The Shortest Radius of Curvature of Bruch's Membrane in Macular Optical Coherence Tomography

ABSTRACT

PURPOSE: To develop software to measure the shortest radius in curvature of Bruch's membrane from optical coherence tomography (OCT), and then to apply it to various types of eyes. METHODS: Macular OCT images consisting of 12 images of 9 mm radial scans were studied. The horizontal to vertical pixel ratios were changed to 11, and Bruch's membrane was marked automatically on each image. Software to measure the radius of Bruch's membrane curvature was developed. The shortest radius on each image was defined as r (mm) and the average r of 12 images was defined as R (mm). The reciprocal of R was multiplied by the constant, 337.5, which was defined as the posterior staphyloma (PS) index. RESULTS: The OCT images of five eyes were analyzed by the software, which could calculate the curvature of Bruch's membrane automatically. The PS indices were 12.7, 23.7, and 66.4 in eyes without refractive error (Case I), in the high myopic group without posterior staphyloma (Case II), and in the high myopic group with posterior staphyloma (Case V), respectively. The PS index gradually increased according to aging in a 37-year-old patient (Case IV) with mild staphyloma from 34.6 to 39.5 over 4 years. CONCLUSIONS: PS index is a novel parameter to reflect the level of posterior staphyloma, but further studies are needed to apply it to clinical patients.