Imaging for pathologic myopia

Recent advances in ocular imaging technology, in particular wide-field optical coherence tomography (OCT), have greatly facilitated the clarification of pathologies and pathogenesis of pathological myopia and related complications, according to Kyoko Ohno-Matsui, MD, PhD. Addressing delegates attending the 19th EURETINA Congress in Paris, Dr Ohno-Matsui, professor in the Department of Ophthalmology and Visual Science and chief of the High Myopia Clinic at Tokyo Medical and Dental University, Japan, focused on the utility of wide-field OCT in imaging posterior staphyloma. “Posterior staphyloma is the posterior outpouching of the wall of the eye and is a hallmark lesion of pathologic myopia. However, despite its importance we really had no reliable standardised methods to detect and analyse staphyloma,” she said. Although 3D magnetic resonance imaging (MRI) has been successfully employed in detecting staphyloma, it is costly to use and is not viable as a screening device in routine clinical practice, said Dr Ohno-Matsui. Similarly, the limited scan length and depth of traditional OCT is unable to visualise the entire extent of wide and deep staphyloma. Using a prototype ultra wide-field swept-source OCT (Canon Corp.), Dr Ohno-Matsui said it was possible to scan up to 24mm horizontally and to a depth of 5mm and to generate detailed three-dimensional reconstructions of posterior staphylomas. She noted that the morphologic hallmarks of the posterior staphylomas on OCT include a smoothly configured border with a gradual thinning of the choroid from the periphery toward the edge of the staphyloma and a gradual rethickening of the choroid in direction toward the posterior pole. There is also a gradual thickening and inward protrusion of the sclera at the staphyloma edge. “Wide-field OCT can provide tomographic images of posterior staphylomas in a resolution and size unachievable so far, and may ultimately come to replace 3D-MRI in assessing posterior staphylomas. The spatial relationship between eye deformity, vitreous changes and retinal complications is clearly visible in a three-dimensional way,” she said. Dr Ohno-Matsui showed several examples of highly-detailed staphyloma images obtained with wide-field OCT and demonstrated how the 3D OCT movie enables clear visualisation of the entire shape of the staphyloma. “Unlike with 3D MRI, the spatial relationship between staphyloma and the optic disc and macular retinal vessels is clearly visible with wide-field OCT. This greatly facilitates the understanding of how visually important tissues are damaged by eye deformity due to staphyloma,” she said. Widefield OCT is also useful in visualising and understanding other features commonly found in pathologic high myopia such as retinoschisis, abnormal vitreous layers and atypical posterior vitreous detachment, she said. Kyoko Ohno-Matsui: k.ohno.oph@tmd.ac.jp

Tags: imaging, widefield oct