Glaucoma detection using scanning laser polarimetry with variable corneal polarization compensation

OBJECTIVE

To compare the ability of scanning laser polarimetry (SLP) to discriminate between healthy and glaucomatous eyes with manufacturer-assumed fixed and subject-specific variable corneal polarization magnitude (CPM) and corneal polarization axis (CPA) values.

METHODS

An SLP was modified to enable the measurement of CPM and CPA values so that compensation for corneal birefringence could be corrected on a subject-specific variable basis. We examined 40 healthy eyes and 54 glaucomatous eyes with repeatable visual field damage (average +/- SD mean deviation, -6.5 +/- 4.9 dB) were examined by SLP using the manufacturer-assumed fixed corneal compensation (FCC-SLP) values and subject-specific variable corneal compensation (VCC-SLP) values. Areas under the receiver operating characteristic (ROC) curve for discriminating between healthy and glaucomatous eyes using FCC-SLP and VCC-SLP parameters were compared.

RESULTS

The areas under the ROC curve increased with VCC-SLP compared with FCC-SLP, particularly for all thickness parameters. The parameters with which the area under the ROC curve improved significantly from FCC-SLP to VCC-SLP included average thickness (ROC curve area, 0.62 vs 0.75), superior integral (0.66 vs 0.79), ellipse average (0.65 vs 0.80), inferior average (0.66 vs 0.80), and superior average (0.68 vs 0.83).

CONCLUSION

Variable corneal compensation to correct for subject-specific CPM and CPA can improve the ability of SLP to discriminate between healthy and glaucomatous eyes.

Comparing neural networks and linear discriminant functions for glaucoma detection using confocal scanning laser ophthalmoscopy of the optic disc

PURPOSE

To determine whether neural network techniques can improve differentiation between glaucomatous and nonglaucomatous eyes, using the optic disc topography parameters of the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany).

METHODS

With the HRT, one eye was imaged from each of 108 patients with glaucoma (defined as having repeatable visual field defects with standard automated perimetry) and 189 subjects without glaucoma (no visual field defects with healthy-appearing optic disc and retinal nerve fiber layer on clinical examination) and the optic nerve topography was defined by 17 global and 66 regional HRT parameters. With all the HRT parameters used as input, receiver operating characteristic (ROC) curves were generated for the classification of eyes, by three neural network techniques: linear and Gaussian support vector machines (SVM linear and SVM Gaussian, respectively) and a multilayer perceptron (MLP), as well as four previously proposed linear discriminant functions (LDFs) and one LDF developed on the current data with all HRT parameters used as input.

RESULTS

The areas under the ROC curves for SVM linear and SVM Gaussian were 0.938 and 0.945, respectively; for MLP, 0.941; for the current LDF, 0.906; and for the best previously proposed LDF, 0.890. With the use of forward selection and backward elimination optimization techniques, the areas under the ROC curves for SVM Gaussian and the current LDF were increased to approximately 0.96.

CONCLUSIONS

Trained neural networks, with global and regional HRT parameters used as input, improve on previously proposed HRT parameter-based LDFs for discriminating between glaucomatous and nonglaucomatous eyes. The performance of both neural networks and LDFs can be improved with optimization of the features in the input. Neural network analyses show promise for increasing diagnostic accuracy of tests for glaucoma.

Comparison of two grading methods to evaluate focal narrowing of retinal arterioles in glaucoma

BACKGROUND

Focal arteriolar narrowing has been reported to be more common in glaucoma eyes compared to normal eyes. The current study was performed to compare two methods for standardized assessment of focal arteriolar narrowing.

MATERIAL AND METHODS

Stereoscopic optic disc photographs (from one randomly selected eye per subject) of 48 normal subjects, 20 ocular hypertensive patients (OHT), and 29 glaucoma patients, were reviewed independently in a masked fashion by two graders. Focal arteriolar narrowing within one disc diameter from the rim edge was evaluated based on two different grading methods: (1) narrowing present if the arteriole was wider distal to the narrowing, and (2) narrowing present if the arteriole was wider both distal and proximal to the narrowing.

RESULTS

Focal arteriolar narrowing was observed with grading method 1 in 37.5% (18/48), 35.0% (7/20), and 65.5% (19/29) of normals, OHT, and glaucoma patients, respectively. It was observed with grading method 2 in 18.8% (9/48), 0% (0/22), and 48.3% (14/29) of normals, OHT, and glaucoma patients, respectively. With both grading methods, focal arteriolar narrowing was significantly more frequent in glaucoma versus normal eyes (chi-square test: grading method 1 P=0.03, and grading method 2 P=0.0001). The number of eyes with focal arteriolar narrowing was significantly more frequent with method 1 than with method 2 across all photographs and all subgroups (chi-square test: P=0.0001). The overall agreement between the two graders was kappa 0.77+/-0.06 for grading method 1, and 0.43+/-0.11 for grading method 2.

CONCLUSIONS

The prevalence of focal arteriolar narrowing is highly dependent upon the grading method. A uniform grading method of focal arterial narrowing is needed to achieve comparable and reproducible results among studies.

Scanning laser polarimetry in monkey eyes using variable corneal polarization compensation

PURPOSE

To determine if scanning laser polarimetry (SLP) using variable anterior segment birefringence compensation can provide meaningful retinal nerve fiber layer (RNFL) thickness measurements in monkey eyes.

METHODS

A scanning laser polarimeter (GDx; Laser Diagnostic Technologies, San Diego, CA) was modified so that anterior segment birefringence could be compensated on an eye-specific basis. Six eyes of three adult Cynomolgus (Macaca fascicularis) monkeys were imaged. The authors determined the corneal polarization magnitude (CPM) and corneal polarization axis (CPA) in these eyes, and compared them with the fixed values in the commercial scanning laser polarimeter. Individually compensated RNFL images, using eye-specific CPM and CPA, were then obtained to determine if the resulting retardation profiles reflected the expected RNFL appearance observed with stereoscopic optic disc photographs. Two of the imaged monkeys had experimental glaucoma of the right eye, which allowed comparison of RNFL thickness measures between healthy eyes and those damaged by experimental glaucoma.

RESULTS

The CPM was small in each of the six eyes examined, ranging from 5.7 to 8.7 nm. The CPA ranged from -62 degrees to 78.7 degrees (nasally upward CPA values were recorded as negative; nasally downward CPA values were recorded as positive). These values are different from the values assumed by the commercially available fixed-compensator GDx. When eye-specific compensation was used, RNFL retardation profiles mimicked the expected appearance of the RNFL in all eyes. The authors also observed a substantial decrease in retardation in experimental glaucoma eyes compared with healthy fellow eyes.

CONCLUSIONS

Scanning laser polarimetry using eye-specific corneal polarization compensation can provide meaningful RNFL thickness measurements in monkey eyes. Observed differences in retardation between healthy and experimental glaucoma eyes suggest that SLP may be useful for detecting and monitoring RNFL loss in experimental primate glaucoma.

Measurement of the magnitude and axis of corneal polarization with scanning laser polarimetry

BACKGROUND

Scanning laser polarimetry uses a polarization compensator to isolate corneal birefringence from the birefringence of the retinal nerve fiber layer. This compensator assumes a fixed corneal polarization magnitude (CPM) of 60 nm and a fixed corneal polarization axis (CPA) of 15 degrees in all subjects.

OBJECTIVES

To measure the CPM and CPA with a scanning laser polarimeter and to determine if the assumed compensation values are representative of those observed in healthy and glaucomatous eyes.

METHODS

The CPM and CPA were measured in 51 healthy eyes and 55 glaucomatous eyes using a modified scanning laser polarimeter (GDx Nerve Fiber Analyzer; Laser Diagnostic Technologies Inc, San Diego, Calif) with an experimental variable CPM and CPA compensator. The CPM and CPA distributions in healthy and glaucomatous eyes were compared, and the CPM and CPA relationships with age, corneal thickness, and corneal curvature were also investigated. Nasally upward CPA values (in degrees) were recorded as negative; nasally downward CPA values were recorded as positive.

RESULTS

The CPM and CPA measurements were normally distributed with many eyes having values different from those assumed by the GDx corneal compensator. For healthy and glaucomatous eyes combined, CPM measurements ranged from 7 nm to 91 nm (mean +/- SD, 40.0 +/- 15.7 nm). The CPA measurements ranged from -13 degrees to 73 degrees (mean +/- SD, 24.5 degrees +/- 17.4 degrees ). A significant effect of age on CPA was observed when all eyes were combined (R(2) = 0.10; P<.001). There were no differences in CPM or CPA between healthy and glaucomatous eyes after adjusting for age. No effects of corneal thickness on CPM (R(2) = 0.04; P =.05) or CPA (R(2) = 0.01; P =.24) or of corneal curvature on CPM (R(2) = 0.002; P =.67) or CPA (R(2) = 0.009; P =.34) were observed.

CONCLUSIONS

The range of CPM and CPA values observed in glaucomatous and healthy eyes suggests that the narrow-band corneal compensator used by the GDx scanning laser polarimeter is inappropriately compensating for anterior segment birefringence in many eyes.

Comparing machine learning classifiers for diagnosing glaucoma from standard automated perimetry

PURPOSE

To determine which machine learning classifier learns best to interpret standard automated perimetry (SAP) and to compare the best of the machine classifiers with the global indices of STATPAC 2 and with experts in glaucoma.

METHODS

Multilayer perceptrons (MLP), support vector machines (SVM), mixture of Gaussian (MoG), and mixture of generalized Gaussian (MGG) classifiers were trained and tested by cross validation on the numerical plot of absolute sensitivity plus age of 189 normal eyes and 156 glaucomatous eyes, designated as such by the appearance of the optic nerve. The authors compared performance of these classifiers with the global indices of STATPAC, using the area under the ROC curve. Two human experts were judged against the machine classifiers and the global indices by plotting their sensitivity-specificity pairs.

RESULTS

MoG had the greatest area under the ROC curve of the machine classifiers. Pattern SD (PSD) and corrected PSD (CPSD) had the largest areas under the curve of the global indices. MoG had significantly greater ROC area than PSD and CPSD. Human experts were not better at classifying visual fields than the machine classifiers or the global indices.

CONCLUSIONS

MoG, using the entire visual field and age for input, interpreted SAP better than the global indices of STATPAC. Machine classifiers may augment the global indices of STATPAC.

Imaging of the optic disc and retinal nerve fiber layer: the effects of age, optic disc area, refractive error, and gender

We cross-sectionally examined the relationship between age, optic disc area, refraction, and gender and optic disc topography and retinal nerve fiber layer (RNFL) measurements, using optical imaging techniques. One eye from each of 155 Caucasian subjects (age range 23.0-80.8 y) without ocular pathology was included. Measurements were obtained by using the Heidelberg Retina Tomography (HRT), the GDx Nerve Fiber Analyzer, and the Optical Coherence Tomograph (OCT). The effects of age were small (R2 < 17%) and were limited to specific HRT, GDx, and OCT parameters. Disc area was significantly associated with most HRT parameters and isolated GDx and OCT parameters. Refraction and gender were not significantly associated with any optic disc or RNFL parameters. Although effects of age on the optic disc and RNFL are small, they should be considered in monitoring ocular disease. Optic disc area should be considered when cross-sectionally evaluating disc topography and, to a lesser extent, RNFL thickness.

Assessment of the retinal nerve fiber layer of the normal and glaucomatous monkey with scanning laser polarimetry

PURPOSE

To describe and test a method for assessment of the monkey retinal nerve fiber layer (RNFL) with scanning laser polarimetry.

METHODS

A scanning laser polarimeter was modified to accommodate a variable corneal polarization compensator. Corneal polarization magnitude (CPM) and corneal polarization axis (CPA) of the anterior segment birefringence of normal and glaucomatous cynomolgus monkey eyes were determined from a polarimetry image of the Henle fiber layer. Next, the variable compensator was adjusted to minimize the anterior segment birefringence. RNFL measurements were then obtained. All images were compared with simultaneous optic disc stereoscopic photographs.

RESULTS

CPM was small in each of the eyes examined, ranging from 5.7 nm to 9.0 nm. CPA ranged from -62 degrees to 79 degrees. (Nasally upward CPA values were recorded as negative; nasally downward CPA values were recorded as positive.) When eye-specific compensation was used, RNFL retardation profiles mimicked the expected appearance of the RNFL in all eyes. We also observed a substantial decrease in retardation in eyes with experimental glaucoma compared with healthy fellow eyes.

CONCLUSIONS

Individualized anterior segment compensation can be achieved in the monkey eye so that the measured birefringence appears to largely reflect the birefringence of the RNFL. Observed differences in retardation between healthy eyes and eyes with experimental glaucoma suggest that scanning laser polarimetry may be useful for detecting and monitoring RNFL loss in experimental primate glaucoma.

Relationship between visual field testing and scanning laser polarimetry in patients with a large cup-to-disk ratio

PURPOSE

To determine the relationship between quantitative nerve fiber layer measurements and visual field testing in patients with large cup-to-disk ratios.

METHODS

Seventy-six patients with vertical cup-to-disk ratios by contour of at least 0.8 on stereoscopic photographs and 50 normal subjects were included. One eye was randomly selected for study. All patients underwent standard achromatic automated perimetry, short-wavelength automated perimetry, and retinal nerve fiber layer measurements with scanning laser polarimetry. Analysis of variance was used to evaluate differences between the subject groups. Significance of pairwise comparisons was determined using the Tukey-Kramer multiple comparison test.

RESULTS

Statistically significant differences in nerve fiber layer measurements between patients with large cup-to-disk ratios and both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry (n = 22) and patients with large cup-to-disk ratios and both normal standard achromatic automated perimetry and short-wavelength automated perimetry (n = 42) were found for superior nasal ratio, maximum modulation, ellipse modulation, and the linear discriminant function (Tukey-Kramer less than.05). There was no significant difference in patients with abnormal short-wavelength automated perimetry only (n = 9) as compared with patients with both normal standard achromatic automated perimetry and short-wavelength automated perimetry and patients with both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry. Statistically significant differences between the normal subjects and patients with large cup-to-disk ratios and both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry were found for all retinal nerve fiber layer parameters, with the exception of symmetry, superior ratio, and inferior ratio.

CONCLUSION

Our results show considerable overlap in nerve fiber layer measurements in eyes with large cup-to-disk ratio and abnormal visual fields as compared with eyes with large cup-to-disk ratios and normal visual fields. This may limit the clinical usefulness of scanning laser polarimetry for detection of early glaucoma in patients with large cup-to-disk ratios. Longitudinal studies are needed to determine if patients with large cup-to-disk ratios with normal standard achromatic automated perimetry and abnormal short-wavelength automated perimetry subsequently develop standard achromatic automated perimetry defects and if scanning laser polarimetry can concurrently detect progression of nerve fiber layer damage.

Using optical imaging summary data to detect glaucoma

PURPOSE

To evaluate the sensitivity and specificity for discriminating between early to moderate glaucomatous and normal eyes using summary data reports from the Heidelberg Retina Tomograph (HRT), the GDx Nerve Fiber Analyzer (GDx), and the Optical Coherence Tomograph (OCT).

DESIGN

Comparative cross-sectional study

PARTICIPANTS

One eye each of 50 normal subjects and 39 glaucoma patients with early to moderate visual field damage (mean deviation, -5.04 +/- 3.32 dB; range, -0.85 to -13.2 dB).

METHODS

Three experienced graders masked to patient identity and diagnosis evaluated each summary data report from the HRT, GDx, and OCT independently.

MAIN OUTCOME MEASURES

Each summary report was classified as either normal or glaucomatous. Sensitivity and specificity are reported for each grader, and agreement between graders is reported.

RESULTS

For the HRT, sensitivity and specificity ranged from 64% to 75% and 68% to 80%, respectively. Agreement (kappa +/- standard error [SE]) between observers one and two, two and three, and one and three was 0.73 +/- 0.07, 0.77 +/- 0.07, and 0.67 +/- 0.08, respectively. For the GDx, sensitivity and specificity ranged from 72% to 82% and 56% to 82%, respectively. Agreement (kappa +/- SE) between observers one and two, two and three, and one and three was 0.66 +/- 0.08, 0.66 +/- 0.08, and 0.50 +/- 0.09, respectively. For the OCT, sensitivity and specificity ranged from 76% to 79% and 68% to 81%, respectively. Agreement (kappa +/- SE) between observers one and two, two and three, and one and three was 0.73 +/- 0.07, 0.58 +/- 0.08, and 0.51 +/- 0.09, respectively.

CONCLUSIONS

When used alone, HRT, GDx, and OCT summary data reports can differentiate between normal and glaucomatous eyes with mild to moderate visual field loss. However, none of the instruments provided sensitivity and specificity that justify summary data reports being used as a screening tool for early to moderate glaucoma.

Detecting early glaucoma by assessment of retinal nerve fiber layer thickness and visual function

PURPOSE

To compare the abilities of scanning laser polarimetry (SLP), optical coherence tomography (OCT), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) perimetry to discriminate between healthy eyes and those with early glaucoma, classified based on standard automated perimetry (SAP) and optic disc appearance. To determine the agreement among instruments for classifying eyes as glaucomatous.

METHODS

One eye of each of 94 subjects was included. Healthy eyes (n = 38) had both normal-appearing optic discs and normal SAP results. Glaucoma by SAP (n = 42) required a repeatable abnormal result (glaucoma hemifield test [GHT] or corrected pattern standard deviation [CPSD] outside normal limits). Glaucoma by disc appearance (n = 51) was based on masked stereoscopic photograph evaluation. Receiver operating characteristic (ROC) curve areas, sensitivities, and specificities were calculated for each instrument separately for each diagnosis.

RESULTS

The largest area under the ROC curve was found for OCT inferior quadrant thickness (0.91 for diagnosis based on SAP, 0.89 for diagnosis based on disc appearance), followed by the FDT number of total deviation plot points of < or =5% (0.88 and 0.87, respectively), SLP linear discriminant function (0.79 and 0.81, respectively), and SWAP PSD (0.78 and 0.76, respectively). For diagnosis based on SAP, the ROC curve area was significantly larger for OCT than for SLP and SWAP. For diagnosis based on disc appearance, the ROC curve area was significantly larger for OCT than for SWAP. For both diagnostic criteria, at specificities of > or =90% and > or =70%, the most sensitive OCT parameter was more sensitive than the most sensitive SWAP and SLP parameters. For diagnosis based on SAP, the most sensitive FDT parameter was more sensitive than the most sensitive SLP parameter at specificities of > or =90% and > or =70% and was more sensitive than the most sensitive SWAP parameter at specificity of > or =70%. For diagnosis based on disc appearance at specificity of > or =90%, the most sensitive FDT parameter was more sensitive than the most sensitive SWAP and SLP parameters. At specificity > or = 90%, agreement among instruments for classifying eyes as glaucomatous was poor.

CONCLUSIONS

In general, areas under the ROC curve were largest (although not always significantly so) for OCT parameters, followed by FDT, SLP, and SWAP, regardless of the definition of glaucoma used. The most sensitive OCT and FDT parameters tended to be more sensitive than the most sensitive SWAP and SLP parameters at the specificities investigated, regardless of diagnostic criteria.

Discriminating between normal and glaucomatous eyes using the Heidelberg Retina Tomograph, GDx Nerve Fiber Analyzer, and Optical Coherence Tomograph

OBJECTIVE

To compare the ability of 3 instruments, the Heidelberg Retina Tomograph (HRT), the GDx Nerve Fiber Analyzer (GDx), and the Optical Coherence Tomograph (OCT), to discriminate between healthy eyes and eyes with early to moderate glaucomatous visual field loss.

SUBJECTS AND METHODS

Forty-one patients with early to moderate glaucomatous visual field loss and 50 healthy subjects were included in the study. The HRT, GDx, and OCT imaging and visual field testing were completed on 1 eye from each subject within a 6-month interval. Statistical differences in sensitivity at fixed specificities of 85%, 90%, and 95% were evaluated. In addition, areas under the receiver operating characteristic (ROC) curve were compared.

RESULTS

No significant differences were found between the area under the ROC curve and the best parameter from each instrument: OCT thickness at the 5-o'clock inferior temporal position (mean +/- SE, 0.87 +/- 0.04), HRT mean height contour in the nasal inferior region (mean +/- SE, 0.86 +/- 0.04), and GDx linear discriminant function (mean +/- SE, 0.84 +/- 0.04). Twelve HRT, 2 GDx, and 9 OCT parameters had an area under the ROC curve of at least 0.81. At a fixed specificity of 90%, significant differences were found between the sensitivity of OCT thickness at the 5-o'clock inferior temporal position (71%) and parameters with sensitivities less than 52%. Qualitative assessment of stereophotographs resulted in a sensitivity of 80%.

CONCLUSION

Although the area under the ROC curves was similar among the best parameters from each instrument, qualitative assessment of stereophotographs and measurements from the OCT and HRT generally had higher sensitivities than measurements from the GDx.

Reproducibility of nerve fiber layer thickness measurements by use of optical coherence tomography

OBJECTIVE

To evaluate the reproducibility of optical coherence tomograph (OCT) retinal nerve fiber layer (RNFL) measurements in normal and glaucomatous eyes by means of the commercially available OCT 2000 instrument (Humphrey Systems, Dublin, CA).

DESIGN

Prospective instrument validation study.

PARTICIPANTS

One eye each from 10 normal subjects and 10 glaucoma patients.

METHODS

Twenty subjects underwent a total of eight scanning sessions during two independent visits. In each session, five circular scans centered on the optic nerve head were performed. The first two sessions were performed by two experienced technicians. Followed by a 30-minute break, a third and a fourth session was completed by the same technicians. This sequence was duplicated on a second visit. Intrasession, intersession, intervisit, and interoperator reproducibility of quadrant and global RNFL measurements were calculated by use of a components of variance model.

MAIN OUTCOME MEASURES

RNFL thickness.

RESULTS

The coefficient of variation for the mean RNFL thickness was significantly smaller (P = 0.02) in normal eyes (6.9%) than in glaucoma eyes (11.8%). The estimated root mean squared error based on the statistical model using three scans per patient was 5.8 and 8.0 micrometer for normal and glaucoma eyes, respectively. A components of variance model showed most of the variance (79%) to be due to differences between patients. Only a modest contribution to variability was found for session (1%), visit (5%), and operator (2%).

CONCLUSION

With the commercially available OCT, our results indicate that the RNFL measurements are reproducible for both normal and glaucomatous eyes.

Short-wavelength automated perimetry and standard perimetry in the detection of progressive optic disc cupping

OBJECTIVE

To compare progression in short-wavelength automated perimetry (SWAP) and white-on-white (standard) perimetry in eyes with progressive glaucomatous changes of the optic disc detected by serial stereophotographs.

METHODS

Forty-seven glaucoma patients with at least 2 disc stereophotographs more than 2 years apart, along with standard perimetry and SWAP examinations within 6 months of each disc photo of the same eye, were included in the study. The mean follow-up time was 4.1 years (range, 2.0-8.9 years). Baseline and follow-up stereophotographs were then graded and compared for the presence of progression. Progression in standard perimetry and SWAP, using the Advanced Glaucoma Intervention Study scoring system and a clinical scoring system, was compared between eyes with progressive change on stereophotographs and those without.

RESULTS

Twenty-two of 47 eyes showed progressive change by stereophotographs. There was a statistically significant difference in the mean change in Advanced Glaucoma Intervention Study scores for both standard perimetry (P<.004) and SWAP (P<.001) between the progressed and nonprogressed groups. The sensitivity, specificity, and area under the receiver operator characteristic curve were higher using SWAP than standard perimetry when evaluated by either algorithm. This was statistically significant only in the area under the receiver operator characteristic curve for the Advanced Glaucoma Intervention Study scoring system (P =.04).

CONCLUSIONS

Short-wavelength automated perimetry identified more patients than standard perimetry as having progressive glaucomatous changes of the optic disc. Compared with standard perimetry, SWAP may improve the detection of progressive glaucoma. Arch Ophthalmol. 2000;118:1231-1236

Optic disk topography after medical treatment to reduce intraocular pressure

PURPOSE

We examined changes in optic disk topography using confocal scanning laser ophthalmoscopy after reducing intraocular pressure with administration of latanoprost.

METHODS

Twenty-nine patients with glaucoma or ocular hypertension were imaged using the Heidelberg Retina Tomograph before and after the administration of latanoprost to decrease intraocular pressure. Average time between pretreatment and posttreatment imaging was 2.7 +/- 1.8 weeks. Heidelberg Retina Tomograph software-measured parameters were mean height of contour, cup area, cup volume, mean cup depth, maximum cup depth, cup shape, rim area, rim volume, cup-to-disk ratio, and retinal nerve fiber thickness.

RESULTS

Average intraocular pressure decreased significantly (mean +/- SD) by 7.2 +/- 5.4 mm Hg (25 +/- 16% decrease). No statistically significant changes in measured topographic parameters were found. When data from patients with decreases in intraocular pressure of 7 mm Hg or greater were analyzed separately (mean intraocular pressure decrease = 10.79 +/- 4.32 mm Hg, 36 +/- 8% decrease), cup area (P =.005), cup volume (P =. 002), and cup-to-disk ratio (P =.005) decreased significantly, and rim area (P =.005) increased significantly. Linear regression analysis of the data from all subjects showed that a change in intraocular pressure after latanoprost administration accounted for 12% or more of the variance in two measured topographic parameters (mean cup depth and cup shape).

CONCLUSIONS

These results suggest that, in some patients, moderate decreases in intraocular pressure may affect disk topography, as measured by Heidelberg Retina Tomograph. Intraocular pressure should be considered when analyzing consecutive confocal scanning laser ophthalmoscopy images for glaucomatous progression.

A comparison of optical coherence tomography and retinal nerve fiber layer photography for detection of nerve fiber layer damage in glaucoma

PURPOSE

To compare optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements with established methods for assessment of glaucomatous damage using RNFL photography and visual field testing.

DESIGN

Cross-sectional study.

PARTICIPANTS

Fifty-eight eyes of 58 healthy volunteer ocular hypertensive patients, glaucoma suspect patients, and glaucoma patients were included.

METHODS

Optical coherence tomography 3.4-mm diameter circular scans were obtained within 3 months of RNFL photography and standard achromatic visual field testing. Three independent observers graded RNFL photographs using two standardized protocols. For each method, superior and inferior arcuate bundles were scored separately, and interobserver and intraobserver variation was measured. Standard achromatic visual field mean deviation in the superior and inferior hemifields was compared with RNFL damage as assessed by photography and OCT RNFL thickness measurements.

MAIN OUTCOME MEASURES

Visual field mean deviation and severity of glaucomatous RNFL damage as assessed by photography.

RESULTS

Optical coherence tomography RNFL thickness decreased with increasing RNFL damage as assessed by photography using both methods of photographic assessment. Standard achromatic perimetry mean deviation was significantly associated with OCT RNFL thickness (R(2) = 35%-43%) and RNFL photography severity score (R(2) = 18%-29%).

CONCLUSIONS

These results suggest that the OCT shows promise for providing quantitative measures of RNFL thickness for diagnosing and monitoring glaucoma.

Sex differentials in predictors of mortality for patients with adult-onset diabetes: a population-based follow-up study in Beer-Sheva, Israel

OBJECTIVE

To test the hypothesis that factors predicting mortality differ between diabetic men and women.

RESEARCH DESIGN AND METHODS

A total of 498 known patients with diabetes residing in a well-defined geographical area and receiving primary health care in 3 primary care community clinics were interviewed and examined between 1988 and 1990.

RESULTS

By 31 July 1998, after a mean follow-up period of 7.8 years, 148 patients (68 men and 80 women) had died (29.7%). No statistical differences in survival rate or in the specific causes of death were found between men and women. In the univariate analysis of factors examined at baseline, GHb levels were significantly higher among women who died compared with women who survived, but this was not the case for men. Conversely, a trend of higher triglyceride and uric acid levels was found for men who died compared with men who survived, but this was not the case for women. Multivariate Poisson regression analysis showed significantly higher risk ratios for mortality in men > or = 63 years of age, men with microalbumin excretion > or = 30 mg/l, and men with higher triglyceride levels. In contrast, the analysis in women showed that higher GHb and creatinine levels and a reported history of heart disease were the only factors at the baseline examination significantly and independently associated with an increased risk ratio of mortality.

CONCLUSIONS

The results suggest the existence of sex-specific interactions with various metabolic factors associated with diabetes that may have a different effect on mortality for each sex.

The retinal nerve fiber layer thickness in ocular hypertensive, normal, and glaucomatous eyes with optical coherence tomography

OBJECTIVE

To quantitatively assess and compare the thickness of the retinal nerve fiber layer (RNFL) in ocular hypertensive eyes with normal and glaucomatous eyes using the Optical Coherence Tomograph (OCT 2000, software version A4X1; Humphrey Instruments, San Leandro, Calif).

METHODS

The mean RNFL thickness of ocular hypertensive (n = 28) eyes was compared with age-matched normal (n = 30) and glaucomatous (n = 29) eyes. Subject eyes were classified into diagnostic groups based on intraocular pressure, stereoscopic disc photographs, and standard automated perimetry. Three circular scans were obtained for each eye at a diameter of 3.4 mm around the optic disc. In each eye, average RNFL thickness measurements were obtained in temporal, superior, nasal, and inferior quadrants. A single index of average RNFL thickness throughout 360 degrees also was obtained.

RESULTS

Mean (95% confidence interval) RNFL was significantly thinner in ocular hypertensive eyes than in normal eyes, 72.8 microm (66.4-78.1 microm) and 85.8 microm (80.2-91.7 microm), respectively. More specifically, RNFL was significantly thinner in ocular hypertensive eyes than in normal eyes in the inferior quadrant, 84.8 microm (75.6-94.0 microm) vs 107.6 microm (99.3-115.9 microm); and in the nasal quadrant, 44.1 microm (37.5-51.7 microm) vs 61.8 microm (53.0-65.6 microm). Retinal nerve fiber layer was significantly thinner in glaucomatous eyes than in ocular hypertensive and normal eyes throughout 360 degrees and in all quadrants.

CONCLUSION

These findings suggest that quantitative differences in RNFL thickness exist between age-matched ocular hypertensive, normal, and glaucomatous eyes.

Optic disc topographic measurements after pupil dilation

PURPOSE

To determine the effect of pupil dilation on topographic optic disc parameters measured with confocal scanning laser ophthalmoscopy.

DESIGN

Prospective, comparative, observational case series.

PARTICIPANTS

Thirty-eight subjects (25 glaucoma patients, 5 glaucoma suspects, and 8 normal subjects) representing a range of lens opacities participated in this study.

METHODS

Topographic optic disc parameter measurements were obtained before and after pupil dilation with a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Cataract severity was measured with the LOCS III grading system. Image quality was assessed using the standard deviation of the mean topography image and an image quality score. Multiple regression techniques were used to evaluate the effect of image quality, cataract density, and pupil size on the change in topographic parameters after dilation.

MAIN OUTCOME MEASURES

Topographic optic disc parameter measurements.

RESULTS

With dilation, mean change in most topographic optic disc parameters was not significantly different from zero. Changes in topographic optic nerve parameters tended to be relatively small when undilated images were of good quality and larger in images of relatively poor quality. The strongest predictor of the absolute value of change in topographic optic disc parameters was the standard deviation of the undilated mean topography image.

CONCLUSIONS

When confocal scanning laser ophthalmoscope images are of good quality, topographic optic disc parameter measurements obtained with a dilated pupil are similar to those obtained with an undilated pupil. However, caution should be exercised when interpreting information from poor quality confocal scanning laser ophthalmoscopic images.

New technologies for diagnosing and monitoring glaucomatous optic neuropathy

BACKGROUND

Recently, instruments have been developed to provide real-time, quantitative measurements of the optic disc and retinal nerve fiber layer (RNFL) for use in glaucoma management. Our objective is to (1) provide an overview of two of these instruments, the confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, HRT) and scanning laser polarimeter (Nerve Fiber Analyzer, NFA) and (2) compare measurements obtained with these instruments to clinical features used in the diagnosis of glaucoma.

METHODS

Twenty glaucoma patients, 4 normal subjects and 20 glaucoma subjects were included. All subjects had images obtained with the HRT and NFA, and RNFL and optic disc photography completed within 5 weeks of each other. The HRT results were compared with qualitative evaluation of stereophotographs of the optic disc, and NFA results were compared against a semi-quantitative RNFL photograph severity score.

RESULTS

Twenty-five (57%) subjects had thinning of the neuroretinal rim identified by evaluation of stereoscopic optic disc photographs. Despite overlap, HRT measurements of rim volume, rim area, and rim/disc ratio were significantly smaller in eyes with evidence of rim thinning than in eyes with no evidence of rim thinning. Moderate to severe RNFL damage was detected by evaluation of photographs in 25 (57%) of subjects. NFA RNFL thickness measures were smaller in eyes with moderate to severe RNFL damage than in relatively healthy eyes.

CONCLUSIONS

Previous studies have documented the reproducibility of these instruments and suggested analytic techniques for improving their ability to differentiate between normal and glaucoma eyes. Our results indicate that despite overlap in values, these instruments provide measurements that reflect clinically relevant features of the optic disc and RNFL. Whether these technologies can improve our ability to detect glaucomatous progression over time needs to be determined with well-designed longitudinal studies and comparison with established diagnostic techniques for evaluating glaucomatous optic neuropathy.

Optic nerve head topography in ocular hypertensive eyes using confocal scanning laser ophthalmoscopy

PURPOSE

To compare measurements of optic nerve topography of ocular hypertensive patients with those of normal subjects and primary open-angle glaucoma patients.

METHODS

Three age-matched study groups of 46 ocular hypertensive patients, 46 primary open-angle glaucoma patients, and 46 normal subjects were recruited from patients and volunteers of a glaucoma referral practice. Optic nerve topography was measured using a confocal scanning laser tomograph, the Heidelberg Retina Tomograph. The following optic nerve parameters were evaluated: disk area, cup/disk area ratio, cup shape, height in contour, rim area, rim volume, maximum cup depth, cup area, cup volume, retinal height, and retinal cross-section area. For this cross-sectional study, analysis of variance was used to evaluate overall differences among the three subject groups and the Tukey-Kramer multiple comparison test to evaluate differences between the means of two groups.

RESULTS

Statistically significant differences among study groups were found for all topographic optic nerve parameters evaluated. Despite considerable overlap in optic nerve parameter measurements among the study groups, mean values of ocular hypertensive eyes were intermediate between those for normal and primary open-angle glaucoma eyes. Statistically significant differences were found between ocular hypertensive and glaucomatous eyes for all optic nerve parameters measured, and between ocular hypertensive and normal eyes for disk area, height in contour, rim area, and rim volume.

CONCLUSIONS

In age-matched groups, mean measurements of certain topographic optic nerve parameters of ocular hypertensive eyes differ from those of normal and glaucomatous eyes.

The correlation between intraocular pressure and refractive status

A comprehensive glaucoma screening of residents of three urban areas in southern Israel, aged 40 years and above, was performed between 1982 and 1984. Among other factors tested, intraocular pressure (IOP) and refractive status were recorded and the association between them was analyzed. Information on both factors was available in 2,403 (4,821 eyes) of the 2,594 persons participating. There were significantly more myopes among persons with IOPs of more than 20 mm Hg than with lower IOPs. Mean IOP increased gradually from 14.19 mm Hg in hypermetropes to 16.00 mm Hg among high myopes. Furthermore, the association between refractive status and IOP was stronger among Jews of North African or Asian origin than among Jews of European origin.