A seven-year-old infant with neurofibromatosis type 1 was referred to the Chelsea and Westminster Hospital craniofacial team for management of a right retro-orbital plexiform neurofibroma and co-existent congenital glaucoma, with buphthalmos. He had no significant vision in the right eye. Management options were isolated neurofibroma debulking, evisceration or enucleation to prevent unwanted bony and adnexal secondary changes. Studies have demonstrated the relationship of intraorbital volume and socket and soft tissue size. A mismatch of intraorbital volumetric growth on the two sides results in orbital and facial asymmetry. Removal of this tissue mass should be deferred, if possible, until the socket and soft tissue proportions reach adult size and the depleted volume should be replaced. It is postulated that the cranio-orbito-zygomatic skeleton reaches more than 85% of adult size by 5 years of age. Accurate orbital volume measurements are difficult to perform. CT based methodologies employing different software and anatomical landmarks have been available since the 1980s. Volume assessment allows comparison with adult size, informing the correct timing of orbital adjustment.

Bilateral orbital volume measurements were made using the Mimics software from CT images.

Right and left orbits were measured at 16575.37mm3 and 10090.85mm3 respectively.

Our patient proposed a challenge in selecting the appropriate timing for intraorbital debulking, evisceration or enucleation. There is a possible subsequent reduction in orbital growth leading to an unacceptable defect into adulthood. An overgrowth of the orbit beyond that of adult size due to the neurofibroma stimulus must also be prevented.