The most revolutionary advance in the treatment of orbital disease was the development of high-resolution, noninvasive imaging techniques. The need for a diagnostic biopsy is currently a relatively rare event due to the characteristic appearance of most orbital lesions . Today the greatest difficulty occurs more from the relatively uniform availability of both computed tomography (CT) and magnetic resonance (MR) imaging technology (see Chap. 32). If the incorrect imaging modality is selected or if inappropriate images are ordered, then inaccurate assessment of the disease process may result. We suggest the following guidelines for appropriate selection of neuroimaging modalities from the perspective of the orbital surgeon.

The first principle is that MR is superior to CT in resolving soft tissue detail, while CT provides better bone resolution. CT is faster and cheaper than MR but produces ionizing radiation, which is generally of low exposure, depending on the extent of the study requested. The recent development of spiral CT imaging has resulted in further savings in imaging time (approximately 40 s for an orbital examination), which routinely eliminates the need for sedation and virtually never requires the general anesthesia or anesthetic monitoring that is occasionally required for MR imaging in the pediatric age group. Spiral CT image acquisition also permits the same volumetric analysis and multiplanar imaging capabilities heretofore available only with magnetic resonance imaging (MRI). This is a low-dose CT protocol now used in children to reduce the overall delivery of radiation during CT studies; nevertheless, one should consider an alternative to CT imaging when possible [1–3].

CT imaging is done in the setting of trauma to rule out retained metallic foreign bodies and to better evaluate for changes to the bony anatomy. We use CT almost exclusively to rule out orbital fractures, as a preoperative assessment for bony orbital decompression and for the assessment of the sinuses and orbits for infection and nasolacrimal obstructions. CT imaging will typically be faster and cheaper to the patient and institution and, in our experience, is more readily available to schedule. MR, on the other hand, is far superior in evaluating any soft tissue lesion within the orbit and is, in fact, necessary when CT can be misleading (see Chaps. 35 and 36). MR has the added advantage of diffusion weighted imaging, which will show that restricted diffusion is lesion suspicious for malignancy [4]. Both CT and MR imaging are covered in great detail in Chap. 32.

Orbital ultrasound imaging was developing at approximately the same time as CT imaging. It is generally more readily available, generates neither a high-field magnetic effect nor ionizing radiation, provides real-time diagnostic information, and is particularly suited to the diagnosis of cystic lesions . Its greatest limitations are the lack of deep orbital imaging (quality images of only the anterior one-half of the orbit are provided by the standard 10-MHz probe), the lack of image resolution relative to CT or MR, and the relative inability to determine anatomical relationships to other orbital structures in a static image for surgical planning. These shortcomings have limited the use of orbital ultrasound in our experience except for the rapid screening of an orbit for the presence of an orbital mass. The 30° test for enlargement of the optic nerve sheath is a useful parameter in detecting optic nerve thickening and sheath expansion. Color Doppler flow ultrasonography is a technique that can add information about vascular lesions and potentially avoid further imaging. A high-flow lesion in an infant with an expanding eyelid mass, for example, would suggest an infantile hemangioma, whereas low or no flow might suggest a veno-lymphatic malformation [5]. We still err on obtaining orbital imaging (usually MR) if there is any suspicion of a growing orbital mass.

Angiographic interventional neuroradiology can be both diagnostic and, in some cases, therapeutic but is now almost never utilized with the advent of MRA and MRV imaging (see Chap. 32).

Predominantly venous lesions can also be outlined with injection techniques and in some cases treated by percutaneous embolization. However, in those cases, the sclerosing agents that are introduced may result in fulminant inflammatory responses. One must be prepared in such cases to operate on an emergency basis if optic neuropathy results from massive postinjection inflammation congestion (see Chap. 35).

Optical coherence tomography is a noninvasive imaging modality that can be used to evaluate the optic nerve and macula. This technology is under intense investigation as a monitoring modality for optic nerve disease as it relates to optic pathway gliomas [6], as well as in patients with suspected raised intracranial pressure due to tumors or craniosynostosis [7].

Many authors have sorted pediatric orbital disorders utilizing a variety of organizational schemes. Pathological series, usually generated at teaching institutions, typically include many examples of rare and unusual orbital tumors, since these are the lesions referred from the outlying community of practitioners due to diagnostic or experienced limitations. Often missing are entities that the comprehensive or pediatric ophthalmologist is most familiar with and most comfortable treating, such as orbital dermoids and orbital cellulitis. Similarly, clinically based series will have a heavy propensity toward these types of orbital processes and will lack a broad expanse and depth of unusual lesions. Additionally, some series may be heavily weighted toward referral of certain lesions to an institution or individual because of personal reputation or interest, thus skewing the series data. Such variability has, no doubt, led to the confusion and debate in the literature about the frequency and incidence of pediatric orbital diseases.

Table 31.1 attempts to rectify and balance these shortcomings by compiling the six largest series of pediatric orbital lesions into one large compendium. These series represent the largest number of patients and should yield a greater dilution of the previously mentioned factors. Even with the obvious limitations mentioned above, it is our hope that this may offer a broader and less biased representation of pediatric orbital tumors. The categories combine both pathological headings and clinical headings in an attempt to include as many entities as close as possible to their author’s original classification. A perusal of this long table yields a wealth of information and comparative data for those who see and treat pediatric orbital conditions. A review of this table may provide a more complete categorization of pediatric orbital disorders for use in both clinical and diagnostic settings. In the succeeding chapters, reference will be made to this table in estimating the occurrence and incidence of specific pediatric orbital disorders.