Chemosis

Chemosis is associated with a variety of usually benign disease processes in the anterior segment, but can also be typical of a group of orbital disorders: orbital inflammatory diseases, such as idiopathic inflammatory pseudotumor, ocular myositis, dysthyroid ophthalmopathy, or any impairment of venous outflow from the orbit (e.g., carotid-cavernous fistula or infiltrating orbital malignancies).

Diagnostic Methods

■ Table 9.3 summarizes the various diagnostic methods used for the study of orbital disease.

A rational plan for treatment also requires additional testing in the form of MRI and/or CT imaging. Ultrasonography is most suited to the study of midorbital structures. Study of anterior orbital structures requires the use of a standoff method, such as immersion of the probe in a water bath that covers the eye. The posterior third of the orbit cannot be imaged by ultrasonography, due to both limited tissue penetration by the sound and by reverberations of the sound off of the closely approximated surfaces of the bony orbital walls. Duplex echography is particularly helpful when studying space-occupying lesions that arise from vascular disorders, such as hemangiomas, arteriovenous communications, and dural sinus fistulas. It can determine the direction and relative volume of blood flow in the orbital vessels, which is a particularly helpful and noninva-sive method. The physician planning the study and treatment of orbital diseases must rely primarily on tissue biopsies, and MRI and CT imaging of orbital hard and soft tissues. The choice between MRI and CT is governed by the nature of the disease (disorders of soft versus those of bone tissues, for example). Additional important considerations include the time needed for the studies. CT scanning is quicker and less affected by movement artifacts, and is thus advantageous for cases of children or elderly patients with a limited capacity to lie quietly still.

j| Note

Patients with cardiac pacemakers cannot be safely scanned by MRI, since the strong magnetic field can cause the device to malfunction or its battery to overheat or change its position, all of which are potentially fatal consequences.

Congenital Ptosis
Fig. 9.4. A small boy with congenital ptosis. Most striking is the asymmetry of the lid folds. On the ptotic side it is hard to identify and less prominently formed than its left hand partner. The optical axis of the eye is unobstructed
Table 9.3. Diagnostic testing for a suspected orbital mass

Signs and symptoms

Methods

Remarks

"My glasses no longer work"

Manifest refraction

Lenticular myopia of uncontrolled diabetes? Axial hyperopia due to proptosis by orbital mass?

Axial proptosis

Hertel exophthalmometry

Mismatch between eyes of up to 2 mm is within normal limits -there is high statistical variance between examiners and examinations.

Always compare to base line measures.

Axial proptosis

View eye position of patient from above and behind, looking down over the patient's brow

Interocular differences >2 mm can be easily seen. Helpful when Hertel values show large interocular mismatch.

Horizontal or vertical globe displacement

Ruler

Kestenbaum glasses

Compare with old photos of patient

Globe displacement

Palpation

Symmetrical resistance to retropulsion? Is there a bruit?

Pulsatile exophthalmos? Crepitation?

Bruit

Auscultation

Murmur

Pupillary motility

See Chap. 5

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