software-assisted depth analysis of optic nerve stereoscopic images in telemedicine

Background. Software guided optic nerve assessment can assist in process automation and reduce interobserver disagreement. We tested depth analysis software (DAS) in assessing optic nerve cup-to-disc ratio (VCD) from stereoscopic optic nerve images (SONI) of normal eyes. Methods. In a prospective study, simultaneous SONI from normal subjects were collected during telemedicine screenings using a Kowa 3Wx nonmydriatic simultaneous stereoscopic retinal camera (Tokyo, Japan). VCD was determined from SONI pairs and proprietary pixel DAS (Kowa Inc., Tokyo, Japan) after disc and cup contour line placement. A nonstereoscopic VCD was determined using the right channel of a stereo pair. Mean, standard deviation, t-test, and the intraclass correlation coefficient (ICCC) were calculated. Results. 32 patients had mean age of 40±14 years. Mean VCD on SONI was 0.36±0.09, with DAS 0.38±0.08, and with nonstereoscopic 0.29±0.12. The difference between stereoscopic and DAS assisted was not significant (p=0.45). ICCC showed agreement between stereoscopic and software VCD assessment. Mean VCD difference was significant between nonstereoscopic and stereoscopic (p<0.05) and nonstereoscopic and DAS (p<0.005) recordings. Conclusions. DAS successfully assessed SONI and showed a high degree of correlation to physician-determined stereoscopic VCD.