Hertel Measurements

An exophthalmometer is used to measure the prominence of the eye; most commonly, the Hertel exophthalmometer is used ( Figure 14.1 ). It measures the anterior projection of the eye, from the lateral orbital rim to the cornea ( Table 14.1 ). When you use the Hertel exophthalmometer, be sure to lightly push the instrument against the lateral orbital rim and make its width or base setting as narrow as is comfortable for the patient. Try to use the same base setting for an individual patient each time you measure the prominence of the eye. Measurements with the Hertel exophthalmometer are not exact, but you should be able to obtain repeatable measurements within 1 to 2 mm. As you are learning to use the Hertel exophthalmometer, compare your readings with those of a more experienced examiner so that you can make sure you are measuring correctly. Because the instrument uses the lateral orbital rim as a reference point, any surgery, disease, or trauma that changes the position of the lateral rim affects the measurements. In cases where the lateral rim is not in normal position, you can use an exophthalmometer designed by Thomas Naugle ( good-lite.com ). This device uses the forehead and cheek as reference points.

Hertel exophthalmometer measures the distance from the lateral canthal angle to the anterior surface of the cornea.

Facial Bone Structure

The normal prominence of the eye in the orbit depends upon the surrounding facial bones, the structure of which varies from individual to individual and among races. The equator of the globe is at the lateral orbital rim in patients with average bone structure. You can appreciate the position of the eye relative to the rim during the physical examination by placing your index finger at the lateral orbital rim and pushing against the eye. The average Hertel measurements range from 18 to 22 mm.

Significant Measurements: Asymmetry and Change over Time

Because the normal position of the eye in the orbit varies from patient to patient, we are more interested in asymmetry in the prominence of the one eye compared with the other or a change in the globe position on one side that has occurred over time. Proptosis implies an anterior displacement of the globe. An orbital mass not centered within the orbit displaces the eye off the axis, as well. Globe ptosis is the term used when the eye is pushed down by a mass (also known as hypoglobus ). As you perform the orbital examination, look for signs of axial and nonaxial globe displacement of the eye to help you locate the mass that is displacing the globe.

Surgical Spaces of the Orbit

The orbit is conceptually and anatomically divided into surgical spaces ( Box 14.1 ).

The intraconal space, sometimes called the central surgical space, contains the optic nerve and orbital fat ( Figure 14.2 ). Many tumors arise within the intraconal space or push their way into this space. The most widely discussed tumors of the orbit, optic nerve glioma and optic nerve meningioma, occur in the intraconal space.

Axial ( A ) and coronal ( B ) views of the surgical spaces of the orbit: intraconal space (central surgical space), extraocular muscles, extraconal space (peripheral surgical space), subperiosteal space, Tenon’s space, extraorbital space (including periocular tissues, brain, nose, sinuses, bone, and surrounding soft tissues).

The extraconal space, sometimes called the peripheral surgical space, contains the lacrimal gland, superior oblique muscle and trochlea, and nerves and vessels in the extraconal orbital fat. The lacrimal gland is a common source of orbital pathologic processes. An enlarged lacrimal gland is often palpable in the upper lid and is readily accessible using an anterior orbitotomy through the upper lid skin crease.

A fibrous membrane, the intermuscular septum, extends between the anterior portion of the extraocular muscles, separating the intraconal and extraconal spaces. The muscles can become involved in neoplastic or inflammatory processes. The most common condition is thyroid orbitopathy (thyroid eye disease). Painful inflammation of the muscles, or myositis, can occur. Primary neoplasms of the muscles are very rare, but metastatic lesions occur more commonly.

The subperiosteal space is a potential space between the orbital bones and the periorbita. A hematoma can collect in this space from an adjacent fracture. A collection of pus, a subperiosteal abscess, often collects medially from an adjacent ethmoid sinus infection.

Tenon’s space lies between the eye and the fibrous capsule. Tenon’s capsule, which surrounds all but the anterior portion of the eye, is the bloodless space in which enucleation and scleral buckle procedures are performed. This space is rarely involved in orbital pathologic processes, the most common lesion being extraocular extension of a choroidal melanoma.

The extraorbital space, or periocular tissue, includes all the structures surrounding the orbit: bone, brain, sinuses, nose, skin, and conjunctiva. A variety of problems originate in these tissues and involve the orbit secondarily. We discuss some of these conditions at the end of this chapter ( Table 14.2 ).

The P ’s of the Orbital History and Physical Examination

In the 1980s, Krohel, Stewart, and Chavis described the familiar mnemonic involving the P ’s of the orbital history and physical examination. Although this system is somewhat contrived, it is a useful way to learn the orbital history and conduct the physical examination, providing a checklist of what to consider. The six P ’s they described are the following:

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  Pain

  
  
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  Progression

  
  
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  Proptosis

  
  
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  Palpation

  
  
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  Pulsation

  
  
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  Periorbital changes

In a few paragraphs, we add a seventh P to the list, the past medical history.

Pain and Progression

Pain and progression are the characteristics of orbital problems that are most helpful in developing the differential diagnosis. Pain is caused by inflammation, infection, acute pressure changes, or bone or nerve involvement. Once you become familiar with the common orbital disorders, you find that the presence or absence of pain is very helpful in developing a differential diagnosis.

Progression is the other P that refines the differential diagnosis easily. As you can imagine, some processes progress quickly, whereas others take months or years to develop. Progression can be classified as follows:

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  Rapid progression: occurring over hours to days

  
  
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  Intermediate progression: occurring over weeks to months

  
  
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  Slow progression: occurring over months to years

History as a Clue to the Pathologic Process

It is impossible to diagnose every cause of proptosis based on pain and progression only, but you may be surprised how easy it is to develop a differential diagnosis of a general pathogenesis. Consider the types of pathologic processes that affect the body as a whole. You probably learned these in your medical school pathology course:

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  Inflammatory

  
  
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  Infectious

  
  
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  Hemorrhagic

  
  
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  Neoplastic

  
  
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  Metastatic

  
  
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  Congenital

Now consider how the symptom of pain fits into the categories. Pain suggests inflammation, infection, hemorrhage, or perhaps a tumor growing into nerves or bone. Neoplasms, in general, do not cause pain until a complication related to the neoplasm arises. You remember from your general surgery days in medical school that the large bowel tumor sits quietly in the abdomen until there is an obstruction that causes secondary inflammation, infection, or hemorrhage. This is true of orbital tumors as well. The majority of orbital neoplasms do not cause pain until late in their course.

A sudden onset with rapid progression over minutes suggests a hemorrhage ( Figure 14.3 ). Acute processes occurring over hours to days suggest inflammation or infection. Slower processes occurring over weeks to months suggest more chronic types of inflammatory processes such as thyroid disease. Chronic conditions with a vague onset and slow progression over months suggest a benign neoplasm or lymphoma. Although this is a generalized discussion of progression, these principles are very helpful in developing a differential diagnosis in cases of proptosis.

Spontaneous orbital hemorrhage. ( A ) Pain and proptosis developed over minutes with no progression after the initial presentation. ( B ) CT scan demonstrates a well-circumscribed mass (based on axial and coronal cuts). Drainage of the hematoma was required because of pain (see Figure 15.16 ). No etiology was determined.

Onset and progression of symptoms and signs are related features. Onset identifies a point in time when the problem started and how it manifested itself initially. Progression describes any change in the symptoms (and the rate of change) occurring over the period of time since the onset. For example, an orbital infection may have an onset 3 days after the start of a respiratory infection. The pain and inflammation are minimal initially but progress rapidly after onset. A contrasting example is the proptosis and globe ptosis resulting from a benign mixed tumor of the lacrimal gland. The progression is so slow, over months or years, that it is difficult for the patient to identify the exact onset of any symptoms. In many chronic conditions, the patient’s perception of the onset and the progression of the disorder may not be accurate. In these cases, the patient’s perception of onset is often when the proptosis was noted, which may not be when the process actually started. In these cases, the use of the so-called family album tomogram scan is useful. The review of these old photos can help to identify the true progression of a disorder.

Past Medical History

Lastly, we should add the past medical history to the list of the original six P ’s. Any previous diagnosis of neoplasm elsewhere in the body must be noted. Past trauma of the face may have caused some facial asymmetry that may accentuate or diminish the appearance of a proptotic eye. Any history of thyroid disease that has already been diagnosed should be noted. This is perhaps the most important information to solicit. Don’t forget to include basic information in the history such as age and sex. Most orbital processes tend to occur at certain ages. The differential diagnoses of childhood and adult orbital disorders don’t have many diseases in common. The most common disorder that has a striking sex difference is thyroid disease, which occurs about six times more often in women than in men.

A typical history might be written like this: “A 65-year-old noted proptosis of the left eye and a mass in the lid 4 months ago. Since that time the proptosis and swelling have progressed slowly. There is no pain. There is no past medical history of trauma or thyroid disease. He was treated for lymphoma in the past. He is currently taking no medications.” Are you getting the idea? Already you are thinking about the possibility of orbital lymphoma and can look for some fullness of the superior fornix, a little globe ptosis, and a palpably enlarged lacrimal gland during the physical examination.

The P ’s of the Physical Examination

We have just reviewed the P ’s of the orbital patient history: pain, progression, and past medical history. You have in mind a differential diagnosis based on this history. The orbital examination can refine this differential diagnosis, and from that point, you can proceed with imaging, any laboratory examinations, a possible orbitotomy, and medical treatment.

The P ’s of the orbital examination are:

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  Proptosis

  
  
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  Palpation

  
  
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  Pulsation

  
  
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  Periocular changes

Proptosis

The most important part of the orbital examination is the evaluation of the proptotic eye. An orbital mass or volume-producing process pushes the eye away. The larger the mass is, the more the displacement of the globe.

In most cases, when we talk about proptosis, we are really talking about an axial displacement of the eye in an anterior direction. When you see axial proptosis, think of thyroid eye disease with enlargement of the extraocular muscles. Other intraconal disorders such as optic nerve tumors or a benign cavernous malformation may occur within that muscle cone as well and cause axial anterior displacement of the eye. In some conditions, you see nonaxial displacement of the eye. If you see the eye pushed downward, think of problems arising in the area of the lacrimal gland or, less commonly, defects in the orbital roof due to trauma, encephalocele, or frontal sinus mucocele formation. When you see the eye displaced laterally, there is usually a problem in the ethmoid sinus. The most common situation that displaces the eye laterally is a subperiosteal abscess (an acute process) arising in the ethmoid sinus and extending into the subperiosteal space. Rarely, a sinus carcinoma (a slowly progressive process) or mucocele (a very slowly progressive process) of the ethmoid sinus can cause this type of lateral displacement. You rarely see the eye being displaced upward. A number of rare conditions can cause this ( Figure 14.4 ). Although lymphoid lesions occur most commonly in the superior orbit, lymphoid lesions are so common that they are the most common cause of an inferior orbital mass. Rarely, tumors arising from the maxillary sinus can erode through the orbital floor and push the eye upward. Likewise, it is rare to see the globe pushed medially. If medial globe displacement is present, the eye usually is also being pushed downward by an enlarged lacrimal gland. You can estimate the nonaxial displacement of the eye with a ruler or use an instrument designed for this purpose known as the McCoy Tri-Square (Tri-Square Facial McCoy Padgett 162-PM-3795 stevens.ca ) ( Figure 14.5 ).

Globe displacement. ( A ) Superior displacement of the right eye. ( B ) CT scan shows a well-circumscribed mass, determined to be an unusual mesenchymal tumor after excisional biopsy.

McCoy Tri-Square measuring millimeters of globe ptosis.

There is an exception to the rule that an orbital mass pushes the eye away from the mass. Scirrhous carcinoma of the breast is an infiltrative sclerosing tumor, which may actually cause an enophthalmos of the eye. You have already asked about the past medical history of other carcinomas, so if you heard that the patient has a history of breast carcinoma and you note that the eye is sunken, think of metastatic breast cancer ( Figure 14.6 ).

Enophthalmos secondary to metastatic breast cancer. ( A ) Note slight enophthalmos of the left eye. ( B ) CT scan shows an infiltrative orbital mass.

We have already talked about the use of the Hertel exophthalmometer to measure the prominence of the eye. Remember that there are normal variations among individuals and races. When you use the Hertel exophthalmometer, asymmetry between the left and right sides is more important than the actual measurement. Any asymmetry measuring more than 2 mm is significant. Don’t forget that trauma or congenital variation may be a cause of the asymmetry. Similarly, a change in the displacement of the eye based on the patient’s history or old photographs is an important finding.

Palpation

The next step in the orbital examination is palpation. Start with palpation of the orbital rims and then move toward the eye, palpating the superior and inferior fornices for any anterior masses. If a mass is palpable, you want to note its shape, size, and position. Often, you can tell if the mass has a smooth border separate from adjacent tissues or is infiltrating into adjacent tissues. In some patients, the mass is fixed to bone or a nearby structure such as an extraocular muscle, suggesting an infiltrative tumor. You should try to determine if there is any tenderness in the area of the lesion as well. Infectious or inflammatory disorders often cause the skin to be erythematous and warm to touch.

Pulsation

Pulsations of the orbit are rare but, when present, are diagnostic. A classic finding is pulsatile proptosis. This pulsation of the eye suggests either an arterial vascular malformation in the orbit or the absence of orbital bone that allows the normal pulsations of the brain to push on the eye. The most common cause of pulsatile proptosis is the absence of the sphenoid wing seen in neurofibromatosis. If you think you are seeing a case of pulsating exophthalmos, it can be useful to confirm the globe pulsations using the Hertel exophthalmometer to view the eye from the side. If you feel the radial pulse at the same time it means that the pulsations are synchronized.

Orbital arterial vascular lesions can pulsate. If the flow is high, you may be able to hear a bruit or feel a thrill. These lesions are rare, also. Vascular abnormalities that are primarily venous are more common than arterial lesions. Venous lesions do not pulsate, but they usually show enlargement with the Valsalva maneuver or with the head in a dependent position ( Figure 14.7 ). You are likely familiar with the term thrill associated with fast-moving blood. This is described for some orbital lesions, but I have yet to ever feel an orbital thrill.

Valsalva maneuver causing swelling of the lid in a patient with a large orbital varix. ( A ) Eyelid without Valsalva maneuver. ( B ) Eyelid swelling with Valsalva maneuver. ( C ) Conjunctival varix engorgement with Valsalva maneuver. ( D ) CT scan showing nondiscrete orbital mass. Note phleboliths and enlargement of the superior orbital fissure.

Periocular Changes

The last point to note in the orbital examination is periocular changes. These include a variety of abnormalities in the skin, conjunctiva, eye, or surrounding periocular tissues. Some periocular changes that are most useful for diagnosis are the temporal flare of the lateral portion of the upper lid and lid lag seen on downgaze in patients with thyroid eye disease ( Figure 14.8 ). Other examples of periocular changes include a conjunctival “salmon patch” suggesting orbital lymphoma (see Figure 14.19 ), fullness of the temple suggesting a sphenoid wing meningioma (see Figure 14.25 ), and periocular skin malignancy suggesting intraorbital spread of cutaneous carcinoma.

Periocular changes associated with thyroid orbitopathy. ( A ) Right upper lid retraction and temporal flare of the lateral upper eyelid, suggesting thyroid orbitopathy. ( B ) Lid lag on downgaze in the same patient.

At this point, stop and think about the orbital examination and the way in which you want to proceed:

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  You start by evaluating the change in the position of the eye in terms of axial and nonaxial displacement, suggesting where a mass might be present and pushing the eye away.

  
  
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  Next you palpate the orbital rims and soft tissues to see if any abnormality is present.

  
  
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  Then you check briefly for any pulsations.

  
  
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  Last, you search for other clues in the periocular area that may provide information to develop a differential diagnosis.

Proptosis? Order a CT Scan

Almost all patients with proptosis require orbital imaging. One exception to this may be the patient with findings typical of stable Graves’ disease in whom the diagnosis is so apparent that no imaging is needed to confirm your clinical suspicion. CT scanning is used as the primary imaging technique for evaluation of any patient with proptosis. You should order a magnetic resonance imaging (MRI) scan of the orbit in special cases, primarily those situations in which imaging of the orbital apex and chiasm is required.

You are undoubtedly familiar with the CT scan technique. CT scanning uses ionizing radiation passed through the tissue to form a computer-generated image. Like other radiographs, excellent views of the bony structure are obtained, making the CT scan the method of choice for viewing bony orbital trauma. Remember that fat is radiolucent (black) on a CT scan. The intraconal fat gives a good natural contrast with adjacent soft tissue structures (shades of gray) without any injection of intravenous contrast agents. For these reasons, the CT scan gives excellent views of the orbital bones and the majority of orbital structures. Bone landmarks are helpful in planning orbitotomy for orbital tumors as well.

CT scanning is essential for the evaluation of orbital trauma, and it is readily available. In modern CT scanners, the orbital scanning times have been reduced to less than a minute per patient. You should order and review axial and coronal projections for all patients. Sagittal views are occasionally helpful. All projections are available without repositioning the patient. Your hospital or imaging center should be providing high-resolution orbital scans with cuts of no more than 1 to 2 mm. The cavernous sinuses and paranasal sinuses should be included with orbital scans. You should order intravenous contrast agent for the evaluation of most tumors. Contrast allergies are not uncommon, so make sure you ask about iodine or fish allergies. CT scanning remains significantly less expensive than MRI.

Magnetic Resonance Imaging

The generation of MR images is based on entirely different principles than those used in CT scanning. No ionizing radiation is used. An image is generated based upon the vibration of protons in tissue when a patient is placed in the magnetic field and then subjected to a series of radio wave pulses. The radiologist can vary the radio wave pulses so that different tissues generate signals (this is how the standard T1- and T2-weighted scans, and the many other specialized sequences, are generated). Some general imaging characteristics are helpful in interpreting MRI scans:

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  You can recognize a T1-weighted scan because the vitreous is dark.

  
  
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  You can recognize a T2-weighted scan because the vitreous is white (bright).

  
  
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  Because the density of the signal depends on the density of protons in the tissue, edema (water, i.e., protons) causes a bright signal on the T2-weighted image.

  
  
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  High vascular flow, such as that in the carotid artery, generates no signal (dark), or a flow void, because the protons are moving too quickly to be imaged.

  
  
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  The protons in bone are too tightly bound to generate a signal, so cortical bone is dark on MRI scans. Marrow spaces generate a signal.

The spatial resolution for MRI is less than for CT scanning. The tissue contrast, however, is better with MRI. However, because the fat provides a contrast to most other structures, CT can be used as the main screening technique for orbital disease. MRI plays an important role in the evaluation of specific orbital diseases and is sometimes used in addition to CT scanning. Obviously, this is an oversimplification of MRI, but these principles can guide you in evaluating the scan.

The main indication for MRI is to view the orbitocranial junction. If you suspect an optical nerve tumor, you should request an MRI scan. Because bone is not visualized, the bony artifact from the dense bones of the orbital apex seen on CT scans is not present. The soft tissues of the apex are visualized in detail. Some intraorbital organic foreign bodies are seen better with MRI scans than with CT scans. Vascular tumors or other very heterogeneous tumors are often seen more clearly on an MRI scan than on a CT scan, as well. Lastly, any secondary orbital disease originating from the brain or paranasal sinus can often be visualized best by both CT and MRI together. This allows the best view of bone and soft tissue. In the case of sinus neoplasms extending into the orbit, T2-weighted MRI sequences help to distinguish a sinus opacity caused by mucus retention (bright signal) from that caused by tumor (dark signal).

Most radiology departments have routine imaging sequences that are used under an orbital protocol. In addition, the intravenous contrast material gadolinium can be injected to enhance some pathologic processes. The imaging sequence known as fat suppression is used with gadolinium. With this technique, the normally bright orbital fat appears dark. Without fat suppression, you do not see any enhanced orbital structures against the normally bright fat background.

There are many specific sequences that help with imaging certain disease processes, for example, the FLAIR sequence is especially good for identifying optic neuritis due to demyelinating disease. Developing a working relationship with a radiologist interested in orbital disease can help you with these nuances. Similarly, working with an interventional radiologist can help you understand and deal with vascular flow issues in some of your orbital patients.

In practice, you look at T1 and T2 scans with contrast injection. Use these tips to evaluate an MRI scan:

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  Look at the T1-weighted scan for the best anatomic detail.

  
  
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  T2-weighted scans show water as bright, emphasizing edema or other fluid within a mass.

  
  
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  As you become familiar with specific disease processes, you can learn the individual characteristics of the T1 and T2 sequences for each process or tumor (don’t worry about that now).

  
  
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  Look at the fat suppression sequence (the fat is dark) on gadolinium-enhanced scans. Enhancement implies a richly vascularized tumor or inflammation (such as sarcoid, often not visible without enhancement).

MRI has several practical disadvantages compared with CT scanning. MRI is still more expensive than CT. Imaging takes significantly longer. Bone is poorly viewed. As we said above, the spatial resolution of MRI is less than that of CT, so the detail is not as clear. MRI is not safe for patients who have metallic foreign bodies or aneurysm clips in place. It is difficult, or impossible, to obtain an MRI scan for any patient who requires a ventilator, pacemaker, or cardiac monitor. MRI is often used as the primary imaging technique for children, especially if repeated scanning over the years is likely. Because there is no associated ionizing radiation, there is no risk of radiation-induced tumors developing at a later time.

Special Imaging Studies

Special imaging studies are available or can be arranged in consultation with your radiology colleagues.

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  CT

  
  
  
  
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    Three-dimensional CT

    
    
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    Imaging for stereotactic navigation

    
    
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    Angiography (CTA)

    
    
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    Valsalva maneuver

  
  
  
  
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  MR

  
  
  
  
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    MR angiography (MRA)

  
  
  
  
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  Angiography

  
  
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  Echography

CT studies for stereotactic navigation are commonly obtained by our ear, nose, and throat (ENT) and neurosurgical colleagues, especially when performing endoscopic operations. You are probably familiar with these studies, but if not, you should see the technique in action. By linking the preoperative high-resolution images with cameras in the operating room that sense the position of your instruments, you can have real-time localization of your position in the patient. This technique is especially useful where the normal anatomy is quite variable (paranasal sinuses) and for reoperations where normal landmarks have been altered. It can be helpful for you when you are operating in less familiar areas. For example, I used this when I was less experienced in skull base procedures. I don’t use navigation routinely, but some surgeons find it helpful for orbital procedures such as orbital decompression. Your hospital operating room probably has a navigation system. The company representative is happy to come to the operating room with you on your first few cases to help set up the equipment. It is worth becoming familiar with the tool, if nothing else as a learning tool.

CT scanning before and during the Valsalva maneuver is helpful for detecting the venous flood seen in orbital varices. Three-dimensional CT scans produce amazing pictures ( Figure 14.9 ). These images are most useful for craniofacial anomalies and extensive facial trauma. Three-dimensional scans are valuable for planning a reconstructive operation and are also useful for teaching residents and patients. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) allow for easy viewing of the blood supply of a tumor. For a number of reasons, MRA is usually the first choice for our purposes. Arteriography remains the gold standard for vascular imaging. At the same time, therapeutic selective occlusion of feeding vessels can cure or decrease vascular flow, decreasing or eliminating the problem or, in some cases, making operation safer. Similarly, direct venous puncture and occlusion can be helpful in selected cases of varix or other mixed venous malformations. If your practice includes these patients, you need a strong working relationship with a neurointerventional radiologist. Echography has been used in the imaging of ocular and orbital diseases for many years. In the hands of experienced practitioners, useful information can be obtained. In most centers, CT and MRI have replaced echography in the study of orbital disease.

Orbital teratoma. ( A ) Extremely rare and large congenital orbital mass in premature infant. ( B ) Three-dimensional CT reconstruction demonstrates soft tissue mass and large bony orbit. ( C ) Axial CT scan of head, soft tissue window, shows a large heterogeneous mass in the orbit without extension into the brain. Eye appears to be flattened at the most anterior portion of the mass. ( D ) Sagittal T1 MRI of the head, gadolinium enhanced, shows heterogeneity prompting vascular studies. ( E ) MR angiogram (MRA) demonstrates prominent vascular flow from the internal carotid artery branches. ( F ) Carotid angiography confirmed carotid artery flow. ( G ) Carotid angiography after occlusion of feeding arterial supply. ( H ) Successful tumor excision (orbital exenteration) with minimal blood loss.

The information that is available with current imaging techniques and the expertise of our radiology colleagues is incredible. This information can be extremely valuable for diagnosis and surgical planning. A good example is Figure 14.9 , which focused our attention on the blood supply of a large congenital mass in a newborn. Vascular studies and embolization made the tumor removal safe for this premature baby weighing only 3 pounds.

Goals of Imaging

As we have already discussed, many patients with proptosis undergo imaging studies. Orbital imaging serves two purposes:

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  Diagnostic information (I want to know what the mass is)

  
  
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  Information used to plan orbitotomy (I want to know the best surgical approach to taking a biopsy of the mass)

Most times, a quick look at the scan provides an idea of what is causing the proptosis. You are likely to see one of two situations:

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  Enlarged orbital structure

  
  
  
  
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    Extraocular muscle(s)

    
    
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    Optic nerve

    
    
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    Lacrimal gland

    
    
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    Eyeball (pseudoproptosis)

  
  
  
  
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  Orbital mass not arising from a specific structure

  
  
  
  
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    Well-circumscribed mass

    
    
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    Infiltrative mass

  
  

In a few situations, you may be able to make the diagnosis based on the scan alone. For example, bilateral enlargement of the extraocular muscles indicates thyroid orbitopathy until proven otherwise. More likely, the imaging suggests a few possible diagnoses. For example, an enlarged optic nerve usually indicates meningioma or glioma.

If a mass appears separate from the surrounding structures, the characteristics of the mass may help you put the lesion in a particular pathogenic category, such as neoplasm or inflammation. Based on the location of the mass in the orbit, you can determine the best surgical approach for biopsy.

Remember, the questions we are trying to answer are What is it? and What is the best surgical approach for biopsy? Some specific characteristics of an orbital mass can help you with the diagnosis and surgical approach:

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  Location

  
  
  
  
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    What is the tissue of origin?

    
    
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    Position of the mass: Which surgical space is involved?

  
  
  
  
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  Imaging clues to the biologic behavior of a mass

  
  
  
  
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    Relationship to adjacent soft tissues

    
    
    
    
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      A “pusher” (benign)

      
      
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      An “eater” (malignant)

    
    
    
    
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    Relationship to adjacent bone

    
    
    
    
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      Fossa formation (benign)

      
      
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      Bone erosion (malignant)

    
    

  
  
  
  
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  Shape of the mass

  
  
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  Size of the mass

  
  
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  Internal characteristics of the mass

  
  
  
  
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    Homogeneous or heterogeneous

  
  
  
  
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  Contrast enhancement

Location of Lesion

Imaging Clues to the Biologic Behavior of the Mass

Relationship to Adjacent Soft Tissue—a Pusher or an Eater?

This is important. Does the mass push the adjacent structures aside or does it infiltrate the adjacent tissues? Infiltrative lesions are usually malignant. Well-circumscribed lesions with smooth borders are usually benign ( Figure 14.10 ). Think of these lesions as pushers or eaters. Pushers are more likely benign. Eaters are more likely malignant. Is the mass pushing against the optic nerve, or is it growing into the optic nerve ( Figure 14.11 ) ? The latter lesion is more likely malignant. The relationship to adjacent structures, or borders, gives you a snapshot-in-time estimate of the biologic behavior of the mass. This concept is simple but extremely important.

Infiltrative mass compared with well-circumscribed mass. ( A ) CT scan of infiltrative lesion shown to be a metastatic breast carcinoma. ( B ) CT scan of a well-circumscribed benign mass, a cavernous malformation. Note that the medial orbital wall is bowed outward but is not eroded.

MRI scan of intraconal mass, medial to the optic nerve, apparently attached to the nerve. Proven by biopsy to be a metastatic cutaneous melanoma. Smooth shape is not characteristic of most metastatic tumors, which are infiltrative in nature.

Relationship to Adjacent Bone Fossa Formation or Bone Erosion

The relationship of a soft tissue mass to the adjacent bone gives similar information about the biologic behavior of the mass. Slow-growing benign masses push the bone or cause fossa formation. Aggressive malignant tumors eat the bone or cause bone erosion. When you evaluate a lacrimal gland mass, the presence of fossa formation is typical of a benign slow-growing mixed tumor of the lacrimal gland ( Figure 14.12 ).

Orbital bone changes. ( A ) Fossa formation secondary to benign mixed tumor of the lacrimal gland. Note how the well-outlined mass pushes the bone away, creating a smooth fossa. ( B ) Bone erosion secondary to adenoid cystic carcinoma of the lacrimal gland. Note how the infiltrative mass creates an irregular change in the contour of the bone.

You learn to use the clinical information you obtain during the history and physical examination to complement the imaging studies. A poorly defined mass with indistinct borders presenting without pain is likely to be a malignant neoplasm. A poorly defined mass with indistinct borders presenting with pain is likely to be idiopathic orbital inflammatory disease, rather than any true neoplasm. Hypesthesia of the temple described by the patient with bone erosion adjacent to the lacrimal gland mass (see Figure 14.12 ) is indicative of the neurotrophic spread typical of the aggressive adenoid cystic carcinoma of the lacrimal gland.

The distinctiveness of the borders helps greatly in determining if the mass can be removed. Infiltrative lesions usually cannot be safely removed (require incisional biopsy). Well-circumscribed masses can often be removed (excisional biopsy).

Internal Characteristics of the Mass

Thyroid Eye Disease

Bilateral Proptosis and Associated Eyelid Findings Are Diagnostic

The proptosis is usually bilateral but can be quite asymmetric (sometimes even appearing to be unilateral disease if you don’t look carefully for associated lid signs). The proptosis is axial. Hertel measurements vary from normal to off the scale, depending on the severity of the disease. Associated periocular signs are important for making the diagnosis. Look for upper and lower lid retraction, lid lag on downgaze, and temporal flare of the eyelid. Temporal flare is the term given to the abnormal contour of the eyelid seen in thyroid disease (see Figures 14.8A and 14.14 ). As you recall, the peak of the normal eyelid is just nasal to the pupil. Typically, the lid in a patient with thyroid disease has no obvious peak. The lid just keeps getting higher toward the lateral canthus. If these associated lid signs are present, they make the diagnosis for you.

Thyroid orbitopathy, in this patient presenting with marked asymmetry. Note the temporal flare in the lesser affected upper eyelid.

Imaging May Not Be Necessary

In some patients, the diagnosis is so obvious that no imaging is necessary. If there is any question, order a CT scan with axial and coronal cuts. It is more accurate to judge the muscle size on cross section as seen on a coronal scan than when viewed on an axial scan ( Figure 14.15 ).

CT scan of enlarged extraocular muscles secondary to thyroid orbitopathy. ( A ) Coronal scan. ( B ) Axial scan.

Treatment Options—Active Versus Chronic Stage

If systemic disease has not been diagnosed, order free thyroxine (T ₄ ) and thyroid-stimulating hormone (TSH) tests. The T ₄ level is likely to be high and the TSH level low, although in 5% to 10% of patients, thyroid eye disease is associated with a euthyroid condition. If the patient is not seeing an internist, you should seek consultation.

Treatment depends on the patient’s symptoms and stage of the disease, and learning to make decisions in this regard is rapid. The severity of the inflammation varies tremendously from patient to patient. Many patients don’t know that they are affected and have only a foreign body sensation or mild lid retraction. At the other extreme is rapidly progressive orbital inflammation manifested by lid swelling, lid retraction, proptosis, diplopia, and, rarely, compressive optic neuropathy causing vision loss (2% of patients) ( Figure 14.16A ).

Stages of thyroid orbitopathy. ( A ) Active stage with prominent inflammation. Note the swelling and erythema of the lids with associated lid retraction. ( B ) Chronic stage where fibrosis has replaced inflammation. Edema is no longer present. This patient underwent bilateral orbital decompressions for compressive optic neuropathy and eye muscle and eyelid surgery.

Before initiating any treatment, you must determine where the patient’s condition falls in the natural history of the disease. Try to determine if your patient is in the active stage or the chronic stage. Typically, patients start with an active stage of showing signs of progressive acute inflammation (swelling or redness of the orbital, lid, and conjunctival tissues). The eyelids look wet, as though you could squeeze edema fluid out of them (see Figure 14.16A ). In patients with less dramatic manifestations you can recognize active inflammation because eyelid swelling and any diplopia are much worse in the morning. This active inflammatory stage can last a year or more. Once you have determined that the patient has active orbitopathy, get an idea of how rapidly the inflammation is progressing, or the tempo of the disease. If the symptoms are progressing rapidly, you need to watch the patient closely. During the active phase, you must monitor the patient’s visual function (e.g., vision, visual acuity, relative afferent pupillary defect, visual fields) to make sure there is no sign of optic nerve compression. If the patient’s symptoms change drastically, you need to repeat these tests. It is rare for a patient to develop any optic neuropathy without a striking change in symptoms or signs.

Thyroid eye disease is the most common orbital disease you see in practice. Research efforts continue in earnest to better understand the pathophysiology and devise treatment plans for thyroid eye disease. The original classification was the NO SPECS classification (Werner, 1969). This considered the severity of soft tissue signs, soft tissue involvement, extraocular muscle signs, corneal involvement, and sight loss. In 1997, Mourits devised a clinical activity scale (CAS) to help differentiate active from chronic disease. In 2006, Dolman and Rootman further refined this scale and named it the VISA Inflammatory Index ( v ision, i nflammation, s trabismus, and a ppearance). The CAS is used primarily in Europe. The VISA is used primarily in North America. It is worth it to take a quick look at the complexity of these scales, but for now just appreciate the variety and degree of inflammatory effects on the visual system and functioning of the patient. A detailed explanation of these systems can be found at dare.uva.nl/document/2/3194 (CAS); Dolman PJ. Grading severity and activity in thyroid eye disease. Ophthalmic Plast Reconstr Surg 2018;34:S34; Barrio-Barrio J, et al. Graves’ ophthalmopathy: VISA versus EUGOGO classification, assessment, and management. J Ophthalmol 2015;249125; Mourits MP, et al. Clinical criteria for the assessment of disease activity in Graves’ ophthalmopathy: a novel approach. Br J Ophthalmol 1989;73:639. Whether you use an established version of a severity scale or not, it is very important to know the stage of thyroid eye disease, active or chronic , that your patient is experiencing!

Most patients require only medical management during the active stage. Follow them for signs of corneal exposure. Treat irritation with lubricating drops and ointment. Elevate the head of the bed using 4-inch blocks to reduce morning swelling or diplopia. Patients require reassurance during this period. They are uncomfortable and fearful of a loss of vision. You are telling them that their vision is fine and that nothing needs to be done, yet they don’t feel that they are making any progress. Perhaps even more significantly, the middle-aged patient (usually a woman) is probably undergoing a change in her facial appearance that may be significant.

The endocrine literature supports the idea that normalization of the systemic thyroid status is important in controlling thyroid eye disease. Most agree that radioactive iodine treatment can exacerbate thyroid eye disease, but this can be attenuated with concomitant steroid treatment. Surgical removal of the thyroid may reduce the antigenic load associated with progressive thyroid eye disease. If you are interested in developing a busy practice related to thyroid eye disease, you want to establish a good clinical relationship with the endocrinologists in your referral region.

Aggressive medical treatment of acute thyroid eye disease remains controversial. Currently, pulsed intravenous methylprednisolone given over a 4- to 6-week period (500 mg intravenously per week) is recommended for moderate to severe cases of congestion and inflammation. This treatment can be repeated for a second 6-week period (250 mg intravenously per week). The antiinflammatory effect of a short-term intravenous steroid is more effective, with fewer side effects, than chronic oral prednisone. Total doses of more than 8 mg of intravenous methylprednisolone have been associated with serious liver toxicity.

Radiation therapy (2000 rads), although unproven, is considered a useful adjunctive treatment for the associated orbital inflammation. Newer medical agents, such as rituximab, show promise, but have not entered mainstream practice (recall that rituximab is the monoclonal antibody that attaches to the CD-20 cell surface marker on B cells; it is a very successful treatment for lymphoma). Compressive optic neuropathy occurs in a small number of patients because of crowding of the orbital apex from the enlarged muscles. Oral prednisone (80 mg/day) can temporize this situation, but it is not a long-term solution. The compression is best treated with orbital decompression (enlarging the orbit by removing two or three of the orbital walls). Extreme edema can be relieved by decompression as well.

Adjuvant oral selenium (200 mg/day) has been suggested to improve the inflammation. Selenium, a trace element, is required for enzyme function of the thyroid gland. No side effects are seen, so it seems reasonable to recommend, although major improvements are not seen. One hopes that organized clinical trials will help find a safe way to control the disease. Currently, a multicenter trial using teprotumumab, an IGF-1R binding agent, is underway and shows promise.

After a period of several months up to 2 years, the active disease subsides to enter a chronic stage. During this period, there is no progression of symptoms, and the signs of acute orbital inflammation subside (the dry, or chronic, phase). The morning eyelid swelling and changes in diplopia are gone. Signs of acute inflammation are no longer present. Any remaining proptosis, lid swelling, diplopia, or lid retraction is not likely to change.

When you have confirmed that there has been no change over 3 to 6 months, your patient may want to consider procedures to improve the remaining proptosis, lid changes, and strabismus. A standard order of procedures should be considered because one operation may affect the following procedure. First, consider decompression to allow the eyes to return to normal position in the orbit. A small percentage of patients (<25%) who undergo medial and lateral wall decompression to relieve some of the proptosis develop strabismus, or the preoperative strabismus pattern changes so that decompression should precede any planned strabismus surgery. If no decompression is planned, consider any ocular alignment issues next. Strabismus surgery, usually a recession of restricted muscles, can improve the field of single vision. Inferior rectus muscle recession can improve a chin-up head position. At the same time, upper eyelid retraction may decrease with this procedure because the pull of the superior rectus muscle (and, consequently, the levator muscle) against a tight inferior rectus muscle is diminished. Inferior rectus muscle recession, however, may cause or exacerbate lower lid retraction because the lower eyelid retractors tend to get recessed as well. For these reasons, strabismus surgery should precede lid surgery. Lower lid retractor extirpation without a spacer elevates the lower lid 1 to 2 mm. You can use hard palate mucosa to push the lower lid up 3 mm or more. Ear cartilage can be used as a spacer to push the lid margin higher and obtain 3 to 10 mm of elevation. Upper eyelid recession is the most common procedure performed on patients with thyroid orbitopathy. Lowering the upper lid improves comfort, reduces corneal exposure, and improves the appearance of the retracted lid.

Undoubtedly, you will see many patients with thyroid eye disease and will provide them a tremendous service by monitoring for signs of optic neuropathy and managing exposure symptoms. Your reassurance is especially helpful. Any operation that you perform on a patient with “burned out” or chronic thyroid disease is technically difficult. Nagging bleeding caused by tissue fibrosis is common. The final result tends to be more unpredictable than similar procedures in patients without thyroid disease. Save these operations until you can perform the easier orbit, lid, and strabismus procedures with confidence. Because thyroid eye disease is the most common orbital disease, I outline the basic treatment in Box 14.2 .

Box 14.2

Thyroid Eye Disease Treatment Principles

What is the disease activity? This determines how often you see the patient.

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  Active: early and progressive?

  
  
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  Stable: chronic and not progressive

Education: Take time to explain the process, priorities. and long-term goals.

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  Share your concern and frustration that there is no magic bullet for improvement.

  
  
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  The disease evolves over 1 to 2 years, and progress is slow.

  
  
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  Most patients have mild disease and recover well.

  
  
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  A few patients require one or more operations.

Priorities for treatment: active progressive disease

• ■
  

  Education: Take time to explain the process, priorities, and long-term goals (share your concern and frustration that there is no magic bullet for improvement; disease evolves over 1 to 2 years and progress is slow; most patients have mild disease and recover well; a few patients require one or more operations)

  
  
• ■
  

  Systemic health: Is the thyroid disease well controlled?

  
  
• ■
  

  Eye health: Identify and treat any optic neuropathy (steroid infusion or orbital decompression).

  
  
• ■
  

  Comfort (lubrication, elevate head of bed; patch or prisms for diplopia)

  
  
• ■
  

  Appearance ( very important ; thyroid eye disease is a lifetime disease; can drastically change the appearance and self-image (empathy and reassurance are important); share your concern and frustration; there is no magic bullet for quick improvement

  
  
• ■
  

  Priorities for treatment: chronic stable disease

  
  
  
  
  • ■
    

    Proptosis: orbital decompression, bone or fat (or combination)

    
    
  • ■
    

    Diplopia: muscle surgery, sometimes prism

    
    
  • ■
    

    Exposure: continued lubrication, orbital decompression, eyelid retraction surgery

    
    
  • ■
    

    Appearance: all of the above! Don’t underestimate the importance of self-image.

  
  

Idiopathic Orbital Inflammatory Disease: Orbital Pseudotumor

Acute Onset of Pain

When you see a patient with an acute onset of pain, think of idiopathic orbital inflammatory disease. You might consider the presentation of inflammation secondary to pseudotumor to be the opposite of the inflammation seen in thyroid eye disease, where the onset is gradual and pain is absent. Idiopathic orbital inflammatory disease is just what the name says. For unknown reasons, any of the orbital tissues may become infiltrated with inflammatory cells (lacrimal gland, dacryoadenitis; muscle, myositis; or a generalized orbital involvement). Both young and old people are affected.

The typical presentation is an acute onset of pain with rapid progression occurring over hours to a day or, at most, 2 days (recall that the inflammation with thyroid eye disease has no real pain and has a vague onset with slow progression). The past medical history is only helpful for children in whom a viral syndrome may precede the onset. When you hear a history of upper respiratory infection preceding painful proptosis, you should be thinking inflammation or infection. Patients with bacterial orbital cellulitis have pain, but the patient is usually sick (e.g., febrile, weak). The onset of orbital cellulitis usually takes place over a few days, and the pain is usually less than with pseudotumor. Another cause of an acute onset of pain is an acute hemorrhage, but the onset is usually more sudden, with progression occurring over a few minutes rather than hours.

Proptosis is usually present with idiopathic orbital inflammatory disease, but periocular signs of acute inflammation predominate in the physical examination. Lid swelling, chemosis, and limited motility are common. The name pseudotumor comes from the clinical appearance of proptosis without the presence of a true mass. Many surgeons have suggested that the term pseudotumor be eliminated, but it persists in common parlance. With palpation, you may feel that the tissues are tense and warm, but no distinct mass is present ( Figure 14.17 ). The inflamed areas are tender to the touch. There are no pulsations.

Idiopathic orbital inflammatory disease: pseudotumor. ( A ) Patient with rapid onset of pain resulting from idiopathic orbital inflammatory disease. Note the inflamed periocular tissues. ( B ) CT scan shows a diffuse mass in the area of the lacrimal gland. The patient responded to oral prednisone treatment within 24 hours. ( A courtesy of American Academy of Ophthalmology.)

IgG4-Related Sclerosing Disease

A complete overview must include the entity IgG4-related sclerosing disease occurring in the orbit. For starters, no one is sure that this disease actually exists, but there is a lot of discussion about it. You may see a patient with enlarged eye muscles or a lacrimal gland and surrounding tissues that look a bit like orbital inflammatory disease but do not have the characteristic pain associated. The biopsy results show an infiltration of lymphocytes and plasma cells with an associated increase in sclerosis of the tissues under light microscopy. Immunologic studies show significantly increased numbers of cells producing immunoglobulin G4 (IgG4). No one really knows what these findings mean. IgG4 is an uncommon subclass of immunoglobulin. IgG4 is unusual in that it cannot stimulate the classical complement pathway of inflammation, so the symptoms and signs of an IgG4 disorder may not be typical of other inflammatory diseases. There are other IgG4-related disorders recognized in the pancreas, biliary tract, and retroperitoneum, among other areas.

Time will tell what these findings mean. At this point, if you see an unusual case of inflammation that doesn’t fit the presentation of acute pain and a pathologic examination shows significant sclerosis, ask your pathologist to do IgG4 immunostains. If the IgG4/IgG ratio is greater than 40% (normally 3% to 6%), you may be dealing with this “new” disorder. Treatment with rituximab has been shown to be effective. I am guessing you will want to get some help with taking care of this patient.

No doubt time will offer us more information about this disorder. It may be like so many other disease conditions (e.g., lymphoid disease and idiopathic orbital inflammation): As we progress in understanding the finer details of a disease, large categories of less-understood disorders are refined, smaller categories are generated, and the eponym “idiopathic” is discarded. For example, in 1966 the Rappaport classification system, based on light microscopy, recognized 3 types of non-Hodgkin lymphoma, but in 2008 the World Health Organization classification system recognized at least 80 types, thanks to newer immunologic and molecular studies!

Cavernous Malformation (Cavernous Hemangioma)

CT Scan: Well-Circumscribed Intraconal Mass

As with most patients with proptosis, a CT scan should be ordered. A cavernous malformation appears as a well-circumscribed oval or round mass, usually in the muscle cone (see Figure 14.10B and Figure 14.18A,B ). If you are sure that the presentation and imaging are typical, observation is an option.

Cavernous malformation. ( A and B ) A large intraconal cavernous malformation (hemangioma) causing vision loss. This is the typical appearance. Despite the large size, vision loss is not present. You can see that the mass is displacing the left optic nerve inferiorly. This mass can be observed or electively removed to confirm the diagnosis, improve proptosis, or relieve corneal exposure. ( C and D ) Vision loss due to a cavernous malformation (hemangioma) deep in the orbital apex. Proptosis, a relative afferent pupillary defect, and 20/70 vision due to optic nerve compression. Axial CT scan showing a large cavernous malformation in the orbital apex extending out into the superior orbital fissure. Deep apical lesions tend to compress the optic nerve more than anterior lesions where the optic nerve can freely move away from the mass. This was removed using a small trans-eyelid craniotomy (see Chapter 15 ). The majority of cavernous malformations are more anterior in the muscle cone and frequently do not require removal.

Most of the well-circumscribed masses that I see now are discovered incidentally on an MRI scan of the head as a part of a workup for headache. Although some would say that observation is the conservative management option, it may be riskier to observe a mass than to remove it. If you choose to observe the lesion, make sure that you have a good orbital CT scan rather than an MRI scan of the brain using thick cuts. Obtain another scan at 3 to 4 months or sooner if any visual loss, pain, or change in proptosis occurs. If growth occurs, you should remove the mass. A majority of well-circumscribed lesions discovered incidentally are benign cavernous malformations where no removal is appropriate. But don’t expect all of these masses to be benign. I have personally observed an optic nerve meningioma and an orbital metastasis, both well-circumscribed intraconal masses when viewed on an MRI scan of the head, which were thought to be cavernous malformations until growth occurred and biopsy proved otherwise.

Lymphoid Lesions of the Orbit

Painless, Slow Progression of a Unilateral (or Bilateral) Anterior Mass

Lymphoid lesions of the orbit are among the most common orbital tumors that you see in adults. A gradual onset with slow progression of a painless orbital mass, often anterior and superior, is typical of the orbital lymphoid lesions. About 25% of patients have a previous diagnosis of lymphoma. Lymphoid lesions occur most commonly in elderly patients but may occur in middle-aged patients.

The proptosis can be axial or nonaxial, depending on the position of the mass. In some patients, the disease may present bilaterally (an exception to the rule that orbital tumors are usually unilateral). Most commonly, you see lymphoid tumors arising in the superior orbital quadrants. The extraconal space, especially with involvement of the lacrimal gland, is a common site. Although the inferior orbit is not the most common site, lymphoid lesions are the most common condition presenting there (not many conditions present inferiorly). You may be able to palpate an orbital mass anteriorly. The lesions are smooth, usually mobile, and firm to the touch. There is no tenderness associated with palpation. The characteristic salmon patch on the conjunctiva is diagnostic for lymphoma ( Figure 14.19 ).

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