Agreement between Heidelberg Retina Tomograph-I and -II in detecting glaucomatous changes using topographic change analysis.

PURPOSE: To evaluate the suitability of including both Heidelberg Retina Tomograph-I (HRT-I) and HRT-II examinations in the same longitudinal series for HRT topographic change analysis (TCA) and to evaluate parabolic error correction (PEC) to improve the agreement between HRT-I and HRT-II examinations. METHODS: A total of 66 eyes from the University of California San Diego Diagnostic Innovations in Glaucoma Study with baseline HRT-I and HRT-II examinations obtained on the same day and ≥ 3 HRT-II follow-up examinations were included. Two TCA analyses, HRT-I examination at baseline (HRT-I-mixed series) and HRT-II examination at baseline (HRT-II-only series) were compared. Agreement between the HRT-I-mixed and HRT-II-only series were estimated using Bland-Altman plots. Agreement was assessed: (1) using the current HRT software settings (PEC applied only to HRT-II-only series), and (2) modified HRT settings (PEC also applied to HRT-I-mixed series). RESULTS: With current HRT software settings, the HRT-I-mixed series significantly overestimated change locations (ie, red pixels) compared with the HRT-II-only series as indicated by statistically significant proportional biases in the Bland-Altman analysis. By applying PEC to HRT-I-mixed series there were no statistically significant biases in the TCA parameter estimates compared with the HRT-II-only series. CONCLUSION: In some eyes, HRT-I and HRT-II baseline examinations are not interchangeable in TCA analysis without parabolic error correction. HRT-I-mixed series detected more changes characteristic of glaucoma when there were only minimal changes in the HRT-II-only series. Our results suggest that in the majority of cases, with PEC, HRT-I examinations may be included in a longitudinal series containing HRT-II examinations.

Pattern electroretinogram association with spectral domain-OCT structural measurements in glaucoma.

PURPOSE: To describe the association between pattern electroretinogram (PERG) amplitude and spectral domain-optical coherence tomography (SD-OCT) macular thickness, retinal nerve fibre layer (RNFL) thickness and optic disc topography measurements. SUBJECTS AND METHODS: Both eyes (n = 132) of 66 glaucoma patients (mean age = 67.9 years) enrolled in the University of California, San Diego, CA, USA, Diagnostic Innovations in Glaucoma Study (DIGS) were included. Eyes were tested with PERG (Glaid PERGLA, Lace Elettronica, Pisa, Italy), RTVue SD-OCT (Optovue Inc., Fremont, CA, USA) GCC, and NHM4 protocols on the same day. Of the 66 enrolled patients, 43 had glaucoma defined by repeated abnormal standard automated perimetry (SAP) results in at least one eye and 23 were glaucoma suspects defined by a glaucomatous-appearing optic disc by physicians' examination in at least one eye and normal SAP results in both eyes. Associations (R(2)) were determined between PERG amplitude (µV) and SD-OCT macular ganglion cell complex (GCC) thickness (µm), macular thickness (µm), macular outer retinal thickness (macular thickness minus GCC thickness) (µm), RNFL thickness (µm), neuroretinal rim area (mm(2)), and rim volume (mm(3)). RESULTS: PERG amplitude was significantly associated with GCC thickness (R(2) = 0.179, P < 0.001), RNFL thickness (R(2) = 0.174, P < 0.001), and macular thickness (R(2) = 0.095, P<0.001). R(2) associations with other parameters were not significant (all P > 0.624). Significant associations remained for GCC and average RNFL thickness when age and intraocular pressure at the time of testing were included in multivariate models (both P ≤ 0.030). CONCLUSIONS: PERG amplitude is significantly (but weakly) associated with macular GCC thickness, RNFL thickness, and macular thickness. The lack of association between PERG amplitude and macular outer retinal thickness supports previous results, possibly suggesting that that the PERG is driven primarily by retinal ganglion cell (inner retinal) responses.

A mathematical description of nerve fiber bundle trajectories and their variability in the human retina.

We developed a mathematical model wherein retinal nerve fiber trajectories can be described and the corresponding inter-subject variability analyzed. The model was based on traced nerve fiber bundle trajectories extracted from 55 fundus photographs of 55 human subjects. The model resembled the typical retinal nerve fiber layer course within 20 degrees eccentricity. Depending on the location of the visual field test point, the standard deviation of the calculated corresponding angular location at the optic nerve head circumference ranged from less than 1 degrees to 18 degrees , with an average of 8.8 degrees .

Agreement between spectral-domain and time-domain OCT for measuring RNFL thickness.

BACKGROUND/AIMS: To evaluate spectral-domain (SD) optical coherence tomography (OCT) reproducibility and assess the agreement between SD-OCT and Time-Domain (TD) OCT retinal nerve fibre layer (RNFL) measurements. METHODS: Three Cirrus-SD-OCT scans and one Stratus-TD-OCT scan were obtained from Diagnostic Innovations in Glaucoma Study (DIGS) healthy participants and glaucoma patients on the same day. Repeatability was evaluated using Sw (within-subject standard deviation), CV (coefficient of variation) and ICC (intraclass correlation coefficient). Agreement was assessed using correlation and Bland-Altman plots. RESULTS: 16 healthy participants (32 eyes) and 39 patients (78 eyes) were included. SD-OCT reproducibility was excellent in both groups. The CV and ICC for Average RNFL thickness were 1.5% and 0.96, respectively, in healthy eyes and 1.6% and 0.98, respectively, in patient eyes. Correlations between RNFL parameters were strong, particularly for average RNFL thickness (R(2) = 0.92 in patient eyes). Bland-Altman plots showed good agreement between instruments, with better agreement for average RNFL thickness than for sectoral RNFL parameters (for example, at 90 microm average RNFL thickness, 95% limits of agreement were -13.1 to 0.9 for healthy eyes and -16.2 to -0.3 microm for patient eyes). CONCLUSIONS: SD-OCT measurements were highly repeatable in healthy and patient eyes. Although the agreement between instruments was good, TD-OCT provided thicker RNFL measurements than SD-OCT. Measurements with these instruments should not be considered interchangeable.

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.

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.

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.

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.

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

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.

Evaluating the optic disc and retinal nerve fiber layer in glaucoma. I: Clinical examination and photographic methods.

Glaucoma is a leading cause of blindness worldwide and is characterized in part by specific changes in the optic disc and retinal nerve fiber layer. Currently, subjective clinical examination and fundus photography are the most common ways of detecting structural change in glaucoma and monitoring its progression. In the first part of this two-part article, the authors overview structural changes of the optic disc and retinal nerve fiber layer in glaucoma and describe and evaluate photographic methods for observing these changes. In the second part of this article (this issue), recent developments in computer-based optical imaging techniques that allow objective evaluation of the optic disc and retinal nerve fiber layer are described.

Evaluating the optic disc and retinal nerve fiber layer in glaucoma. II: Optical image analysis.

Glaucoma is a widespread, blindness-causing disease that is characterized in part by specific and sometimes subtle changes in optic disc and retinal nerve fiber layer topography. Several recently developed computer-based optical imaging techniques allow objective evaluation of the optic disc and retinal nerve fiber layer. These techniques use different optical properties and different properties of the retina to provide micron scale measurements of many aspects of optic disc and retinal nerve fiber layer structure. This article describes and evaluates 3 of these techniques: confocal scanning laser ophthalmoscopy, scanning laser polarimetry, and optical coherence tomography.

The relationship between structural and functional alterations in glaucoma: a review.

This article reviews the relationships between structural changes and visual function losses produced by glaucomatous damage. Structural characteristics of the optic nerve head and retinal nerve fiber layer include both qualitative and semi-quantitative clinical assessment methods as well as quantitative imaging techniques. Visual function properties include standard (white-on-white) automated perimetry and new techniques such as short wavelength automated perimetry and motion displacement threshold perimetry. Previous investigations consistently report a significant relationship between structural and functional deficits in glaucoma, with structural changes usually being reported to occur earlier than functional losses. In cases of focal damage, there appears to be a good topographic relationship between structural and functional losses. Several optic nerve head and retinal nerve fiber layer measures are reported to be good predictors of glaucomatous visual field loss. However, previous investigations of structure-function relationships in glaucoma are limited by the small number of patients evaluated in most studies, the lack of well-defined inclusion/exclusion criteria as well as detailed descriptions of the patient population, and the paucity of prospective longitudinal studies that have been performed.

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 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.