Biomedical subjects

Hans G Lemij

Publications and source records attributed to Hans G Lemij.

16 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

Modeling of scanning laser polarimetry images of the human retina for progression detection of glaucoma.

The development of methods to detect slowly progressing diseases is often hampered by the time-consuming acquisition of a sufficiently large data set. In this paper, a method is presented to model the change in images acquired by scanning laser polarimetry, for the detection of glaucomatous progression. The model is based on image series of 23 healthy eyes and incorporates colored noise, incomplete cornea compensation and masking by the retinal blood vessels. Additionally, two methods for detecting progression, taking either one or two follow-up visits into account, are discussed and tested on these simulated images. Both methods are based on Student's t-tests, morphological operations and anisotropic filtering. The images simulated by the model are visually pleasing, show corresponding statistical properties to the real images and are used to optimize the detection methods. The results show that detecting progression based on two follow-up visits greatly improves the sensitivity without adversely affecting the specificity.

Algorithms↗

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

Variable corneal compensation improves discrimination between normal and glaucomatous eyes with the scanning laser polarimeter.

PURPOSE: The presently available scanning laser polarimeter (SLP) has a fixed corneal compensator (FCC) that neutralizes corneal birefringence only in eyes with birefringence that matches the population mode. A prototype variable corneal compensator (VCC) provides neutralization of individual corneal birefringence based on individual macular retardation patterns. The aim of this study was to evaluate the relative ability of the SLP with the FCC and with the VCC to discriminate between normal and glaucomatous eyes. DESIGN: Prospective, nonrandomized, comparative case series. PARTICIPANTS: Algorithm-generating set consisting of 56 normal eyes and 55 glaucomatous eyes and an independent data set consisting of 83 normal eyes and 56 glaucomatous eyes. TESTING: Sixteen retardation measurements were obtained with the SLP with the FCC and the VCC from all subjects. MAIN OUTCOME MEASURES: Dependency of parameters on age, gender, ethnic origin, and eye side was sought. Logistic regression was used to evaluate how well the various parameters could detect glaucoma. Discriminant functions were generated, and the area under the receiver operating characteristic (ROC) curve was determined. RESULTS: Discrimination between normal and glaucomatous eyes on the basis of single parameters was significantly better with the VCC than with the FCC for 6 retardation parameters: nasal average (P = 0.0003), superior maximum (P = 0.0003), ellipse average (P = 0.002), average thickness (P = 0.003), superior average (P = 0.010), and inferior average (P = 0.010). Discriminant analysis identified the optimal combination of parameters for the FCC and for the VCC. When the discriminant functions were applied to the independent data set, areas under the ROC curve were 0.84 for the FCC and 0.90 for the VCC (P<0.021). When the discriminant functions were applied to a subset of patients with early visual field loss, areas under the ROC curve were 0.82 for the FCC and 0.90 for the VCC (P<0.016). CONCLUSION: Individual correction for corneal birefringence with the VCC significantly improved the ability of the SLP to distinguish between normal and glaucomatous eyes and enabled detection of patients with early glaucoma.

Adult↗

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

Sensitivity and specificity of new GDx parameters.

PURPOSE: The GDx is a scanning laser polarimeter that assesses peripapillary nerve fiber layer thickness. In addition to the 14 existing outcome parameters, four new parameters have been described recently: the Ellipse Standard Deviation (ESD), the Normalized Superior Area (NSA), the Normalized Inferior Area (NIA) and the Discriminant Analysis (DA). The aim of this study was to investigate the sensitivity and specificity of these four new parameters. METHODS: Only one randomly selected eye of 263 healthy volunteers and 241 glaucoma patients was considered. The healthy group was randomly divided into a reference set (n = 132) to calculate the tenth percentile of the normal distribution and a test set (n = 131) to calculate the specificity against these newly established cut-off points. Sensitivity was calculated for all glaucoma patients (n = 241) and again for three separate subgroups: early glaucoma (n = 90), moderate glaucoma (n = 93), and advanced glaucoma (n = 58). RESULTS: When the tenth percentile of the normal distribution was used as a cut-off point, the sensitivity and specificity pairs of the new parameters were 61.8% and 87.6%, 61.8% and 89.1%, 50.2% and 92.2% and 72.6% and 95.3% for the ESD, NSA, NIA, and the DA, respectively. The Area under the ROC curve was 0.86, 0.86, 0.87, and 0.90, respectively. Among the existing parameters, the Number discriminated best (sensitivity and specificity: 76.8% and 89.1%, respectively; area under the ROC curve: 0.90). When compared with The Number, the DA was equally good, whereas the other three new parameters performed statistically significantly worse. In general, the area under the ROC curve increased from early to moderate to advanced glaucoma. CONCLUSIONS: The new GDx parameters discriminated well between normal subjects and glaucoma patients. None of the new parameters discriminated better than The Number.

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↗

PubMed2003

Sensitivity and specificity of the GDx: clinical judgment of standard printouts versus the number.

PURPOSE: The Number is a standard parameter of the GDx that reportedly distinguishes normal and glaucomatous eyes. The authors evaluated the sensitivity and specificity of the Number and examined whether expert clinical judgment of GDx printouts leads to a better separation. MATERIALS AND METHODS: Two experienced observers judged 800 GDx scans on 400 randomly presented printouts from 200 glaucoma patients and 200 age-matched normal subjects. The diagnosis was based on the symmetry analysis printout and was per patient rather than per eye. The observers assessed sensitivity for all glaucoma patients together, and separately for mild, moderate, and severe glaucoma. Their specificity was determined in the group of normal subjects. The same procedure was performed for the Number, at various critical values. RESULTS: Both observers discriminated better than the Number. At a critical value of 23, the specificity of the Number was 81.5%, which matched the lowest specificity of the 2 observers: 82.5% and 92.0% for observers 1 and 2, respectively. At these specificities, the sensitivity of the 2 observers and of the Number were 92.0%, 89.5%, and 85.5%, respectively. The sensitivity increased with the severity of glaucoma. The Kappa values for intraobserver agreement were 0.80 and 1.0. CONCLUSIONS: The Number yielded acceptable sensitivity and specificity values at a critical value of 23 in this test population. However, the clinical judgments of the printouts by both expert observers resulted in a better separation between normal and glaucomatous eyes, particularly in the group with mild glaucoma.

Adult↗

PubMed2002

Clinician change detection viewing longitudinal stereophotographs compared to confocal scanning laser tomography in the LSU Experimental Glaucoma (LEG) Study.

PURPOSE: To compare optic nerve head (ONH) surface change detection by confocal scanning laser tomography (CSLT) within the LSU Experimental Glaucoma (LEG) study to expert clinicians viewing the LEG stereophotographs. DESIGN: Experimental study. PARTICIPANTS: Four fellowship-trained glaucoma specialists. METHODS: In the LEG study, six 15 CSLT images (TopSS, Laser Diagnostics Technologies, San Diego, CA) and four 2x optic disc stereophotographs were obtained from both eyes of 12 monkeys on 3 separate days and then every 2 weeks after laser to one eye (study eye) to elevate intraocular pressure. ONH surface change detection within the CSLT images is described in our companion report. In this report, the preliminary study compared change detection by the CSLT multivariate strategy with that of a single clinician viewing stereophotograph pairs on three separate occasions as the "gold standard." The main study compared change detection by three additional clinicians viewing a subset of LEG stereophotograph pairs on three separate occasions with that of the CSLT multivariate strategy as the "gold standard." Clinician change detection was assessed for partial (two of three occasions) or complete (three of three occasions) agreement. Three comparison groups within the main study are emphasized: 44 group A comparisons assessed false-positive change detection (specificity); 38 group B comparisons assessed change detection within 38 instances (11 onset and 27 progression events) of CSLT-detected study eye change; and 30 group C comparisons assessed change detection within 30 instances in which the CSLT failed to detect change in study eyes. MAIN OUTCOME MEASURES: Clinician change detection within each comparison with either partial or complete agreement. RESULTS: Within the main study, intrareading (-.29 to 0.67) and interreading (0.24--0.56) session agreement for each clinician was slight to moderate by kappa test. Good specificity (less than 10% false-positive change detection) was achieved within the 44 group A comparisons by two of the three clinicians, but only when the more stringent criterion (change detection on three of three occasions) was applied. Of the 38 group B comparisons (in which the CSLT detected change), the two clinicians who achieved good specificity in group A failed to detect change in 25 and 16 instances, respectively, using the more stringent (three of three) criterion. Similarly, of the 30 group C comparisons (in which the CSLT failed to detect change), these two clinicians detected change in three and seven instances, respectively, but in only one comparison did they both detect change. CONCLUSIONS: This study provides the first direct evidence that an existing CSLT may reasonably meet or exceed the ONH surface change detection performance of fellowship-trained glaucoma specialists in at least those eyes with good CSLT reproducibility.

Animals↗

PubMed2002

Motion artifacts in scanning laser polarimetry.

PURPOSE: The GDx (Laser Diagnostic Technologies, San Diego, CA) is a scanning laser polarimeter that measures retardation to assess retinal nerve fiber layer thickness in vivo. Eye movements during image acquisition may result in motion artifacts in the GDx image. The aims of this study were to investigate the effect of motion artifacts on the retardation values and to illustrate how motion artifacts can be identified. DESIGN: Observational case series. PARTICIPANTS: Thirty-two normal subjects and 28 glaucoma patients participated. METHODS: We imaged all 60 subjects with the GDx. Images with identified motion artifacts were compared with images without motion artifacts from the same eye and the same session. In 25 cases, the artifact was identified in the superior segment only, and the effect on the superior maximum parameter was calculated. In 26 cases, the artifact was observed in the inferior segment only, and the effect on the inferior maximum parameter was calculated. In nine cases, the artifact was observed superiorly and inferiorly, and the effect on both parameters was calculated. In all 60 cases, the effect on The Number (a summary parameter) was calculated. We also analyzed the groups of glaucoma patients and normal subjects separately. MAIN OUTCOME MEASURES: Superior maximum parameter, inferior maximum parameter, The Number parameters. RESULTS: In general, the identified motion artifacts led to an increase in retardation, reflected by an increase in the superior maximum and inferior maximum parameter by 5.9 micro m and 3.4 micro m, respectively (P < 0.001). The Number decreased by 3.4 with motion artifacts (P = 0.001). The variability of this effect was large. In one case, the motion artifact increased retardation by as much as 28.6 micro m. The effect of motion artifacts was greater in glaucoma patients than in normal subjects. CONCLUSIONS: The identified motion artifacts generally increase retardation values. This increase, however, is highly variable. Therefore, images with such motion artifacts should be viewed with caution or excluded from analysis.

Adult↗

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↗