Publications (37)144.33 Total impact
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Article: Assessment of optic disc photographs for glaucoma by UK optometrists: the Moorfields Optic Disc Assessment Study (MODAS).
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ABSTRACT: PURPOSE: To assess the ability of UK optometrists to accurately discriminate between stereoscopic photographs of healthy and glaucomatous optic discs. METHODS: An online survey, including questions relating to qualification, practice environment, and diagnostic methods was completed by 1256 optometrists. Based on their responses, 208 (17%) were selected to undertake an online disc assessment exercise. Optometrists evaluated the same disc images previously assessed by European ophthalmologists as part of the European Optic Disc Assessment Trial (EODAT); the task was to state if the disc appeared healthy or glaucomatous. There were 110 stereoscopic disc images, of which 40 were healthy, 48 glaucomatous, and six ocular hypertensive, with 16 duplicates images. Sensitivity, specificity and overall accuracy were calculated and compared between optometrist groups and with the EODAT ophthalmologists using permutation analysis. RESULTS: Median sensitivity was 0.92 (95% CI: 0.70, 1.00) and median specificity was 0.74 (95% CI: 0.62, 0.88). Median overall accuracy was 80% (95% CI: 67%, 88%). Agreement between optometrists was moderate (Fleiss' κ: 0.57). Optometrists with higher qualifications did not have overall higher sensitivity than those without (p = 0.23), but had higher specificity (p = 0.001) and higher overall accuracy (p < 0.001). Optometrists displayed higher sensitivity but lower specificity than the EODAT ophthalmologists. CONCLUSION: UK optometrists displayed a high sensitivity and moderate specificity when assessing optic discs for the presence of glaucoma, in the context of this study.Ophthalmic and Physiological Optics 05/2013; · 1.58 Impact Factor -
Article: Why a successful task substitution in glaucoma care could not be transferred from a hospital setting to a primary care setting: a qualitative study.
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ABSTRACT: BACKGROUND: Healthcare systems are challenged by a demand that exceeds available resources. One policy to meet this challenge is task substitution-transferring tasks to other professions and settings. Our study aimed to explore stakeholders' perceived feasibility of transferring hospital-based monitoring of stable glaucoma patients to primary care optometrists. METHODS: A case study was undertaken in the Rotterdam Eye Hospital (REH) using semi-structured interviews and document reviews. They were inductively analysed using three implementation related theoretical perspectives: sociological theories on professionalism, management theories, and applied political analysis. RESULTS: Currently it is not feasible to use primary care optometrists as substitutes for optometrists and ophthalmic technicians working in a hospital-based glaucoma follow-up unit (GFU). Respondents' narratives revealed that: the glaucoma specialists' sense of urgency for task substitution outside the hospital diminished after establishing a GFU that satisfied their professionalization needs; the return on investments were unclear; and reluctant key stakeholders with strong power positions blocked implementation. The window of opportunity that existed for task substitution in person and setting in 1999 closed with the institutionalization of the GFU. CONCLUSIONS: Transferring the monitoring of stable glaucoma patients to primary care optometrists in Rotterdam did not seem feasible. The main reasons were the lack of agreement on professional boundaries and work domains, the institutionalization of the GFU in the REH, and the absence of an appropriate reimbursement system. Policy makers considering substituting tasks to other professionals should carefully think about the implementation process, especially in a two-step implementation process (substitution in person and in setting) such as this case. Involving the substituting professionals early on to ensure all stakeholders see the change as a normal step in the professionalization of the substituting professionals is essential, as is implementing the task substitution within the window of opportunity.Implementation Science 01/2013; 8(1):14. · 3.10 Impact Factor -
Article: Challenges in estimating the accuracy of imaging-based detection methods for glaucomatous progression.
The British journal of ophthalmology 01/2013; · 2.92 Impact Factor -
Article: RPE-Normalized RNFL Attenuation Coefficient Maps Derived from Volumetric OCT Imaging for Glaucoma Assessment.
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ABSTRACT: Purpose. We present spatial retinal nerve fiber layer (RNFL) attenuation coefficient maps for healthy and glaucomatous eyes based on optical coherence tomography (OCT) measurements. Quantitative analyses of differences between healthy and glaucomatous eyes were performed. Methods. Peripapillary volumetric images of 10 healthy and 8 glaucomatous eyes were acquired by a Spectralis OCT system. Per A-line, the attenuation coefficient of the RNFL was determined based on a method that uses the retinal pigment epithelium as a reference layer. The attenuation coefficient describes the attenuation of light in tissue due to scattering and absorption. En-face maps were constructed and visually inspected. Differences between healthy and glaucomatous eyes were analyzed (Mann-Whitney U test), both globally (average values) and spatially (concentric and per segment). Results. RNFL attenuation coefficient maps of healthy eyes showed relatively high and uniform values. For glaucomatous eyes, the attenuation coefficients were much lower and showed local defects. Normal and glaucomatous average RNFL attenuation coefficients were highly significantly different (P < 0.0001) and fully separable. The RNFL attenuation coefficient decreased with increasing optic nerve head distance for both groups, with highly significant differences for all distances (P < 0.001). The angular dependency showed high superio- and inferiotemporal and low nasal values, with most significant differences superio- and inferiotemporally. Conclusions. Maps of RNFL attenuation coefficients provide a novel way of assessing the health of the RNFL and are relatively insensitive to imaging artifacts affecting signal intensity. The highly significant difference between normal and glaucomatous eyes suggests using RNFL attenuation coefficient maps as a new clinical tool for diagnosing and monitoring glaucoma.Investigative ophthalmology & visual science 08/2012; 53(10):6102-8. · 3.43 Impact Factor -
Article: Common genetic determinants of intraocular pressure and primary open-angle glaucoma.
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ABSTRACT: Intraocular pressure (IOP) is a highly heritable risk factor for primary open-angle glaucoma and is the only target for current glaucoma therapy. The genetic factors which determine IOP are largely unknown. We performed a genome-wide association study for IOP in 11,972 participants from 4 independent population-based studies in The Netherlands. We replicated our findings in 7,482 participants from 4 additional cohorts from the UK, Australia, Canada, and the Wellcome Trust Case-Control Consortium 2/Blue Mountains Eye Study. IOP was significantly associated with rs11656696, located in GAS7 at 17p13.1 (p=1.4×10(-8)), and with rs7555523, located in TMCO1 at 1q24.1 (p=1.6×10(-8)). In a meta-analysis of 4 case-control studies (total N = 1,432 glaucoma cases), both variants also showed evidence for association with glaucoma (p=2.4×10(-2) for rs11656696 and p=9.1×10(-4) for rs7555523). GAS7 and TMCO1 are highly expressed in the ciliary body and trabecular meshwork as well as in the lamina cribrosa, optic nerve, and retina. Both genes functionally interact with known glaucoma disease genes. These data suggest that we have identified two clinically relevant genes involved in IOP regulation.PLoS Genetics 05/2012; 8(5):e1002611. · 8.69 Impact Factor -
Article: The effect of glaucoma on the optical attenuation coefficient of the retinal nerve fiber layer in spectral domain optical coherence tomography images.
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ABSTRACT: To demonstrate the effect of glaucoma on the optical attenuation coefficient of the retinal nerve fiber layer (RNFL) in Spectral Domain Optical Coherence Tomography (SD-OCT) images. We analyzed images of the peripapillary areas in 10 healthy and 30 glaucomatous eyes (mild, moderate, and advanced glaucoma, 10 eyes each), scanned with the Spectralis OCT (Heidelberg Engineering GmbH, Dossenheim, Germany). To calculate the RNFL attenuation coefficient (μ(att)), determined by the scattering properties of the RNFL, we used a model that normalized the reflectivity of the RNFL by the retinal pigment epithelium. The analysis was performed at four preset locations at 1.3 and 1.7 mm from the center of the optic nerve head (ONH) (i.e., temporally, superiorly, nasally, and inferiorly) and on averages per eye. To assess the structure-function relationship, we correlated the μ(att) to the mean deviation (MD) in standard automated perimetry. The μ(att) of the RNFL decreased up to 40% with increasing disease severity, on average as well as in each location around the ONH (Jonckheere-Terpstra test, P < 0.019 in all tests). The μ(att) of the RNFL depended significantly on the location around the ONH in all eyes (Kruskal-Wallis test, P < 0.014) and was lowest nasally from the ONH. The μ(att) correlated significantly with the MD in SAP (R(2) = 0.337). The measurements clearly demonstrated that the μ(att) of the RNFL decreased with increasing disease severity. The RNFL attenuation coefficient may serve as a new method to quantify glaucoma in SD-OCT images.Investigative ophthalmology & visual science 03/2012; 53(4):2424-30. · 3.43 Impact Factor -
Article: A genetic epidemiologic study of candidate genes involved in the optic nerve head morphology.
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ABSTRACT: The size of the optic nerve head, referred to as disc area (DA), and the vertical cup-disc ratio (VCDR), are clinically relevant parameters for glaucomatous optic neuropathy. Although these measures have a high heritability, little is known about the underlying genes. Previously, the genes SALL1 and SIX1 were found to be genome-wide significantly associated with DA and VCDR. The purpose of the present study was to investigate whether genes encoding protein known to interact with protein encoded by SALL1 and SIX1 are also associated with either DA or VCDR. A total of 38 candidate genes were chosen covering all known proteins interacting with SALL1 and SIX1. These were initially studied in the Rotterdam Study (RS)-I, including 5312 Caucasian subjects characterized for DA and VCDR. Positive findings were further investigated in two independent cohorts (RS-II and RS-III) and finally replicated in a fourth population (ERF). Bonferroni correction was applied to the meta-analyses. Three loci were found to be associated with DA. The only locus significant after correcting for multiple testing is located on chromosome 11p13. Three single nucleotide polymorphisms (SNPs) in ELP4, a gene which neighbors and plays a crucial role in the expression of PAX6, show association in meta-analysis of the four cohorts yielding P values of respectively 4.79 × 10(-6), 3.92 × 10(-6), and 4.88 × 10(-6) which is below the threshold dictated by the most conservative Bonferroni correction (P = 5.2 × 10(-6)). This study suggests that the ELP4-PAX6 region plays a role in the DA. Further research to confirm this finding is needed.Investigative ophthalmology & visual science 01/2012; 53(3):1485-91. · 3.43 Impact Factor -
Article: Linkage and association analyses of glaucoma related traits in a large pedigree from a Dutch genetically isolated population.
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ABSTRACT: Despite extensive research on the genetic determinants of glaucoma, the genes identified to date explain only a small proportion of cases in the general population. Genome-wide linkage and association analyses of quantitative traits related to glaucoma were performed: intraocular pressure, size and morphology of the optic disc (individual and combined by method of principal components) and thickness of the retinal nerve fibre layer (RNFL), in a large pedigree from a genetically isolated Dutch population. For the size of the optic disc, the study demonstrated a significant linkage signal (logarithm of odds (LOD)=3.6) at the LRP1B region on chromosome 2q21.2-q22.2 and significant association (p=8.95×10(-12)) with the previously reported CDC7/TGFBR3 locus at 1p22. For parameters describing morphology of the optic disc, the study obtained significant linkage signal (LOD=4.6) at regions SIRPA and RNF24/PANK2 at 20p13 (false discovery rate (FDR) based q value <0.05) and genome-wide significant association (p=2.38×10(-9)) with a common variant in the RERE gene at 1p36. Suggestive linkage and association signals indicated loci for morphology of the optic disc at 2q31-q33 (IGFBP2 locus) and for RNFL thickness at 3p22.2 (DCLK3 locus) and 14q22-q23 (SIX1 locus). This study identified new linkage regions at 20p13 (SIRPA and RNF24/PANK2 loci) and 2q33-q34 (IGFBP2 locus) for parameters describing morphology of the optic disc. The results of the study also suggested common genetic control of these parameters and RNFL thickness by SIX1 and doublecotin family genes. Finally, association signals for the recently reported RERE and LRP1B loci and the well known CDC7, TGFBR3, and ATOH7 loci were replicated.Journal of Medical Genetics 11/2011; 48(12):802-9. · 6.36 Impact Factor -
Article: Clinical implications of old and new genes for open-angle glaucoma.
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ABSTRACT: Genome-wide association studies have revealed new insights into the genetic determinants of open-angle glaucoma (OAG). This study was performed to determine to what extent variants within established genes (MYOC, OPTN, and WDR36) and newly identified common genetic variants (ATOH7, CDKN2B, and SIX1) contribute to the risk of OAG. Population-based setting, family-based setting, and a case-control study. The Rotterdam Study I cohort (N = 5312; mean age±standard deviation [SD], 68.0±8.4 years). Findings were replicated in the Genetic Research in Isolated Populations combined with the Erasmus Rucphen Family study (N = 1750; mean age±SD, 48.3±15.2 years), and a cohort from Southampton (N = 702; mean age±SD, 72.5±10.7 years). After identifying common variants associated with OAG within the established genes, the risk of OAG was analyzed using logistic regression. Discriminative accuracy was assessed by comparing the area under the receiver operator characteristic curve (AUC) for models, including the number of risk alleles, intraocular pressure, age, and gender, with the AUC for the same model but without the risk alleles. Odds ratios and AUCs of individual and combined risk alleles. No consistent significant associations for the established genes (MYOC, OPTN, and WDR36) with OAG were found. However, when comparing the load of risk variants between cases and controls, 2 of 3 studies showed a significant increased risk of OAG for participants carrying more risk alleles of the 3 established genes. When combining all 6 genes, participants carrying a high number of risk alleles (highest tertile) had a 2.29-fold to 3.19-fold increase in risk of OAG compared with those carrying only a few risk alleles. The addition of the newly identified genes to IOP, age, and gender resulted in a higher AUC compared with the AUC without the newly identified genes (P = 0.027). A significant contribution to the risk of OAG was found for the new common variants identified by recent genome-wide association studies, but not for variants within the established genes. Participants carrying a high number of risk alleles had an approximately 3-fold increase in the risk of OAG compared with those with a low number of risk alleles. The author(s) have no proprietary or commercial interest in any materials discussed in this article.Ophthalmology 08/2011; 118(12):2389-97. · 5.45 Impact Factor -
Article: Common genetic variants associated with open-angle glaucoma.
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ABSTRACT: Open-angle glaucoma (glaucoma) is a major eye disorder characterized by optic disc pathology. Recent genome-wide association studies identified new loci associated with clinically relevant optic disc parameters, such as the optic disc area and vertical cup-disc ratio (VCDR). We examined to what extent these loci are involved in glaucoma. The loci studied include ATOH7, CDC7/TGFBR3 and SALL1 for optic disc area, and CDKN2B, SIX1, SCYL1/LTBP3, CHEK2, ATOH7 and DCLK1 for VCDR. We performed a meta-analysis using data from six independent studies including: the Rotterdam Study (n= 5736), Genetic Research in Isolated Populations combined with Erasmus Rucphen Family study (n= 1750), Amsterdam Glaucoma Study (n= 296) and cohorts from Erlangen and Tübingen (n= 1363), Southampton (n= 702) and deCODE (n= 36 151) resulting in a total of 3161 glaucoma cases and 42 837 controls. Of the eight loci, we found significant evidence (P= 1.41 × 10(-8)) for the association of CDKN2B with glaucoma [odds ratio (OR) for those homozygous for the risk allele: 0.76; 95% confidence interval (CI): 0.70-0.84], for the role of ATOH7 (OR: 1.28; 95% CI: 1.12-1.47) and for SIX1 (OR: 1.20; 95% CI: 1.10-1.31) when adjusting for the number of tested loci. Furthermore, there was a borderline significant association of CDC7/TGFBR3 and SALL1 (both P= 0.04) with glaucoma. In conclusion, we found consistent evidence for three common variants (CDKN2B, ATOH7 and SIX1) significantly associated with glaucoma. These findings may shed new light on the pathophysiological protein pathways leading to glaucoma, and point to pathways involved in the growth and development of the optic nerve.Human Molecular Genetics 03/2011; 20(12):2464-71. · 7.64 Impact Factor -
Article: Cost-effectiveness of monitoring glaucoma patients in shared care: an economic evaluation alongside a randomized controlled trial.
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ABSTRACT: Population aging increases the number of glaucoma patients which leads to higher workloads of glaucoma specialists. If stable glaucoma patients were monitored by optometrists and ophthalmic technicians in a glaucoma follow-up unit (GFU) rather than by glaucoma specialists, the specialists' workload and waiting lists might be reduced.We compared costs and quality of care at the GFU with those of usual care by glaucoma specialists in the Rotterdam Eye Hospital (REH) in a 30-month randomized clinical trial. Because quality of care turned out to be similar, we focus here on the costs. Stable glaucoma patients were randomized between the GFU and the glaucoma specialist group. Costs per patient year were calculated from four perspectives: those of patients, the Rotterdam Eye Hospital (REH), Dutch healthcare system, and society. The outcome measures were: compliance to the protocol; patient satisfaction; stability according to the practitioner; mean difference in IOP; results of the examinations; and number of treatment changes. Baseline characteristics (such as age, intraocular pressure and target pressure) were comparable between the GFU group (n = 410) and the glaucoma specialist group (n = 405).Despite a higher number of visits per year, mean hospital costs per patient year were lower in the GFU group (€139 vs. €161). Patients' time and travel costs were similar. Healthcare costs were significantly lower for the GFU group (€230 vs. €251), as were societal costs (€310 vs. €339) (p < 0.01). Bootstrap-, sensitivity- and scenario-analyses showed that the costs were robust when varying hospital policy and the duration of visits and tests. We conclude that this GFU is cost-effective and deserves to be considered for implementation in other hospitals.BMC Health Services Research 11/2010; 10:312. · 1.66 Impact Factor -
Article: Genetic architecture of open angle glaucoma and related determinants.
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ABSTRACT: Although the vertical cup-disc ratio (VCDR) and intraocular pressure (IOP) are important determinants of open angle glaucoma (OAG), it is unclear to what extent the genetic origin of these traits overlap with those of OAG. We evaluated whether the same genes that determine VCDR and IOP also predict OAG. Genetic risk scores were constructed from single nucleotide polymorphisms (SNPs) using genome wide association data of 9326 participants from the Rotterdam Study cohorts (mean ± SD age: 64.6 ± 9.1 years). These risk scores were used to calculate the explained variance of VCDR and IOP in an independent cohort (Erasmus Rucphen Family study) consisting of 1646 participants (mean ± SD age: 46.8 ± 14.1 years) and the OAG risk in a subset of the Rotterdam Study cohorts. To evaluate false positive findings, we generated two new variables containing randomly sampled values to serve as a negative control. The explained variance of VCDR increased when increasing the number of SNPs included in the risk score, suggesting a polygenic model. We found no clear evidence for a similar model for IOP, suggesting that a small number of SNPs determine the susceptibility to IOP. The SNPs related to IOP in terms of p values contributed little to VCDR. The risk scores associated with VCDR were also associated significantly with OAG. This suggests a common polygenic background for VCDR and OAG CONCLUSIONS: We found evidence for a polygenic model underlying one of the major traits of OAG, VCDR, and OAG itself. The IOP did not show any evidence for such a model.Journal of Medical Genetics 11/2010; 48(3):190-6. · 6.36 Impact Factor -
Article: Predicting visual function from the measurements of retinal nerve fiber layer structure.
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ABSTRACT: To develop and validate a method of predicting visual function from retinal nerve fiber layer (RNFL) structure in glaucoma. RNFL thickness (RNFLT) measurements from scanning laser polarimetry (SLP) and visual field (VF) sensitivity from standard automated perimetry were made available for 535 eyes from three centers. In a training dataset, structure-function relationships were characterized by using linear regression and a type of neural network: radial basis function customized under a Bayesian framework (BRBF). These two models were used in a test dataset to (1) predict sensitivity at individual VF locations from RNFLT measurements and (2) predict the spatial relationship between VF locations and positions at a peripapillary RNFLT measurement annulus. Predicted spatial relationships were compared with a published anatomic structure-function map. Compared with linear regression, BRBF yielded a nearly twofold improvement (P < 0.001; paired t-test) in performance of predicting VF sensitivity in the test dataset (mean absolute prediction error of 2.9 dB [SD 3.7] versus 4.9 dB [SD 4.0]). The predicted spatial structure-function relationship showed better agreement (P < 0.001; paired t-test) with anatomic prior knowledge when the BRBF was compared with the linear regression (median absolute angular difference of 15° vs. 62°). The BRBF generates clinically useful relationships that relate topographical maps of RNFL measurement to VF locations and allows the VF sensitivity to be predicted from structural measurements. This method may allow clinicians to evaluate structural and functional measures in the same domain. It could also be generalized to use other structural measures.Investigative ophthalmology & visual science 11/2010; 51(11):5657-66. · 3.43 Impact Factor -
Article: A genome-wide association study of optic disc parameters.
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ABSTRACT: The optic nerve head is involved in many ophthalmic disorders, including common diseases such as myopia and open-angle glaucoma. Two of the most important parameters are the size of the optic disc area and the vertical cup-disc ratio (VCDR). Both are highly heritable but genetically largely undetermined. We performed a meta-analysis of genome-wide association (GWA) data to identify genetic variants associated with optic disc area and VCDR. The gene discovery included 7,360 unrelated individuals from the population-based Rotterdam Study I and Rotterdam Study II cohorts. These cohorts revealed two genome-wide significant loci for optic disc area, rs1192415 on chromosome 1p22 (p = 6.72x10(-19)) within 117 kb of the CDC7 gene and rs1900004 on chromosome 10q21.3-q22.1 (p = 2.67x10(-33)) within 10 kb of the ATOH7 gene. They revealed two genome-wide significant loci for VCDR, rs1063192 on chromosome 9p21 (p = 6.15x10(-11)) in the CDKN2B gene and rs10483727 on chromosome 14q22.3-q23 (p = 2.93x10(-10)) within 40 kbp of the SIX1 gene. Findings were replicated in two independent Dutch cohorts (Rotterdam Study III and Erasmus Rucphen Family study; N = 3,612), and the TwinsUK cohort (N = 843). Meta-analysis with the replication cohorts confirmed the four loci and revealed a third locus at 16q12.1 associated with optic disc area, and four other loci at 11q13, 13q13, 17q23 (borderline significant), and 22q12.1 for VCDR. ATOH7 was also associated with VCDR independent of optic disc area. Three of the loci were marginally associated with open-angle glaucoma. The protein pathways in which the loci of optic disc area are involved overlap with those identified for VCDR, suggesting a common genetic origin.PLoS Genetics 06/2010; 6(6):e1000978. · 8.69 Impact Factor -
Article: Clinical assessment of stereoscopic optic disc photographs for glaucoma: the European Optic Disc Assessment Trial.
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ABSTRACT: 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'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.Ophthalmology 04/2010; 117(4):717-23. · 5.45 Impact Factor -
Article: The ability of short-wavelength automated perimetry to predict conversion to glaucoma.
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ABSTRACT: Short-wavelength automated perimetry (SWAP) has been claimed to predict conversion to glaucoma 3 to 4 years before standard automated perimetry (SAP) defects occur. This study compared the moment of glaucomatous conversion between SWAP and SAP. Prospective, longitudinal follow-up study. Four hundred sixteen subjects with ocular hypertension (intraocular pressure >/=22 and </=32 mmHg and normal visual fields). A Humphrey Field Analyzer (24-2 program; Carl Zeiss Meditec, Dublin, CA) was used to perform both SWAP and SAP. All participants were tested once every half year during 7 to 10 years or until the onset of conversion (study end point). The conversion to glaucoma was defined as a reproducible glaucomatous visual field defect in SAP. The moment of onset of a reproducible defect in SAP was compared with that in SWAP. Of the 416 initial participants, 24 eyes of 21 subjects showed conversion in SAP. Of these eyes, 22 did not show earlier conversion in SWAP than in SAP. Standard automated perimetry even showed earlier conversion than SWAP in 15 cases. In only 2 eyes did SWAP show earlier conversion by up to 18 months. These results do not support the notion that SWAP generally predicts conversion to glaucoma in SAP. Instead, SAP appears to be at least as sensitive to conversion as SWAP in a large majority of eyes. The author(s) have no proprietary or commercial interest in any materials discussed in this article.Ophthalmology 11/2009; 117(1):30-4. · 5.45 Impact Factor -
Article: Creating patient value in glaucoma care: applying quality costing and care delivery value chain approaches--a five-year case study in the Rotterdam Eye Hospital.
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ABSTRACT: The 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. In 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. The 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 involved and related reimbursement needs to depend on realised outcomes. The case study just focused on one specific care process in one hospital. To determine effects in other areas of health care, it is important to study the use and applicability of the QCM and the CDVC in other care processes and settings. QCM and a CDVC can be useful tools for hospital management to manage the outcomes on both quality and costs, but impact is dependent on the incentives in the context of the existing organisational and reimbursement system and asks for an agreed on operationalisation among the various stakeholders of the notion of patient value.International Journal of Health Care Quality Assurance 02/2009; 22(3):232-51. -
Article: Longitudinal measurement variability of corneal birefringence and retinal nerve fiber layer thickness in scanning laser polarimetry with variable corneal compensation.
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ABSTRACT: To investigate the longitudinal corneal birefringence (corneal polarization axis [CPA] and corneal polarization magnitude [CPM]) variability in scanning laser polarimetry with variable corneal compensation and its effect on retinal nerve fiber layer measurements. Method We analyzed scanning laser polarimetry images obtained every 6 months for 3.2 years in 16 healthy eyes, 38 eyes with ocular hypertension, and 53 eyes with glaucoma in 107 white participants. Differences in values between each intraeye CPA and CPM measurement and the first measurement were used to investigate the variability and any trend with time, and any association with age or diagnosis. We also calculated the percentage of these values within the range of +/-5 degrees or +/-5 nm, respectively. Any effect of corneal birefringence variability on the retinal nerve fiber layer measurements was also evaluated. The CPA and CPM measurement variability showed no trend with time and did not differ between diagnostic groups. It did not appear to be affected by age. With more than 90% of the CPA and CPM measurement variability within the range of +/-5 degrees or +/-5 nm, no significant effect on the retinal nerve fiber layer measurements was observed. The CPA and CPM measurement variability did not differ between groups, showed no trend over time, was independent of subject age, and did not seem to systematically affect retinal nerve fiber layer reproducibility.Archives of ophthalmology 11/2008; 126(10):1359-64. · 3.86 Impact Factor -
Article: New developments in scanning laser polarimetry for glaucoma.
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ABSTRACT: Scanning laser polarimetry is a technique that is used to evaluate the thickness of the retinal nerve fiber layer. It has been shown to have a high accuracy for diagnosing glaucoma. In a subset of eyes, atypical retardation patterns may be present that do not match the expected retinal nerve fiber layer appearance. This review summarizes recent advances made to reduce the frequency and severity of these patterns. In addition, recent progress in the development of algorithms for detecting progression is discussed. A new measurement algorithm--enhanced corneal compensation--has been developed to improve the instrument's signal-to-noise ratio. Enhanced corneal compensation has been shown to improve the accuracy of scanning laser polarimetry for diagnosing glaucoma. In addition, enhanced corneal compensation improves the relationship between standard automated perimetry and scanning laser polarimetry measurements. Furthermore, research is being done on detecting progression in glaucoma. Recently, a method for simulating progression has been proposed, thereby diminishing the need for long-term studies to validate numerous measurement algorithms. With enhanced corneal compensation, the diagnostic accuracy of scanning laser polarimetry has been further improved for glaucoma. Newly developed algorithms for detecting any progressive retinal nerve fiber layer thinning await clinical validation.Current Opinion in Ophthalmology 04/2008; 19(2):136-40. · 2.65 Impact Factor -
Article: Genetic contributions to glaucoma: heritability of intraocular pressure, retinal nerve fiber layer thickness, and optic disc morphology.
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ABSTRACT: The genetic etiology of primary open-angle glaucoma (POAG) is still largely unknown, because of its complexity and disparities in its classification. This study was undertaken to determine the genetic contribution to various early, continuous markers of POAG by assessing the heritability of intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, and neuroretinal rim and optic disc parameters in a genetically isolated population. A total of 2620 subjects (mean age, 48 years; range 18-86) from extended pedigrees living in a small town in The Netherlands underwent an extensive ophthalmic examination. Their IOP was measured by Goldmann applanation tonometry, their RNFL thickness by scanning laser polarimetry (GDx VCC), and their optic disc parameters by confocal scanning laser ophthalmoscopy (HRT II). Risk associations were explored by linear regression analyses and heritability estimates by variance component methods. Inbreeding was present in 2042 (81%) participants, and was significantly associated with a higher IOP (P < 0.001). The heritability estimate for IOP was 0.35 (95% confidence interval [CI], 0.27-0.43); for RNFL thickness, 0.48 (95% CI, 0.35-0.60); and for neuroretinal rim area, 0.39 (95% CI, 0.20-0.58). Nongenetic factors accounted for only a small proportion (<or=0.13) of the variance in all three traits. Early, continuous markers of POAG are strongly determined by additive genetic effects. The results support a quantitative trait linkage strategy to discover new genes for POAG.Investigative Ophthalmology & Visual Science 08/2007; 48(8):3669-76. · 3.60 Impact Factor
Top co-authors
Top Journals
Institutions
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2002–2013
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Het Oogziekenhuis Rotterdam
Rotterdam, South Holland, Netherlands
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2010–2012
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Erasmus MC
- Department of Epidemiology
Rotterdam, South Holland, Netherlands
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2008
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University of Groningen
- Department of Ophthalmology
Groningen, Province of Groningen, Netherlands
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