Influence of orbital morphology on proptosis reduction and ocular motility after decompression surgery in patients with Graves’ orbitopathy

Abstract

Purpose Orbital decompression surgery is performed in patients with Graves’ orbitopathy to treat dysthyroid optical neuropathy (DON) and reduce disfiguring proptosis. The intended proptosis reduction can deviate from the postoperative result and changes of motility with consecutive diplopia can occur. We performed a retrospective study to identify anatomical factors in computed tomography (CT), which influence the surgical effect and postoperative ocular motility and diplopia. Methods Pre- and postoperative CT-scans of 125 eyes of 68 patients, who mainly underwent a balanced orbital decompression for disfiguring proptosis (≥18mm Hertel Index), have been analyzed. Proptosis, ductions, misalignment and diplopia were assessed before and after surgery. Medial and lateral orbital wall length, conus angle, depth of ethmoidal sinus, orbital surface, length of medial and orbital defect, depth of tissue prolapse and horizontal muscle diameters were analyzed in CT scans before and after surgery. With linear regression and multivariate analyses these parameters have been correlated with postoperative proptosis, abduction deficit, deviation and binocular single vision (BSV). Results Proptosis could be reduced by 5.3±2mm. Patients with <5mm proptosis reduction had significantly less often new onset of diplopia compared to patients with >5mm reduction (13% vs. 56%, p = 0.02). Multiple linear regression showed a significant correlation between tissue prolapse and depth of the ethmoidal sinus as well as age (p<0.001, r = 0.71). Proptosis reduction could not be predicted by tissue prolapse, defect length or depth of ethmoidal sinus. The abduction deficit correlated significantly with tissue prolapse and orbital surface area (p<0.001, r = 0.37) but not with the horizontal muscle diameter. Conclusion We were able to show that orbital morphology influences the outcome of balanced orbital decompression surgery in terms of proptosis reduction and motility. However, the rather low coefficients of correlation show that the surgical outcome cannot be predicted with simple CT measurements, although risk factors for postoperative abduction deficit could be found. Therefore, preoperative planning should consider especially the orbital surface area and depth of ethmoidal sinus. Patients should be informed about the higher risk of diplopia with higher proptosis reduction.

Proposing a surgical algorithm for graduated orbital decompression in patients with Graves’ orbitopathy

“…The individual anatomy of the orbit also determines the reduction of exophthalmos. The larger the area of the medial and lateral orbital wall, the greater the possible prolapse of the orbital tissue [24] (Fig. 2).…”

Update endokrine Orbitopathie

“…Bei den chirurgischen Korrekturen sollte eine bestimmte Reihenfolge eingehalten werden. ▪ Eine Reduktion des Exophthalmus kann durch eine knöcherne Orbitadekompression und / oder durch eine sogenannte Fettdekompression erreicht werden [69]. Durch die Dekompression vermindert sich die Lidspalte, und es kann bei Dekompression der medialen Orbitawand durch den Prolaps der medialen geraden Augenmuskeln in die Siebbeinzellen eine Schielstellung entstehen oder aggraviert werden.…”

18 F-FDG-PET/MRI in patients with Graves’ orbitopathy.

“…In some countries, teprotumumab, a new targeted therapy, is already approved and can be used [12]. Sightthreatening GO due to optic nerve compression or corneal exposure ulcers needs immediate treatment mostly with orbital decompression [13,14]. However, these patients often do not show severe clinical inflammation and might be detected first with decreased visual acuity [15].…”