Purpose: To evaluate current patient demographics and surgical outcomes from a large series of 733 surgically treated orbital fractures from an ophthalmologist’s perspective. Methods: We reviewed the medical records of 733 patients with orbital fracture, who were treated surgically by one of the authors at Gil Hospital, Gachon University, from May 2000 until September 2007. Data regarding patient demographics, signs and symptoms at presentation, cause of injury, nature of fracture, associated ocular and nonocular injury, surgical outcome and complications were collected. Results: Male patients outnumbered female patients, and blowout fracture occurred most frequently between the ages of 20 and 29 years (mean age 30.7 years). Violent assault was the leading cause of the fractures, followed by fall/slip and traffic accidents. Common signs and symptoms were periorbital ecchymosis, ocular motility restriction, diplopia and enophthalmos. In the pediatric group, diplopia and ocular motility restriction were the most common. Subconjunctival hemorrhage, hyphema and commotio retinae were the most commonly associated ocular injuries. As for the location of fractures, medial wall fractures were the most common, followed by fractures of the inferior wall, and both medial and inferior walls, in order. The most common type of fracture was the ‘comminuted’ one. In the pediatric group, the percentage of trapdoor-type fracture was higher than in the adult group. Forty-four percent of the patients had diplopia preoperatively and 8.7% postoperatively. The average measurement of difference in the enophthalmos (≧2 mm) patient population was improved from 2.62 (±SD 0.9) to 1.73 (±SD 1.3) after surgery. Ocular motility restriction was preoperatively noted in 297 patients (40.5%), and only 18 patients (2.5%) showed restriction after surgery. Conclusion: Young male individuals are at the highest risk for orbital fractures. There are marked differences in the clinical symptomatology and findings between pediatric and adult orbital fractures. Diplopia, enophthalmos and ocular motility restriction improved by repair of fracture.

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This paper proposes a constructive representation scheme for heterogeneous objects (or FGMs). In particular, this scheme focuses on the construction of complicated heterogeneous objects, guaranteeing desired material continuities at all the interfaces. In order to create various types of heterogeneous primitives, we first describe methods for specifying material composition functions such as geometry-independent, geometry-dependent functions, and multiple sets of these functions. Constructive Material Composition (CMC) and corresponding heterogeneous Boolean Operators (e.g., material union, difference, intersection, and partition) are then proposed to illustrate how material continuities are dealt with. Finally, we will describe the model hierarchy and data structure for computer representation. Even though the constructive representation alone is sufficient for modeling heterogeneous objects, the proposed scheme pursues a hybrid representation between decomposition and construction. That is because hybrid representation can avoid unnecessary growth of binary trees.

Introduction Design of heterogeneous objectsRecent developments in the field of structural optimization have lead to techniques in which geometry and material distribution are both optimized simultaneously (Bendsoe and Kikuchi, 1988;Bendsoe et al., 1993;Cherkaev, 1994;Cherakaev and Kohn, 1997). These techniques result in heterogeneous objects in which there is a continuous material variation along with the geometry. Such optimization techniques are automated and output the final (optimal) geometry and material distribution for a given set of loading, domain specification and boundary conditions. However, there are situations which require the designer to create heterogeneous objects. For example, a number of emerging applications in various fields of engineering require materials to satisfy multiple objectives (Markworth and Saunders, 1995;Tanaka et al., 1996;Kwon, 1994;Suh, 1999). Rather than abruptly joining the different materials, each of which satisfies a specific objective, it is advantageous from the standpoint of maximizing structural performance gradually to vary the material composition from one material to the other in a controlled manner (Holt et al., 1993). The designer has the flexibility to tailor the material distribution to achieve a desired set of objectives. This design scenario is elucidated with the following example.The specific example under consideration is a heterogeneous pressure vessel, cross section shown in Figure 1 (Kwon, 1994). The pressure vessel is subjected to a high temperature/pressure on the inside while the outer surface is subjected to ambient conditions. It is desirable to have ceramic on the inner surface of the pressure vessel due to its good high temperature properties while it is also desirable to have metal away from the inner surface owing to its good mechanical properties. Joining the two materials abruptly will lead to high stresses at the interface. The composition of the metal is therefore gradually increased in a controlled manner starting with zero at the inner surface and gradually increasing to unity on the outer

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