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° 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° to 18°, with an average of 8.8°.
Both small splinter haemorrhages of the optic disc and retinal nerve fibre layer (RNFL) defects have been reported to be the first signs of glaucomatous development before visual field defects. In this study their time- and location-based relationship to each other was investigated by means of repeated optic disc stereophotography of 25 patients who showed a disc haemorrhage but no disc and field involvement in their ocular hypertensive eyes. During a mean follow-up time of 6 years, 8 patients developed glaucomatous damage. Their sequential stereo-photographs showed that disc haemorrhages preceded both development and progression of RNFL defects. Location of a defect was accurately predicted by the haemorrhage. In 4 patients the first visual field defects were detected with routine perimetry only 1 to 2 years after the RNFL defects had been observed. Three patients still show normal fields.
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