of providing basic LV services or LV rehabilitation were assessed. We measured consequences as changes in functional visual ability from baseline to follow-up 4 months after randomization using the VA Low Vision Visual Functioning Questionnaire. Visual ability was measured in dimensionless log odds units (logits).

Results

Of 323 randomized patients, the mean (SD) age was 80 (10.5) years, 314 (97.2%) were men, and 292 (90.4%) were white. One hundred sixty (49.5%) received basic LV services and 163 (50.1%) received LV rehabilitation. The mean (SD) total direct health care costs per patient were similar between patients who were randomized to receive basic LV services ($1662 [$671]) or LV rehabilitation ($1788 [$864]) (basic LV services, $126 lower; 95% CI, $299 lower to $35 higher; P = .15). However, basic LV services required less time and had lower transportation costs. Patients receiving LV rehabilitation had greater improvements in overall visual ability, reading ability, visual information processing, and visual motor skill scores.

Performance of the Veterans Affairs Low Vision Visual Functioning Questionnaire

The purpose of this study was to develop an instrument that would be sensitive to the visual difficulties of persons with low vision and that could be used to evaluate outcomes and plan vision rehabilitation services. Toward that end, the Veterans Affairs Low Vision Visual Functioning Questionnaire was administered to 117 participants in rehabilitation programs in Veterans Affairs medical centers and in the private sector. The results demonstrate that the questionnaire is an effective instrument for measuring vision difficulties in persons who receive low-vision rehabilitation.

Preliminary Evaluation of Two Digital Image Processing Strategies for Head-Mounted Magnification for Low Vision Patients

Purpose

In an observational clinical outcome study, we tested the effectiveness and use of the combination of two innovative approaches to magnification: a virtual bioptic telescope and a virtual projection screen, implemented with digital image processing in a head-mounted display (HMD) equipped with a high-resolution video camera and head trackers.

Methods

We recruited 30 participants with best-corrected visual acuity <20/100 in the better-seeing eye and bilateral central scotomas. Participants were trained on the HMD system, then completed a 7- to 10-day in-home trial. The Activity Inventory was administered before and after the home trial to measure the effect of system use on self-reported visual function. A simulator sickness questionnaire (SSQ) and a system-use survey were administered. Rasch analysis was used to assess outcomes.

Results

Significant improvements were seen in functional ability measures estimated from goal difficulty ratings (Cohen's d = 0.79, P < 0.001), and reading (d = 1.28, P < 0.001) and visual information (d = 1.11, P < 0.001) tasks. There was no improvement in patient-reported visual motor function or mobility. One participant had moderately severe discomfort symptoms after SSQ item calibration. The average patient rating of the system's use was 7.14/10.

Conclusions

Use of the system resulted in functional vision improvements in reading and visual information processing. Lack of improvement in mobility and visual motor function is most likely due to limited field of view, poor depth perception, and lack of binocular disparity.

Translational Relevance

We determine if these new image processing approaches to magnification are beneficial to low vision patients performing everyday activities.

Successful Outcomes from a Structured Curriculum Used in the Veterans Affairs Low Vision Intervention Trial

A low vision rehabilitation program with a structured curriculum was evaluated in a randomized controlled trial. The treatment group demonstrated large improvements in self-reported visual function (reading, mobility, visual information processing, visual motor skills, and overall). The team approach and the protocols of the treatment program are described.

Method of successive dichotomizations: An improved method for estimating measures of latent variables from rating scale data

The most commonly used models for estimating measures of latent variables from polytomous rating scale data are the Andrich rating scale model and the Samejima graded response model. The Andrich model has the undesirable property of estimating disordered rating category thresholds, and users of the model are advised to manipulate data to force thresholds to come out ordered. The Samejima model estimates ordered thresholds, but has the undesirable property of estimating person measures on a non-invariant scale-the scale depends on which items a person rates and makes comparisons across people difficult. We derive the rating scale model logically implied by the generally agreed upon definition of rating scale-a real line partitioned by ordered thresholds into ordered intervals called rating categories-and show that it estimates ordered thresholds as well as person and item measures on an invariant scale. The derived model turns out to be a special case of the Samejima model, but with no item discrimination parameter and with common thresholds across items. All parameters in our model are estimated using a fast and efficient method called the Method of Successive Dichotomizations, which applies the dichotomous Rasch model as many times as there are thresholds and demonstrates that the derived model is a polytomous Rasch model that estimates ordered thresholds. We tested both the Method of Successive Dichotomizations and the Andrich model against simulated rating scale data and found that the estimated parameters of our model were nearly perfectly correlated with the true values, while estimated thresholds of the Andrich model became negatively correlated with the true values as the number of rating categories increased. Our method also estimates parameters on a scale that remains invariant to the number of rating categories, in contrast to the Andrich model.

Validation of an Objective Measure of Dry Eye Severity

Purpose

We evaluated the validity of a single dry eye severity measure estimated using Rasch analysis from a battery of clinical tests and patient symptoms.

Methods

This study included 203 dry eye patients and 51 controls. Administered tests included the Ocular Surface Disease Index (OSDI), tear osmolarity, Schirmer's test, noninvasive break-up time, and ocular surface staining. Each of the 12 OSDI questions and each clinical test was defined to be a separate indicator to estimate a single dry eye severity measure from Rasch analysis. Measures of severity were estimated for each subject (person measures) and measures of sensitivity to severity were estimated for each sign and symptom (indicator measures).

Results

The average severity measure for dry eye patients was significantly greater than the average severity measure for controls (−0.39 vs. −1.2, P < 0.001). The distribution of indicator measures was well matched to the distribution of person measures. No indicator carried >10% of the total information about dry eye severity carried by all indicators together. However, the most informative indicators were corneal and conjunctival staining.

Conclusions

Our study indicated that there is no single “best” dry eye test. Clinical tests and symptoms should be used in combination to estimate a single dry eye severity measure.

Translational Relevance

There is no single “gold standard” testing method for dry eye that correlates with the severity of disease. We propose that Rasch analysis can be used to calculate an objective dry eye severity score from a battery of clinical indicators.

Functional Outcomes of the Low Vision Depression Prevention Trial in Age-Related Macular Degeneration

Purpose

To compare the efficacy of behavioral activation (BA) plus low vision rehabilitation with an occupational therapist (OT-LVR) with supportive therapy (ST) on visual function in patients with age-related macular degeneration (AMD).

Methods

Single-masked, attention-controlled, randomized clinical trial with AMD patients with subsyndromal depressive symptoms (n = 188). All subjects had two outpatient low vision rehabilitation optometry visits, then were randomized to in-home BA + OT-LVR or ST. Behavioral activation is a structured behavioral treatment aiming to increase adaptive behaviors and achieve valued goals. Supportive therapy is a nondirective, psychological treatment that provides emotional support and controls for attention. Functional vision was assessed with the activity inventory (AI) in which participants rate the difficulty level of goals and corresponding tasks. Participants were assessed at baseline and 4 months.

Results

Improvements in functional vision measures were seen in both the BA + OT-LVR and ST groups at the goal level (d = 0.71; d = 0.56 respectively). At the task level, BA + OT-LVR patients showed more improvement in reading, inside-the-home tasks and outside-the-home tasks, when compared to ST patients. The greatest effects were seen in the BA + OT-LVR group in subjects with a visual acuity ≥20/70 (d = 0.360 reading; d = 0.500 inside the home; d = 0.468 outside the home).

Conclusions

Based on the trends of the AI data, we suggest that BA + OT-LVR services, provided by an OT in the patient's home following conventional low vision optometry services, are more effective than conventional optometric low vision services alone for those with mild visual impairment. (ClinicalTrials.gov number, NCT00769015.)

Multivariable Regression Model of the EuroQol 5-Dimension Questionnaire in Patients Seeking Outpatient Low Vision Rehabilitation

PURPOSE

To understand the source of between-person variance in baseline health utilities estimated from EuroQol 5-dimension questionnaire (EQ-5D) responses of a representative sample of the US low vision outpatient population prior to rehabilitation.

METHODS

A prospective, observational study of 779 new low vision patients at 28 clinic centers in the US. The EQ-5D, Activity Inventory (AI), Telephone Interview for Cognitive Status (TICS), Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36) physical functioning component, and Geriatric Depression Scale (GDS) were administered by telephone interview prior to rehabilitation. EQ-5D responses were transformed into health utilities, which served as the dependent variable in all analyses. Data were then analyzed to determine how much overall visual ability, functional domains of visual ability, and comorbidities (e.g. physical functioning, depression, cognition) independently contribute to the EQ-5D-based health utility index.

RESULTS

Multivariable regression analyses showed that the GDS and SF-36 physical account for nearly 40% of the variance observed in health utilities estimated from EQ-5D responses of low vision patients. Age was also a significant predictor of health utilities, but accounted for very little variance. None of the other variables were significant predictors.

CONCLUSIONS

Health utilities of low vision patients estimated from the EQ-5D primarily are associated with comorbid factors that are not likely to be responsive to low vision rehabilitation, thereby rendering the EQ-5D an unsuitable outcome measure for this population. However, because the EQ-5D is responsive to comorbid states, it could be a useful tool for evaluating the impact of comorbidities on low vision patient quality of life.

The Veterans Affairs Low Vision Intervention Trial (LOVIT): Design and Methodology

Background Visual impairment is a major public health problem. Vision rehabilitation programs have the potential to restore independence and improve quality of life for persons with permanent vision loss, and few have been evaluated in randomized controlled trials.

Purpose The Veterans Affairs (VA) Low Vision Intervention Trial is a multicenter randomized clinical trial to evaluate the effectiveness of a new outpatient low vision rehabilitation program.

Methods 126 patients with moderate and severe vision loss due to macular diseases are randomized to low vision treatment in an outpatient setting or a usual care control group at two VA facilities in Hines, Illinois, and Salisbury, North Carolina. The primary outcome is the change in visual reading ability from baseline to four months measured with the Veterans Affairs Low Vision Visual Functioning Questionnaire-48 (VA LV VFQ-48). Secondary outcomes compare the mean change in visual ability measured with the VA LV VFQ-48 (overall ability, mobility, visual information processing, visual motor skills) for the treatment and control groups. Costs and cost effectiveness of outpatient treatment are evaluated.

Results The low vision rehabilitation setting, use of a waiting list control group to address ethical issues, development of the treatment protocol, development of a vision function questionnaire for patients to self-report the difficulty they experience performing daily activities, and the use of Rasch analysis to develop and estimate this outcome measure are described.

Limitations If the new low vision rehabilitation program is proven effective, studies will be needed to determine which of the multiple aspects of the intervention are necessary and sufficient.

Conclusions The challenges of conducting clinical trials in a rehabilitation setting and use of a waiting list (deferred treatment) control group extend beyond LOVIT. The design and methods of LOVIT may be applicable to other trials of rehabilitation services and to outcomes for which reliable and valid measurement tools must be developed. Clinical Trials 2007; 4: 650—660. http://ctj.sagepub.com

Clinically Meaningful Rehabilitation Outcomes of Low Vision Patients Served by Outpatient Clinical Centers

IMPORTANCE

To facilitate comparative clinical outcome research in low vision rehabilitation, we must use patient-centered measurements that reflect clinically meaningful changes in visual ability.

OBJECTIVE

To quantify the effects of currently provided low vision rehabilitation (LVR) on patients who present for outpatient LVR services in the United States.

DESIGN, SETTING, AND PARTICIPANTS

Prospective, observational study of new patients seeking outpatient LVR services. From April 2008 through May 2011, 779 patients from 28 clinical centers in the United States were enrolled in the Low Vision Rehabilitation Outcomes Study. The Activity Inventory, a visual function questionnaire, was administered to measure overall visual ability and visual ability in 4 functional domains (reading, mobility, visual motor function, and visual information processing) at baseline and 6 to 9 months after usual LVR care. The Geriatric Depression Scale, Telephone Interview for Cognitive Status, and Medical Outcomes Study 36-Item Short-Form Health Survey physical functioning questionnaires were also administered to measure patients' psychological, cognitive, and physical health states, respectively, and clinical findings of patients were provided by study centers.

MAIN OUTCOMES AND MEASURES

Mean changes in the study population and minimum clinically important differences in the individual in overall visual ability and in visual ability in 4 functional domains as measured by the Activity Inventory.

RESULTS

Baseline and post-rehabilitation measures were obtained for 468 patients. Minimum clinically important differences (95% CIs) were observed in nearly half (47% [95% CI, 44%-50%]) of patients in overall visual ability. The prevalence rates of patients with minimum clinically important differences in visual ability in functional domains were reading (44% [95% CI, 42%-48%]), visual motor function (38% [95% CI, 36%-42%]), visual information processing (33% [95% CI, 31%-37%]), and mobility (27% [95% CI, 25%-31%]). The largest average effect size (Cohen d = 0.87) for the population was observed in overall visual ability. Age (P = .006) was an independent predictor of changes in overall visual ability, and logMAR visual acuity (P = .002) was predictive of changes in visual information processing.

CONCLUSIONS AND RELEVANCE

Forty-four to fifty percent of patients presenting for outpatient LVR show clinically meaningful differences in overall visual ability after LVR, and the average effect sizes in overall visual ability are large, close to 1 SD.

Equating Visual Function Scales to Facilitate Reporting of Medicare Functional G-Code Severity/Complexity Modifiers for Low-Vision Patients

OBJECTIVE

To present a method of estimating and equating scales across functional assessment instruments that appropriately represents changes in a patient's functional ability and can be meaningfully mapped to changes in Medicare G-code severity modifiers.

DESIGN

Previously published measures of patients' overall visual ability, estimated from low-vision patient responses to 7 different visual function rating scale questionnaires, are equated and mapped onto Medicare G-code severity modifiers.

SETTING

Outpatient low-vision rehabilitation clinics.

PARTICIPANTS

The analyses presented in this article were performed on raw or summarized low-vision patient ratings of visual function questionnaire (VFQ) items obtained from previously published research studies.

INTERVENTIONS

Previously published visual ability measures from Rasch analysis of low-vision patient ratings of items in different VFQs (National Eye Institute Visual Functioning Questionnaire, Index of Visual Functioning, Activities of Daily Vision Scale, Visual Activities Questionnaire) were equated with the Activity Inventory (AI) scale. The 39 items in the Self-Report Assessment of Functional Visual Performance (SRAFVP) and the 48 items in the Veterans Affairs Low Vision Visual Functioning Questionnaire (VA LV VFQ) were paired with similar items in the AI in order to equate the scales.

MAIN OUTCOME MEASURES

Tests using different observation methods and indicators cannot be directly compared on the same scale. All test results would have to be transformed to measures of the same functional ability variable on a common scale as described here, before a single measure could be estimated from the multiple measures.

RESULTS

Bivariate regression analysis was performed to linearly transform the SRAFVP and VA LV VFQ item measures to the AI item measure scale. The nonlinear relationship between person measures of visual ability on a logit scale and item response raw scores was approximated with a logistic function, and the 2 regression coefficients were estimated for each of the 7 VFQs. These coefficients can be used with the logistic function to estimate functional ability on the same interval scale for each VFQ and for transforming raw VFQ responses to Medicare's G-code severity modifier categories.

CONCLUSIONS

The principle of using equated interval scales allows for comparison across measurement instruments of low-vision functional status and outcomes, but can be applied to any area of rehabilitation.

Comparing the Impact of Refractive and Nonrefractive Vision Loss on Functioning and Disability: The Salisbury Eye Evaluation

PURPOSE

To compare the effects of uncorrected refractive error (URE) and nonrefractive visual impairment (VI) on performance and disability measures.

DESIGN

Cross-sectional, population-based study.

PARTICIPANTS

A total of 2469 individuals with binocular presenting visual acuity (PVA) of ≥ 20/80 who participated in the first round of the Salisbury Eye Evaluation study.

METHODS

The URE was defined as binocular PVA of ≤ 20/30, improving to >20/30 with subjective refraction. The VI was defined as post-refraction binocular best-corrected visual acuity (BCVA) of ≤ 20/30. The visual acuity decrement due to VI was calculated as the difference between BCVA and 20/30, whereas visual acuity due to URE was taken as the difference between PVA and BCVA. Multivariable regression analyses were used to assess the disability impact of (1) vision status (VI, URE, or normal vision) using the group with normal vision as reference and (2) a 1-line decrement in acuity due to VI or URE.

MAIN OUTCOME MEASURES

Objective measures of visual function were obtained from timed performance of mobility and near vision tasks, self-reported driving cessation, and self-reported visual difficulty measured by the Activities of Daily Vision (ADV) scale. The ADV responses were analyzed using Rasch analysis to determine visual ability.

RESULTS

Compared with individuals with normal vision, subjects with VI (n = 191) had significantly poorer objective and subjective visual functioning in all metrics examined (P < 0.05), whereas subjects with URE (n = 132) demonstrated slower walking speeds, slower near task performance, more frequent driving cessation, and lower ADV scores (P < 0.05), but did not demonstrate slower stair climbing or descent speed. For all functional metrics evaluated, the impact of VI was greater than the impact of URE. The impact of a 1-line VA decrement due to VI was associated with greater deficits in mobility measures and driving cessation when compared with a 1-line VA decrement due to URE.

CONCLUSIONS

Visual impairment is associated with greater disability than URE across a wide variety of functional measures, even in analyses adjusting for the severity of vision loss. Refractive and nonrefractive vision loss should be distinguished in studies evaluating visual disability and be understood to have differing consequences.

Visual ability of patients seeking outpatient low vision services in the United States

IMPORTANCE

Most patients with low vision are elderly and have functional limitations from other health problems that could add to the functional limitations caused by their visual impairments.

OBJECTIVE

To identify factors that contribute to visual ability measures in patients who present for outpatient low vision rehabilitation (LVR) services.

DESIGN, SETTING, AND PARTICIPANTS

As part of a prospective, observational study of new patients seeking outpatient LVR, 779 patients from 28 clinical centers in the United States were enrolled in the Low Vision Rehabilitation Outcomes Study (LVROS) from April 25, 2008, through May 2, 2011. The Activity Inventory (AI), an adaptive visual function questionnaire, was administered to measure overall visual ability and visual ability in 4 functional domains (reading, mobility, visual motor function, and visual information processing) at baseline before LVR. The Geriatric Depression Scale, Telephone Interview for Cognitive Status, and Medical Outcomes Study 36-Item Short-Form Health Survey physical functioning questionnaires were also administered to measure patients' psychological, cognitive, and physical health states, respectively.

MAIN OUTCOMES AND MEASURES

Predictors of visual ability and functional domains as measured by the AI.

RESULTS

Among the 779 patients in the LVROS sample, the mean age was 76.4 years, 33% were male, and the median logMAR visual acuity score was 0.60 (0.40-0.90 interquartile range). Correlations were observed between logMAR visual acuity and baseline visual ability overall (r = -0.42) and for all functional domains. Visual acuity was the strongest predictor of visual ability (P  < .001) and reading ability (P < .001) and had a significant independent effect on the other functional domains. Physical ability was independently associated with (P < .001) overall visual ability as well as mobility and visual motor function. Depression had a consistent independent effect (P < .001) on overall visual ability and on all functional domains, whereas cognition had an effect on only reading and mobility (P < .001).

CONCLUSIONS AND RELEVANCE

Visual ability is a multidimensional construct, with visual acuity, depression, physical ability, and cognition explaining more than one-third of the variance in visual ability as measured by the AI. The significant contributions of the nonvisual factors to visual ability measures and the rehabilitation potential (ie, ceiling) effects they may impose on LVR are important considerations when measuring baseline visual ability and ultimately LVR outcomes in ongoing clinical research.

Reading ability and reading engagement in older adults with glaucoma

PURPOSE

We evaluated the impact of glaucoma-related vision loss on reading ability and reading engagement in 10 reading activities.

METHODS

A total of 63 glaucoma patients and 59 glaucoma suspect controls self-rated their level of reading difficulty for 10 reading items, and responses were analyzed using Rasch analysis to determine reading ability. Reading engagement was assessed by asking subjects to report the number of days per week they engaged in each reading activity. Reading restriction was determined as a decrement in engagement.

RESULTS

Glaucoma subjects more often described greater reading difficulty than controls for all tasks except puzzles (P < 0.05). The most difficult reading tasks involved puzzles, books, and finances, while the least difficult reading tasks involved notes, bills, and mail. In multivariable weighted least squares regression models of Rasch-estimated person measures of reading ability, less reading ability was found for glaucoma patients compared to controls (β = -1.60 logits, P < 0.001). Among glaucoma patients, less reading ability was associated with more severe visual field (VF) loss (β = -0.68 logits per 5-dB decrement in better-eye VF mean deviation [MD], P < 0.001) and contrast sensitivity (β = -0.76 logits per 0.1-unit lower log CS, P < 0.001). Each 5-dB decrement in the better-eye VF MD was associated with book reading on 18% fewer days (P = 0.003) and newspaper reading on 10% fewer days (P = 0.008). No statistically significant reading restriction was observed for other reading activities (P > 0.05).

CONCLUSIONS

Glaucoma patients have less reading ability and engage less in a variety of different reading activities, particularly those requiring sustained reading. Future work should evaluate the mechanisms underlying reading disability in glaucoma to determine how patients can maintain reading ability and engagement.

Low vision depression prevention trial in age-related macular degeneration: a randomized clinical trial

PURPOSE

To compare the efficacy of behavior activation (BA) + low vision rehabilitation (LVR) with supportive therapy (ST) + LVR to prevent depressive disorders in patients with age-related macular degeneration (AMD).

DESIGN

Single-masked, attention-controlled, randomized, clinical trial with outcome assessment at 4 months.

PARTICIPANTS

Patients with AMD and subsyndromal depressive symptoms attending retina practices (n = 188).

INTERVENTIONS

Before randomization, all subjects had 2 outpatient LVR visits, and were then randomized to in-home BA+LVR or ST+LVR. Behavior activation is a structured behavioral treatment that aims to increase adaptive behaviors and achieve valued goals. Supportive therapy is a nondirective, psychological treatment that provides emotional support and controls for attention.

MAIN OUTCOME MEASURES

The Diagnostic and Statistical Manual IV defined depressive disorder based on the Patient Health Questionnaire-9 (primary outcome), Activities Inventory, National Eye Institute Vision Function Questionnaire-25 plus Supplement (NEI-VFQ), and NEI-VFQ quality of life (secondary outcomes).

RESULTS

At 4 months, 11 BA+LVR subjects (12.6%) and 18 ST+LVR subjects (23.4%) developed a depressive disorder (relative risk [RR], 0.54; 95% CI, 0.27-1.06; P = 0.067). In planned adjusted analyses the RR was 0.51 (95% CI, 0.27-0.98; P = 0.04). A mediational analysis suggested that BA+LVR prevented depression to the extent that it enabled subjects to remain socially engaged. In addition, BA+LVR was associated with greater improvements in functional vision than ST+LVR, although there was no significant between-group difference. There was no significant change or between-group difference in quality of life.

CONCLUSIONS

An integrated mental health and low vision intervention halved the incidence of depressive disorders relative to standard outpatient LVR in patients with AMD. As the population ages, the number of persons with AMD and the adverse effects of comorbid depression will increase. Promoting interactions between ophthalmology, optometry, rehabilitation, psychiatry, and behavioral psychology may prevent depression in this population.

Personality and Functional Vision in Older Adults with Age-Related Macular Degeneration

Introduction

The purpose of the study was to determine whether personality traits influence self-reported functional vision in patients with age-related macular degeneration (AMD).

Methods

This is a prospective cross-sectional analysis of baseline data from the Low Vision Depression Prevention Trial. Participants ( N = 182) over age 65 with bilateral AMD, visual acuity worse than 20/70 in the better-seeing eye, and subthreshold depression were recruited from the Wills Eye Hospital retina practice. Assessments included visual acuity, contrast sensitivity, National Eye Institute Visual Function Questionnaire–25 plus Supplement (NEI VFQ–25) near and distance subscales, depression, and personality testing. Structural equation models were used to investigate the relationship of the NEI VFQ near activities and distance activities with the various demographic, clinical, and psychological predictors.

Results

In the single-predictor model for near functional vision, visual acuity at logMAR ≤ 1 (estimate = −0.33 [95% confidence interval {CI} −0.46, −0.20]; p ≤ 0.001), neuroticism (estimate = −0.05 [95% CI −0.08, −0.01]; p = 0.01), and education (estimate = −0.08 [95% CI 0.01, 0.15]; p = 0.03) were statistically significant predictors. In the single-predictor model for distance functional vision, only visual acuity at logMAR ≤ 1 (estimate = −0.49 [95% CI −0.69, −0.29]; p ≤ 0.001) and neuroticism (estimate = −0.09 [95% CI −0.15, 0.02]; p = 0.008) were statistically significant predictors. Discussion: Self-reported functional vision depends on the severity of vision loss as well as the personality trait of neuroticism.

Implications for practitioners

Assessment of personality traits, particularly neuroticism, may increase the precision of rating scales of functional vision and suggest new rehabilitative interventions to improve the functional vision and quality of life of patients with AMD.

Responsiveness of the EQ-5D to the effects of low vision rehabilitation

PURPOSE

This study is an evaluation of the responsiveness of preference-based outcome measures to the effects of low vision rehabilitation (LVR). It assesses LVR-related changes in EQ-5D utilities in patients who exhibit changes in Activity Inventory (AI) measures of visual ability.

METHODS

Telephone interviews were conducted on 77 low-vision patients out of a total of 764 patients in the parent study of "usual care" in LVR. Activity Inventory results were filtered for each patient to include only goals and tasks that would be targeted by LVR.

RESULTS

The EQ-5D utilities have weak correlations with all AI measures but correlate best with AI goal scores at baseline (r = 0.48). Baseline goal scores are approximately normally distributed for the AI, but EQ-5D utilities at baseline are skewed toward the ceiling (median, 0.77). Effect size for EQ-5D utility change scores from pre- to post-LVR was not significantly different from zero. The AI visual function ability change scores corresponded to a moderate effect size for all functional domains and a large effect size for visual ability measures estimated from AI goal ratings.

CONCLUSIONS

This study found that the EQ-5D is unresponsive as an outcome measure for LVR and has poor sensitivity for discriminating low vision patients with different levels of ability.

Fear of falling in age-related macular degeneration

Background

Prior studies have shown age-related macular degeneration (AMD) to be associated with falls. The purpose of this study is to determine if (AMD) and AMD-related vision loss are associated with fear of falling, an important and distinct outcome.

Methods

Sixty-five persons with AMD with evidence of vision loss in one or both eyes and 60 glaucoma suspects with normal vision completed the University of Illinois at Chicago Fear of Falling questionnaire. Responses were Rasch analyzed. Scores were expressed in logit units, with lower scores demonstrating lesser ability and greater fear of falling.

Results

Compared to glaucoma suspect controls, AMD subjects had worse visual acuity (VA) (median better-eye VA = 20/48 vs. 20/24, p < 0.001) and worse contrast sensitivity (CS) (binocular CS = 1.9 vs. 1.5 log units, p < 0.001). AMD subjects were also older, more likely to be Caucasian, and less likely to be employed (p < 0.05 for all), but were similar with regards to other demographic and health measures. In multivariable models controlling for age, gender, body habitus, strength, and comorbid illnesses, AMD subjects reported greater fear of falling as compared to controls (β = -0.77 logits, 95% CI = -1.5 to -0.002, p = 0.045). In separate multivariable models, fear of falling increased with worse VA (β = -0.15 logits/1 line decrement, 95% CI = -0.28 to -0.03, p = 0.02) and CS (β = -0.20 logits/0.1 log unit decrement, 95% CI = -0.31 to -0.09, p = 0.001). Greater fear of falling was also associated with higher BMI, weaker grip, and more comorbid illnesses (p < 0.05 for all).

Conclusions

AMD and AMD-related vision loss are associated with greater fear of falling in the elderly. Development, validation, and implementation of methods to address falls and fear of falling for individuals with vision loss from AMD are important goals for future work.

Improving function in age-related macular degeneration: a randomized clinical trial

PURPOSE

To compare the efficacy of problem-solving therapy (PST) with supportive therapy (ST) to improve targeted vision function (TVF) in age-related macular degeneration (AMD).

DESIGN

Single-masked, attention-controlled, randomized clinical trial with outcome assessments at 3 months (main trial endpoint) and 6 months (maintenance effects).

PARTICIPANTS

Patients with AMD (n = 241) attending retina practices.

INTERVENTIONS

Whereas PST uses a structured problem-solving approach to reduce vision-related task difficulty, ST is a standardized attention-control treatment.

MAIN OUTCOME MEASURES

We assessed TVF, the 25-item National Eye Institute Vision Function Questionnaire plus Supplement (NEI VFQ), the Activities Inventory (AI), and vision-related quality of life (QoL).

RESULTS

There were no between-group differences in TVF scores at 3 (P = 0.47) or 6 (P = 0.62) months. For PST subjects, mean ± standard deviation TVF scores improved from 2.71±0.52 at baseline to 2.18±0.88 at 3 months (P = 0.001) and were 2.18±0.95 at 6 months (change from 3 to 6 months, P = 0.74). For ST subjects, TVF scores improved from 2.73±0.52 at baseline to 2.14±0.96 at 3 months (P = 0.001) and were 2.15±0.96 at 6 months (change from 3 to 6 months, P = 0.85). Similar proportions of PST and ST subjects had less difficulty performing a TVF goal at 3 months (77.4% vs 78.6%, respectively; P = 0.83) and 6 months (76.2% vs 79.1%, respectively; P = 0.61). There were no changes in the NEI VFQ or AI. Vision-related QoL improved for PST relative to ST subjects at 3 months (F(4, 192) = 2.46; P = 0.05) and at 6 months (F(4, 178) = 2.55; P = 0.05). The PST subjects also developed more adaptive coping strategies than ST subjects.

CONCLUSIONS

We found that PST was not superior to ST at improving vision function in patients with AMD, but that PST improved their vision-related QoL. Despite the benefits of anti-vascular endothelial growth factor treatments, AMD remains associated with disability, depression, and diminished QoL. This clinical reality necessitates new rehabilitative interventions to improve the vision function and QoL of older persons with AMD.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Driving patterns in older adults with glaucoma

Background

The ability to drive is important for ensuring quality of life for many older adults. Glaucoma is prevalent in this age group and may affect driving. The purpose of this study is to determine if glaucoma and glaucomatous visual field (VF) loss are associated with driving cessation, limitations, and deference to another driver in older adults.

Methods

Cross-sectional study. Eighty-one glaucoma subjects and 58 glaucoma suspect controls between age 60 and 80 reported if they had ceased driving, limited their driving in various ways, or preferred another to drive.

Results

Twenty-three percent of glaucoma subjects and 6.9% of suspects had ceased driving (p = 0.01). Glaucoma subjects also had more driving limitations than suspects (2.0 vs. 1.1, p = 0.007). In multivariable models, driving cessation was more likely for glaucoma subjects as compared to suspects (OR = 4.0; 95% CI = 1.1-14.7; p = 0.03). The odds of driving cessation doubled with each 5 decibel (dB) decrement in the better-eye VF mean deviation (MD) (OR = 2.0; 95% CI = 1.4-2.9; p < 0.001). Glaucoma subjects were also more likely than suspects to report a greater number of driving limitations (OR = 4.7; 95% CI = 1.3-16.8; p = 0.02). The likelihood of reporting more limitations increased with the VF loss severity (OR = 1.6 per 5 dB decrement in the better-eye VF MD; 95% CI = 1.1-2.4; p = 0.02). Neither glaucoma nor VF MD was associated with other driver preference (p > 0.1 for both).

Conclusions

Glaucoma and glaucomatous VF loss are associated with greater likelihood of driving cessation and greater limitation of driving in the elderly. Further prospective study is merited to assess when and why people with glaucoma change their driving habits, and to determine if their observed self-regulation of driving is adequate to ensure safety.

A general theoretical framework for interpreting patient-reported outcomes estimated from ordinally scaled item responses

A simple theoretical framework explains patient responses to items in rating scale questionnaires. Fixed latent variables position each patient and each item on the same linear scale. Item responses are governed by a set of fixed category thresholds, one for each ordinal response category. A patient's item responses are magnitude estimates of the difference between the patient variable and the patient's estimate of the item variable, relative to his/her personally defined response category thresholds. Differences between patients in their personal estimates of the item variable and in their personal choices of category thresholds are represented by random variables added to the corresponding fixed variables. Effects of intervention correspond to changes in the patient variable, the patient's response bias, and/or latent item variables for a subset of items. Intervention effects on patients' item responses were simulated by assuming the random variables are normally distributed with a constant scalar covariance matrix. Rasch analysis was used to estimate latent variables from the simulated responses. The simulations demonstrate that changes in the patient variable and changes in response bias produce indistinguishable effects on item responses and manifest as changes only in the estimated patient variable. Changes in a subset of item variables manifest as intervention-specific differential item functioning and as changes in the estimated person variable that equals the average of changes in the item variables. Simulations demonstrate that intervention-specific differential item functioning produces inefficiencies and inaccuracies in computer adaptive testing.

Measurements of street-crossing decision-making in pedestrians with low vision

PURPOSE

Crossing the street is an important but risky activity of daily living. If a pedestrian makes a poor street-crossing decision, the consequence could be serious injury or death. In order to advance our understanding of how visual and auditory information is sampled and processed to make street-crossing decisions, an accurate, reliable, and sensitive psychophysical and/or psychometric method of measurement of the street-crossing decision variable must first be developed and validated. The aim of this paper is to develop and validate a new metric for this variable.

METHODS

Using a 5 point rating scale, safety ratings for eight different vehicular gap times of different durations were recorded along an unsignalized, two-lane street of one-way traffic. Safety ratings were collected from 12 normally sighted and 10 visually impaired subjects. Receiver Operating Characteristic (ROC) curves were estimated for all possible gap pairs and the discriminability (d') of the street-crossing decision variable for all gap pairs was estimated from the area under the ROC curve.

RESULTS

We found that our data conform with the assumptions that the underlying distributions of the decision variable are continuous, monotonic and unbounded. Using the dissimilarity matrix of d' values for each person (which were computed for all pairings of gap times) in a one-dimensional scaling model, we estimated the means of each distribution of the decision variable relative to a center of gravity (COG) for the person. When plotting the means of the distributions against vehicular gap time, the data are best described as a non-linear function symmetric about the COG. We showed that the x-intercept (t(COG)) and slope from the non-linear function can be used to assess a person's street-crossing decision-making performance for different amounts of sensory information. Using our newly developed metrics, we found no significant difference in t(COG) (p=0.30) and in the slopes of the model (p=0.85) between normally sighted and visually impaired subjects. In addition, both subject groups centered their t(COG) close to their actual crossing time.

CONCLUSIONS

A newly developed model for measuring a street-crossing decision variable functions as a valid metric that can be used to quantify street-crossing decision-making performance in pedestrians. Using this new metric, we observed that visually impaired subjects who travel independently are able to make street-crossing judgments that are comparable to those of normally sighted subjects.

Baseline traits of low vision patients served by private outpatient clinical centers in the United States

OBJECTIVE

To characterize the traits of low vision patients who seek outpatient low vision rehabilitation (LVR) services in the United States.

METHODS

In a prospective observational study, we enrolled 764 new low vision patients seeking outpatient LVR services from 28 clinical centers in the United States. Before their initial appointment, multiple questionnaires assessing daily living and vision, physical, psychological, and cognitive health states were administered by telephone. Baseline clinical visual impairment measures and disorder diagnoses were recorded.

RESULTS

Patients had a median age of 77 years, were primarily female (66%), and had macular disease (55%), most of which was nonneovascular age-related macular degeneration. More than one-third of the patients (37%) had mild vision impairment with habitual visual acuity (VA) of 20/60 or greater. The VA correlated well with contrast sensitivity (r = -0.52) but poorly with self-reported vision quality. The intake survey revealed self-reported physical health limitations, including decreased endurance (68%) and mobility problems (52%). Many patients reported increased levels of frustration (42%) and depressed mood (22%); memory and cognitive impairment (11%) were less frequently endorsed. Patients relied on others for daily living support (87%), but many (31%) still drove.

CONCLUSIONS

Most patients seeking LVR are geriatric and have macular disease with relatively preserved VA. The disparity between VA and subjective quality of vision suggests that LVR referrals are based on symptoms rather than on VA alone. Patients seen for LVR services have significant physical, psychological, and cognitive disorders that can amplify vision disabilities and decrease rehabilitation potential.

VA LOVIT II: a protocol to compare low vision rehabilitation and basic low vision

PURPOSE

To compare the effectiveness of low vision rehabilitation (LVR) and basic low vision (LV) in a single masked multicentre randomised controlled trial (RCT).

METHODS

Three hundred and thirty patients eligible for US. Veterans Affairs (VA) healthcare services with primary eye diagnosis (better-seeing eye) of macular disease and best-corrected distance visual acuity of 0.40-1.00 logMAR (6/15 to 6/60 or 20/50 to 20/200 Snellen) are being enrolled at seven VA facilities. All participants receive an optometric LV examination; and they are eligible to receive the same LV devices that are provided without charge. In LVR, a LV therapist dispenses devices and provides 2 or 3 (1½ to 2½ h) therapy sessions with assigned homework to teach effective use of remaining vision and LV devices. Contact time with the therapist depends upon the devices prescribed and the patient's progress in learning the skills that are taught. In basic LV, devices are dispensed by the optometrist without LV therapy. Contact time for dispensing is one hour or less depending on LV devices prescribed. The primary outcome measure is a comparison of the changes in visual reading ability (estimated from patients' difficulty ratings of reading items on the VA LV VFQ-48 questionnaire) between the treatment and control arms from pre-intervention baseline to 4 months (2 months after completion of treatment). Secondary outcome measures are changes in overall visual ability, visual ability domain scores calculated from subsets of items (mobility, visual information processing and visual motor skills), Short Form-36, and Minnesota Low Vision Reading Test scores. Cost-effectiveness analysis will be conducted using VA LV VFQ-48 scores and QALYS computed from EuroQol scores.

RESULTS

A total of 137 patients representing 41.5% of the study target of 330 patients were randomised from October 2010 to March 2012. Among those 137 patients, mean age was 80.2 (S.D. ± 9.9) years at enrollment; 97.1% of the patients were males; 94.2% were white. Mean best corrected VA was 0.65 (S.D. ± 0.3) logMAR (approximately Snellen 6/27 or 20/90) at baseline.

CONCLUSIONS

LOVIT II is the first multicentre RCT comparing the effectiveness and cost-effectiveness of LVR and basic LV for patients with macular diseases and near normal or moderate levels of visual impairment.

Latent dry eye disease state variable

PURPOSE

Evidence is growing that dry eye represents a common disease process resulting from a number of underlying pathologies that impact the ocular surface and that clinical estimates of dry eye severity reflect the magnitude of a single dry eye disease state variable, Θ. A theory for estimating Θ from scaled clinical observations is developed, and the hypothesis is tested that Θ exists.

METHODS

The theory is developed around three assumptions: (1) a monotonic function unique to each person and indicator maps the indicator onto Θ, (2) between-person differences in mapping functions are random, and (3) observed indicator values include random perturbations. Data recently published by Sullivan and his colleagues were digitized from scatter plots of seven different indicators versus a composite severity score (square root of summed weighted squared indicator scores).

RESULTS

The data were analyzed with a model derived under the specific assumptions that between-person variance in mapping functions is independent of the indicator value and random perturbations in observed indicator values are normally distributed. Tear osmolarity was the most sensitive indicator, and tear breakup time was the least. The distribution of residuals (squared difference between observed and predicted indicator values) agreed with model expectations for all indicators except tear osmolarity, which had larger residuals than expected, and the composite severity score, which had smaller residuals than expected.

CONCLUSIONS

The results are consistent with the existence of a single latent dry eye disease state variable. Only tear osmolarity does not appear to map monotonically and/or unidimensionally onto the latent variable.

Fear of falling and visual field loss from glaucoma

OBJECTIVE

To determine if visual field (VF) loss resulting from glaucoma is associated with greater fear of falling.

DESIGN

Prospective, observational study.

PARTICIPANTS

Fear of falling was compared between 83 glaucoma subjects with bilateral VF loss and 60 control subjects with good visual acuity and without significant VF loss recruited from patients followed up for suspicion of glaucoma.

METHODS

Participants completed the University of Illinois at Chicago Fear of Falling Questionnaire. The extent of fear of falling was assessed using Rasch analysis.

MAIN OUTCOME MEASURES

Subject ability to perform tasks without fear of falling was expressed in logits, with lower scores implying less ability and greater fear of falling.

RESULTS

Glaucoma subjects had greater VF loss than control subjects (median better-eye mean deviation [MD] of -8.0 decibels [dB] vs. +0.2 dB; P<0.001), but did not differ with regard to age, race, gender, employment status, the presence of other adults in the home, body mass index (BMI), grip strength, cognitive ability, mood, or comorbid illness (P ≥ 0.1 for all). In multivariate models, glaucoma subjects reported greater fear of falling as compared with controls (β = -1.20 logits; 95% confidence interval [CI], -1.87 to -0.53; P = 0.001), and fear of falling increased with greater VF loss severity (β = -0.52 logits per 5-dB decrement in the better eye VF MD; 95% CI, -0.72 to -0.33; P<0.001). Other variables predicting greater fear of falling included female gender (β = -0.55 logits; 95% CI, -1.03 to -0.06; P = 0.03), higher BMI (β = -0.07 logits per 1-unit increase in BMI; 95% CI, -0.13 to -0.01; P = 0.02), living with another adult (β = -1.16 logits; 95% CI, -0.34 to -1.99 logits; P = 0.006), and greater comorbid illness (β = -0.53 logits/1 additional illness; 95% CI, -0.74 to -0.32; P<0.001).

CONCLUSIONS

Bilateral VF loss resulting from glaucoma is associated with greater fear of falling, with an impact that exceeds numerous other risk factors. Given the physical and psychological repercussions associated with fear of falling, significant quality-of-life improvements may be achievable in patients with VF loss by screening for, and developing interventions to minimize, fear of falling.

Is the partial credit model a Rasch model?

A balance scale metaphor is offered as a tool for explaining the principles of measurement and for visualizing the internal structure of dichotomous and polytomous Rasch models. The balance scale metaphor is used to guide the derivation of a general polytomous Rasch model and to illustrate the additional assumptions subsequently required to derive the Andrich (1978) rating scale model (RSM) and the Masters (1982) partial credit model (PCM). The metaphor is used to present the argument that the RSM conforms to the rules of measurement, but the PCM has interactions implicit in its structure that violate specific objectivity and sufficiency of raw scores, which challenge its status as a Rasch model. Using the metaphor and a literal interpretation of the narrative description of the PCM by Masters (1982), a new version of the PCM is derived that does conform to the rules of measurement.

Psychological and cognitive determinants of vision function in age-related macular degeneration

OBJECTIVE

To investigate the effect of coping strategies, depression, physical health, and cognition on National Eye Institute Visual Function Questionnaire scores obtained at baseline in a sample of older patients with age-related macular degeneration (AMD) enrolled in the Improving Function in AMD Trial, a randomized controlled clinical trial that compares the efficacy of problem-solving therapy with that of supportive therapy to improve vision function in patients with AMD.

METHODS

Baseline evaluation of 241 older outpatients with advanced AMD who were enrolled in a clinical trial testing the efficacy of a behavioral intervention to improve vision function. Vision function was characterized as an interval-scaled, latent variable of visual ability based on the near-vision subscale of the National Eye Institute Vision Function Questionnaire-25 plus Supplement.

RESULTS

Visual ability was highly correlated with visual acuity. However, a multivariate model revealed that patient coping strategies and cognitive function contributed to their ability to perform near-vision activities independent of visual acuity.

CONCLUSIONS

Patients with AMD vary in their coping strategies and cognitive function and in their visual acuity, and that variability determines patients' self-report of vision function. Understanding patient coping mechanisms and cognition may help increase the precision of vision rating scales and suggest new interventions to improve vision function and quality of life in patients with AMD. Trial Registration  clinicaltrials.gov Identifier: NCT00572039.

The impact of cataract surgery on patients from a low-vision clinic

OBJECTIVE

To evaluate the effects of cataract extraction with intraocular lens implantation (CE-IOL) in low-vision patients.

DESIGN

Prospective, interventional case series.

PARTICIPANTS

Twenty low-vision patients (30 eyes) underwent CE-IOL by 1 surgeon at an academic institution.

METHODS

Pre- and post-CE-IOL visual acuities and responses to a 23-page survey (self-reported functioning in general vision, mobility, illumination, and ability to see faces) were compared.

RESULTS

Sixteen patients had age-related macular degeneration (AMD); 1 patient each had rod-cone dystrophy, oculocutaneous albinism, retinitis pigmentosa, or cerebrovascular accident. The average age was 78 years (range: 53-96 years). Preoperative best-corrected visual acuity (BCVA) ranged from 20/70 to count fingers; postoperative BCVA at 8 weeks was 20/40 to 20/400, with improvement in 25 (83%) eyes of 15 patients, and no change in the rest. The average change in logMAR of BCVA in the 1 eye or in the eye with better preoperative vision in bilateral surgery was an improvement of 0.6 logMAR units (p = 0.0001). Seventeen (85%) patients noted an improvement in visual function and would consent to CE-IOL again. Twelve patients completed the survey pre- and post-CE-IOL at 3 months. More patients could read with a magnifier after surgery. On average, self-reported functioning was improved.

CONCLUSIONS

In this small study, CE-IOL offered subjective and objective benefits to patients from a low vision clinic, many of whom may have been dissuaded from CE-IOL. Most patients had moderately dense cataracts and moderate to advanced AMD, and these features may help form clinical recommendations. Expectations are important to elicit preoperatively. Postoperatively, patients may be more receptive to low-vision services and devices when the prognosis for visual rehabilitation is better.

Improving function in age-related macular degeneration: design and methods of a randomized clinical trial

Age-Related Macular Degeneration (AMD) is the leading cause of severe vision loss in older adults and impairs the ability to read, drive, and live independently and increases the risk for depression, falls, and earlier mortality. Although new medical treatments have improved AMD's prognosis, vision-related disability remains a major public health problem. Improving Function in AMD (IF-AMD) is a two-group randomized, parallel design, controlled clinical trial that compares the efficacy of Problem-Solving Therapy (PST) with Supportive Therapy (ST) (an attention control treatment) to improve vision function in 240 patients with AMD. PST and ST therapists deliver 6 one-hour respective treatment sessions to subjects in their homes over 2 months. Outcomes are assessed masked to treatment assignment at 3 months (main trial endpoint) and 6 months (maintenance effects). The primary outcome is targeted vision function (TVF), which refers to specific vision-dependent functional goals that subjects highly value but find difficult to achieve. TVF is an innovative outcome measure in that it is targeted and tailored to individual subjects yet is measured in a standardized way. This paper describes the research methods, theoretical and clinical aspects of the study treatments, and the measures used to evaluate functional and psychiatric outcomes in this population.

Medicare coverage for vision assistive equipment

Vision loss that cannot be corrected medically, surgically, or by refractive means is considered low vision. Low vision often results in impairment of daily activities, loss of independence, increased risk of fractures, excess health care expense, and reduced physical functioning, quality of life, and life expectancy. Vision rehabilitation can enable more independent functioning for individuals with low vision. The Centers for Medicare and Medicaid Services recognizes the importance of rehabilitation for achieving medically necessary goals but has denied Medicare coverage for vision assistive equipment that is necessary to complete these goals, although they provide coverage for assistive equipment to provide compensation for other disabilities. We believe that this is discriminatory and does not comport with congressional intent. The Centers for Medicare and Medicaid Services should provide coverage for vision assistive equipment, allowing beneficiaries with vision loss to benefit fully from Medicare-covered rehabilitation to achieve the cost-effective results of these services.

A clinically meaningful theory of outcome measures in rehabilitation medicine

Comparative effectiveness research in rehabilitation medicine requires the development and validation of clinically meaningful and scientifically rigorous measurements of patient states and theories that explain and predict outcomes of intervention. Patient traits are latent (unobservable) variables that can be measured only by inference from observations of surrogate manifest (observable) variables. In the behavioral sciences, latent variables are analogous to intensive physical variables such as temperature and manifest variables are analogous to extensive physical variables such as distance. Although only one variable at a time can be measured, the variable can have a multidimensional structure that must be understood in order to explain disagreements among different measures of the same variable. The use of Rasch theory to measure latent trait variables can be illustrated with a balance scale metaphor that has randomly added variability in the weights of the objects being measured. Knowledge of the distribution of the randomly added variability provides the theoretical structure for estimating measures from ordinal observation scores (e.g., performance measures or rating scales) using statistical inference. In rehabilitation medicine, the latent variable of primary interest is the patient's functional ability. Functional ability can be estimated from observations of surrogate performance measures (e.g., speed and accuracy) or self-report of the difficulty the patient experiences performing specific activities. A theoretical framework borrowed from project management, called the Activity Breakdown Structure (ABS), guides the choice of activities for assessment, based on the patient's value judgments, to make the observations clinically meaningful. In the case of low vision, the functional ability measure estimated from Rasch analysis of activity difficulty ratings was discovered to be a two-dimensional variable. The two visual function dimensions are independent of physical limitations and psychological state. To explain outcome measures (latent variable estimated from difficulty ratings), a theory must be developed that explicitly defines how latent variables are related to the observed manifest variables and to each other. The latent variables are categorized as primary variables, which in the case of low vision are the two visual function dimensions, and as effect modifiers, which in the case of low vision are other physical and psychological latent traits of the patients that can influence the outcome measures. Interventions give rise to latent intervention effect variables that can alter the latent primary variables or independently affect the outcome measures. The latent effect modifier variables, in turn, can alter the latent intervention effect variables. Once developed and validated, a theory of this form will predict the rehabilitation potential of individual patients, i.e., the probability of obtaining criterion outcome measures given the observed state of the patient and the choice of interventions.