| Purpose Orbital development is retarded in children with congenital microphthalmia,，and face development is delayed on the same side. The aim of this study was to evaluate the asymmetry of bilateral orbit development, and thus to provide a rationale for tailoring treatment timing and therapy.
Methods By combining multisection helical computerized tomography imaging with a computer-aided design system (iPlan cranial software, version 2.5 by BrainLAB, Germany), we measured the various indices of 38 eyes in 38 children aged 0-6 with congenital microphthalmia, and 70 orbits in unaffected children aged 0-6. Variables measured included orbital volume, orbital depth, width, height and eyeball volume. Displacement of the orbital rims was calculated by mirroring the unaffected orbit by the midline.
Results Differences between the orbital volume, eyeball volume, orbital width and height of the affected and unaffected sides were significant (all P=0.000). The difference between the orbital depth of the affected and unaffected sides was not significant（P=0.055). Growth of the inferior and lateral rims was retarded by an average of 3mm, while that of the medial and superior rims was retarded by less than 1mm.
Conclusions Decreases in orbital volume in children with congenital microphthalmia depend on the severity of the disease (the decrease in the affected eyeball) but not on age. Retarded orbital development is evident primarily in the inferior and lateral rims, correlating mostly with the zygomatic and then the maxilla and frontal bone. The growth of the affected orbit retards or even stagnates by 3 years of age. Intervention therapy before 3 years of age is therefore critical. | 
