Stereo digital photography demonstrates excellent reproducibility with stereo slide film for the evaluation of glaucomatous optic disc features

Abstract

 

Purpose

 

To determine the sensitivity, specificity, and reproducibility of stereo digital photography in detecting optic nerve head features of glaucoma

 

Methods

 

192 eyes with glaucomatous, suspicious, or normal optic nerves were imaged to produce stereoscopic digital photographs (Secure Diagnostic Imaging) and stereo slide film images. The primary observation of interest was the vertical cup-to-disc ratio (VCDR); secondary features assessed were disc hemorrhage and notching. Images were graded by each of 4 glaucoma specialists in a random order. The mean from all 4 specialists was used to combine VCDR evaluations into a single grade. VCDR was reviewed for images in which the standard deviation of the mean was >0.2. For disc hemorrhage and notching, the majority opinion was used for the final grade; in cases without a majority, the final grading was determined via consensus discussion. Weighted kappa was calculated to identify the reproducibility of digital imaging using film as the gold standard. A Bland-Altman (BA) plot was used to analyze the agreement between formats for VCDR. Sensitivity, specificity, and area under ROC curve (AUC) were also calculated for disc hemorrhage and notching.

 

Results

 

There were 192 eyes imaged using both formats. The overall mean VCDR for digital and film was 0.588±0.068 vs. 0.593±0.068, respectively. The weighted kappa between film and digital was 0.781 (95% CI 0.740-0.823). The BA plot demonstrated fairly random distribution of points above and below a mean difference of 0, although there was less variability for higher cup-disc ratios, suggesting better agreement for larger VCDR. Sensitivity and specificity of digital imaging to detect notching was 95.2% and 95.2% respectively with an AUC=0.953. For disc hemorrhage, sensitivity and specificity were 77.8% and 98.9% respectively with an AUC=0.883. For disc hemorrhage, weighted kappa was 0.767 (95% CI 0.546-0.988). For notching, weighted kappa was 0.868 (95% CI 0.784-0.952).

 

Conclusions

 

Digital stereoscopic imaging demonstrates excellent reproducibility in comparison to stereo slide film when evaluating 3 important features of glaucoma: VCDR, notching and disc hemorrhage Acknowledgement: Abshir Moalin provided technical assistance

 

 

ROC curves for digital imaging detecting notching (A) and disc hemorrhage (B) compared to film

 

 

BA plot correlation between formats for VCDR

 

Keywords: 550 imaging/image analysis: clinical