Catalogue Search | MBRL
Search Results Heading
Explore the vast range of titles available.
MBRLSearchResults
-
DisciplineDiscipline
-
Is Peer ReviewedIs Peer Reviewed
-
Item TypeItem Type
-
SubjectSubject
-
YearFrom:-To:
-
More FiltersMore FiltersSourceLanguage
Done
Filters
Reset
103
result(s) for
"Crabb, David P"
Sort by:
How does age-related macular degeneration affect real-world visual ability and quality of life? A systematic review
by
Taylor, Deanna J
,
Crabb, David P
,
Hobby, Angharad E
in
Age Factors
,
Humans
,
Macular Degeneration - physiopathology
2016
ObjectivesTo review systematically the evidence of age-related macular degeneration (AMD) affecting real-world visual ability and quality of life (QoL). To explore trends in specific topics within this body of the literature.DesignSystematic review.MethodsA systematic literature search was carried out using MEDLINE, EMBASE, CINAHL, PsycINFO, PsychARTICLES and Health and Psychosocial Instruments for articles published up to January 2015 for studies including people diagnosed with AMD, assessing real-world visual ability or QoL as an outcome. Two researchers screened studies for eligibility. Details of eligible studies including study design, characteristics of study population and outcomes measured were recorded in a data extraction table. All included studies underwent quality appraisal using the Mixed Methods Appraisal Tool 2011 Version (MMAT).ResultsFrom 5284 studies, 123 were eligible for inclusion. A range of approaches were identified, including performance-based methods, quantitative and qualitative patient-reported outcome measures (PROMs). AMD negatively affects tasks including mobility, face recognition, perception of scenes, computer use, meal preparation, shopping, cleaning, watching TV, reading, driving and, in some cases, self-care. There is evidence for higher rates of depression among people with AMD than among community dwelling elderly. A number of adaptation strategies have been associated with AMD of varying duration. Much of the research fails to report the type of AMD studied (59% of included studies) or the duration of disease in participants (74%). Of those that do report type studied, the breakdown is as follows: wet AMD 20%, dry AMD 4% and both types 17%.ConclusionsThere are many publications highlighting the negative effects of AMD in various domains of life. Future research should focus on delivering some of this research knowledge into patient management and clinical trials and differentiating between the types of AMD.
Journal Article
Measures of multiple deprivation and visual field loss in glaucoma clinics in England: lessons from big data
by
Shweikh, Yusrah
,
Rathore, Mehal
,
Kelly, Stephen R.
in
692/699/3161/3172
,
692/700/478/174
,
Big Data
2023
Background/Objectives
To examine the association between multiple deprivation with late diagnosis and rapid worsening of glaucoma in patients in English hospital eye services (HES).
Methods
602,439 visual fields (VFs) were extracted from five regionally different glaucoma clinics in England. Mean Deviation (MD) worse than −12 dB was used as a surrogate definition for advanced VF loss at diagnosis in patients with ≥2 reliable VF records. MD loss worse than -1 dB per year was used to define rapid VF progression in patients with ≥6 VFs. Patient data were stratified into deciles of the Index of Multiple Deprivation (IMD) from residential postcodes.
Results
There was an association between IMD and advanced VF loss at diagnosis in 44,956 patients with 18% (293/1608) and 11% (771/6929) in the most and least deprived IMD decile, respectively. Age-corrected odds ratio (OR) for having advanced VF loss at entry into HES was 1.42 (95% confidence interval [CI] 1.21–1.67) and 0.75 (95% CI: 0.66–0.85) in the most and least deprived IMD decile respectively (reference = fifth decile). In 15,094 patients with follow up data (median [interquartile range] of 6.9 [4.5, 10.0] years), the proportion having rapid VF progression did not differ across the IMD spectrum.
Conclusion
Large-scale VF data from clinics indicates that glaucoma severity at presentation to English HES is associated with levels of multiple deprivation. We found no evidence to suggest likelihood of having rapid VF progression during follow-up is associated with IMD; this hints at equity of glaucoma care and outcomes once patients are in English HES.
Journal Article
More frequent, more costly? Health economic modelling aspects of monitoring glaucoma patients in England
2016
Background
Chronic open angle glaucoma (COAG) is an age-related eye disease causing irreversible loss of visual field (VF). Health service delivery for COAG is challenging given the large number of diagnosed patients requiring lifelong periodic monitoring by hospital eye services. Yet frequent examination better determines disease worsening and speed of VF loss under treatment. We examine the cost-effectiveness of increasing frequency of VF examinations during follow-up using a health economic model.
Methods
Two different VF monitoring schemes defined as
current practice
(annual VF testing) and
proposed practice
(three VF tests per year in the first 2 years after diagnosis) were examined. A purpose written health economic Markov model is used to test the hypothesis that cost effectiveness improves by implementing
proposed practice
on groups of patients stratified by age and severity of COAG. Further, a new component of the model, estimating costs of visual impairment, was added. Results were derived from a simulated cohort of 10000 patients with quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) used as main outcome measures.
Results
An ICER of £21,392 per QALY was derived for
proposed practice
improving to a value of £11,382 once savings for prevented visual impairment was added to the model.
Proposed practice
was more cost-effective in younger patients.
Proposed practice
for patients with advanced disease at diagnosis generated ICERs > £60,000 per QALY; these cases would likely be on the most intensive treatment pathway making clinical information on speed of VF loss redundant. Sensitivity analysis indicated results to be robust in relation to hypothetical willingness to pay threshold identified by national guidelines, although greatest uncertainty was allied to estimates of implementation and visual impairment costs.
Conclusion
Increasing VF monitoring at the earliest stages of follow-up for COAG appears to be cost-effective depending on reasonable assumptions about implementation costs. Our health economic model highlights benefits of stratifying patients to more or less monitoring based on age and stage of disease at diagnosis; a prospective study is needed to prove these findings. Further, this works highlights gaps in knowledge about long term costs of visual impairment.
Journal Article
Contrast Sensitivity and Night Driving in Older People: Quantifying the Relationship Between Visual Acuity, Contrast Sensitivity, and Hazard Detection Distance in a Night-Time Driving Simulator
2022
Purpose: (i) To assess how well contrast sensitivity (CS) predicts night driving ability in normally sighted older drivers, relative to a conventional measure of high contrast visual acuity (VA); (ii) To evaluate whether CS can be accurately quantified within a night driving simulator. Methods: Participants were fifteen (five female) ophthalmologically healthy adults, aged 55 to 81 years. CS was measured in a driving simulator using Landolt Cs, presented under static or dynamic driving conditions, and with or without glare. In the dynamic driving condition, the participant was asked to simultaneously maintain a (virtual) speed of 60 km/h on a country road. In the (dynamic) with glare condition, two calibrated LED arrays, moved by cable robots, simulated the trajectories and luminance characteristics of the (low beam) headlights of an approaching car. For comparison, CS was also measured clinically (with & without glare) using an Optovist I instrument modified for an enhanced contrast range towards low contrast levels (Vistec Inc., Olching/FRG). Visual acuity (VA) thresholds were also assessed at high and low contrast using the Freiburg Visual Acuity Test (FrACT) under photopic conditions. As a measure of driving performance, median hazard detection distance (MHDD) was computed, in meters, across three kinds of simulated obstacles of varying contrast. Results: CS and low contrast VA were both significantly associated with driving performance (both P < 0.01), whereas conventional high contrast acuity was not (P = 0.10). There was good agreement (P < 0.01) between CS measured in the driving simulator and a conventional clinical instrument (Optovist). As expected, CS was shown to decrease in the presence of glare, in dynamic driving conditions, and as a function of age (all P < 0.01). Conclusions: CS and low contrast VA predict night driving ability (operationalized as median hazard detection distance) in a manner that conventional high contrast VA does not. Either may therefore provide a useful metric for assessing fitness to drive at night, particularly in older individuals. CS measurements can be made within a driving simulator, and the data are in good agreement with conventional clinical methods (Optovist I).
Journal Article
Seeing other perspectives: evaluating the use of virtual and augmented reality to simulate visual impairments (OpenVisSim)
by
Somoskeöy, Tamás
,
Jones, Pete R.
,
Chow-Wing-Bom, Hugo
in
692/1807/2781
,
692/308/575
,
692/699/3161/3178
2020
Simulations of visual impairment are used to educate and inform the public. However, evidence regarding their accuracy remains lacking. Here we evaluated the effectiveness of modern digital technologies to simulate the everyday difficulties caused by glaucoma. 23 normally sighted adults performed two everyday tasks that glaucoma patients often report difficulties with: a visual search task in which participants attempted to locate a mobile phone in virtual domestic environments (virtual reality (VR)), and a visual mobility task in which participants navigated a physical, room-scale environment, while impairments were overlaid using augmented reality (AR). On some trials, a gaze-contingent simulated scotoma—generated using perimetric data from a real patient with advanced glaucoma—was presented in either the superior or inferior hemifield. The main outcome measure was task completion time. Eye and head movements were also tracked and used to assess individual differences in looking behaviors. The results showed that the simulated impairments substantially impaired performance in both the VR (visual search) and AR (visual mobility) tasks (both
P
< 0.001). Furthermore, and in line with previous patient data: impairments were greatest when the simulated Visual Field Loss (VFL) was inferior versus superior (
P
< 0.001), participants made more eye and head movements in the inferior VFL condition (
P
< 0.001), and participants rated the inferior VFL condition as more difficult (
P
< 0.001). Notably, the difference in performance between the inferior and superior conditions was almost as great as the difference between a superior VFL and no impairment at all (VR: 71%; AR: 70%). We conclude that modern digital simulators are able to replicate and objectively quantify some of the key everyday difficulties associated with visual impairments. Advantages, limitations, and possible applications of current technologies are discussed. Instructions are also given for how to freely obtain the software described (OpenVisSim).
Journal Article
Impact of superior and inferior visual field loss on hazard detection in a computer-based driving test
by
Crabb, David P
,
Smith, Nicholas D
,
Glen, Fiona C
in
Accidents, Traffic - prevention & control
,
Adult
,
Automobile Driver Examination
2015
Purpose Binocular visual field (VF) loss is linked to driving impairment, guiding authorities to implement fitness to drive requirements for VFs. Yet, evidence is limited regarding the specific types of VF defect that impede driving. This study used a novel gaze-contingent display to test the hypothesis that superior VF loss impacts detection of driving hazards more than inferior loss. Methods The Hazard Perception Test (HPT) is a computer-based component of the UK examination for learner drivers. It measures the response rate for detecting hazards in a series of real-life driving films, yielding a score out of 75, calculated based on the efficiency of detecting 15 hazards. Thirty UK drivers with healthy vision completed three versions of the HPT in a random order. In two versions, a computer set-up incorporating an eye-tracker modified a simulated VF defect in the superior and inferior VFs, respectively, according to the users’ real-time gaze as they completed the HPT. The other version was unmodified to measure the baseline performance. Results Participants’ mean score at baseline was 49/75 (SD=9). Mean (SD) performance fell by 18% (40(11)) when viewing films with a superior defect and 12% with an inferior defect (43(10)). These average differences were statistically significant (p<0.001; 95% CI for mean difference=1–7) Conclusions In this study, simulated VF defects impaired the ability to detect driving hazards relative to participants’ normal performances, with superior defects having more impact than inferior defects. These results could help inform the design of fairer tests of the VF component for fitness to drive.
Journal Article
Detecting Changes in Retinal Function: Analysis with Non-Stationary Weibull Error Regression and Spatial Enhancement (ANSWERS)
by
Ceccon, Stefano
,
Garway-Heath, David F.
,
Saunders, Luke J.
in
Alzheimer's disease
,
Analysis
,
Automation
2014
Visual fields measured with standard automated perimetry are a benchmark test for determining retinal function in ocular pathologies such as glaucoma. Their monitoring over time is crucial in detecting change in disease course and, therefore, in prompting clinical intervention and defining endpoints in clinical trials of new therapies. However, conventional change detection methods do not take into account non-stationary measurement variability or spatial correlation present in these measures. An inferential statistical model, denoted 'Analysis with Non-Stationary Weibull Error Regression and Spatial enhancement' (ANSWERS), was proposed. In contrast to commonly used ordinary linear regression models, which assume normally distributed errors, ANSWERS incorporates non-stationary variability modelled as a mixture of Weibull distributions. Spatial correlation of measurements was also included into the model using a Bayesian framework. It was evaluated using a large dataset of visual field measurements acquired from electronic health records, and was compared with other widely used methods for detecting deterioration in retinal function. ANSWERS was able to detect deterioration significantly earlier than conventional methods, at matched false positive rates. Statistical sensitivity in detecting deterioration was also significantly better, especially in short time series. Furthermore, the spatial correlation utilised in ANSWERS was shown to improve the ability to detect deterioration, compared to equivalent models without spatial correlation, especially in short follow-up series. ANSWERS is a new efficient method for detecting changes in retinal function. It allows for better detection of change, more efficient endpoints and can potentially shorten the time in clinical trials for new therapies.
Journal Article
Heterogeneity of patient-reported outcome measures in clinical research
by
Jungblut, Julie
,
Terheyden, Jan Henrik
,
Holz, Frank G.
in
Bibliometrics
,
Biomedical Research
,
Brief Report
2024
Background
The use of patient-reported outcome measures (PROMs) in clinical research increases and use of heterogeneous instruments reflects how well diverse traits are captured by a medical specialty. In order to reflect the heterogeneity of current PROM use in ophthalmology, we reviewed the available literature.
Methods
The medical literature database Web of Science was searched for the most cited articles in clinical ophthalmology. Titles, abstracts and full text articles were reviewed for the use of PROMs and a list of the 100 most cited articles using PROMs was obtained and stratified by year of publication.
Results
A total of 1,996 articles were screened. Seventy-seven out of the 100 articles identified included one PROM, and the average number of instruments was 1.5 ± 1.1. The most widely used PROMs were the National Eye Institute Visual Function Questionnaire (33%), the Ocular Surface Disease Index (14%) and the Medical Outcomes Study Short Form (13%). A simulation analysis suggested that the distribution of PROM use in ophthalmology study did not significantly differ from a power law distribution. Twenty-two percent and fifteen percent of articles did not reference and did not specify the PROM used, respectively. This rate decreased in the more recently published articles (
p
= 0.041).
Conclusions
Our data suggest that the heterogeneity of PROMs applied in ophthalmology studies is low. The selection of PROMs for clinical studies should be done carefully, depending on the research goal.
Journal Article
Novel computer-based assessments of everyday visual function in people with age-related macular degeneration
2020
To test the hypothesis that the performance in novel computer-based tasks of everyday visual function worsens with disease severity in people with non-neovascular age-related macular degeneration.
Participants with and without non-neovascular age-related macular degeneration (≥60 years, minimum logMAR binocular visual acuity 0.7) performed a series of standard visual function tests and two novel computer-based tasks. In a visual search task, participants had to locate an image of a single real-world object within an array of 49 distractor images. Next, in a series of simulated dynamic driving scenes, participants were asked to identify one or two approaching real-world road signs and then select these road signs from four options. Outcome measures were median response times and total correct responses.
Forty-nine participants had no macular disease (n = 11), early/intermediate age-related macular degeneration (n = 16) or geographic atrophy (n = 22). Groups were age-similar with median (interquartile range) logMAR visual acuity of 0.00 (-0.08,0.12), 0.13 (-0.08,0.70) and 0.32 (0.12,0.70) respectively. Median (interquartile range) visual search response times were 1.9 (1.0,2.4), 1.8 (1.1,3.7) and 2.4 (1.2,6.0) seconds respectively. Median (interquartile range) road sign response times (single road signs) were 1.2 (0.4,1.7), 1.5 (0.9,2.8) and 1.8 (1.0,5.5) seconds respectively. Median (interquartile range) road sign response times (double road signs) were 1.7 (0.7,2.4), 2.3 (1.2,3.1) and 2.5 (1.7,6) seconds respectively. Participants with geographic atrophy recorded slower response times in all tasks and over 50% performed outside the normative limit for task performance. There were no significant differences between groups in total correct responses across all tasks.
In a novel computer-based assessment, people with increasing severity of age-related macular degeneration take longer to perform visual search of everyday objects and take longer to identify road signs than those with no age-related macular degeneration. These novel assessments could be useful as patient-relevant, secondary outcomes for clinical trials.
Journal Article
Assessing the resilience of portable vision tests to an uncontrolled home environment
by
Rathore, Mehal
,
Jones, Pete R.
,
Crabb, David P.
in
Adult
,
Contrast Sensitivity
,
Eye examinations
2026
In ophthalmology (and medicine more widely) there is increasing interest in telemedicine: having patients perform tests at home for greater efficiency and to meet growing demand. However, despite this increased interest in vision home monitoring, many vision tests are evaluated in standardised clinical settings, not home environments. Here, we investigated the resilience of two portable contrast sensitivity tests to the sorts of potentially confounding factors that may be encountered in a home setting.
Normally sighted adults (
= 107) performed two contrast sensitivity tests (one pen-and-paper and one tablet-based). Testing took place in a furnished apartment, where we could control/measure various extraneous factors (including illumination, time of day, seating type, screen cleanliness). Key outcome measures were raw contrast sensitivity scores, test-retest repeatability, and test duration; and how these metrics varied with extraneous factors.
No effect of time of day, participant motivation, or seating type was observed (all
> 0.140). Scores on the pen-and-paper test were not affected by illumination (
= 0.348), except when tests were conducted in extreme darkness (≤1 lux;
= 0.036). A follow-up study indicated that screen smudging (caused by fingerprints) had no significant effect on the outcome of the tablet-based test (
= 0.573).
Taken together, the results indicate that, contrary to our expectations, both digital and pen-and-paper contrast sensitivity tests appear relatively resilient to many of the sorts of extraneous factors encountered in a home setting. This speaks to the potential viability of vision home monitoring, though study limitations and necessary future work are discussed.
Journal Article