Anatomy-based surgical concepts for individualized orbital decompression surgery in graves orbitopathy. I. Orbital size and geometry.
OBJECTIVE
To analyze orbital morphological parameters that potentially could influence the effect of decompression surgery on exophthalmos reduction in Graves orbitopathy, thus making decompression surgery more predictable.


METHODS
To generate a reference database, a CT-based study was performed in 140 orbits obtained from adult patients with unaffected orbits in a European white ethnicity. The following parameters were chosen: orbital volume, globe volume, globe to orbital volume ratio, and orbital cone angle. Volumes were measured on postprocessed CT data using morphometric techniques. To define the cone angle, a 3-dimensional approach was chosen using the program Amira.


RESULTS
Significant interindividual variation was found in orbital volume from 18.9 to 33.4 ml and in globe volume from 6.0 to 10.1 ml. The globe to orbital volume ratio showed a relatively broad variation from 0.25 to 0.4. Differences in the orbital cone angle from 39.7° to 65.7° were observed.


CONCLUSIONS
The experienced large variations in orbital morphology might significantly influence the degree of exophthalmos reduction, which can be obtained by standardized decompression procedures. Based on our results, a prospective clinical study will be conducted to test our hypothesis.
Kamer
Lukas
L
AO Research Institute Davos, Davos, Switzerland. lukas.kamer@aofoundation.org
Noser
Hansrudi
H
Schramm
Alexander
A
Hammer
Beat
B
Kirsch
Eberhard
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001837:Body Weights and Measures; D019299:Decompression, Surgical; D005094:Exophthalmos / Q000601:surgery*; D005260:Female; D049970:Graves Ophthalmopathy / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000000981:diagnostic imaging*; D012016:Reference Values; D036542:Tomography, Spiral Computed; D044465:White People; D055815:Young Adult