Thyroid surgery techniques evolve to treat patient upsurge

La Jolla — Benefiting from the experience of seeing large number of patients with thyroid eye disease, surgeons at the Shiley Eye Centre continue to refine surgical procedures used to improve patients’ appearance and visual function.

“Thyroid related ophthalmopathy can be a devastating disease for the patient. The effects of exophthalmos and eyelid retraction, along with the restricted eye movement have a significant impact on the patients’ functional ability but also on the psychological and social environment.

“The surgical procedures we perform provide improved functionality along with a return to normal appearance,” noted David Granet MD, Co-director of the Shiley Eye Centre’s Thyroid Clinic.

Following assessment, patients with thyroid-related ophthalmopathy typically undergo a staged series of surgical procedures. Patients might first undergo orbital decompression surgery to relieve exophthalmos. Surgeons may then perform strabismus surgery. Finally, the oculoplastic surgeon performs eyelid surgery, if required.

Battle of the Bulge: Strabismus surgery, decompression and proptosis
Dr Granet and colleagues recently performed a study, the first of its kind, looking at changes in exophthalmometry after strabismus surgery. They reviewed the charts of all patients seen at the Shiley Thyroid Eye Centre who underwent strabismus surgery over a 15-month period.

The review revealed significant differences among eyes that had undergone previous orbital decompression surgery compared to those that had not. The eyes with prior orbital decompression averaged a +1.7 mm increase in proptosis following strabismus repair. In contrast, those that had not had prior decompression procedures averaged a +0.5 mm decrease in proptosis.

The increase in proptosis was greater in eyes undergoing surgery on multiple muscles. Those eyes saw an increase in proptosis of +1.25 mm.
The eyes in which only a single muscle was operated had an increase in proptosis of +0.8 mm. If the inferior rectus muscle was operated on, the average increase was +0.83 mm.

“This study tells us that strabismus surgery on patients with thyroid-related ophthalmopathy can affect proptosis, especially in those patients with prior orbital decompression.
“When planning for orbital decompression, the surgeon may choose to include this effect. The patient should be made aware of the possible changes to their appearance," Dr Granet said.

Strabismus sutures - OK to wait before adjustments
Strabismus is a not an uncommon manifestation of thyroid eye disease. In many cases, surgeons may opt to perform adjustable suture surgery. Adjustable sutures allow the surgeon to make adjustments based on the patient’s physical and innervational response to surgery.

New research conducted by Dr Granet and colleagues suggests it may be better to wait a week to perform needed suture adjustments, rather than perform them the same day or one day after surgery as is now common practice.

“Current surgical techniques require some form of postoperative procedure to finish the surgery. This adds discomfort and concern to the patient’s postoperative course. The first 24 hours after surgery are often associated with recovery from anaesthesia, pain and swelling of ocular tissues. Delaying adjustment may afford a more accurate postoperative alignment, obviating these problems,” explained Dr Granet.
He added that sparing the patient the need for an additional in-office procedure if the alignment is acceptable not only reduces patient discomfort, but saves the surgeon some time as well.

His study evaluated the effects of adjustable suture surgery in 60 consecutive strabismus patients. Surgeons created the adjustable sutures using a 6-0 vicryl and the cinch knot technique, placing a conjunctival retraction suture at the insertion. They tucked the sutures under the conjunctiva on either side of the incision, and then closed with 8-0 vicryl. The muscles were then irrigated subconjunctivally with dexamethasone/neomycin followed by hyaluraonic acid (Provisc). The patients were not patched.

The researchers examined the patients immediately after surgery; four to six days later; and again five to seven weeks later. Significant changes in deviation (greater than five prism dioptres) warranting a change in adjustment procedure occurred in 10 patients. Nine of these patients eventually required adjustments.
More than 80% of those that did not require any immediate suture adjustments remained within five prism dioptres of their one-week vision measurements at the five to seven week follow-up. Six of the patients who drifted were exotropes and were intentionally overcorrected. Three were thyroid patients in whom surgeons had planned for a later vertical shift. One patient was nonfusing.

Dr Granet believes that delaying the adjustment can give the surgeon a better picture of where a patient’s motility will stabilise, since the one-week measurements were stable when compared to the five to seven week measurements.
He explained that leaving the cinch knot untouched in the immediate postoperative period might prevent the need for an additional procedure without an added risk of misalignment.

“Because of the stability noted in this study, we think the surgeon can aim for an exact surgical correction, rather than over-recess in anticipation of adjustment. The percentage of patients requiring adjustment drops and this increases the benefit of adjustable sutures, while decreasing both the patient and surgeon discomfort," he emphasised.

Graded orbital decompression approach
Don Kikkawa MD, Director of the Orbital and Oculoplastic service, is the surgeon thyroid patients are likely to see for orbital decompression surgery, as well as for follow-up work such as lid repair.

Dr Kikkawa recently completed a study involving a graded approach to decompression surgery. This approach bases the amount of decompression on the degree of preoperative proptosis, rather than the size of the extraocular muscles or the degree of preoperative diplopia.

The study, published in the journal Ophthalmology, determined the amount of preoperative proptosis in a series of patients with the Naugle exophthalmometry. The amount of surgery was based on the grade of proptosis from <22.0 mm to >25.0 mm.
“Our research indicated that this graded approach to orbital decompression produces predictable results with minimal complications. We believe this could form the basis for reasonable and practical guidelines for the orbital surgeon,” he said.

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