The orbit, a confined space of 30 cc with four walls (roof, lateral wall, medial wall and floor), is bordered by the brain on one side and sinuses on two of the other, and can be the host to numerous disease processes including tumors, inflammations and infections.
When confronted with a patient having an orbital disease the clinician should not feel perplexed as there are basic clinical patterns that provide a framework for analyzing each case. The clinical assessment sets the stage for further investigations. History taking and physical examination should be directed to answering three questions:
1) Where is the disease located?
2) How has the disease developed (i.e. the temporal sequence of events)?
3) How has the disease affected the orbital structures? (The abnormal process)1
Location of the Disease
Clues to the location of a disease process can be obtained by observing the mechanical displacement of the orbital structures. When a disease process shifts orbital structures, the direction of the shift is a clue to the location of the disease. The effect can be viewed as positive if the disease occupies space and pushes structures away (ex. – a tumor in lacrimal glad fossa shifting the globe down, a medial wall sub-periosteal abscess displacing the globe outward, a tumor behind the globe pushing the globe forward) and negative if it draws structures towards it through cicatrization (metastatic breast cancer), excavation (atrophy of tissue, lytic lesions of bone), or both.
How has the disease developed (temporal sequence)?
The time of onset and rapidity of development are clues to the diagnosis of the disease process as are diurnal variation and an intermittent nature to the process. A catastrophic change occurring over several minutes to hours, suggests either hemorrhage into a pre-existing lesion or fulminant inflammation. A change that is somewhat less rapid (days to weeks) but progressive suggests either an inflammatory process or rapidly developing neoplasm. On the other hand, an insidious change (weeks to months) may be due to low-grade inflammation or neoplasm (either benign or malignant). Diurnal variation with more proptosis, lid edema and diplopia in the morning is a result of accentuation of orbital swelling due to lying prone all night and is often seen in thyroid patients. An intermittent change such as pulsation or alteration with Valsalva maneuver, suggests either a bony defect in the wall of the orbit or a relation between the lesion and the vascular system (ex. orbital varix). In some instances patients have no idea how long a disease process has been there or how long their eyeball has appeared more prominent on one side than the other. In these instances having a look at old photos can be extremely beneficial in determining the duration of the process.
How has the disease affected the orbital structures? (The Abnormal Process)
Abnormal changes occurring within the orbit can be divided into four basic clinical categories. There may be more than one acting in any given process.
Inflammatory signs – inflammation is characterized by redness, swelling, warmth, pain, loss of function, + a mass effect. The degree to which one categorizes the process as either acute or chronic depends upon the rapidity of onset and severity of the signs and symptoms.
Mass effect – consists of displacement with or without signs of involvement of sensory or neuromuscular structures. Displacement points to the location of the disease and may help to characterize the nature of the disease.
Infiltrative change – infiltrative diseases are usually associated with evidence of destruction, entrapment or both. These include effects on ocular movement or neurosensory function (ex. diplopia, muscle restriction or fibrosis, optic neuropathy, pain or paresthesia).
Vascular change – alteration in the character, size and structural integrity of vessels may imply an underlying vascular process. Features implying vascular disease consist of venous dilation, tissue exudation, hemorrhage, infarction, intermittent proptosis or proptosis with exertion.
Examination of the orbital patient
General assessment of the patient should include observing facial contours, looking at the symmetry on each side of the face, eyelids, and orbit as well as the peri-ocular structures (ex. brows). Attention should also be paid to changes in colour and pigmentation of the skin.
Examination of the orbital patient may involve a number of tests and measurements. Not every patient will require each of the tests and measurements to be discussed. A basic eye exam is essential. Physical findings often provide clues to the area of concern and direct testing at characterizing the problem.
A best corrected visual acuity is essential in all basic eye examinations. The bony orbital rim and periorbital structures can be easily palpated as are the preauricular and cervical lymph nodes. The lids and conjunctiva are assessed for position and alteration in structure. The eyelid fissure height and levator function are recorded. Lid retraction, scleral show and lagophthalmos are noted if present. Injection and/or vascular dilation of the conjunctiva should be noted if present. Confrontation visual fields and colour vision assessment are important and can be carried out with little equipment. Pupillary examination should assess size, symmetry, reaction to light and near accommodating reaction as well as an afferent pupil defect. The sensory function of the fifth nerve (V1 and V2) can be assessed both for light touch and pain. Orbital examination should allow an estimate of the degree of horizontal and vertical displacement of the globe as well as any proptosis (measured with an exophthalmometer). Ocular motility can be simply documented by recording directions in the horizontal and vertical planes of movement. Further ocular examination may include an assessment of the cornea, anterior chamber, vitreous, retina and optic nerve head, depending upon the disease process.
Following a thorough history taking and physical examination, it is very helpful to write down a synopsis of the positive features, ex. – sudden onset of proptosis (over weeks), associated with restriction of extraocular movement, lid retraction and pain. This generally allows the formation of an investigative plan (ex. blood testing – TSH, and computerized tomography, etc).
Investigative testing is based on the clinical analysis and aimed at further characterizing and defining the abnormal orbital disease process. Not every patient requires every test.
There are a host of blood tests that may or may not be required depending upon the nature of the problem. If the patient presents with proptosis, lid retraction and double vision, a TSH test would be important. If the patient had proptosis, nose bleeding and kidney disease, an ANCA-test (suspecting Wegener’s granulomatosis) would be important. In an African-American patient with proptosis and enlarged lacrimal glands, one would be suspicious of sarcoid and order a serum ACE, calcium level as well as a chest x-ray and gallium scan. Carcinoembryonic antigen (CEA) levels may be elevated in patients with metastatic tumors of the intestine and other areas.
Orbital imaging with routine x-rays may be of value in detecting sinus opacification or lytic lesions of bone. Bony tumors (ex. osteoma) may also be visible as well expansion of the orbital cavity from destructive processes. Computerized tomography however is the hallmark of orbital investigation. It not only localizes the abnormal disease process but helps characterize it (ex. smooth, lobular, infiltrative, well defined, poorly defined, etc). Properly performed and analyzed, CT scans provide the most useful information for diagnosing orbital disease. For accurate localization in most cases both axial and coronal scans should be performed. Magnetic resonance imaging is also very useful in the investigation of orbital disease and most helpful when apical, optic canal or cavernous sinus lesions are present. It does not replace orbital CT scanning but is complimentary to it.
Orbital ultrasound is another non-invasive test that can be very useful in determining the location, size, shape, tissue characteristics as well as vascular features of the orbital process. Arteriography may be helpful in studying vascular abnormalities such as cartoid-cavernous sinus fistulas and diurnal shunts, as well as certain tumors such as meningiomas to localize feeding vessels.
Tissue biopsy can be extremely helpful in identifying the disease process and often does. Occasionally however, it is not conclusive and the physician has to continue following the patient or look to other body systems for further clues to the diagnosis.
The patient with an orbital disease certainly can be a challenge not only to diagnose but also to manage once the etiology of the disease process is determined. Establishing the historical development of the process (i.e. temporal onset) and analyzing how the process has affected the orbital tissue will help one decide upon the initial investigations which subsequently should allow a provisional diagnosis of the process and appropriate treatment plan.
1. Rootman J. In Diseases of the Orbit: Pathophysiologic Patterns of Orbital Disease, Anatomic Patterns of Orbital Disease, Pathophysiologic Approach to Clinical Analysis of Orbital Disease, Investigation of Orbital Disease and its Effect on Function. J.B. Lippincott Co, Philadelphia, 1988, Chapters 4,5,6,7, pages 51-117.