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Biomedical subjects

L Zangwill

Publications and source records attributed to L Zangwill.

At least 19 recordsLinked to original sources
PubMed2001

Interobserver variability of optic disk variables measured by confocal scanning laser tomography.

PURPOSE: To assess the interobserver variation of confocal laser scanning tomographic measurements of the optic nerve head and to address the question of whether the addition of clinical optic disk photographs is helpful in outlining the optic disk margin and in reducing the observer-related variation of the measurements. PATIENTS AND METHODS: Optic disk variables for 16 eyes of 16 patients with glaucoma, generated by confocal laser scanning laser tomography (Heidelberg Retina Tomograph), were independently evaluated by four experienced glaucoma specialists, and the interobserver variability was calculated. A second separate review by the same observers included the use of clinical stereoscopic color optic nerve head photographs to aid definition of the optic disk margin. RESULTS: Optic disk parameters with the smallest interobserver variation were cup shape measure, maximum cup depth, height variation contour, and mean height contour. The intraobserver variation of these parameters did not increase when clinical optic disk slides were additionally available. Parameters with the highest interobserver variation were volume below surface, volume below reference, volume above surface, and volume above reference. The observer variation of these optic disk parameters increased significantly for two of the four examiners when clinical optic disk slides were additionally available for outlining the optic disk margin. CONCLUSION: Confocal laser scanning tomography of the optic nerve head can be improved significantly if clinical optic disk photographs are additionally available to help in outlining the optic disk margin. Because interobserver variation in the tomographic optic disk measurements can be significant, even if experienced observer are involved, tomographic optic disk measurements may be centralized in reading centers in the case of multicenter studies.

Diagnostic Techniques, Ophthalmological↗
PubMed2000

Comparison of long-term variability for standard and short-wavelength automated perimetry in stable glaucoma patients.

PURPOSE: To quantify and compare, on a point-by-point basis, the long-term variability of standard and short-wavelength automated perimetry in a group of stable glaucoma patients. METHODS: From a group of 53 glaucoma patients experienced in visual field testing, we identified one eye, randomly chosen, from each of 25 glaucoma patients whose condition was found to be stable, based on both standard and short-wavelength automated perimetry visual field criteria. On each of three visits during a period of up to 3 months, each patient performed one standard and one short-wavelength automated perimetry 24-2 visual field in a random order on a Humphrey visual field analyzer. The long-term variability (also referred to as test-retest variability) was defined as the SD of the three threshold decibel values at each test location. The long-term variability for each test point (mean +/- SD) was determined separately for both standard visual fields and short-wavelength automated perimetry. RESULTS: With all 52 test locations of the 24-2 field averaged, the global long-term variability, mean (+/- SD) for standard visual fields and short-wavelength automated perimetry was 2.37 +/- 2.03 dB (95% confidence interval, 2.26-2.48 dB) and 2.92 +/- 2.03 dB (95% confidence interval, 2.81-3.03 dB), respectively (P <.0001). In 16 of the 52 visual field locations, long-term variability on short-wavelength automated perimetry was significantly higher than long-term variability on standard visual fields. In addition, the long-term variability increased with greater distance from the point of fixation for both standard visual fields and short-wavelength automated perimetry. The long-term variability decreased closer to fixation, more for standard visual fields than for short-wavelength automated perimetry. CONCLUSIONS: In a group of stable glaucoma patients, mean long-term variability was 0.55 dB higher for short-wavelength automated perimetry than for standard visual fields. This needs to be taken into consideration when serial visual fields are evaluated for change.

Adult↗
PubMed1999

Achromatic and short-wavelength automated perimetry in patients with glaucomatous large cups.

OBJECTIVE: To evaluate visual function and optic disc features in patients with large cup-disc ratios (C/Ds). METHODS: One eye of 86 patients with vertical C/Ds by contour of at least 0.8, who had undergone both standard achromatic automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) testing, was selected retrospectively. Two masked glaucoma specialists independently graded stereoscopic photographs for vertical C/Ds, rim thinning, notching, excavation, optic disc hemorrhages, and nerve fiber layer defects. Visual fields were classified as abnormal if the glaucoma hemifield test result, corrected pattern standard deviation, or mean deviation was outside age-specific normal limits. Confocal scanning laser ophthalmoscopy was used to determine disc area. RESULTS: SAP and SWAP results were abnormal in 44 (51%) and 52 (60%) of 86 patients, respectively. In patients with normal SAP results, SWAP results were abnormal in 14 (33%) of 42 patients. In patients with normal SWAP results, SAP results were abnormal in 6 (18%) of 34 patients. Small discs are associated with an abnormal SAP result (P = .01) and an abnormal SWAP result (P = .09). An increased vertical C/D greater than the qualifying level of 0.8 was associated with an abnormal SAP or SWAP result (P< or =.001). Rim thinning (P = .01) and disc hemorrhages (P = .04) were associated with an abnormal SAP result. CONCLUSIONS: Many patients with large C/Ds have normal SAP and SWAP results. Compared with SAP, SWAP results were abnormal in a higher percentage of these patients. If a patient has a large C/D and normal SAP results, SWAP testing may detect functional loss earlier. If glaucoma is defined by both structural and functional loss, patients with large vertical C/Ds, normal SAP results, and abnormal SWAP results may have glaucoma. Longitudinal studies are needed to assess this hypothesis and determine whether these patients subsequently develop abnormal SAP results as well.

Adult↗
PubMed1999

Relationship between parapapillary atrophy and visual field abnormality in primary open-angle glaucoma.

PURPOSE: To investigate the relationship of parapapillary atrophy measured by confocal scanning laser ophthalmoscopy to visual field sensitivity measured with standard automated perimetry and short-wavelength automated perimetry in patients with primary open-angle glaucoma. METHODS: Forty-seven eyes of 47 primary open-angle glaucoma patients with increased intraocular pressure (> or = 22 mm Hg) were enrolled. Optic nerve head topography and parapapillary atrophy (beta and alpha zones) were assessed by confocal scanning laser ophthalmoscopy. Mean deviation and corrected pattern SD were assessed with standard automated perimetry and short-wavelength automated perimetry. RESULTS: Beta and alpha zones were found in 23 (49%) and 47 (100%) eyes with primary open-angle glaucoma, respectively. The area of beta zone showed significant correlations with MD of standard automated perimetry, corrected pattern SD of standard automated perimetry, and corrected pattern SD of short-wavelength automated perimetry (Spearman r = -0.366, P = .012; r = 0.327, P = .025; and r = 0.436, P = .002, respectively). The area of alpha zone showed a significant correlation with mean deviation of standard automated perimetry (r = -0.378, P = .009). Mean MD of standard automated perimetry, mean corrected pattern SD of standard automated perimetry, and mean corrected pattern SD of short-wavelength automated perimetry were significantly worse in eyes with beta zone than in eyes without beta zone. CONCLUSIONS: Parapapillary atrophy measured by confocal scanning laser ophthalmoscopy, especially beta zone, is associated with glaucomatous visual field loss demonstrated by standard automated perimetry and short-wavelength automated perimetry.

Adult↗
PubMed1999

Change in optic disc topography associated with diurnal variation in intraocular pressure.

PURPOSE: A case demonstrating significant changes in optic disc topography from variation in intraocular pressure (IOP) is demonstrated. METHODS: Within a single 24-hour period, confocal scanning laser ophthalmoscopic images were obtained in the left eye of a patient during an IOP peak (60 mmHg) and during an IOP trough (18 mmHg). RESULTS: During an IOP trough, paired t tests showed significant reduction in cup area, cup volume, mean cup depth, and maximum cup depth, and a significant increase in rim area and cup-to-disc (CD) ratio. CONCLUSION: Under certain conditions, optic disc topography may be affected by diurnal variations in IOP.

Adult↗
PubMed1999

Agreement of measurement of parapapillary atrophy with confocal scanning laser ophthalmoscopy and planimetry of photographs.

PURPOSE: To evaluate whether parapapillary atrophy can be measured interactively using confocal scanning laser ophthalmoscopy. METHODS: For 36 patients with open-angle glaucoma or suspected of having glaucoma, confocal scanning laser ophthalmoscopy of the optic nerve head was performed using the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany). Alpha and beta zones of parapapillary atrophy were plotted independently by two examiners on HRT images before and after reviewing optic disc photographs. These data were compared with planimetric measurements obtained from analyzing the disc photographs. RESULTS: Before viewing the disc photographs, assessment using the HRT images correlated better with the beta zone than alpha zone planimetric measurements. If the HRT images were evaluated while simultaneously viewing disc photographs, correlation coefficients increased for both examiners 1 and 2. Interobserver and intraobserver reliability were 0.431 and 0.802, respectively, for alpha zone, and 0.882 and 0.948, respectively, for beta zone. CONCLUSION: Parapapillary atrophy can be estimated with confocal scanning laser ophthalmoscopy. Correlation with planimetric measurements is best if conventional optic disc photographs are simultaneously viewed. Intraobserver and interobserver reliability are higher for beta zone than for alpha zone.

Adult↗
PubMed1999

Spatial relationship of motion automated perimetry and optic disc topography in patients with glaucomatous optic neuropathy.

PURPOSE: To compare the spatial relationship of focal motion automated perimetry (MAP) visual field defect with focal defect in optic disc topography. METHODS: Patients (n = 12) with focal MAP visual field loss and focal change in optic disc topography were studied. The MAP visual field was divided into 12 field zones representing retinal nerve fiber layer arcuate bundles. Zones of MAP loss were related to rim area ratio (RAR), which was obtained by dividing the rim area, measured by the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany), into 36 10 degrees sectors and then dividing the area of each sector by the total rim area for each subject. Rim area ratio was compared to a normative database (n = 76) to quantify change in optic disc topography. In these same patients, the spatial relationship between standard automated perimetry (SAP) and short-wavelength perimetry (SWAP) and optic disc topography was also assessed. RESULTS: Motion automated perimetry superior visual field zones 14 through 19 were most often associated with a reduction in RAR for inferior sectors 24 through 29, and inferior visual field zones 4 through 7 were most often associated with a reduction in RAR for superior temporal sectors 11 through 16. Similar spatial relationships were found between SWAP and SAP and the RAR. CONCLUSION: Focal MAP visual field loss and focal changes in optic disc topography are spatially related. This relationship is similar to that found between SWAP and SAP with optic disc topography. Focal thinning or notching detected by RAR analysis might be independent of the specific functional test employed.

Glaucoma, Open-Angle↗
PubMed1998

Detection of glaucoma with scanning laser polarimetry.

OBJECTIVE: To determine which retinal nerve fiber layer (RNFL) measures obtained with scanning laser polarimetry are most useful in detecting early to moderate glaucomatous visual field loss. SUBJECTS AND METHODS: One eye from 84 healthy individuals and 83 patients with early to moderate glaucomatous visual field loss (167 eyes) was assessed with a scanning laser polarimeter (Laser Diagnostic Technologies, San Diego, Calif). Three separate scans were obtained, and a baseline scan was created and used in the analyses. Integrated software (program GDx, version 1.0.02; Laser Diagnostic Technologies) was evaluated by assessing its sensitivity and specificity for detecting early and moderate glaucomatous visual field loss. Fisher linear discriminant functions also were developed in this population to assess sensitivity and specificity and were compared with the GDx analyses. RESULTS: There were statistically significant differences between the healthy and glaucomatous eyes for 14 of the 15 RNFL measures (P = .001). However, considerable overlap in measurements between groups was found. With the GDx number, the area under the receiver operator characteristic (ROC) curve was 0.78, and the sensitivity and specificity were 82% and 62%, respectively. Applying the best discriminant function using 3 variables (average thickness, ellipse modulation, and average ellipse thickness) to our study population resulted in an area under the ROC curve of 0.89 and a sensitivity and specificity of 74% and 92%, respectively. CONCLUSIONS: A combination of RNFL measures obtained using the scanning laser polarimeter improved the ability to differentiate between healthy eyes and eyes with early and moderate glaucomatous visual field loss. Analyses using GDx software did not differentiate between healthy and glaucomatous eyes as well as the discriminant analysis function did.

Aged↗
PubMed1998

Relationship of optic disc topography to optic nerve fiber number in glaucoma.

OBJECTIVE: To assess the relationship between in vivo measurements of optic disc topography and histomorphometric measurements of optic nerve fiber number in glaucoma. METHODS: Both eyes of 10 monkeys (Macaca fascicularis) with laser-induced glaucoma in the right eye were studied. Optic disc topography was measured in vivo with a confocal scanning laser ophthalmoscope. Histomorphometry was performed on optic nerve cross sections using bright-field microscopy with camera lucida. Nerve fiber density was estimated by unbiased random sampling. Nerve fiber number was estimated for each sector by multiplying nerve fiber density with neuroglial area. Nerve fiber count was compared with each of 13 global optic disc topographic parameters. RESULTS: For neuroretinal measurements in the glaucomatous eyes, rim area, retinal nerve fiber layer (RNFL) cross-sectional area, rim volume, and RNFL thickness correlated significantly with optic nerve fiber number. Differences in nerve fiber count between control and glaucomatous optic nerves showed the strongest correlation with differences in mean height contour; this was followed by RNFL cross-sectional area, RNFL thickness, rim volume, and differences in rim area. For cup measurements in the glaucomatous eyes, cup volume below reference, cup area, mean cup depth, the ratio of cup area to disc area, and cup shape correlated significantly with nerve fiber number. Differences in nerve fiber number between control and glaucomatous optic nerves showed the strongest correlation with differences in cup shape; this was followed by mean cup depth, cup volume below reference, the ratio of cup area to disc area, cup area, and differences in cup volume below surface. No association was found between optic nerve fiber number and optic disc area in glaucomatous eyes. CONCLUSIONS: In experimental glaucoma, most optic disc topography measures correlated significantly with optic nerve fiber number. The results of this histomorphometric study support the use of confocal scanning laser ophthalmoscopy to evaluate optic nerve damage in glaucoma.

Animals↗
PubMed1998

Patterns of optic disk damage in patients with early focal visual field loss.

PURPOSE: To study the patterns of structural damage of the optic disk in patients with early focal visual field loss using a confocal scanning laser ophthalmoscope. METHODS: Thirty-nine subjects with repeatable early focal visual field loss were included. The Heidelberg Retina Tomograph (Heidelberg Engineering, Heidelberg, Germany) was used to obtain topographic optic disk measurements. For analysis of structural damage, the topographic measurements were divided into 36 10-degree sectors. Sector analysis was performed using sector rim area to sector disk area ratio. Patients were assigned to one of three groups based on the measurement of the optic disk damage: (1) diffuse disk damage; (2) focal disk damage; or (3) no detectable disk damage. RESULTS: Approximately half of the patients with early focal glaucomatous visual field loss showed diffuse optic disk damage, one quarter to one third had focal damage, and one sixth had no detectable damage. Optic disk area was smallest in the no-detectable-damage group (1.71 + 0.19 mm2), followed by the focal-damage group (2.06 + 0.54 mm2), and was largest in the diffuse damage group (2.29 + 0.48 mm2; P = .22). CONCLUSION: In patients with early focal glaucomatous visual field loss, observable optic disk damage can be diffuse, focal, or undetectable. The Heidelberg Retina Tomograph may be capable of detecting different patterns of diffuse or focal structural damage.

Adult↗
PubMed1998

Mapping structural to functional damage in glaucoma with standard automated perimetry and confocal scanning laser ophthalmoscopy.

PURPOSE: To develop a quantitative method for analysis of the topographic relationship between structural and functional damage in patients with glaucoma. METHODS: We studied 26 patients with primary open-angle glaucoma, focal optic disk damage, and focal visual field loss. The visual field was evaluated with automated perimetry, and the optic disk topography was assessed with a confocal scanning laser ophthalmoscope. Topographic measurements were calculated in 10-degree sectors and compared with a normative database (n=52). The topographic relationship of structural damage and functional loss was analyzed. RESULTS: Rim area ratio was defined as the ratio of rim area in each 10-degree sector divided by the total rim area. This ratio resulted in the identification of one (46%) or more (54%) clusters of optic disk sectors as outside normal limits in all 26 patients (12 and 14 patients, respectively). Twenty-two patients (84%) with superior hemifield sensitivity loss tended to have inferior rim defects, and vice versa. Nasal visual field defects close to the horizontal midline were matched with damaged rim areas close to the vertical midline. CONCLUSIONS: This mapping method allows an objective and quantitative evaluation of the optic disk and visual field in patients with glaucoma and focal damage. Although the topographic relationship between structure and function is characterized by considerable interindividual variability, the identification of certain patterns may be useful to aid in the evaluation of glaucomatous damage.

Adult↗
PubMed1998

Detection of early glaucomatous structural damage with confocal scanning laser tomography.

PURPOSE: The authors determine which optic disc topographic parameters obtained by the Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany) are most useful in detecting individuals with early glaucomatous visual field loss. METHODS: Ninety-nine eyes of 49 healthy individuals and 50 age-matched individuals with early glaucomatous visual field loss were included. Three images were obtained and the mean topography image was created and used in the analyses. The HRT discriminant analysis function (software version 2.01) was applied and compared to the Fisher linear discriminant function developed in this population. Analysis was repeated after stratifying by disc area (< 2 mm2 or 2-3 mm2). RESULTS: There were statistically significant differences between the healthy and glaucomatous groups for all optic disc topographic parameters (p < 0.05) measured. These differences remained after the analysis was repeated controlling for disc size, except for height variation contour. Applying the HRT discriminant function to this study population resulted in sensitivity and specificity of 62% and 94%, respectively. The sensitivity was 83% while specificity remained high (91%) for larger disc sizes. Using this data, additional discriminant functions that differentiated similarly between the two groups were found. The best formula used cup-shape measure (third moment), rim area, height variation contour, and retinal nerve fiber layer thickness and had a sensitivity and specificity of 78% and 88%, respectively. CONCLUSIONS: Several different discriminant analysis formulas are capable of detecting early glaucomatous visual field loss in a comparable manner. The characteristics of the study population are likely to influence the discriminating power of these various formulas.

Adult↗
PubMed1998

Changing definition of glaucoma.

OBJECTIVE: The authors assess whether there has been a change in the definition of open-angle glaucoma (OAG) in peer-reviewed articles during the past 15 years. METHODS: A literature review was conducted (via Medline) to identify all articles on OAG from the American Journal of Ophthalmology, Ophthalmology, and Archives of Ophthalmology for the years 1980, 1985, 1990, and 1995. One hundred eighty-two articles were reviewed to identify optic nerve, visual field, and intraocular pressure (IOP) criteria used to define glaucoma. Articles were classified and analyzed by study design, severity, and type of glaucoma. RESULTS: Of the 182 articles, 120 (66%) included a definition of OAG. Among these, approximately 36% used both optic disc and visual field criteria, 13% used optic disc or visual field criteria, 26% used only visual field criteria, 20% used only IOP, and 5% used only optic disc criteria. In the 1980s, when both disc and/or field parameters were used in the definition, 74% of the publications used general qualitative statements such as "characteristic glaucomatous changes." In the 1990s, 34% of articles provided specific descriptions of the optic disc and 61% provided specific visual field criteria. A similar proportion of reviewed articles published in the 1980s (20.4%) and 1990s (19.7%) used IOP as its sole criterion for defining glaucoma. A significantly larger proportion of prospective studies (38/46; 83%) provided specific criteria to define glaucoma compared to cross-sectional (67/111; 60%) and retrospective studies (15/25; 60%). CONCLUSION: There is a lack of consistency in how glaucoma is defined in current clinical research. Although recent studies provide more specific criteria, there is a need to obtain a consensus definition.

Glaucoma, Open-Angle↗
PubMed1997

Nerve fiber layer measurements with scanning laser polarimetry in ocular hypertension.

OBJECTIVE: To measure and compare scanning laser polarimeter measurements of the nerve fiber layer in normal subjects and in patients with ocular hypertension (OHT). METHODS: Scanning laser polarimetry was performed in 39 normal subjects and 39 age-matched patients with OHT. One eye of each patient was randomly selected for the study. For each eye, a mean retardation map was calculated from 3 separate scans of 65536 individual retinal locations (256 x 256 pixels). Retardation measurements within a 10-pixel-wide band located concentrically with the disc margin at 1.7-disc diameters were evaluated. RESULTS: Mean (+/-SD) retardation (in degrees) was significantly higher (P = .03) in normal subjects (10.4 +/- 1.5 degrees) than in patients with OHT (9.7 +/- 1.0 degrees). In the inferior retina, mean +/-SD retardation was higher (P = .03) in normal subjects (10.8 +/- 1.7 degrees) than in patients with OHT (10.1 +/- 1.0 degrees). In the superior retina, mean +/-SD retardation also was higher in normal subjects (9.8 +/- 1.6 degrees) than in patients with OHT (9.3 +/- 1.2 degrees), although the difference was not statistically significant (P = .19). Retardation measurements for 3 of eight 45 degrees sectors around the disc were significantly higher in normal subjects than in patients with OHT. CONCLUSION: Retardation measurements with the scanning laser polarimeter were significantly lower in patients with OHT than in normal subjects.

Adult↗
PubMed1997

Effect of cataract and pupil size on image quality with confocal scanning laser ophthalmoscopy.

OBJECTIVE: To determine the effect of pupil size and cataract on the reproducibility and image quality obtained with confocal scanning laser ophthalmoscopy. METHODS: Three image series were obtained with a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, Heidelberg, Germany) before and after pupillary dilation in each of 39 subjects (8 normal subjects, 5 glaucoma suspects, and 26 patients with glaucoma). The cataract density was measured with both a lens opacity meter and the Lens Opacities Classification System III system. The image quality of each image series was subjectively scored on a scale of 0 (poor) to 9 (high) by 2 independent observers who were unaware of the cataract density and pupil size during image acquisition. The image quality and reproducibility were objectively evaluated using the SD of the mean topography image of each subject. RESULTS: The mean pupil diameter in all subjects before and after dilation was 2.5 +/- 0.8 mm and 5.8 +/- 1.4 mm, respectively. After pupillary dilation, both the mean image quality score and mean SD of the mean topography image improved (from 4.5 +/- 3.5 to 7.4 +/- 2.3 and from 48.6 +/- 18.8 microns to 35.6 +/- 15.5 microns, respectively). The quality score of the images that were obtained before pupillary dilation was associated with the pupil size and density of nuclear and posterior subcapsular cataracts. The SD of the mean topography images that were obtained before pupillary dilation increased with a decreasing pupil size (P = .003) and an increasing density of the nuclear (P < .03), cortical (P = .02), and posterior subcapsular (P = .002) opacity. CONCLUSIONS: Although pupillary dilation improved the image quality in most subjects, the improvement was sometimes small. Those subjects with small undilated pupils and/or cataracts may benefit most from pupillary dilation.

Aged↗
PubMed1997

Mapping structural damage of the optic disk to visual field defect in glaucoma.

PURPOSE: To evaluate the relation between the location of focal visual field defects and optic disk damage in eyes with glaucoma by short-wavelength automated perimetery and confocal scanning laser ophthalmoscopy. METHODS: In 14 patients (14 eyes) with open-angle glaucoma, focal optic disk damage, and focal visual field loss, we obtain visual fields with short-wave-length automated perimetry. The short-wavelength automated perimetry visual field was divided into 21 zones, representing retinal nerve fiber layer arcuate bundles. Test points were compared with a normative database. The optic disk was assessed with a confocal scanning laser ophthalmoscope. Optic disk measurements were calculated in 10-degree sectors and compared with a normative database using a new measure, the rim area ratio, which adjusts for individual differences in disk size. RESULTS: The mean number (+/-SD) of damaged visual field zones was 3.9 (+/-1.9), and the mean number of damaged rim sectors was 5.0 (+/-2.9). Focal defects on the optic disk and on short-wavelength automated perimetry were topographically related with specific damaged visual field zones corresponding to specific damaged rim sectors. CONCLUSIONS: In patients with open-angle glaucoma with focal optic disk damage and focal visual field loss, defects in optic disk and short-wavelength automated perimetry are topographically related. The rim area ratio can be used to identify focal optic nerve defects.

Adult↗