Nicolaas J. Reus

Clinical Assessment of Stereoscopic Optic Disc Photographs for Glaucoma: The European Optic Disc Assessment Trial

PURPOSE To determine the diagnostic accuracy of judging optic disc photographs for glaucoma by ophthalmologists. DESIGN Evaluation of diagnostic test and technology. PARTICIPANTS A total of 243 of 875 invited ophthalmologists in 11 European countries. METHODS 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. MAIN OUTCOME MEASURES Accuracy of classification, expressed as sensitivity, specificity, and overall accuracy. Intraobserver agreement (kappa). RESULTS 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 HRTs 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). CONCLUSIONS 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. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

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 (κ) 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 (κ, 0.68) was statistically significantly higher (p<0.001; paired t-test) than between observers and SLP-VCC NFI (κ, 0.60) and CSLO Bathija LDF (κ, 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.

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 Henles 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.

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.

Predicting Visual Function from the Measurements of Retinal Nerve Fiber Layer Structure

PURPOSE To develop and validate a method of predicting visual function from retinal nerve fiber layer (RNFL) structure in glaucoma. METHODS 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. RESULTS 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°). CONCLUSIONS 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.

The Ability of Short-Wavelength Automated Perimetry to Predict Conversion to Glaucoma

PURPOSE 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. DESIGN Prospective, longitudinal follow-up study. PARTICIPANTS Four hundred sixteen subjects with ocular hypertension (intraocular pressure >/=22 and </=32 mmHg and normal visual fields). METHODS 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. MAIN OUTCOME MEASURES The moment of onset of a reproducible defect in SAP was compared with that in SWAP. RESULTS 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. CONCLUSIONS 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. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Retinal nerve fiber layer measurement repeatability in scanning laser polarimetry with enhanced corneal compensation.

ObjectiveTo investigate the measurement repeatability of the various standard retinal nerve fiber layer (RNFL) parameters in scanning laser polarimetry (SLP) with enhanced corneal compensation (ECC, released for investigational use on the commercially available GDx with variable corneal compensation, Carl Zeiss Meditec Inc, Dublin, CA) in healthy eyes, eyes with ocular hypertension (OHT), and glaucomatous eyes. DesignCross-sectional observational study. ParticipantsSixteen healthy subjects, 32 subjects with OHT, and 35 patients with primary open-angle glaucoma. MethodsEighty-three eyes of eighty-three white participants were imaged with SLP ECC 3 times on a same day. We determined the intraeye RNFL measurement repeatability. Main Outcome MeasuresIntraeye within-subject standard deviation (Sw), repeatability coefficient, and the 2-way mixed intraclass correlation coefficient for various standard RNFL parameters in SLP ECC. ResultsThe repeatability of the RNFL measurements was generally good. In glaucomatous eyes, the Sw and repeatability coefficient for the nerve fiber indicator and temporal-superior-nasal-inferior-temporal average were statistically significantly higher than in healthy eyes and eyes with OHT. In each group, the intraclass correlation coefficient values were generally similar across the parameters, except for the intereye symmetry. The Sw values for various parameters were generally considerably less than 9% of the measurement spectrum. ConclusionsRNFL measurements by SLP ECC had, in general, a good measurement repeatability, although some parameters seemed to be less stable in glaucomatous eyes than in healthy eyes and eyes with OHT. SLP ECC may therefore probably be employed for the detection of glaucomatous progression.

New developments in scanning laser polarimetry for glaucoma.

Purpose of review 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. Recent findings A new measurement algorithm – enhanced corneal compensation – has been developed to improve the instruments 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. Summary 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.

Imaging of Forward Light-Scatter by Opacified Posterior Capsules Isolated from Pseudophakic Donor Eyes

PURPOSE Posterior capsule opacification (PCO) degrades visual function by reducing visual acuity, but also by increasing intraocular light-scatter. An in vitro model was used to elucidate the effect of PCO-morphology on light-scatter and its functional aspect, as can be assessed with straylight measurement. METHODS Forward PCO-scatter by opacified capsular bags was recorded with a goniometer and camera. The camera position mimicked the anatomic position of retinal photoreceptors; the camera recorded the scattered light that the photoreceptors would sense in an in vivo situation. Scattered light was recorded at different wavelengths and scatter angles, which were divided into a near (1° < θ ≤ 7°) and far (θ > 7°) large-angle domain. Using scattered light, the camera produced grayscale PCO images. The nature of the angular dependence of PCO-scatter was compared with that of scatter in the normal eye, by rescaling PCO images relative to the normal eyes point-spread function. RESULTS The scattered light images closely followed PCO severity. The angular dependence of PCO-scatter resembled that of scatter in the normal eye, irrespective of severity and PCO type. PCO shows the type of wavelength dependence that is normal for small particles: monotonically decreasing with increasing wavelength. At the near large-angle domain, the angular dependence of PCO scatter resembled the angular dependence of scatter in the normal eye less closely. CONCLUSIONS Surprisingly, PCO scatter and scatter in the normal eye have similar underlying scattering processes. However, data obtained at the near large-angle domain demonstrates that, apart from scatter, PCO may also have a refractile component, which is most pronounced in pearl-type PCO.

Assessment of optic disc photographs for glaucoma by UK optometrists: The Moorfields Optic Disc Assessment Study (MODAS)

To assess the ability of UK optometrists to accurately discriminate between stereoscopic photographs of healthy and glaucomatous optic discs.