Relation of optic disc topography and age to thickness of retinal nerve fibre layer as measured using scanning laser polarimetry, in normal subjects.

AIMS To evaluate the relation of the optic nerve head topographic measurements and age with the thickness of the retinal nerve fibre layer (RNFL) in normal Caucasoid subjects by means of scanning laser polarimetry and tomography. METHODS Topographic optic disc measurements and RNFL thickness values of 38 normal Caucasoid subjects of both sexes aged 20 to 78 were measured using a confocal scanning laser ophthalmoscope and a confocal scanning laser polarimeter. One eye was randomly selected for statistical analysis. The effects of optic disc size, age, and optic disc head topographic measurements of total and regional RNFL thickness were evaluated. RESULTS Age showed a significant correlation with the integral of the total RNFL thickness (R=-0.341, p<0.05). The optic disc size showed a significant correlation with the integral of the total, superior, and inferior quadrant RNFL thickness (R=0.425, p<0.01), (R=0.361, p<0.05), (R=0.468, p<0.05). Neuroretinal rim area (NRA) had a correlation with the superior and inferior quadrant RNFL thickness values (R=0.339, p<0.05) (R=0.393, p<0.05). There was no significant correlation between the other optic disc topographic measurements and RNFL thickness values (p>0.05). CONCLUSION The thickness of total as well as superior and inferior quadrant peripapillary RNFL as measured by scanning laser polarimetry increased significantly with an increase in optic disc size. The cross sectional area occupied by superior and inferior polar RNFL increased significantly with an increase in NRA. The total cross sectional area occupied by RNFL decreased significantly with an increase in age. The effects of optic disc size, age, and NRA should be considered when the peripapillary RNFL thickness is evaluated.