Optic disc progression in glaucoma: Comparison of confocal scanning laser tomography to optic disc photographs in a prospective study

Purpose: To compare confocal scanning laser tomography (CSLT) to optic disc photography for detecting progressive glaucomatous disc changes. Methods: Four expert observers first examined a training set of 40 pairs of monoscopic disc photographs to help set a criterion for change. They then classified 44 pairs of monoscopic photographs of patients followed prospectively as having either definitely no change, probably no change, probably change, or definitely change (score, 0, 1, 2, or 3, respectively). Observers were unaware that 10 pairs were photographs of fellow eyes obtained the same day to measure specificity. These patients were imaged with the Heidelberg Retina Tomograph every 6 months. Topographic change analysis (TCA) software with three criteria (yielding specificity of 81%, 94%, or 97%) was used. Comparisons between the TCA results and those of observers were made for a range of liberal to conservative criteria and for individual and combined observer scores. Results: The median follow-up was 9.0 years with 18 CSLT images. Observer specificity varied from 50% to 90% (using score 0) and 60% to 100% (using score 0 or 1). Interobserver κ ranged from 0.22 to 0.38 from the most liberal to conservative criterion and was generally higher than corresponding TCA- observer agreement. For most criteria, observers had either a high hit rate with low specificity or high specificity with a low hit rate compared with the TCA. Similar results were obtained when observer scores were combined to derive a broader range of criteria. Conclusions: The results indicate that the TCA performs at least as well as either the individual or best combination of observer classifications of disc photographs.