Digital Evaluation of Orbital Cyst Associated with Microphthalmos: Characteristics and Their Relationship with Orbital Volume

PURPOSE: To study the characteristics of orbital cyst associated with microphthalmos in a group of Chinese patients, and to analyze the relationship between orbital cyst and orbital volume. DESIGN: Cross-sectional comparative study. PARTICIPANTS: 120 patients who were diagnosed as unilateral clinical blind microphthalmos, in which 20 patients had orbital cyst in the affected eye. METHOD: Participants had computed tomography (CT) scan. CT images were analyzed with a computer-aided software. MAIN OUTCOME MEASURES: Volume and position of orbital cyst, microphthalmic to contralateral ratio (MCR) of orbital volume, height and depth and orbital rim displacement. RESULTS: 38.1% of the cysts located anterior to or at the equator of the globe, 75% of which located infratemporally and all of which were outside the muscle cone. Most (84.6%) of the posterior cysts were inside the muscle cone. The anterior cysts were larger than the posterior cysts (p = 0.005). MCR of orbital volume (p<0.001), height (p = 0.004) and width (p = 0.043) were significantly higher in patients with orbital cyst than controls. For patients with orbital cyst, larger cyst-plus-globe volume of the affected eye was associated with higher MCR of orbital volume (r = 0.630, p = 0.003). Patients with large cyst-plus-globe volume had higher MCR of orbital volume (p = 0.002), height (p = 0.014), width (p = 0.005) and depth (p = 0.002) and less displacement in inferior (p = 0.004) orbital rim, compared with patients with small cyst-plus-globe volume, but the differences between patients with small cyst-plus-globe volume and patients without cyst were not significant. CONCLUSIONS: Microphthalmic eyes with large cyst-plus-globe volume showed better similarity with the contralateral eyes, comparing with microphthalmic eyes without orbital cyst or with small cyst-plus-globe volume. It suggested that the existence of orbital cysts (especially large cysts) in microphthalmic eyes might play a positive role in the orbital development.