title: Effective orbital volume and eyeball position: an MRI study.
abstract: OBJECTIVE
  Previous studies have examined factors affecting the position of the eyeball to the orbit. This study examined the role of effective orbital volume (EOV), defined as the difference between orbital and eyeball volume, as a determinant of eyeball position, using MRI scans.
  
  
  METHODS
  Forty-six patients were recruited from the Department of Ophthalmology of the University Hospital of Heraklion, Crete Greece. Patients with a history of orbital disease were excluded. Distances between eyeball poles and orbital landmarks were measured in T1 weighted transverse, sagittal and coronal orbital images. The protrusion of the eyeball in the sagittal and transverse planes was recorded. The volume of the eyeball and bony orbit, the EOV, the volume of the extraocular muscles as well as clinical information (age, gender, Hertel exophthalmometry) were also recorded.
  
  
  RESULTS
  EOV was significantly associated with orbital volume but not with eyeball volume. EOV was also significantly associated with transverse and sagittal globe protrusions. Females displayed significantly lower orbital and eyeball volumes as well as EOV than males but higher transverse globe protrusion than males.
  
  
  CONCLUSIONS
  Variations in EOV are associated with orbital volume rather than with eyeball volume. EOV is associated with globe protrusion and may be taken into account in the planning of various procedures, including orbital decompression, treatment of enophthalmos or the size of orbital implants following enucleation.
authors.affiliation: Department of Ophthalmology, University Hospital of Heraklion, Crete, Greece. detorakis@hotmail.com
authors.forename: Efstathios T
authors.initials: ET
authors.lastname: Detorakis
authors.forename: Eleni
authors.initials: E
authors.lastname: Drakonaki
authors.forename: Efrosini
authors.initials: E
authors.lastname: Papadaki
authors.forename: Ioannis G
authors.initials: IG
authors.lastname: Pallikaris
authors.forename: Miltiadis K
authors.initials: MK
authors.lastname: Tsilimbaris
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry; D001837:Body Weights and Measures; D005123:Eye / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000033:anatomy & histology; D009915:Orbit / Q000033:anatomy & histology*; D011446:Prospective Studies; D044465:White People