REPRODUCIBILITY STUDY OF POSTERIOR SUBCAPSULAR OPACITIES ON THE NEI RETROILLUMINATION IMAGE-ANALYSIS SYSTEM

We developed a semi-automated retroillumination image analysis system which combines speed, ease of operation and interactive analysis. The system measures cataract area and integral of cataract density (ID). F or system reproducibility evaluation, 20 eyes with posterior subcapsul ar opacities were captured twice by two photographers. Variability was estimated under a random effects analysis of variance model. Measurem ent errors for area and for ID were each small contributors to total v ariability (the sum of variability between study eyes plus measurement error), being 0.4% and 0.1% respectively. The largest contributor to area measurement error was image analysis variability (97%). For ID me asurement error, the variability in images (44%) and in image analysis (46%) were major contributors. The reproducibility is comparable to p reviously described retroillumination analysis systems. This easy to u se system may therefore be useful in clinical research studies includi ng possible clinical trials of anti-cataract drugs.