[3-dimensional topographic analysis of the papilla as a component of glaucoma diagnosis]

Abstract

Three-dimensional topography of the optic nerve head can be objectively described by means of quantitative parameter values. Owing to interindividual variability in the disc configuration, new structural variables, such as the relative height of the peripapillary retinal nerve fiber layer in stereo-videography and height variations in the contour line along the disc border in laser scanning tomography, have been shown to differentiate normal optic discs and optic nerve heads with pathological alterations better than standard volumetric data. Using laser scanning tomography, the effect of age on the parameter values of disc area, rim area and the ratio of the cup-to-disc area was evaluated in 61 healthy subjects (age 14 to 77) who had normal visual fields on computerized static perimetry. The rim area decreased with age (rs = -0.26, P < 0.05); the ratio of the cup area to disc area increased (rs = 0.25; P < 0.05). No relationship was found between patient age and disc area (Spearman correlation). Although the coefficients of correlation are rather small, they may reflect the physiological age-related decline in axonal count. The high resolution of strictly confocal laser scanning microscopy allows for visualization of nerve fiber bundle defects underneath a surface of regular reflectivity. The existence of such hidden nerve fiber bundle defects has been postulated before on the basis of experimental studies and may be an early morphological sign of glaucomatous damage.