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Abstract #5601 Published in IGR 2-1
Scanning laser polarimetry of the normal human retinal nerve fiber layer: a quantitative analysis
Morgan JE; Waldock AAmerican Journal of Ophthalmology 2000; 129:76-82
PURPOSE: To provide a quantitative comparison of retardation values obtained with the scanning laser polarimeter (Nerve Fiber Layer Analyzer; Laser Dignostic Technologies, San Diego, CA) in normal subjects, with the known histological properties of the human retinal nerve fiber layer. METHODS: Scanning laser polarimetry was performed on 48 normal subjects. The retardation values obtained from each eye were processed to remove reflections from the optic nerve head vasculature and to derive peripapillary polar retardation profiles. The location of the maximum and minimum retardation values superior and inferior to the disc was determined. Retardation values were also determined along lines running radially from the center of the optic disc to through the points of maximal retardation. RESULTS: Retardation values were greater in the superior and inferior quadrants of the peripapillary retinal nerve fiber layer compared with the nasal and temporal quadrants. Superiorly, peak retardation values were nasal to the vertical meridian by 22.9° (SD, 17.5) in right eyes and by 15.7° (SD, 17.7) in left eyes. Inferiorly, the peak showed a closer correspondence with the vertical meridian, lying nasal to this by 0.8° (SD, 14.9) in right eyes and temporal to this by 2.8° (SD, 15.4) in left eyes. Radial analysis showed that the peak retardation occurred approximately (0.5 to 0.7 disc diameters from the optic disc margin) at the superior and inferior aspect of the disc. The degree of modulation of retardation around the optic disc was less than would be expected from the variation in peripapillary nerve fiber layer thickness seen histologically. CONCLUSIONS: The location of the peak retardation values shows reasonable agreement with the angular location of the peak values of nerve fiber layer thickness published for humans. By contrast, the modulation of retardation values around the disc and the change with eccentricity from the optic disc center differ from the anatomic data. The Nerve Fiber Layer Analyzer appears to measure a correlate of nerve fiber layer thickness, but it is important that any discrepancies between the retardation and anatomical data are recognized in the clinical interpretation of polarimetric data.
Dr. J.E. Morgan, Department of Ophthalmology, University of Wales College of Medicine, Cardiff, UK morganje3@cardiff.ac.uk
Classification:
2.13 Retina and retinal nerve fibre layer (Part of: 2 Anatomical structures in glaucoma)
6.9.1 Laser scanning (Part of: 6 Clinical examination methods > 6.9 Computerized image analysis)