The Effect of Optic Disc Size or Age on Evaluation of Optic Disc Parameters

ABSTRACT

It has been reported that the number of optic nerve fibers decrease with age, and the C/D ratio increases as the optic disc size increases. Consequently, the normal values of the optic disc parameters measured by an optic disc analyser may change according to the optic disc size or age. We attempted to investigate the effect of individual variations in optic disc size or age on interpretation of optic disc parameters. Topographic disc parameters of 104 normal subjects aged 40 to 69 were measured using a confocal scanning laser ophthalmoscope (TopSSTM , Laser Diagnostic Technologies, Inc.). Fourteen parameters were evaluated according to the optic disc size or age. Statistical analysis was done by regression analysis. With an increase in optic disc size, the increase in cup shape, effective area, 1/2 depth area, C/D ratio, neuroretinal rim area, volume above, volume below, and 1/2 depth volume were statistically significant (p0.1). Age did not show any statistically significant influence on optic disc parameters (p>0.1). In conclusion, optic disc size, but not age, should be considered in the interpretation of optic disc parameters.