Retinal nerve fiber bundle trajectories in Chinese myopic eyes: Comparison with a Caucasian based mathematical model.

Previously we developed a mathematical model for describing the retinal nerve fiber bundle (RNFB) trajectories in the human retina. The model was based on Caucasian eyes that were not selected regarding refraction. The aim of this study was to determine the characteristics of the RNFB trajectories in Chinese myopic eyes. We collected high quality red free fundus images from 80 eyes of 80 Chinese myopic subjects (median [interquartile range/range] refraction -3.9 [-6.0 to -2.5/-10 to -1] D). We traced all visible RNFBs (n = 1460) and evaluated their trajectories using the previously published mathematical model. In the superior-temporal region, the RNFB trajectories of the Chinese myopic eyes were similar to that of the Caucasian eyes (86% of trajectories within the 95% central range of the Caucasian model). In the inferior-temporal region, the trajectories of the Chinese low to moderate myopic eyes were also similar to that of the Caucasian eyes (85%); trajectories of the high myopic eyes (spherical equivalent beyond -6.00 D) were clearly less curved (75%). Associations between individual deviations from the model and axial length, retinal vessel course, and optic disc anatomy were studied with multiple linear regression analysis. In the superior-temporal region, the trajectories were associated with retinal vessel course (P = 0.008) and optic disc size (P = 0.016). In the inferior-temporal region, there was a significant association with axial length (P < 0.001), retinal vessel course (P = 0.006), and disc torsion (P = 0.009).

A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position.

Previously we developed a mathematical model for describing the retinal nerve fiber bundle trajectories in the superior-temporal and inferior-temporal regions of the human retina, based on traced trajectories extracted from fundus photographs. Aims of the current study were to (i) validate the existing model, (ii) expand the model to the entire retina and (iii) determine the influence of refraction, optic disc size and optic disc position on the trajectories. A new set of fundus photographs was collected comprising 28 eyes of 28 subjects. From these 28 photographs, 625 trajectories were extracted. Trajectories in the temporal region of the retina were compared to the existing model. In this region, 347 of 399 trajectories (87%) were within the 95% central range of the existing model. The model was extended to the nasal region. With this extension, the model can now be applied to the entire retina that corresponds to the visual field as tested with standard automated perimetry (up to approximately 30° eccentricity). There was an asymmetry between the superior and inferior hemifields and a considerable location-specific inter-subject variability. In the nasal region, we found two "singularities", located roughly at the one and five o'clock positions for the right optic disc. Here, trajectories from relatively widespread areas of the retina converge. Associations between individual deviations from the model and refraction, optic disc size and optic disc position were studied with multiple linear regression. Refraction (P = 0.021) and possibly optic disc inclination (P = 0.09) influenced the trajectories in the superior-temporal region.

Specification of progression in glaucomatous visual field loss, applying locally condensed stimulus arrangements.

PURPOSE: The goal of this work was to (i) determine patterns of progression in glaucomatous visual field loss, (ii) compare the detection rate of progression between locally condensed stimulus arrangements and conventional 6 degrees x 6 degrees grid, and (iii) assess the individual frequency distribution of test locations exhibiting a local event (i.e., an abrupt local deterioration of differential luminance sensitivity (DLS) by more than -10 dB between any two examinations). METHODS: The visual function of 41 glaucomatous eyes of 41 patients (16 females, 25 males, 37 to 75 years old) was examined with automated static perimetry (Tuebingen Computer Campimeter or Octopus 101-Perimeter). Stimuli were added to locally enhance the spatial resolution in suspicious regions of the visual field. The minimum follow-up was four subsequent sessions with a minimum of 2-month (median 6-month) intervals between each session. Progression was identified using a modified pointwise linear regression (PLR) method and a modified Katz criterion. The presence of events was assessed in all progressive visual fields. RESULTS: Eleven eyes (27%) showed progression over the study period (median 2.5 years, range 1.3-8.6 years). Six (55%) of these had combined progression in depth and size and five eyes (45%) progressed in depth only. Progression in size conformed always to the nerve fiber course. Seven out of 11 (64%) of the progressive scotomata detected by spatially condensed grids would have been missed by the conventional 6 degrees x 6 degrees grid. At least one event occurred in 64% of all progressive eyes. Five of 11 (46%) progressive eyes showed a cluster of events. CONCLUSIONS: The most common pattern of progression in glaucomatous visual fields is combined progression in depth and size of an existing scotoma. Applying individually condensed test grids remarkably enhances the detection rate of glaucomatous visual field deterioration (at the expense of an increased examination time) compared to conventional stimulus arrangements.

Influence of the Retinal Blood Vessel Topography on the Variability of the Retinal Nerve Fiber Bundle Trajectories in the Human Retina.

PURPOSE: To determine the relationship between the retinal blood vessel topography and the retinal nerve fiber bundle (RNFB) trajectories in the human retina. METHODS: A previously collected dataset comprising 28 fundus photographs with traced RNFB trajectories was used. For all traced trajectories, the departure from our previously published RNFB trajectory model was calculated. Subsequently, we calculated, per subject, a "mean departure" for the superior-temporal and inferior-temporal region. We measured angles between a line connecting the optic nerve head (ONH) center and the fovea and lines connecting the ONH center and the crossings of the superior and inferior temporal arteries (arterial angles) and veins (venous angles) with circles around the ONH; circle radii were 25%, 50%, and 100% of the ONH center-to-fovea distance. We also defined two angles based on the location of the first arteriovenous crossing. Multiple linear regression analysis was performed with mean departure as dependent variable and refraction, ONH inclination, and vessel angles as independent variables. RESULTS: In the superior-temporal region, refraction (P = 0.017), ONH inclination (P = 0.021), and the arterial angle corresponding to the middle circle (P < 0.001) were significant determinants of mean departure. Explained variance was 0.54. In the inferior-temporal region, the arterial angle corresponding to the largest circle (P = 0.002) was significant. Explained variance was 0.32. CONCLUSIONS: The retinal blood vessel topography explains a significant part of the RNFB trajectory variability but only if (1) the vessel topography is assessed at an appropriate distance from the ONH and (2) the superior and inferior hemifield are addressed independently.