Frederick S. Mikelberg

Ability of the heidelberg retina tomograph to detect early glaucomatous visual field loss.

PurposeThe Heidleberg Retina Tomograph provides rapid, reproducible measurements of optic disc topography as well as calculations of disc parameters. We used a stepwise discriminant analysis to determine which parameters were most useful in detecting individuals with early glaucomatous visual field loss. MethodsWe studied one eye in each of 45 normal individuals and one eye in each of 46 individuals with early glaucomatous visual field loss. The appearance of the optic disc was not used for classification purposes so as not to bias the diagnostic determination obtained by the instrument. The data were analyzed using the reference plane of the software version 1.10 and using a method incorporating the height of the papillomacular bundle as reference level with and without age correction. ResultsWe obtained an 89% sensitivity and 78% specificity for the detection of early visual field loss using the standard reference level. The jackknife classification revealed lower sensitivity of 87% and an unchanged specificity of 78%. With the method incorporating the height of the papillomacular bundle as reference level, the sensitivity was 87% and the specificity was 84% for detecting early visual field loss. The jackknife classification revealed a sensitivity of 87% and a specificity of 82%. With the age correction, the sensitivity was 87%, specificity 84% with regular and jackknife classification. With the standard reference level, the important parameters were the third moment and the maximum depth, with the papillomacular bundle reference level volume above reference level added as important, and with age correction, height variation in contour replaced maximum depth in the analysis. ConclusionThree significant shape parameters of the optic disc can be used to detect early glaucomatous visual field loss.

Reproducibility of topographic parameters obtained with the heidelberg retina tomograph.

The Heidelberg retina tomograph is a confocal scanning laser ophthalmoscope that permits recording of topographic information related to the optic nerve and retina. We studied the reproducibility of the topographic parameters obtained by recording five times sequentially the images obtained from one eye of five healthy people and five glaucoma patients. The reproducibility coefficients ranged from 60.5 to 99.4%. The results indicate that, for the parameters examined, the instrument has a high level of reproducibility.

The Normal Human Optic Nerve: Axon Count and Axon Diameter Distribution

Computerized image analysis was used to determine the normal axonal count and axon diameter distribution in 12 normal human eyes. Mean axon count per nerve was 969,279 +/- 239,740 and mean axon diameter was 0.72 +/- 0.07 micron. Multiple linear regression disclosed 4909 axons lost yearly (P = 0.08). Statistical analysis did not show a relationship between axon diameter and age or time to fixation. The inferotemporal sector of the nerve had the highest fiber density (P = 0.02). The superonasal nerve had higher mean diameters (P = 0.02). This study may provide a baseline for future pathologic studies.

Correlation Between the Visual Field Indices and Heidelberg Retina Tomograph Parameters

Purpose:We wished to determine whether a relationship exists between Heidelberg retina tomograph (HRT) parameters and the visual field indices. Methods:One eye was randomly chosen from 59 normal patients [normal visual field and normal optic nerve head (ONH) and intraocular pressure (IOP) <21 mm Hg], 64 ocular hypertensive patients (normal visual field and normal OHN and IOP >22 mm Hg), 124 high-tension glaucoma patients (abnormal visual field and/or abnormal optic nerve and IOP >22 mm Hg) and 47 lowtension glaucoma patients (abnormal visual field and or optic disc and IOP <21 mm Hg). All the patients were examined with Humphrey Perimeter, program 30–2, and HRT. Findings were assessed by analysis of variance, Pearsons correlation coefficient, and multiple linear regression. Results:Among all subjects, we noted a statistically significant correlation (Pearsons r, p < 0.001) between cup area, cup/disc area ratio, rim area, rim volume, cup shape measure, and retinal nerve fiber layer cross-section area with mean deviation and corrected pattern SD. Multiple linear regression analysis demonstrated that rim area was the most important predictor of mean deviation and corrected pattern SD. Conclusions:The presence of significant correlations between some HRT parameters, such as rim area and cup shape measure and visual field indices, suggests that these HRT parameters could be good indicators of the degree of glaucomatous ONH damage.

Canadian Glaucoma Study: 2. Risk Factors for the Progression of Open-angle Glaucoma

OBJECTIVE To determine systemic and ocular risk factors for visual field progression in open-angle glaucoma. METHODS In the Canadian Glaucoma Study, a multicenter prospective longitudinal study of 258 patients (131 men and 127 women; median age, 65.0 years), baseline systemic measures included assessment of peripheral vasospasm and markers for hematopathology, coagulopathy, and immunopathology. Patients were followed up at 4-month intervals with perimetry, optic disc imaging, and a standardized interventional protocol for intraocular pressure control. Univariate and proportional hazards models were used to identify factors that predicted progression. MAIN OUTCOME MEASURE Visual field progression with standard automated perimetry. RESULTS Median follow-up was 5.3 years, with 167 patients (64.7%) completing 5 years or more and 67 patients (26.0%) completing 7 years or more. Abnormal baseline anticardiolipin antibody levels (hazard ratio [HR], 3.86; 95% confidence interval [CI], 1.60-9.31), higher baseline age (HR per year, 1.04; 95% CI, 1.01-1.07), female sex (HR, 1.94; 95% CI, 1.09-3.46), and higher mean follow-up intraocular pressure (HR per 1 mm Hg, 1.19; 95% CI, 1.05-1.36) before progression were associated with progression. CONCLUSIONS The Canadian Glaucoma Study identified 4 independent predictive factors for glaucomatous field progression. Application to Clinical Practice While confirming the importance of intraocular pressure in glaucoma progression, this study determined other risk factors that merit awareness.

Reliability of Optic Disk Topographic Measurements Recorded with a Video-Ophthalmograph

The video-ophthalmograph records the topography of the optic disk via simultaneous stereoscopic images which are stored and analyzed with the help of a microcomputer. This information is used to generate the vertical cup-disk ratio, the vertical optic disk diameter, the cup volume, and the neuroretinal rim area. To determine the reliability of the data, we recorded information for one eye of each of five patients ten times to determine the interphotographic error variance. We also analyzed one photograph for each of five patients ten times to determine the intraphotographic variance attributable to repeated analysis of the same photograph. The interphotographic and intraphotographic coefficients of variation were 2% to 18% and 2% to 7% respectively for these measurements.

The Mode of Progression of Visual Field Defects in Glaucoma

We retrospectively studied 42 eyes of 42 patients with glaucoma to determine the pattern of progression of their visual field defects. In 33 eyes (79%) the scotomas became denser. Enlargement occurred in 22 eyes (52%) and 21 eyes (50%) developed new scotomas. Increased density of the scotomas was the only manifestation of change in ten eyes (24%), three eyes (7%) showed enlargement only, and six (14%) showed only new scotomas. Seventeen eyes (57%) with single hemifield involvement maintained a defective single hemifield throughout the follow-up period.

Sector-based analysis of optic nerve head shape parameters and visual field indices in healthy and glaucomatous eyes.

PurposeTo evaluate the correlations between the sector optic nerve head parameters measured by Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg, Germany), version 1.1 IS, and the visual field. MethodsOne eye was randomly chosen from 55 individuals with glaucoma and 50 healthy individuals. Each participant had at least one Humphrey visual field, program 30–2 (Humphrey Instruments. San Leandro, CA. U.S.A.), and three 10° HRT pictures. From the mean of the three HRT pictures, global measurements, superior (45°-135°). nasal (135°-225°), inferior (225°-315°), and temporal (315°-45°) sector measurements were calculated for the following parameters: disc area, effective area, area below reference, mean height of contour, volume below surface, volume above surface, volume below reference, volume above reference, and third moment. From the visual field results, mean deviation (MD). superior MD. and inferior MD were calculated. For each HRT parameter we calculated the “r” Pearson correlation with the corresponding visual field measures. ResultsWithin the combined healthy and glaucomatous groups we found highly significant (p < 0.001) correlations between the following HRT parameters and the visual field MD: inferior and mean hight of contour (r = −0.53), inferior and third moment (r = −0.52). global and third moment (r = −0.49). inferior and volume above reference (r = 0.47). superior and third moment (r = −0.46), and superior and area below reference (r = −0.44). Correlations between global mean deviation and nasal or temporal sector parameters were generally smaller and less significant. ConclusionsInterior and superior HRT sector parameters were correlated with the respective visual field indices. In many cases these correlations were as strong or stronger than with the global equivalent shape measures.

A comparison of healthy, ocular hypertensive, and glaucomatous optic disc topographic parameters.

PurposeTo compare the optic discs of 62 healthy individuals 68 patients who have ocular hypertension (OH), and 182 patients with primary open-angle glaucoma (132 high-tension glaucoma (HTG) and 50 normal-tension glaucoma (NTG)), and determine whether disc size exerted an influence on the group differentiation. Patients and MethodsStandard criteria were used to define glaucoma and normality. Ocular hypertension was defined as having raised intraocular pressure, a normal visual field, and a healthy optic disc/retinal nerve fiber layer (RNFL). The optic disc of one eye from each individual was analyzed using a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph software version 1.11, Heidelberg Engineering, Heidelberg. Germany). Thirteen topographical, volumetric, and shape parameters were compared between the three diagnostic groups. In addition, the individuals were divided into subgroups on the basis of disc size to determine any effect of disc size on the differentiating ability of the confocal scanning laser ophthalmoscope. Differences between the groups were evaluated using an analysis of variance. ResultsGlaucomatous optic discs were found to differ from both healthy and OH discs, although no differences in disc area between the groups were identified. On the basis of disc size, differentiating the glaucomatous discs was best for midsized discs of 2 mm2 to 3 mm2. However, no difference was found between healthy and OH discs, even when allowing for disc size. ConclusionsOcular hypertensive optic discs (with a clinically normal appearance) could not be distinguished from healthy discs using a confocal scanning laser ophthalmoscopic technique. Glaucomatous optic discs were found to differ from both healthy and OH discs, with a limited effect of disc size.

Relation between Optic Nerve Axon Number and Axon Diameter to Scleral Canal Area

To determine whether there are more axons present in eyes with larger optic discs, the authors studied 16 eyes from 16 individuals whose eyes were donated for corneal transplantation. For each nerve, the axon count, axon diameter, and scleral canal area was measured. Total axon count decreased with age. Mean axon diameter increased with age. There was no statistically significant relation detected between axon count and scleral canal area. Multiple regression revealed that when corrected for the effect of age, eyes with smaller scleral canal areas had larger number of axons.