Diplopia occurring after orbital trauma is a complex and difficult clinical problem. Numerous potential mechanisms exist by which it may occur. Restrictive ocular dysmotility caused by intraorbital scarring is a major component in diplopia's pathogenesis. The current large animal study was conducted to develop an experimental model of restrictive ocular dysmotility that would quantitatively characterize the biomechanical properties of the globe rotations. Using this model, a novel method of restoring the low- friction milieu within the orbit by interposing a buccal fat graft was tested. In the initial stage, the baseline force duction was measured in 20 pig eyes using a highly sensitive, digital tensiometer. Traumatic violation of Tenon's fascia with electrocautery into the extraconal fat and the periorbita was followed by direct suturing of the extraocular muscle to the nearest orbital periosteum. After 6 weeks, the measurements (again in the field of the traumatized muscle) were repeated, and the eyes were divided into two treatment groups (n = 10 eyes per group). The left eye received the standard lysis of adhesion, whereas the right eye received lysis and buccal fat interposition grafting. The third and final force measurements were performed 6 weeks after treatment. The results showed a baseline linear load- displacement curve of 0 to 8 mm, with the globe rotating 400 μm for every 1000 mg of tensile load. Surgical trauma increased the slope as defined by load/displacement but, surprisingly, the relationship remained linear in the entire range from 2 to 8 mm. This linear relationship was seen in all stages: baseline, after trauma to Tenon's fascia, after surgical lysis alone, and after lysis with buccal fat interposition. The difference was in the slope, or stiffness. Lysis alone partially reduced the slope, but it was still higher than baseline. Lysis and buccal fat grafting returned the slope to near baseline. This, however, did not reach the level of statistical significance. It seems that a focal intervention along the course of an extraocular muscle altered the composite behavior of orbital resistance to globe rotation. Although buccal fat grafting did not significantly improve motility, it did not worsen it.
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