Quantitative Assessment of Orbital Decompression Surgery Using Photogrammetric Stereoimaging.

ABSTRACT

PURPOSE: To evaluate periorbital volume changes, using quantitative photogrammetric stereoimaging, after bony orbital decompression for thyroid eye disease (TED) and compare this to changes in Hertel exophthalmometry. Tissue volumes of the upper and lower eyelids were also assessed independently. DESIGN: Prospective, nonrandomized, nonconsecutive series of patients. SUBJECTS: Adults with inactive TED who had elected to undergo bony orbital decompression at Moorfields Eye Hospital between 2015 and 2017. METHODS: With their eyes gently closed, patients with inactive TED underwent imaging using the VECTRA M3 system (Canfields Imaging, Fairfield, NJ), both before and at least 3 months after orbital decompression. Proptosis was assessed by Hertel exophthalmometry. Using the manufacturer's software, changes in periorbital volumes between the preoperative and postoperative images were calculated for the upper and lower eyelids. The Pearson product-moment correlation coefficient was used to assess the linear relationship between changes in periorbital volume and exophthalmometry. MAIN OUTCOME MEASURES: Change in stereoimaging volumes of the upper and lower eyelids, and clinical proptosis as measured with Hertel exophthalmometry. RESULTS: Thirty-three patients (11 males; 33%) underwent lateral decompression (39 orbits in 26 patients), lateral decompression with complete ethmoidectomy (3 orbits in 3 patients), combined decompression of lateral wall, medial wall, and medial half of floor (10 orbits in 6 patients), or bilateral lateral, medial, and complete floor decompression (1 patient). The corresponding average volumetric changes were 1.74 ml (median 1.64; range 0.39-3.73 ml), 3.38 ml (median 3.38, range 1.89-4.88 ml), 4.05 ml (median 3.53, range 1.72-6.43 ml), and 4.52 ml (range 4.36-4.68 ml), respectively. Similarly, the average reduction in proptosis was 3.6 mm (median 3; range 1.5-7 mm), 5.3 mm (median 5; range 5-6 mm), 7.4 mm (7.5; range 6-9 mm), and 9 mm (range 8-10 mm). Periorbital volume changes were related to the reduction in exophthalmometry (r = 0.713, p < 0.0001), and reduction of lower eyelid volume did not increase further with more than two-wall decompression. CONCLUSION: Graded orbital decompression reduces both proptosis and the upper and lower eyelid tissue volumes, the eyelid changes being likely to influence decisions about future restorative eyelid surgery. The significant changes in eyelid profiles underlines the established principle of thyroid periocular rehabilitation, namely decompression, then strabismus surgery, and finally eyelid surgery.