A glance through older textbooks of ophthalmology reveals a number of orbital disorders almost unknown to the modern ophthalmologist. Duke-Elder, in his seminal System of Ophthalmology,1 describes such conditions as orbital syphilis (syphilitic periostitis, orbital gummas, etc.), orbital tuberculosis (which may return to the West with the emergence of resistant strains of Mycobacteria and the increase in immunosuppression), and echinococcus (hydatid disease) of the orbit (still common in some parts of the world). The most significant change, however, has been in the classification and nomenclature of disorders that have probably always existed but are now better understood. These include the idiopathic inflammatory disorders ("pseudotumors"), lymphoproliferative disorders, and the vascular lesions of the orbit.
Some orbital tumors have increased in incidence over time. One of the commonest tumors of the orbit in current clinical practice is non-Hodgkin's lymphoma (NHL). Although the classification of NHL has changed, making comparison of older reports with current reports difficult, good epidemiological data confirm the clinical impression of many specialists that NHL is increasing in incidence over time, including NHL of the orbit. Margo and Mulla examined the Florida Cancer Registry from 1981 through 1993 and showed a large increase in orbital NHL over this time, with a steady but smaller increase in primary orbital malignancy in general.2 A study from Singapore failed to show any significant change over the period 1968 to 1995,3 but given the widely reported increase in NHL, it is likely the increase noted in Florida is real. In Australia, there was a steady increase in the incidence of NHL (whole body) between 1982 and 1989
among both males and females,4 but between 1993 and 1998 the increase was confined to females, with an increase of 1.8% per year.5 There is no adequate explanation for this observed increase. A study from Denmark, where a national orbital tumor registry was established in 1974, has also shown a steady increase in the incidence of both benign and malignant orbital tumors over the period 1974 to 1997.6 All tissue specimens derived from the orbit were registered during this time, making the increased incidence observed very likely to be a real increase rather than an artifact. Data are limited on changes in incidence of secondary orbital tumors, but one study from Japan has shown a small but steady increase in orbital metastasis from primary tumors in the lung, liver, and adrenal gland since 1980.7 As the incidence of primary tumors changes over time, it is likely the pattern of orbital metastases will change also.
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