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Purpose: In eye movement perimetry, peripheral stimuli are confirmed by goal-directed eye movements toward the stimulus. The saccadic reaction time (SRT) is regarded as an index of visual field responsiveness, whereas in standard... more
Purpose: In eye movement perimetry, peripheral stimuli are confirmed by goal-directed eye movements toward the stimulus. The saccadic reaction time (SRT) is regarded as an index of visual field responsiveness, whereas in standard automated perimetry (SAP), the visual field sensitivity is tested. We investigated the relation between visual field sensitivity and responsiveness in corresponding locations of the visual field in healthy controls and in patients with mild, moderate and advanced glaucoma.Materials and Methods: Thirty-four healthy control subjects and 42 glaucoma patients underwent a 54-point protocol in eye movement perimetry (EMP) and a 24-2 SITA standard protocol in a Humphrey Field Analyzer. The visual field points were stratified by total deviation sensitivity loss in SAP into 6 strata. A generalized linear mixed model was applied to determine the influence of the various factors.Results: The generalized linear mixed model showed that the mean SRT increased with increa...
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BackgroundPatient‐reported outcome measures (PROMs) are valuable supplements in regular care to facilitate routine monitoring of quality of life from the patient’s perspective. The 25‐item National Eye Institute Visual Function... more
BackgroundPatient‐reported outcome measures (PROMs) are valuable supplements in regular care to facilitate routine monitoring of quality of life from the patient’s perspective. The 25‐item National Eye Institute Visual Function Questionnaire (NEI‐VFQ‐25) is a widely used PROM in ophthalmology. However, the NEI‐VFQ‐25 is too time‐consuming and cumbersome for routine evaluations in regular care. The aim of this study is to construct a 7‐item questionnaire of which only 3 items are presented to the patient, by means of routing. This VFQ 3 out of 7 (VFQ‐3oo7) should have a minimal loss of information compared with the NEI‐VFQ‐25.MethodsAn historical database including 3293 administrations of the NEI‐VFQ‐25 was constructed involving patients with retinal detachment, cataract, corneal diseases, glaucoma, macular degeneration, uveal melanoma and a normal population sample. The data were subjected to Rasch analyses, in particular a generalized partial credit model. Items were sorted on the ...
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PurposeTo study whether a clinically significant increase in intraocular pressure (IOP) occurs during simulated sleep conditions with the subject's head turned comfortably into a pillow (the simulated sleep position) and the effect of... more
PurposeTo study whether a clinically significant increase in intraocular pressure (IOP) occurs during simulated sleep conditions with the subject's head turned comfortably into a pillow (the simulated sleep position) and the effect of protective glasses on any such IOP rise.MethodsA specially developed electronic epipalpebral pressure (EPP) sensor was attached to an eyelid of the right eye of all participants: 11 patients with primary open‐angle glaucoma and 11 healthy volunteers. During calibration, mechanical pressure was applied to the EPP sensor taped to the lower eyelid and the IOP was measured simultaneously at the slit lamp by Goldmann applanation tonometry. The EPP was increased in a stepwise fashion to assess the relationship between EPP and IOP for each individual eye. Thereafter, EPP (with the sensor now taped to the upper eyelid) measurements were performed in the simulated sleep position, both with and without protective glasses. The EPP was determined in each indiv...
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Corneal endothelium images obtained by in vivo specular microscopy provide important information to assess the health status of the cornea. Estimation of clinical parameters, such as cell density, polymegethism, and pleomorphism, requires... more
Corneal endothelium images obtained by in vivo specular microscopy provide important information to assess the health status of the cornea. Estimation of clinical parameters, such as cell density, polymegethism, and pleomorphism, requires accurate cell segmentation. State-of-the-art techniques to automatically segment the endothelium are error-prone when applied to images with low contrast and/or large variation in cell size. Here, we propose an automatic method to segment the endothelium. Starting with an oversegmented image comprised of superpixels obtained from a stochastic watershed segmentation, the proposed method uses intensity and shape information of the superpixels to identify and merge those that constitute a cell, using Support Vector Machines. We evaluated the automatic segmentation on a dataset of in vivo specular microscopy images (Topcon SP-1P), obtaining 95.8merged cells and 2.0the parameter estimation against the results of the vendor's builtin software, obtain...
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The Bayesian approach has become increasingly popular because it allows to fit quite complex models to data via Markov chain Monte Carlo sampling. However, it is also recognized nowadays that Markov chain Monte Carlo sampling can become... more
The Bayesian approach has become increasingly popular because it allows to fit quite complex models to data via Markov chain Monte Carlo sampling. However, it is also recognized nowadays that Markov chain Monte Carlo sampling can become computationally prohibitive when applied to a large data set. We encountered serious computational difficulties when fitting an hierarchical model to longitudinal glaucoma data of patients who participate in an ongoing Dutch study. To overcome this problem, we applied and extended a recently proposed two-stage approach to model these data. Glaucoma is one of the leading causes of blindness in the world. In order to detect deterioration at an early stage, a model for predicting visual fields (VFs) in time is needed. Hence, the true underlying VF progression can be determined, and treatment strategies can then be optimized to prevent further VF loss. Because we were unable to fit these data with the classical one-stage approach upon which the current p...
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Purpose. To determine how different grades of cataract affect sensitivity threshold and saccadic reaction time (SRT) in eye movement perimetry (EMP).Methods. In EMP, the visual field is tested by assessing the saccades that a subject... more
Purpose. To determine how different grades of cataract affect sensitivity threshold and saccadic reaction time (SRT) in eye movement perimetry (EMP).Methods. In EMP, the visual field is tested by assessing the saccades that a subject makes towards peripheral stimuli using an eye tracker. Forty-eight cataract patients underwent pre- and postoperative EMP examination in both eyes. The subjects had to fix a central stimulus presented on the eye tracker monitor and to look at any detected peripheral stimulus upon its appearance. A multilevel mixed model was used to determine the factors that affected the sensitivity threshold and the SRT as a function of cataract grade.Results. We found no effect of cataract severity (LOCS III grades I through IV) on SRT and the sensitivity thresholds. In cataract of LOCS III grade V, however, we found an increase by 27% and 21% (p<0.001), respectively, compared to the SRT and the sensitivity threshold in LOCS III grade I. Eyes that underwent catarac...
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To study the metrics of lid saccades in blepharoptosis and to distinguish any differences in the dynamics of eyelid movements that are related to the cause of blepharoptosis and to aging. The lid and vertical eye saccades of 7 patients... more
To study the metrics of lid saccades in blepharoptosis and to distinguish any differences in the dynamics of eyelid movements that are related to the cause of blepharoptosis and to aging. The lid and vertical eye saccades of 7 patients with congenital blepharoptosis and those of 18 patients with aponeurogenic blepharoptosis, either involutional or rigid-contact-lens-induced, were recorded with electromagnetic search coils. For each saccade, two parameters were assessed: amplitude and peak velocity. Two age-matched control groups were assessed in the same manner. Repeated measures analysis of variance was used to investigate any observed differences between the included groups. Congenital and rigid-contact-lens-induced blepharoptosis were readily distinguishable from one another, as well as from the age-matched control group, in both lid saccadic amplitude and peak velocity. For example, 40 degrees downward lid saccades in the congenital blepharoptosis group averaged 22.9 degrees +/-...
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Objectives. To determine if hyperopia is a risk factor for primary angle-closure glaucoma (PACG) in the Dutch population and to identify other biometrical parameters as risk factors for PACG including axial length (AL), anterior chamber... more
Objectives. To determine if hyperopia is a risk factor for primary angle-closure glaucoma (PACG) in the Dutch population and to identify other biometrical parameters as risk factors for PACG including axial length (AL), anterior chamber depth (ACD), andkvalues.Methods. The study population consisted of PACG patients that had undergone a laser peripheral iridotomy (LPI). The control group consisted of age- and gender-matched cataract patients. The main outcome was hyperopia (spherical equivalent ≥+0.5 dioptres) measured with IOL Master or autorefractor. Refractive error, ACD, AL, andkvalues were tested with a Mann-WhitneyUtest and by logistic regression.Results. 117 PACG patients and 234 controls were included (mean age = 80 years ± 3.6). The prevalence of hyperopia in patients and controls was 69.6% and 61.1%, respectively (Fisher’s testP=0.076). Mann-WhitneyUtest showed no statistically significant relation with refractive error (P=0.068) orkvalues (P=0.607). In contrast, ACD and A...
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PurposeThe purpose of this paper is to explore in a specific hospital care process the applicability in practice of the theories of quality costing and value chains.Design/methodology/approachIn a retrospective case study an in‐depth... more
PurposeThe purpose of this paper is to explore in a specific hospital care process the applicability in practice of the theories of quality costing and value chains.Design/methodology/approachIn a retrospective case study an in‐depth evaluation of the use of a quality cost model (QCM) and the applicability of Porter's care delivery value chain (CDVC) was performed in a specific care process: glaucoma care over the period 2001 to 2006 in the Rotterdam Eye Hospital in The Netherlands.FindingsThe case study shows a reduction of costs per product by increasing the number of outpatient visits and surgery combined with a higher patient satisfaction. Reduction of costs of non‐compliance by using the QCM is small, due to the absence of (external) financial incentives for both the hospital and individual physicians. For CDVC to be supportive to an integrated quality and cost management the notion “patient value” needs far more specification as mutually agreed on by the stakeholders invol...
Research Interests: Business, Health Care, Health, Medicine, Cost Management, and 15 moreHumans, Cost Model, Activity based costing, Health Services, Case Study, Glaucoma, Data Collection, Netherlands, Design Methodology, Eyes, Hospital Care, Costs and Cost Analysis, Organizational case studies, Health Services Accessibility, and Delivery of Health Care
Research Interests: Optometry, Primary Health Care, Implementation Science, Quality of Mental Health Care, Qualitative Research, and 14 moreHealth Administration, Medicine, Humans, Hospitalization, Glaucoma, Feasibility Studies, Diffusion of Innovation, Netherlands, Access to Health Care, Reimbursement, Health Services Accessibility, Quality of health care, Medical and Health Sciences, and Patient transfer
Research Interests: Computer Science, Algorithms, Artificial Intelligence, Ophthalmology, Computer Vision, and 15 moreImage Processing, Medicine, Humans, Segmentation, Retinal, Theoretical Models, Sensitivity and Specificity, Laplace, Blood Vessel, Retinal imaging, Specular Reflection, Retinal Nerve Fiber Layer, Psychology and Cognitive Sciences, Medical and Health Sciences, and Retinal vessels
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Primary open angle glaucoma (POAG) is a complex disease with a major genetic contribution. Its prevalence varies greatly among ethnic groups, and is up to five times more frequent in black African populations compared to Europeans. So... more
Primary open angle glaucoma (POAG) is a complex disease with a major genetic contribution. Its prevalence varies greatly among ethnic groups, and is up to five times more frequent in black African populations compared to Europeans. So far, worldwide efforts to elucidate the genetic complexity of POAG in African populations has been limited. We conducted a genome-wide association study in 1113 POAG cases and 1826 controls from Tanzanian, South African and African American study samples. Apart from confirming evidence of association at TXNRD2 (rs16984299; OR 1.20; P = 0.003), we found that a genetic risk score combining the effects of the 15 previously reported POAG loci was significantly associated with POAG in our samples (OR 1.56; 95% CI 1.26-1.93; P = 4.79 × 10). By genome-wide association testing we identified a novel candidate locus, rs141186647, harboring EXOC4 (OR 0.48; P = 3.75 × 10), a gene transcribing a component of the exocyst complex involved in vesicle transport. The lo...
Research Interests: Genetics, Human Genetics, Complementary and Alternative Medicine, Aging, Biology, and 15 moreMedicine, Neurodegenerative Diseases, Humans, Glaucoma, Female, Male, Aged, Middle Aged, Human Genome, Genetic Association, Neurosciences, Thioredoxin reductase, Primary Open Angle Glaucoma, Paediatrics and reproductive medicine, and Open Angle
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One of the difficulties in modeling visual field (VF) data is the sometimes large and correlated measurement errors in the point-wise sensitivity estimates. As these errors affect all locations of the same VF, we propose to model them as... more
One of the difficulties in modeling visual field (VF) data is the sometimes large and correlated measurement errors in the point-wise sensitivity estimates. As these errors affect all locations of the same VF, we propose to model them as global visit effects (GVE). We evaluate this model and show the effect it has on progression estimation and prediction. Visual field series (24-2 Full Threshold; 15 biannual VFs per patient) of 125 patients with primary glaucoma were included in the analysis. The contribution of the GVE was evaluated by comparing the fitting and predictive ability of a conventional model, which does not contain GVE, to such a model that incorporates the GVE. Moreover, the GVE's effect on the estimated slopes was evaluated by determining the absolute difference between the slopes of the models. Finally, the magnitude of the GVE was compared with that of other measurement errors. The GVE model showed a significant improvement in both the model fit and predictive a...
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Amblyopia is characterized by histopathological changes in the visual cortex and lateral geniculate nucleus. In the retina, however, no abnormalities have yet been reported. The purpose of this study was to compare the nerve fiber layer... more
Amblyopia is characterized by histopathological changes in the visual cortex and lateral geniculate nucleus. In the retina, however, no abnormalities have yet been reported. The purpose of this study was to compare the nerve fiber layer (NFL) thickness in the amblyopic eye with that in the sound eye of patients with strabismic amblyopia. As a practical implication, we investigated the validity of comparing Nerve Fiber Analyzer (NFA) measurements obtained in amblyopic eyes to the normative database built into the NFA. NFL thickness was measured with a third generation NFA, the GDx (Laser Diagnostic Technologies, San Diego, CA). This is a scanning laser polarimeter, designed for monitoring glaucoma. The following NFL thickness parameters (all in microns) were compared: average thickness, superior maximum, inferior maximum, superior average, inferior average, nasal median and temporal median. Twenty patients with strabismic amblyopia were imaged with the NFA. Patients had no nystagmus,...
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To determine the diagnostic accuracy of judging optic disc photographs for glaucoma by ophthalmologists. Evaluation of diagnostic test and technology. A total of 243 of 875 invited ophthalmologists in 11 European countries. We determined... more
To determine the diagnostic accuracy of judging optic disc photographs for glaucoma by ophthalmologists. Evaluation of diagnostic test and technology. A total of 243 of 875 invited ophthalmologists in 11 European countries. We determined how well each participant classified 40 healthy eyes and 48 glaucomatous eyes with varying severity of the disease on stereoscopic slides. Duplicate slides were provided for determining intraobserver agreement. All eyes were also imaged with the GDx with variable corneal compensation (GDx-VCC) (Carl Zeiss Meditec AG, Jena, Germany) and the Heidelberg Retina Tomograph (HRT) I (Heidelberg Engineering GmbH, Heidelberg, Germany). Diagnostic accuracies of clinicians were compared with those of the best machine classifiers. Accuracy of classification, expressed as sensitivity, specificity, and overall accuracy. Intraobserver agreement (kappa). The overall diagnostic accuracy of ophthalmologists was 80.5% (standard deviation [SD], 6.8; range, 61.4%-94.3%). The machine classifiers outperformed most observers in diagnostic accuracy; the GDx-VCC nerve fiber indicator and the HRT&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s best classifier correctly classified 93.2% and 89.8% of eyes, respectively. The intraobserver agreement (kappa) varied between -0.13 and 1.0 and was on average good (0.7). In general, ophthalmologists classify optic disc photographs moderately well for detecting glaucoma. There is, however, large variability in diagnostic accuracy among and agreement within clinicians. Common imaging devices outperform most clinicians in classifying optic discs. Proprietary or commercial disclosure may be found after the references.