Сomputed tomography anatomy of the orbital apex

Abstract

The apex of the bony orbit and its soft tissues are most difficult to investigate. Meanwhile just pathological processes in this area cause several serious conditions which could lead to blindness and in many cases to disability. Purpose: to study linear and volume indices of the bony orbital apex and its soft content in normal conditions. Material and methods: 210 patients (266 orbits) are examined. Both orbits were investigated in 56 patients (112 orbits) with no orbital pathology. In patients with unilateral orbital involvement, the normal orbit was investigated (154 orbits). Among examined patients, 86 were men and 124 women. Mean age was 41.2 ± 10.4 years. The CT scan according to the standard technique obtaining axial and frontal sections was carried out in all patients (section thickness was 1.0 mm; interval - 1.0 mm). Results and discussions: The average horizontal size of the external part of an orbit in men was 22.2 ± 0.41 mm (range 17-28 mm). The same size in women was 21.4 ± 0.23 mm (17-26 mm). The vertical size of the external part of the orbit in men is equal to 23.12 ± 0.38 mm, in average and at women - 23.4 ± 0.31 mm. Orbital apex length is 16-24 mm (average 20.1 ± 0.47 mm) in men, in women it is 15-23 mm (average 19,2 ± 0,35 mm). In the article, normal volume of the orbital apex, of the optic nerve, extraocular muscles and orbital fat are presented. Ratios of volume characteristics of studied structures of the orbital apex are displayed. Conclusions: Volume characteristics of the orbital apex and its soft content could be useful to understand the pathogenesis of pathological processes in this area. They could be also used to carry out the differential diagnosis between true and false proptosis, and for surgery planning.