VARIATION OF NERVE-FIBER LAYER THICKNESS MEASUREMENTS WITH AGE AND ETHNICITY BY SCANNING LASER POLARIMETRY

Aims - Scanning laser polarimetry is a new technique allowing quantita tive analysis of the retinal nerve fibre layer in vivo. This technique was employed to investigate the variation of the retinal nerve fibre layer thickness in a group of normal subjects of different ages and et hnic groups. Methods - 150 normal volunteers of different ages and eth nic groups were recruited for this study Three consecutive 15 degree p olarimetric maps were acquired for each subjects. Nerve fibre layer th ickness measurements were obtained at 1.5 disc diameters from the opti c nerve. Four 90 degree quadrants were identified. Results - The mean nerve fibre layer thickness varied from a minimum of 55.4 mu m to a ma ximum of 105.3 mu m, with a mean thickness value of 78.2 (SD 10.6) mu m Superior and inferior quadrants showed a comparatively thicker nerve fibre layer than nasal and temporal quadrants. Retinal nerve fibre la yer thickness is inversely correlated with age (p < 0.001). White peop le showed thicker nerve fibre layers than Afro-Caribbeans (p = 0.002). Conclusion - The results indicate a progressive reduction of the nerv e fibre layer thickness with increasing age. This may be due to a prog ressive loss of ganglion axons with age as suggested in postmortem stu dies. A racial difference in nerve fibre layer thickness is present be tween whites and Afro-Caribbeans.