[Fundus photoplanimetry of the optic nerve head in the Sakurae Study]

To explore the fundus photoplanimetric distribution of the optic nerve head in a population-based health survey conducted in Sakurae area, in Shimane, Japan(the Sakurae Study).

After the exclusion of poor quality images from the 1660 right eye-fundus photos obtained from the Sakurae Study in 1991, 1583 photos were digitized, and then were planimetrically analyzed using a newly developed computer software, CDSketch. The parameters calculated included vertical and horizontal cup-to-disc (C/D) ratios, superior and inferior rim-to-disc (R/D) ratios, disc and cup vertical-to-horizontal (V/H) ratios, and disc-macular distance-to-disc diameter (DM/DD) ratio.

For the vertical and horizontal C/D, superior and inferior R/D, disc and cup V/H, and DM/DD ratios, mean values were calculated to be 0.58, 0.59, 0.20, 0.18, 1.11, 1.09, 2.60, respectively, and median values were calculated to be 0.58, 0.59, 0.19, 0.18, 1.11, 1.09, 2.57, respectively; no parameter showed any remarkably skewed distribution. The vertical C/D ratio was positively correlated with the cup V/H ratio, but was not correlated with the disc V/ H ratio. The vertical and horizontal C/D, and the disc and cup V/H ratios were negatively correlated with the DM/DD ratio.

The distributions of the various optic nerve head parameters and their correlations in the Sakurae Study are reported. Both mean and median values of the vertical C/D ratio were approximately 0.6 in this study population. These values were larger than the previously reported C/D ratios obtained by direct ophthalmoscopic observations and/or by subjective methods.