Researchers call for new standards in strabismus surgery for Graves’ orbitopathy

A standard measurement and grading system for the field of binocular single vision (BSV) should be combined with a quality of life (QoL) questionnaire to assess the success of strabismus surgery in patients with diplopia from Graves’ orbitopathy researchers said.

Hinke Marijke Jellema, MMedSci, of the Department of Ophthalmology, Academic Medical Center, Amsterdam, The Netherlands, and her colleagues noted this approach could fill a gap in research on the procedure. They published their proposal in Acta Ophthalmologica.

“The lack of standardisation hampers comparative studies and thus the search for the best surgical treatment for diplopia in patients with Graves’ orbitopathy,” they wrote.

Surgery is the standard treatment for residual diplopia when the disease and motility pattern in  Graves’ orbitopathy have become stable, the researchers said, with the goal of a field of BSV as large as possible.

Other options surgeons might consider include resection, Faden procedures, recessions of the involved muscle with or without adjustable sutures, and interposition of spacers to lengthen the affected extra-ocular muscle.

But without a consensus on the definition of success, researchers cannot compare the efficacy of these approaches, Dr. Jellema and her colleagues wrote.

As a first step toward proposing such a standard, the researchers undertook a review of literature on the subject.

They identified 789 unique publications, from which they found 42 articles reporting on success criteria. These articles used the following measurements:

·       BSV in primary position

·       Differentiation between near and distance

·       BSV in reading gaze and other gazes

·       Ability to fuse

·       Prism required

·       Abnormal head posture

·       Equipment used for measurement

·       Number of surgeries

·       Complications

The researchers found that BSV in primary position and reading gaze was the most frequently used outcome measure.

Many of the papers modified the outcome criteria using a grading system with designations such as excellent, fair, and poor. These papers rarely elaborated on the assessment of the field of BSV, and most lacked quantification of this measurement.

The three studies Dr. Jellema and her colleagues considered “most sophisticated” used a graded system of the field of BSV and described a tool for measuring it: either the Goldmann perimeter or the Harmswand.

Of these, the Goldmann perimeter is far better known around the world and is considered the gold standard, according to Dr. Jellema and her colleagues.

One alternative, the cervical range of motion device, measures the diplopia-free zone in daily life Though a scoring system has already been devised for it, few orthoptic practices make use of it. Because of this, Dr. Jellema and her colleagues argue that the Goldmann perimeter is the most suitable instrument for quantifying the field of BSV.

As for grading systems, most left something to be desired, the reviewers reported.  For example, some do not take into consideration the greater importance of single vision in primary and reading position than side gaze. Others cannot register fine gradations.

The most useful scheme the reviewers found was one by Sullivan et al. in 1992. It uses a weighted scoring system, giving higher scores to the field of BSV in primary and reading positions with a total score of 100 points.

“This latter score is to be preferred because a direct expression of a percentage of normal is possible,” Dr. Jellema and her colleagues wrote.

Citing their own previous research, these reviewers argued that strabismus surgery can significantly improve QoL as measured on the Graves’ orbitopathy-specific QoL questionnaire, but that these scores don’t correlate with the field of BSV.

This questionnaire, published by Terwee et al. in 1998, captures QoL concerns of Graves’ orbitopathy patients better than other questionnaires because it is more specific to their concerns, the reviewers wrote. The questionaire is also “generally accepted and implemented worldwide,” they noted.

Dr. Jellema and her colleagues proposed that researchers use the Goldmann perimeter with the scoring system devised by Sullivan et al. along with the QoL questionnaire of Terwee et al. to create a reliable measurement of strabismus surgical outcomes in Graves’ orbitopathy.

To properly assess these outcomes, researchers should compare pre- and post-surgical measurements on both the field of BSV and QoL with each surgery, the researchers stipulated.

They add that changes over time in the field of BSV can be used along with “the other available tools” including clinical activity score, Hertel measurement, ductions, and eye position to evaluate whether Graves’ orbitopathy is still active or to plan surgery.

Hinke Marijke Jellema, MMedSci

E: h.m.jellema@amc.nl