Retinal Physician

JAN-FEB 2017

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38 R E T I N A L P H Y S I C I A N | J A N U A R Y / F E B R U A R Y 2 0 1 7 Posterior Staphyloma in Pathologic Myopia KYOKO OHNO-MATSUI, MD, PHD P osterior staphyloma, the posterior outpouching of the wall of the eye, is an important component of the diagnosis of pathologic myopia; indeed, it is one of the hallmarks of pathologic myopia. 1-5 With the exception of inferior staphyloma related to tilted disc syndrome, it does not occur in pathologies other than pathologic myopia. us, the presence of staphyloma is specific to pathologic myopia and critically important in dif- ferentiating simple school myopia with good best corrected visual acuity (BCVA) and pathologic myopia that could cause the loss of BCVA. is review shows the current definition, clinical char- acteristics, and a classification based on the recent imaging technologies for posterior staphyloma. Future approaches to treat and prevent staphyloma are also mentioned. DEFINITION OF POSTERIOR STAPHYLOMA ere is some confusion about the definition of posterior staphyloma. e steepened curve of the posterior sclera, caused by an axial elongation, has tended to be confused with a staphyloma in some optical coherence tomography (OCT) studies. In Pathologic Myopia 2 (Figure 1), Spaide clearly defines posterior staphyloma as "an outpouching of the wall of the eye that has a radius of curvature that is less than the sur- rounding curvature of the wall of the eye." e author added nasally distorted eye shape to the definition based on results of three-dimensional magnetic resonance imaging (3D MRI) study. 4 Staphyloma also can occur in eyes that do not have long axial length. Curtin 1 showed that in eyes with type I staphy- loma, the most common type, the axial length ranged from 25 mm to 38 mm. He therefore emphasized that axial length was not a reliable marker to define pathologic myopia, and he concluded that pathologic myopia should be defined by the presence of staphyloma. Wang et al 6 recently reported clinical features of staphylomas in eyes whose axial lengths measured fewer than 26.5 mm. us, outpouching of the wall of eyes without long axial length is also considered to be posterior staphyloma (Figure 1D). METHODS TO DETECT POSTERIOR STAPHYLOMA Problems with Conventional Methods e most common methods to detect staphylomas have been color fundus photography and ultrasonography. Especially, conventional 50° fundus photos are widely used in many epidemiological studies. However, most staphylomas involve wide areas of the fundus (especially the upper and temporal direction), and thus the entire extent of the staphyloma does not fit within the 50° field of view of conventional fundus photographs (Figure 2). Similarly, in most cases, staphy- lomas are too wide to fit into the length of an OCT scan (Figure 3). 3D MRI To overcome these problems, Moriyama and the author 4,7,8 established a new technique called 3D MRI to analyze the Figure 1. Definition of a posterior staphyloma (modified from reference #2). A. Normal eye shape. B. Axial length elongation occurring in the equatorial region that does not induce any alteration in the curvature of the posterior part of the eye. is eye would have axial myopia, but no staphyloma. C. A second curvature develops in the posterior portion of the eye, and this second curvature has a shorter radius (r2) of curvature than the surrounding eye wall (r1). is secondary curve is due to a staphyloma. D. Posterior staphyloma can also develop in eyes without high axial myopia. e deformity of posterior segment characterized by staphyloma; it therefore, can independently occur from an elongation of the equatorial region. Kyoko Ohno-Matsui, MD, PhD, is a professor in the Department of Oph- thalmology and Visual Science and chief of the High Myopia Clinic, both at Tokyo Medical and Dental University. She reports no financial inter- est in any products mentioned in this article. Dr. Ohno-Matsui can be reached via e-mail at k.ohno.oph@tmd.ac.jp.

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