Michele Iester

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.

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.

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.

Retinal nerve fiber layer and physiological central corneal thickness.

PurposeTo determine the relationship between central corneal thickness and the measurement of retinal nerve fiber layer thickness around the optic nerve head using a confocal scanning laser polarimeter such as the Nerve Fiber Analyzer (GDx). MethodsForty-four eyes were recruited for this study. Each patient had a normal visual field and a healthy optic nerve head, which was assessed by slit-lamp biomicroscopy with a 90-diopter lens and by a scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Using the GDx, retinal nerve fiber layer thickness was calculated from 1.75 disc diameters together with some standard GDx parameters, including the number, symmetry, superior ratio, inferior ratio, maximum modulation, and ellipse modulation. Corneal thickness was measured with the DGH-1000 ultrasonic pachymeter. Descriptive analysis was used and Pearsons r coefficient of correlation was calculated. ResultsCorneal thickness was not significantly correlated to retinal nerve fiber layer thickness, but it was significantly (P < 0.05) correlated to the other GDx parameters. ConclusionFrom these data, peripapillary retinal nerve fiber layer thickness is shown not to be significantly correlated to the corneal thickness, even if for the standard GDx parameters a significant correlation was found.

Retinal Nerve Fiber Layer Height in High-Tension Glaucoma and Healthy Eyes

Purpose: To determine the correlations between the retinal nerve fiber layer height measured by Heidelberg Retina Tomograph, version 1.11, and visual field indices in healthy individuals and patients with glaucoma.Methods: One eye was randomly chosen from 48 patients with glaucoma and 60 healthy individuals. All participants were classified using Humprey visual field, program 30–2 (Humphrey Instruments, Inc., San Leandro, CA, U.S.A.); mean deviation, pattern standard deviation, short-term fluctuation, and corrected pattern standard deviation were measured. Superior and inferior mean deviation were calculated. For each participants the mean Heidelberg Retina Tomograph was generated from three 10° Heidelberg Retina Tomograph pictures. The Student t test was used to compare healthy and glaucomatous retinal nerve fiber layer (RNFL) mean degree values every 5°. A global measurement, superior sector (25°-125°), nasal sector (130°-230°), inferior sector (235°-335°), temporal sector (340°-20°), and polar sector (superior + inferior) were calculated. The global, superior, nasal, inferior, temporal, and polar RNFL height (RNFLH) were compared between healthy individuals and patients with glaucoma. The correlation between global, superior, inferior, and polar retinal nerve fiber layer height and visual field was calculated.Results: A significant difference was found for RNFLH mean from 45° to 330° and for the distribution of the means (as reflected by the standard deviation) from 85° to 100°, 260° to 295°, and 335° to 5°. From these data we created three new sectors: new superior sector (from 85° to 100°), new inferior sector (from 260° to 295°), and new polar sector (combining the new superior and the new inferior sector). Comparing the healthy individuals to the patients with glaucoma, the mean RNFLH values for each sector were found to differ significantly (p < 0.001), with the exception of the temporal sector. Significant correlations (p < 0.001) between the global RNFLH and mean deviation (r = −0.36), pattern standard deviation (r = 0.49), and corrected pattern standard deviation (r = 0.48) were found in healthy participants and those with glaucoma. The strongest correlations (p < 0.001) were found between the pattern standard deviation and the corrected pattern standard deviation with the new polar sector (r = 0.60 and r = 0.59, respectively).Conclusions: We found that the strongest correlations with the visual field were with the new polar and new inferior sector.

Normal retinal nerve fiber layer thickness in the peripapillary region measured by scanning laser polarimetry.

PurposeTo measure retinal nerve fiber layer thickness (RNFLT) as a function of distance from the optic nerve head using a confocal scanning laser polarimeter, such as the Nerve Fiber Analyzer (GDx). MethodsTwenty eyes of 20 healthy patients were recruited for this study. Each patient had a normal visual field and a healthy optic nerve head, which was assessed by slit-lamp biomicroscopy using a 90-diopter lens and by a scanning laser ophthalmoscope. Using the GDx, RNFLT was calculated from 1.1 disc diameters (DD) to 2.5 DD in 0.1-DD increments from the outer edge of the optic disc rim. RNFLT was successively evaluated for the entire annulus surface, for each quadrant, and for every 10° sector. RNFLT was calculated in retardation degrees. Differences in RNFLT were calculated by analysis of variance. ResultsWhen the entire RNFLT was considered, the measurements close to the optic nerve head (at 1.1 and 1.2 DD) were found to be significantly (0.05 ≤P ≤ 0.01) different from those measured far from the disc (at 2.4 and 2.5 DD). The inferior quadrant had the greatest RNFLT followed by the superior quadrant. When RNFLT was analyzed for every 10°, RNFLT at 1.1 and 1.2 DD was significantly (P ≤0.001) different from that measured at 2.4 and 2.5 DD in almost all 36 sectors. In the 36 considered sectors, no significant difference was found for all the RNFLT values that were calculated in all the positions of the annulus surface between 1.1 and 1.7 DD. ConclusionFrom these data, peripapillary RNFLT is shown to be significantly (P ≤0.001) thinner in the periphery (2.5 DD) than around the optic disc (1.1 DD). However, the lack of any difference in RNFLT from 1.1 to 1.7 DD suggested that the mild variations to locate the optic disc contour line do not change the results of the analysis if the RNFLT is calculated within 1.8 DD.