High resolution B-scan ultrasonography of the orbit. V. Eye changes of Graves' disease

Occult thyroid eye disease in patients with unexplained ocular misalignment identified by standardized orbital echography

PURPOSE

To describe the clinical presentation, orbital echography (OE) findings, and neuroimaging results of patients with chronic unexplained ocular misalignment, which includes patients with clinically occult thyroid eye disease (TED) that is identifiable through a characteristic OE appearance.

DESIGN

Retrospective observational case series.

METHODS

Seventy-eight patients with chronic ocular misalignment suspected of TED because of a history of systemic thyroid disease, proptosis, dysmotility, positive forced ductions, or eyelid retraction or lag were categorized as TED positive, negative, and indeterminate with the use of standardized OE. Demographic, clinical, OE, computed tomography, and magnetic resonance imaging information was collected. Analyses determined the prevalence of TED and differences between TED positive, negative, and indeterminate groups.

RESULTS

Fifty-five percent of the findings were suspicious for and most consistent with TED (TED positive); 26% of the findings were TED negative, and 19% of the findings were TED indeterminate. Of 30 patients with newly diagnosed TED by OE, 70% had no lid retraction, and 20% had no other findings of TED. The inferior rectus followed by the superior rectus/levator complex, medial rectus, and lateral rectus muscles were the most frequently involved muscles. Neuroimaging that was performed in only 26 of 78 patients (33%) did not appear to yield additional diagnostic information.

CONCLUSION

TED is a potential cause of chronic unexplained ocular misalignment in a substantial proportion of patients. These patients frequently present in an occult fashion without other clinical findings that are typical of TED. In these patients, a diagnosis of TED by OE can reduce further costly evaluation. OE appears to have significant clinical usefulness in the diagnosis of TED in patients with unexplained ocular misalignment.

Echographic monitoring of response of extraocular muscles to irradiation in Graves' ophthalmopathy

PURPOSE

Confirmation of the efficacy of orbital irradiation in Graves' ophthalmopathy is needed due to the unpredictable natural history of the disease, the variation in individual clinical presentations, the contribution of other simultaneous treatments, and the lack of controlled studies using objective criteria to classify and assess response over time. Orbital echography before and at select intervals following orbital irradiation is proposed as an objective parameter of tissue response to orbital irradiation over time.

METHODS AND MATERIALS

From January, 1983 to September, 1993, 55 patients with progressive Graves' ophthalmopathy underwent 20 Gy retrobulbar irradiation. On retrospective review, standardized orbital echography was performed randomly prior to irradiation in 37 of the 55 patients to assess the acoustic characteristics of the extraocular muscles and to quantitate their individual and summed diameters. Twenty-one patients had at least one follow-up echographic evaluation at random intervals of 0 to 27.5 months following completion of irradiation. Twelve patients received steroids before or during irradiation, which were tapered in proximity to completion of radiation. Follow-up ranged from 2 to 65 months with the majority followed at least 6 months (18 patients).

RESULTS

Of the 21 patients with serial studies, 18 showed an interval decrease in individual and summed muscle size over time and return of symmetry. Interval improvement was documented as early as the 1 month follow-up study, with continued improvement seen during the 3-9-month studies, with stability typically achieved within 12 months. One patient had further changes between the 21 and 27.5 month follow-up studies. Exacerbation of disease was, however, echographically demonstrated in three patients at 6.5, 8.5, and 13 months. Follow-up studies in two of these patients again revealed improvement, one following tapered steroids. The third patient required orbital decompression.

CONCLUSION

Objective parameters of response are needed to document both the immediate and long-term outcome of orbital irradiation on the course of Graves' ophthalmopathy and confirm its efficacy. Serial echography is proposed as a new technique for providing parameters to judge response.

The ophthalmopathy of Graves' disease

Fortunately, most patients with thyroid-related eye disease have mild ocular involvement that spontaneously involutes. Less than 5% of patients with hyperthyroidism will develop sufficiently severe ocular abnormalities that will require surgical intervention. Most patients with thyroid eye findings should be symptomatically managed. Some will require use of either topical drops or oral steroids to alleviate their eye problems. In approximately one half of those patients who present acutely with severe thyroid orbital finding, nonsurgical therapies will be sufficient to control their eye disease. In the other half, eventually multiple surgical procedures may be required, and as discussed previously, the timing and sequence of those procedures are crucial to achieve optimal results.

Ophthalmopathy in early thyrotoxicosis--relationship to thyroid receptor antibodies and effects of treatment

A prospective study of 25 newly diagnosed thyrotoxic patients was undertaken to determine the incidence and severity of ophthalmopathy in the early stages of the disease. A quantitative analysis of the ocular muscle changes was made using B scan ultrasonography, and the effects of treatment for the thyroid disease on the course of the eye changes was assessed. Although the majority (75%) of patients showed only mild clinical signs of ophthalmopathy (Werner Class 3 or less), 92% had ultrasonographic evidence of ocular muscle enlargement. Clinical involvement of the extraocular muscles was seen in 12% of the cases. There was an inverse correlation between the serum level of thyroid stimulating hormone receptor antibody (TR Ab) and the size of the extraocular muscles. Recovery of the euthyroid state with treatment was accompanied by a decrease in orbital infiltration in some cases, both clinically (reduced amplitude of intraocular pressure rise on elevation of the globe) and by ultrasonography, but the improvement was not statistically significant.

Diagnosis and management of endocrine ophthalmopathy

Most patients with Graves' hyperthyroidism have mild or inapparent ophthalmopathy. For the unusual patient with severe ophthalmopathy, a generally successful, coordinated, combined interdisciplinary medical and surgical management program is outlined.

Computed tomography of the orbit

Computerized tomography (CT) has revolutionized the analysis of patients with orbital tumors. A new CT scanner devised by the author resolves structures less than 1 mm with an image section as thin as 2 mm. This improved resolution shows all the extraocular muscles, including the obliques; enlargement of the optic nerve to the orbital end of the optic canal; and the sclera, crystalline lens, aqueous, and vitreous. Experience with 700 orbital studies shows that CT scanning now identifies pathologic changes in the orbital soft tissues with the same diagnostic accuracy as bone pathology.

Reliability of orbital diagnostic tests: ultrasonography, computerized tomography, and radiography

A series of 342 patients with unilateral exophthalmos underwent orbital diagnostic studies including ultrasonography, computerized tomography, radiographic studies, and vascular contrast studies. Each test was found to have diagnostic capabilities that complemented other studies depending upon the specific disease process involved. No one test was entirely adequate without supplementary information from the other tests. Radiographic studies demonstrated bony abnormality in 50% of the tumor cases, but in only 28% of the entire series of exophthalmos cases. Computerized tomography demonstrated diagnostic soft tissue abnormality in 86% of tumors, 43% of inflammatory diseases, and an overall yield of 62% positive results. Ultrasonography proved the most versatile test for evaluation of orbital soft tissues, with 80% positive results for tumors, 87% for inflammatory disorders, and 78% overall accurate orbital diagnosis. Erroneous tumor diagnosis of 7% with computerized tomography and 3% with ultrasonography were corrected by combining these two studies, because they tend to err in opposite directions. Combination of ultrasound and CT scan resulted in a 98% correct diagnosis of all types of orbital diseases.

An introduction to the use of diagnostic ultrasound

This article is meant to serve as a simple introduction to diagnostic ultrasound, explaining the nature of sonar and the basic equipment for its production and use. A scans, B scans, time-position scans, and Doppler-shift techniques are described, with some examples of the clinical applications of each. Some recent innovations such as scan conversion to improve gray scaling and electrocardiographically triggered cardiac sector scans are mentioned. The limitations of the technique are indicated, with measures that can be adopted to reduce them. The safety of the procedure is emphasized, with its freedom from the known biological effects of ionizing radiation.