Managing dysthyroid ophthalmopathy involves multidisciplinary approach

Surgery of restrictive hypotropia and esotropia helps to eliminate diplopia.

ST. LOUIS — Dysthyroid ophthalmopathy encompasses a wide range of ocular and orbital conditions that can often be successfully treated by surgery.

“This is a multisystem disorder that requires collaboration not only among other ophthalmologists who might care for the patient, but with radiation oncologists and endocrinologists as well. Both dry eye and strabismus are associated with dysthyroid ophthalmopathy. There are also neuro-ophthalmic, orthoptics and oculoplastics considerations,” said Oscar A. Cruz, MD, chair man and associate professor of ophthalmology and pediatrics at St. Louis University.

Dr. Cruz said there is “considerable inconsistency” in the literature over nomenclature when describing the disease.

“Graves’ ophthalmopathy, I believe, discounts the fact that many patients don’t have Graves’ hyperthyroidism and can be euthyroid or hyperthyroid,” he said.

The acronym TED, for thyroid eye disease, is also commonly used.

“I personally prefer dysthyroid ophthalmopathy because I think it simply identifies the etiology, the dysfunction of the thyroid status,” he said.

Incidence

Dysthyroid ophthalmopathy is most common in women 45 to 60 years old, but is often more severe in older men. It is usually bilateral, often asymmetrical, Dr. Cruz said. The disease is also the most frequent cause of bilateral or unilateral proptosis. Other external ocular signs include lid retraction and lid lag, periorbital involvement (periorbital edema, chemosis), tearing, photophobia and increased blink rate. It also presents a surgical dilemma.

“The motility abnormalities are most commonly upgaze deficiency — worse in abductions than in adduction,” Dr. Cruz said. “There is often an incompetent vertical deviation with significant hypotropia in primary position in other fields of gaze, but often with fusion and orthophoria in downgaze. How do we improve things in primary position without disrupting the person’s fusion in downgaze?”

Testing

The laboratory evaluation of dysthyroid ophthalmopathy has evolved greatly over the past 10 years, mainly because the thyroid stimulating hormone (TSH) assay has become a much more sensitive laboratory test. A change in free T4 will result in about a 30-fold change in the TSH. A less-than-normal TSH “almost certainly” indicates a hyperthyroid patient.

“Some people feel that the free T4 should also be performed to confirm the hyperthyroidism, but almost always the decreased TSH will make that diagnosis,” he said.

However, patients often seen are not hyperthyroid but appear to have thyroid eye disease. In these patients, the thyrotropin receptor antibodies are very useful, particularly the thyroid stimulating immunoglobulin (TSI). TSH binding inhibitory immunoglobulin (TBII) is also commonly tested for.

“TSI is present in about 80% of patients with euthyroid, while TBII is not present in a very high percent,” Dr. Cruz said. Furthermore, the antithyroid antibodies are usually not very helpful in patients who are euthyroid.

Imaging studies have also evolved immensely, with magnetic resonance imaging (MRI) the most promising.

“Some MRI studies are being conducted using T2 relaxation time, for which the authors feel they can predict activity of the disease. This may also be very useful for determining the appropriate time for strabismus surgery and how patients will respond to treatment for acute, active disease,” he said.

Surgical indications

According to Dr. Cruz, dysthyroid ophthalmopathy should be present and stable for at least 6 months before performing surgery. Stable measurements should also be at least 2 months apart.

“This is very difficult for some patients, but if they realize from the beginning that I’m going to wait until their endocrine status has been normalized, they are okay. This is important if other therapy is going on, including radiation therapy, which can change the measurements,” he said.

When talking to patients about the goals of surgery, Dr. Cruz is very specific and blunt.

“A reasonable goal is restoration of single binocular vision in primary and reading gaze,” he said. “I tell them they will see diplopia in far-extreme lateral gaze. I tell them they will see diplopia in upgaze. In fact, I will even sacrifice up gaze for downgaze and reading comfort.”

Recession, recession, recession, is key.

“I still occasionally see patients who’ve had a resection which I don’t think is indicated. If they’ve been recessed, you can often recess these muscles further than you feel commonly. I’ve even set the inferior rectus back just on a hang back and let it find its own place — as far back as 17 mm or 18 mm,” he said.

With these extreme recessions, Dr. Cruz uses a permanent or Mersilene suture.

Horizontal strabismus

Surgery for horizontal strabismus is almost exclusively reserved for esotropia. In most cases, these patients can be treated with a bimedial rectus recession.

“If there is exotropia, look for myasthenia gravis. I use adjustable sutures on all these patients for basal metabolic rates on the tightest medial rectus, as determined at surgery,” Dr. Cruz said.

Bilateral surgery for restrictive hypotropia is valuable as well.

“I believe this minimizes the creation of a progressive hypodeviation in downgaze especially, and it decreases the risk of progressive overcorrection which can occur over time and can occur months later. If there is restriction to upgaze on the inferior rectus muscle on forced ductions, I perform a bilateral, asymmetric rectus recession with only one adjustable suture,” he said.

Indications for unilateral surgery are no restrictions of the contralateral inferior rectus and any restriction of the contralateral superior rectus, or a hypotropia greater than 25 prism diopters.

“This is because of the magnitude of the inferior rectus recession that you’ll need,” said Dr. Cruz, who was moderator of a workshop on dysthyroid ophthalmopathy at the annual meeting of the American Association for Pediatric Ophthalmology and Strabismus.

Surgical complications associated with dysthyroid ophthalmopathy include progressive overcorrection, A-pat tern exotropia, Pulled in Two Syndrome and lower lid retraction. For the latter, Dr. Cruz advocates careful dissection of Lockwood’s ligament.

“Although it helps bring the lower lid forward, I’m concerned that it affects the placement of the inferior rectus muscle,” he said.

Photographing patients from the beginning is also important.

“They often have a false notion that their lid is much, much worse than it was before. If you have a photograph that shows that there was eyelid retraction before, even lower lid retraction, they are okay,” Dr. Cruz said.

For Your Information:

• Oscar A. Cruz, MD, can be reached at 1755 S. Grand, St. Louis, MO 63104; (314) 577-8660; fax: (314) 771-0596; e-mail: cruzoa@slu.edu.