Retrobulbar Filling for Enophthalmos Treatment in Dogs: Technique, Description and Computed-Tomographic Evaluation. Preliminary Cadaveric Study

SIMPLE SUMMARY: In human medicine, a treatment modality for the sunken eye (enophthalmos) is retrobulbar fat injection. This preliminary study aimed to assess the feasibility and standardize the modalities of retrobulbar injection for enophthalmos treatment in dogs. Using an ultrasound-guided approach, two solutions, similar to adipose tissue, were injected within the retrobulbar space of dogs’ cadavers. The amount of solution to be injected was estimated using formulas described for ocular-regional anesthesia. Eyeball displacement was evaluated using two different computed tomography (CT)-based methods. The damage to retrobulbar structures due to the maneuver was assessed by necropsy and histopathological examination. A few milliliters of solution were needed to achieve the resolution of enophthalmos. The postmortem and histopathological examination did not find damage to the retrobulbar structures. Both proposed CT methods could quantify the eyeball displacement. Retrobulbar fat injection may represent a treatment modality for enophthalmos in dogs. ABSTRACT: A new therapeutic approach for enophthalmos may be retrobulbar lipofilling. This study aims to standardize the intraconal filling technique and to evaluate the degree of eyeball displacement by computed tomography (CT). Skull CT was performed on six dog cadavers before and after intraconal injection of two 5% iodinated, viscoelastic solutions, one per eye, using an ultrasound-guided supratemporal approach. The volume to be injected was calculated using formulas for retrobulbar cone anesthesia. After CT, the dogs underwent necropsy and histopathology to evaluate damages that eventually occurred to retrobulbar structures. Eyeball displacement was estimated using two CT-based methods, named M(1) and M(2). The Wilcoxon signed-rank test revealed no significant difference between the two injected materials in both M(1) (p > 0.99), and M(2) (lateral p = 0.84 and rostral p = 0.84 displacement). A statistically significant difference was found between the pre- and post-injection group M(1) (p = 0.002), M(2) (p = 0.004) for the lateral and (p = 0.003) for rostral displacement. Although the slight eyeball displacement, the retrobulbar filling can lead to enophthalmos resolution. Compared to M(1), the M(2) method has better-defined anatomical landmarks. Further, preclinical in vivo studies are necessary to assess retrobulbar filling efficacy and safety.