Biomedical subjects

Nicolaas J Reus

Publications and source records attributed to Nicolaas J Reus.

10 recordsLinked to original sources

PubMed2006

Accuracy of GDx VCC, HRT I, and clinical assessment of stereoscopic optic nerve head photographs for diagnosing glaucoma.

AIMS: To determine and compare the accuracy and reproducibility of GDx variable cornea compensation (VCC) scanning laser polarimetry (SLP) with VCC, Heidelberg retina tomograph (HRT) I confocal scanning laser ophthalmoscopy (CSLO), and clinical assessment of stereoscopic optic nerve head (ONH) photographs for diagnosing glaucoma. METHODS: One eye each of 40 healthy subjects, 48 glaucoma patients, and six patients with ocular hypertension were measured with SLP-VCC and CSLO. Simultaneous stereoscopic ONH photographs were also obtained. Sixteen photographs of healthy and glaucomatous eyes were duplicated for assessing intraobserver agreement. Four glaucoma specialists, four general ophthalmologists, four residents in ophthalmology, and four optometrists classified the ONH photographs as normal or glaucomatous. For SLP-VCC, the nerve fiber indicator (NFI) was evaluated. For CSLO, the Moorfields regression analysis (MRA) and the Bathija linear discriminant function (LDF) were used. Sensitivity, specificity, percentage of correctly classified eyes, and intra- and interobserver agreement, expressed as kappa (kappa) were calculated. RESULTS: SLP-VCC had the highest diagnostic accuracy, with a sensitivity, specificity, and overall correct classification of 91.7%, 95.0% and 93.2%, respectively. CSLO, expressed as Bathija LDF and MRA, had a diagnostic accuracy comparable to glaucoma specialists and general ophthalmologists with an overall accuracy of 89.8%, 86.4%, 86.7% and 85.2%, respectively. Residents classified the fewest eyes correctly. Intraobserver agreement for classifying the ONH photographs ranged between 0.48 (within residents) and 0.78 (within glaucoma specialists). The interobserver agreement ranged between 0.45 (between residents) and 0.74 (between glaucoma specialists). The agreement between observers and CSLO MRA (kappa, 0.68) was statistically significantly higher (p<0.001; paired t-test) than between observers and SLP-VCC NFI (kappa, 0.60) and CSLO Bathija LDF (kappa, 0.62). CONCLUSION: Automated analysis of measurements with GDx VCC and HRT had a similar diagnostic accuracy for glaucoma as classification of stereoscopic ONH photographs by glaucoma specialists, thus bringing all eye-care professionals to this desirable level. The intra- and interobserver agreement for ONH analysis was only moderate to good. We think these imaging techniques may assist clinicians in diagnosing glaucoma.

Adult↗

PubMed2006

Enhanced imaging algorithm for scanning laser polarimetry with variable corneal compensation.

PURPOSE: To describe and investigate a method of improving assessment of retinal nerve fiber layer (RNFL) morphology with scanning laser polarimetry (SLP) with variable corneal compensation (VCC). METHODS: By neutralizing anterior segment birefringence with a variable compensator, the current VCC method allows direct measurement of RNFL retardation. In the new method, enhanced corneal compensation (ECC), the variable compensator was set to introduce a "bias" birefringence. This bias was removed mathematically for each individual pixel to produce the RNFL image. In 177 eyes of healthy subjects, patients with glaucoma, and subjects with ocular hypertension, retardation images were obtained with both VCC and ECC. RESULTS: In the tested eyes, images obtained with ECC showed the expected RNFL appearance better than those obtained with VCC. In addition, the typical scan score, which quantifies the amount of atypia, was higher with ECC than with VCC. The amount of residual anterior segment birefringence dropped significantly with ECC in the various groups. Measurements of peripapillary RNFL retardation showed reduced temporal and nasal values with ECC, whereas superior and inferior values were not significantly different between VCC and ECC. The dynamic range appeared to have increased with ECC. The accuracy of the TSNIT (temporal, superior, nasal, inferior, temporal) average and inferior average for detecting glaucoma was higher with ECC than with VCC. CONCLUSIONS: RNFL morphology may be better assessed with the presented ECC method than with standard VCC. ECC may be implemented in the current VCC systems by means of a software upgrade. It may enhance the clinical utility of the GDx VCC in glaucoma management.

Algorithms↗

PubMed2005

The prevalence of glaucomatous defects with short-wavelength automated perimetry in patients with elevated intraocular pressures.

PURPOSE: To determine the prevalence of abnormal short-wavelength automated perimetry (SWAP) visual fields in subjects with elevated intraocular pressures (IOP) for 7 existing definitions of mild glaucomatous loss, and to explore the agreement between them. PATIENTS AND METHODS: Seven hundred and forty-four eyes of 379 subjects with an IOP > or = 22 and < or = 32 mm Hg and normal visual fields with standard automated perimetry (SAP) were tested with SWAP on 3 separate occasions, of which the second and third visual field were used for analysis. The appearance of the optic disc was not an eligibility criterion. We determined the number of visual fields classified as abnormal on 2 successive occasions by 7 existing definitions. In addition, we explored the agreement between the various definitions. RESULTS: The proportion of eyes with a glaucomatous visual field with SWAP ranged between 0% and 9.9%, depending on the criterion used to define abnormality. A pairwise comparison of the various definitions showed that several definitions classified different eyes as having an abnormal field. CONCLUSIONS: We found a large variation in the proportion of visual fields with SWAP classified as abnormal by the various definitions. More importantly, various definitions identified different individuals to have an abnormal field with SWAP. Therefore, the diagnostic accuracy and clinical significance of all definitions must be determined before SWAP is used in routine clinical care.

Female↗

PubMed2005

Relationships between standard automated perimetry, HRT confocal scanning laser ophthalmoscopy, and GDx VCC scanning laser polarimetry.

PURPOSE: This study was designed to determine and compare the relationships between visual function measured with standard automated perimetry (SAP) and structure, either as neuroretinal rim area measured with confocal scanning laser ophthalmoscopy (CSLO), or as retinal nerve fiber layer thickness determined by scanning laser polarimetry with variable corneal compensation (SLP-VCC). METHODS: Forty-six healthy subjects and 76 glaucoma patients were examined with SAP, with CSLO by means of the commercially available Heidelberg Retina Tomograph I (HRT), and with SLP-VCC by means of the commercially available GDx VCC. The relationships between SAP, expressed either in the typically used decibel scale or as number of abnormal points in the total deviation probability plot, and CSLO and between SAP and SLP-VCC were described with linear and logarithmic regression analysis for global data and six individual sectors. The relationship between measurements with CSLO and SLP-VCC was fit with linear regression analysis. RESULTS: The relationships between SAP and CSLO and between SAP and SLP-VCC appeared curvilinear for all sectors except the temporal one between SAP and SLP-VCC. For CSLO, a logarithmic fit was significantly better than a linear one for the global data and in the superotemporal and inferonasal sectors. For SLP-VCC, a curvilinear fit was better for the global data and in the superotemporal, superonasal, and inferonasal sectors. CSLO data correlated linearly with SLP-VCC data in all sectors, except temporally. CONCLUSIONS: CSLO and SLP-VCC showed a very similar curvilinear relationship with SAP. The observed curvilinear relationships confirm earlier reports that these imaging devices appear to detect glaucomatous loss earlier than SAP.

Birefringence↗

PubMed2004

Diagnostic accuracy of the GDx VCC for glaucoma.

PURPOSE: To determine the diagnostic accuracy of the GDx VCC in the diagnosis of glaucoma. DESIGN: Prospective, comparative, observational, clinic-based case series. PARTICIPANTS: One eye each of 77 healthy subjects and 162 patients with primary open-angle glaucoma of Caucasian racial origin. Healthy subjects had normal visual fields (VFs), healthy-looking optic discs, and intraocular pressures of < or =21 mmHg in both eyes. Glaucoma patients had a reproducible glaucomatous VF defect and a glaucomatous appearance of the optic disc in at least one eye. METHODS: All subjects were measured with the GDx VCC with an automated variable corneal compensator. We constructed receiver operating characteristic (ROC) curves for all available parameters. Subsequently, we calculated sensitivity, specificity, and multilevel likelihood ratios for the best discriminating parameter in the entire group. In addition, we calculated sensitivity and specificity in patients with mild, moderate, and severe glaucomatous damage separately. MAIN OUTCOME MEASURES: Software-derived parameters TSNIT (temporal, superior, nasal, inferior, temporal) Average, Superior Average, Inferior Average, TSNIT Std. Dev. (standard deviation), and Nerve Fiber Indicator (NFI). RESULTS: The areas under the ROC curve for TSNIT Average, Superior Average, Inferior Average, TSNIT Std. Dev., and NFI were 0.93, 0.94, 0.90, 0.92, and 0.98, respectively. For the best discriminating parameter NFI, the sensitivity and specificity with a cutoff point of > or =40 were 89.0% and 95.9%, respectively. The multilevel likelihood ratios for glaucoma were 0.07 at NFI values of <35, 1.30 at values between 35 and 44, and 61.50 at values of > or =44. At the cutoff level of > or =40, the sensitivities of the NFI for correctly identifying glaucoma patients with mild, moderate, and severe damage were 83.8%, 92.9%, and 90.1%, respectively. CONCLUSIONS: The GDx VCC allowed easy, rapid, and accurate discrimination between healthy and glaucomatous eyes. The NFI was the best discriminating parameter. The GDx VCC seems to fulfill criteria for a glaucoma screening device.

Adult↗

PubMed2004

Scanning laser polarimetry of the retinal nerve fiber layer in perimetrically unaffected eyes of glaucoma patients.

PURPOSE: To compare scanning laser polarimetry (SLP) measurements of retinal nerve fiber layer (RNFL) thickness in perimetrically unaffected eyes of glaucoma patients with those in their fellow eyes with field loss and eyes of healthy subjects. DESIGN: Observational case-control study. PARTICIPANTS AND CONTROLS: Twenty-three glaucoma patients with a reproducible visual field (VF) defect in one eye (mean mean deviation [MD], -5.71 decibels [dB]) and a normal VF in the other one (i.e., < or =1 VF test point below the 5% probability level [mean MD, -0.01 dB]) and 73 control eyes of as many age-matched healthy subjects (mean MD, 0.39 dB). The MDs and pattern standard deviations of the glaucoma patients' eyes with normal VFs and the control eyes did not statistically significantly differ (independent samples t test, P = 0.15 and P = 0.61, respectively). METHODS: All subjects were measured in both eyes with the GDxVCC, a commercially available instrument featuring SLP with automated variable corneal compensation. Standard automated perimetry was assessed by means of the Humphrey Field Analyzer (24-2 Full Threshold or Swedish interactive threshold algorithm Standard achromatic test program). MAIN OUTCOME MEASURES: The standard GDxVCC parameters TSNIT (temporal, superior, nasal, inferior, temporal) Average, Superior Average, Inferior Average, TSNIT Std. Dev., and Nerve Fiber Indicator (NFI) were determined. We also assessed the thickness values in 6 parapapillary sectors. In addition, we calculated the proportion of eyes per group with an NFI of > or =40. RESULTS: GDxVCC measurements showed more RNFL thinning in the perimetrically unaffected eyes of glaucoma patients than in the healthy control eyes. The RNFL in the perimetrically unaffected eyes of glaucoma patients was thicker than that in their fellow eyes with field loss. The NFI had a value of > or =40 in 11 of 23 (47.8%) perimetrically unaffected eyes of glaucoma patients, 19 of 23 (82.6%) eyes with VF loss of glaucoma patients, and 3 of 73 (4.1%) healthy control eyes. CONCLUSION: With the GDxVCC, thinning of the RNFL may be detected in perimetrically unaffected eyes of glaucoma patients with field loss in their fellow eyes.

Adult↗

PubMed2004

The relationship between standard automated perimetry and GDx VCC measurements.

PURPOSE: To investigate the relationship between retinal light sensitivity measured with standard automated perimetry (SAP) and retardation of the peripapillary retinal nerve fiber layer (RNFL) measured with the GDx VCC (Laser Diagnostic Technologies, Inc., San Diego, CA). METHODS: Forty-seven healthy subjects and 101 patients with glaucoma were examined with SAP and with the commercially available scanning laser polarimeter GDx VCC, with automated individualized compensation of anterior segment birefringence. Individual visual field test points and peripapillary RNFL retardation measurements were grouped into six corresponding sectors. The correlation between perimetry and GDx VCC measurements was determined, and the relationship between RNFL retardation and perimetry, expressed both in the standard decibel scale and in an unlogged scale, was described with linear regression analysis. RESULTS: A statistically significant correlation was found in most sectors between perimetry and GDx VCC measurements in patients with glaucoma, but not in healthy subjects. A linear relationship was found between the unlogged sensitivities and GDx VCC measurements for the superotemporal and inferotemporal sectors. In the decibel scale, this relationship was curvilinear. CONCLUSIONS: GDx VCC measurements of the peripapillary RNFL relate well with functional loss in glaucoma. Based on the observed relationships between function and structure, patients with mild to moderate visual field loss in glaucoma may be better monitored with the GDx VCC and patients who have severe loss, with SAP.

Female↗

PubMed2004

Improving the quality of eye care with tele-ophthalmology: shared-care glaucoma screening.

We evaluated a shared-care tele-ophthalmology service initiated by the Rotterdam Eye Hospital and 10 optometrists working in retail optician stores. The optometrists screened their clients with a nerve fibre analyser and the resulting images were then further assessed by trained technicians at the hospital. We analysed data from 1729 patients and measured several indicators of the quality of the work as well as its efficiency and effectiveness. The quality of the images was at least satisfactory in most cases (89%), and the agreement between the optometrists and the hospital about normal or suspect test results was high (81%). Only 27% of the patients were called for additional testing at the hospital department and 11% consulted an ophthalmologist. Eighty new cases of glaucoma were detected. The combination of task redesign and telemedicine accounted for the success of the screening service. Task redesign was needed to transfer screening from the hospital to primary care in a safe and responsible way. Telemedicine was crucial for assuring quality, facilitating information exchange and for coordination.

Diagnostic Techniques, Ophthalmological↗

PubMed2003

Visualization of localized retinal nerve fiber layer defects with the GDx with individualized and with fixed compensation of anterior segment birefringence.

PURPOSE: To compare the visualization of localized retinal nerve fiber layer (RNFL) defects in GDx images with fixed and with individualized compensation of anterior segment birefringence (FC and IC, respectively) with their visualization in red-free fundus photographs. DESIGN: Observational case series. PARTICIPANTS: Eight eyes of six glaucoma patients with localized, wedge-shaped RNFL defects in red-free fundus photographs with matching visual field defects. METHODS: We imaged all eyes with a GDx equipped with a variable corneal compensator (VCC). The VCC replaced the standard fixed compensator and could be set to compensate for birefringence of up to 120 nm at any axis. Individual anterior segment birefringence was estimated from a macular retardation profile that resulted from the interaction between birefringence of the anterior segment and that of Henle's fiber layer. Measurements of RNFL retardation were made with the GDx with FC (60 nm of retardation with a slow axis of 15 degrees nasally downward) and with IC. Maps of retardation measurements with FC and IC were superimposed on red-free fundus photographs. MAIN OUTCOME MEASURES: Visualization of localized RNFL defects. RESULTS: Localized RNFL defects were visible in GDx retardation maps obtained with IC. The defects closely matched those observed in red-free fundus photographs. With FC, however, the GDx retardation images did not correlate well with red-free fundus photography. CONCLUSIONS: An individualized anterior segment compensation in the GDx improves the visualization of localized glaucomatous loss.

Aged↗

PubMedDate not supplied

Effects of inadequate anterior segment compensation on measurements with scanning laser polarimetry.

The effects of poor anterior segment compensation on scanning laser polarimetry measurements of the retinal nerve fiber layer (RNFL) were systematically explored. A prototype scanning laser polarimeter with an adjustable compensator to neutralize anterior segment birefringence was used. By systematically varying the magnitude and axis of anterior segment compensation in a healthy and a glaucomatous eye, marked changes were observed in RNFL appearance: the healthy eye could appear to have glaucomatous damage, whereas the glaucomatous eye could appear to have a thicker and healthier RNFL. Even small amounts of uncompensated corneal birefringence, which may occur in routine clinical use, resulted in apparent changes in RNFL morphology. Knowledge of this effect is important for clinicians when using scanning laser polarimetry in clinical practice.

Anterior Eye Segment↗