Intraobserver and interobserver agreement of computer software-assisted optic nerve head photoplanimetry

To report the reproducibility profile of optic nerve head parameters obtained by computer software-assisted fundus photoplanimetry.

Fundus photographs obtained during a population-based health survey (Sakurae Study) were planimetrically analyzed using newly developed computer software, CDSketch. The parameters assessed 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 intraobserver and interobserver agreement assessments, we calculated the coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) of the mean of three measurements obtained by one observer and a one-time measurement by three observers, respectively.

The intraobserver CVs were between 2.4 % (DM/DD ratio) and 11.0 % (inferior R/D ratio), and the ICCs were between 0.868 (cup V/H ratio) and 0.976 (DM/DD ratio); all intraobserver ICCs had almost perfect agreement (>0.81). The interobserver CVs were between 2.6 % (disc V/H ratio) and 18.0 % (inferior R/D ratio), and the ICCs were between 0.762 (cup V/H ratio) and 0.930 (DM/DD ratio); the interobserver ICCs were categorized as substantial (0.61-0.80) for the inferior R/D and cup V/H ratios and as almost perfect for the other five parameters.

The consistent profiles of the planimetric parameters suggest the suitability of software-assisted photoplanimetry for assessing optic disc characteristics in glaucoma clinical study and practice.