Staphyloma II: Analyses of Morphological Features of Posterior Staphyloma in Pathologic Myopia Analyzed by a Combination
Posterior staphyloma is an integral condition for pathologic myopia. Curtin classified a posterior staphyloma into ten distinct types, and his classification has been widely used to date. Types I through V are primary staphyloma, and types VI through X ar
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13
Kyoko Ohno-Matsui and Muka Moriyama
13.1
Introduction
In 1977, Curtin [1] classified a posterior staphyloma in eyes with pathologic myopia into ten different types. Types I to V are considered a primary staphyloma, and types VI to X are considered a combined staphyloma (see Staphyloma (I) of Chap. 13 for details). To date, this has been the most frequently used classification for staphyloma. Although this is a very useful classification, some improvements can be made. For example, this classification is based solely on ophthalmoscopic examination, and thus, the classification is rather subjective. Also, there are some types which are uncommon especially in the types of combined staphyloma, like type VI, VIII, or X. Finally, it is difficult to remember and routinely use as many as ten different types; thus, a simpler classification is needed. Most of the staphyloma involves a wide area of the fundus; thus, the entire extent of staphyloma often does not fit within the 50° angle of the conventional fundus photos. Optical coherence tomography (OCT) is a useful tool for analyzing the curvature of the eye; however, the maximum scan length of commercially available OCT is not long enough to cover the entire extent of a wide staphyloma. A relatively new technology, the Optos Optomap Panoramic 200A imaging system (Optos, PLC, Dunfermline, Scotland), combines both an ellipsoid mirror and a scanning laser ophthalmoscope (SLO) to obtain noncontact, nonmydriatic, panoramic fundus images. Optos allows for ultrawide-field fundus imaging of nearly the entire retina (up
K. Ohno-Matsui, MD, PhD (*) • M. Moriyama, MD, PhD Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan e-mail: [email protected]
to 200°), during which the peripheral retina is captured simultaneously without the need for patient refixation. Recently, we used three-dimensional magnetic resonance imaging (3D MRI) to analyze the entire shape of the eye [2, 3]. 3D MRI is considered suitable to analyze the eye shape of wide region like posterior staphyloma in a 3D way from any angle. There have been no studies analyzing how the entire eye looks like according to each type of staphyloma. It is also unclear whether the staphyloma affects the posterior eye segment only or it affects much broader range of the eye. Thus, in this chapter, we propose a simple classification and examined the features of Optos images and 3D MRI images of the same individual. We also analyzed how the staphyloma seen in Optos images corresponds to the abnormal shape of the entire globe in 3D MRI images.
13.2
Principles for Classification of Staphyloma
1. Only the contour of the outermost border of posterior staphyloma was analyzed: • Combined staphylomas in Curtin’s classification [1] are characterized by the presence of irregularities within the staphylomatous area. However, recent enhanced depth imaging OCT (EDI-OCT) [4] and swept-source OCT have shown that there are more numerous and more complicat
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